Heinberg: Prospects for Alternative Energies to Replace Fossil Fuels

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Heinberg: Prospects for Alternative Energies to Replace Fossil Fuels

Richard Heinberg's Museletter: The Conservation Imperative: Energy Limits to Growth and the Path to Sustainability - Part 2
by Richard Heinberg

Download printable pdf version here (PDF, 248 KB); Read onlind version with charts/graphics here.

While this report is focused on the prospects for alternative energy sources to replace fossil fuels, it is useful to apply the above criteria first to oil, coal, and gas so that comparisons can be made with their potential replacements.

Oil. As the world’s current primary energy source, oil fuels nearly all global transportation—cars, planes, trains, and ships (the exceptions, such as electric cars and subways, electric trains, and sailing ships, are statistically insignificant). Petroleum provides about 40 percent of total world energy, or about 40 EJ per year. The world currently uses about 74 million barrels of oil per day, or 30 billion barrels per year, and reserves amount to about one trillion barrels (though the figure is disputed).

Plus: Petroleum has become so widely relied upon because of its basic characteristics: it is highly transportable as a liquid at room temperature and is easily stored. It is energy dense (a cup of oil contains as much energy as 1 ½ lbs of wood, or 42 MJ per kilogram). Historically, oil has been cheap to produce, and easy to transport and use, and can be procured from a very small land footprint.

Minus: Oil’s downsides are as plain as its advantages.

Its environmental impacts are significant. Extraction is especially damaging in poorer nations such as Ecuador and Nigeria, where the industry tends to spend minimally on the kinds of remediation efforts that are required by law in the US; as a result, rivers and wetlands are fouled, air is polluted, and indigenous people see their ways of life threatened. Meanwhile, burning oil releases climate-changing CO2 (about 800 to 1000 lbs CO2 per barrel [13]), as well as other pollutants such as nitrogen oxides and particulates.

Oil is also non-renewable, and many of the world’s largest oilfields are already significantly depleted. Most oil-producing nations are seeing declining rates of extraction, and future sources of the fuel are increasingly concentrated in just a few countries—principally, the members of OPEC. The geographic occurrence of oil deposits has led to competition for supplies, and sometimes to war over access to the resource. As oil becomes scarcer due to depletion, even worse oil wars may occur.[14]

EROEI: The net energy (compared to gross energy) from global oil production is difficult to ascertain precisely, because many of the major producing nations do not readily divulge statistics that would make detailed calculations possible. About 750 kilojoules of energy are required to lift 15kg of oil 5 meters—an absolute minimum energy investment for pumping oil that no longer flows out of the ground under pressure. But energy is expended also in exploration, drilling, refining, and so on. A rough total number can be derived by dividing the energy produced by the global oil industry by the energy equivalent of the dollars spent by the oil industry for exploration and production. According to Hall, this number—for oil and gas together—was about 23:1 in 1992, increased to about 32:1 in 1999, and has since declined steadily, reaching 19 in 2005. If the recent trajectory is projected forward, the EROEI for global oil and gas would decline to 10:1 soon after 2010.

It is important to remember that this number is a global average: some producers enjoy much higher net energy than others. There is every reason to assume that most of the high-EROEI oil producers are OPEC-member nations.

Prospects: Oil production has peaked and is in decline in most producing countries, and nearly all of the world’s largest oilfields are seeing falling production. The all-time peak of global oil production occurred in July, 2008 at 75.1 million barrels per day. At the time, the per-barrel price had skyrocketed to its all-time high of $147. Since then, declining demand and falling price have led producing nations to cut back on pumping significantly. Declining price has also led to a significant slowing of investment in exploration and production, which virtually guarantees production shortfalls in the future. It therefore seems unlikely that the July 2008 rate of production will ever be exceeded.

Declining EROEI and limits to global oil production will therefore constrain future world economic activity unless alternatives to oil can be found.

Natural Gas was formed by geological processes similar to those that produced oil, and it often occurs together with liquid petroleum. In the early years of the oil industry, gas was simply flared (burned); today, it is regarded as a valuable energy resource and is used globally for space heating and cooking fuel; it also has many industrial uses where high temperatures are needed, and is increasingly burned to generate electricity. Of the world’s total energy, natural gas supplies 23.5 percent; global reserves amount to about 6300 trillion cubic feet, which represents an amount of energy equivalent to 890 billion barrels of oil. [15]

Plus: Natural gas is the least carbon intensive of the fossil fuels (58 kg CO2 per GJ). Like oil, natural gas is energy dense (weight density, volume density), and is extracted from a small land footprint. It is easily transported through systems of pipelines and pumps, though it cannot be transported by ship as conveniently as oil, as that typically requires pressurization.

Minus: Natural gas is a hydrocarbon fuel, which means that burning it releases CO2 even if the amounts are less than would be the case to yield a similar amount of energy from coal or oil. Like oil, natural gas is non-renewable and depleting. Environmental impacts from the production of natural gas are similar to those with oil. Recent disputes between Russia, Ukraine, and Europe over Russian natural gas supplies underscore the increasing geopolitical competition for access to this valuable resource.

EROEI: The net energy of global natural gas is even more difficult to calculate than that of oil, because oil and gas statistics are often aggregated. A recent study that incorporates both direct energy (diesel fuel used in drilling and completing a well) and indirect energy (used to produce materials like steel and cement consumed in the drilling process) found that as of 2005, the EROEI for US gas fields was 10:1. [16] However, newer "unconventional" natural gas extraction technologies (coal bed methane and production from low-porosity reservoirs using "fracing" technology) probably have significantly lower net energy yields: the technology itself is more energy intensive, and wells deplete quickly, thus requiring increased drilling rates to yield equivalent amounts of gas. Thus as conventional gas depletes and unconventional gas makes up a greater share of total production, the EROEI of natural gas production will decline, possibly dramatically.

Prospects: During the past few years, North America has averted a natural gas supply crisis as a result of the deployment of new production technologies, but it is unclear how long the reprieve will last given the low EROEI of these production techniques (and the fact that the best unconventional deposits, such as the Barnett Shales of Texas, are being exploited first). European gas production is declining and Europe’s reliance on Russian gas is increasing—but it is difficult to tell how long Russia can maintain current flow rates. In short, while natural gas has fewer environmental impacts than the other fossil fuels, especially coal, its future is clouded by supply issues and declining EROEI.

Coal was the first fossil fuel and the primary energy source of the Industrial Revolution. While it formerly was used for space heating, cooking, and various industrial processes, coal is today burned mainly for the production of electricity and for making steel. Coal has been the fastest growing energy source (by quantity) in recent years due to prodigious consumption growth in China, which is by far the word’s foremost producer and user of the fuel. The world’s principal coal deposits are located in the US, Russia, India, China, Australia, and South Africa. World coal reserves are estimated at 850 billion metric tons (though this figure is disputed), with annual production running at just over four billion tons. Coal produces 134.6 EJoules annually, or 27 percent of total world energy. The US relies on coal for 49 percent of its electricity, and 23 percent of total energy. [17] Its energy density by weight is variable (from 30 MJ/kg for high-quality anthracite to as little as 5.5 MJ/kg for lignite).

Plus: Coal currently is a cheap, reliable source of electricity. It is easily stored, though bulky. However, long-distance transport makes economic sense only for higher-quality coals.

Minus: Coal has the worst environmental impacts of the conventional fossil fuels, both in the process of obtaining the fuel (mining) and in that of burning it to release energy. Because coal is the most carbon-intensive of the conventional fossil fuels (290 kg CO2 are emitted for every GJ of energy produced), it is the primary source of greenhouse gas emissions leading to climate change, even though it contributes less energy to the world economy than petroleum does.

Coal is non-renewable, and some nations (UK and Germany) have already used up most of their original coal reserves. Even the US, the "Saudi Arabia of coal," is seeing declining production from its highest quality deposits.

EROEI: Historically, the net energy from coal was very high, at an average of 177:1 according to one study [18], but it has fallen substantially to a range of 50:1 to 85:1. Moreover, the decline is continuing, with one estimate suggesting that by 2040 the EROEI for US coal will be .5:1 [19].

Prospects: While official reserves figures suggest that world coal supplies will be sufficient for a century or more, recent studies suggest that supply limits may appear globally, and especially regionally, much sooner. According to a 2007 study by Energy Watch Group of Germany, world coal production is likely to peak around 2025 or 2030, with a gradual decline thereafter. China’s production peak could come sooner if economic growth (and hence energy demand growth) returns soon. For the US, coal production may peak in the period 2030 to 2035.

New coal technologies such as carbon capture and storage could reduce the climate impact of coal, but at a significant economic and energy cost (by one estimate, about 40 percent of the energy from coal would go toward mitigating climate impact, with the other 60 percent being available for economically useful work). Coal prices increased substantially in 2007-2009, as the global economy heated up, which suggests that the existing global coal supply system was near its limit. Prices have declined sharply since then as a result of the world economic crisis and falling energy demand. Prices for coal will almost certainly increase in the future, in inflation- or deflation-adjusted terms, as high-quality deposits are exhausted and energy demand recovers.

Tar sands, sometimes called "oil sands," consist of bitumen embedded in sand or clay. The resource is essentially petroleum that formed without an impervious geological "cap," so that lighter hydrocarbon molecules rose to the surface and volatized long ago rather than remaining trapped underground.

The material is fairly useless in its raw state, and requires substantial processing or upgrading, the finished product being referred to as "syncrude." The process can be accomplished in situ through the underground injection of steam, or in above-ground refineries after the material has been mined with giant mechanized shovels.

The sites of greatest commercial concentration of the resource are in Alberta, Canada and the Orinoco Basin of Venezuela. Current production of syncrude from operations in Canada amounts to about 1.5 million barrels per day, which accounts for 1.7 percent of total world liquid fuels production, or a little less than 0.7 percent of total world energy. Reserves amount to about 1.7 trillion barrels of oil equivalent in Canada and 235 billion barrels of extra heavy crude in Venezuela, though it is likely that a large portion of what has been classified as "reserves" should be considered unrecoverable "resources" given the likelihood that deeper and lower-quality tar sands will require more energy for their extraction and processing than they will yield.

Plus: The only advantages of tar sands over conventional petroleum are that (1) large amounts remain to be extracted, and (2) the place where the resource exists in greatest quantity (Canada) is geographically close and politically friendly to the country that imports the most oil (the US).

Minus: Tar sands have all of the negative qualities associated with the other fossil fuels (they are nonrenewable, polluting, and climate-changing), but in greater measure than is the case with natural gas or conventional petroleum. Tar sands production is the fastest-growing source of Canada’s greenhouse gas emissions, with the production and use of a barrel of syncrude ultimately doubling the amount of CO2 that would be emitted by the production and use of a barrel of conventional petroleum. Extraction of tar sands has already caused extensive environmental damage across a broad expanse of Northern Alberta.

All of the techniques used to upgrade tar sands into syncrude require other resources: some of the technologies require significant amounts of water and natural gas—as much as 4.5 barrels of water and 1200 cubic feet (34 cubic meters) of natural gas for each barrel of syncrude.

As a result, syncrude is costly to produce. A fixed per-barrel dollar cost is relatively meaningless given the recent volatility in input costs; however, it is certainly true that production costs for syncrude are much higher than historic production costs for crude oil, and compare favorably only with the higher costs for the production of a new marginal barrel of crude using expensive new technologies.

EROEI for tar sands and syncrude production is difficult to assess directly. Various past net energy analyses for tar sands range from 1.5:1 to 7:1, with the most robust and recent of analyses suggesting a range of 5.2:1 to 5.8:1. [20] This is a small fraction of the net energy historically derived from conventional petroleum, and it is likely to be insufficient to enable tar sands to serve as a primary energy source for industrial economies.

Prospects: The International Energy Agency expects syncrude production in Canada to expand to 5 mb/d by 2030, but there are good reasons for questioning this. The environmental costs of expanding production to this extent may be unbearable. Further, investment in tar sands expansion is now declining, with more than US$60 billion worth of projects having been delayed in the last three months of 2008 as the world skidded into recession. A more realistic prospect for tar sands production may be a relatively constant production rate, rising perhaps only to two mb/d.

Oil shale. If tar sands are oil that was "spoiled," oil shale (or kerogen, as it is more properly termed) is oil that was undercooked: it consists of source material that was not buried at sufficient depth or for long enough to be chemically transformed into the shorter hydrocarbon chains found in crude oil or natural gas. Deposits of potentially commercially extractable oil shale exist in 33 countries, with the largest being found in the western region of the US (Colorado, Utah, and Wyoming). Oil shale is used to make liquid fuel in Estonia, Brazil, and China; it is used for power generation in Estonia, China, Israel, and Germany; for cement production in Estonia, Germany, and China; and for chemicals production in China, Estonia, and Russia. As of 2005, Estonia accounted for about 70 percent of the world’s oil shale extraction and use. The percentage of world energy currently derived from oil shale is negligible, but world reserves are estimated at 2.8 trillion barrels of liquid fuel. [21]

Plus: As with tar sands, the only real upside to oil shale is that there is a large quantity of the resource in place. In the US alone, shale oil resources are estimated at two trillion barrels, nearly twice the amount of the world’s remaining conventional oil resources.

Minus: Oil shale suffers from low energy density, about one sixth that of coal. The environmental impacts from its extraction and burning are very high, and include severe air and water pollution and the release of half again as much CO2 as the burning of conventional oil. The use of oil shale for heat is far more polluting than natural gas or even coal.

EROEI: Reported EROEI (energy return on investments) for oil produced from oil shale are generally in the range of 1.5:1 to 4:1 [22]. Net energy for this process is likely to be lower than the production of oil from tar sands because of the nature of the material itself.

Prospects: During the past decades most commercial efforts to produce liquid fuels from oil shale have ended in failure. Production of oil shale worldwide has actually declined significantly since 1980. While low levels of production are likely to continue in several countries that have no other domestic fossil fuel resources, the large-scale development of production from oil shale deposits seems unlikely anywhere for both environmental and economic reasons.

Nuclear. Producing electricity from controlled nuclear fission reactions has long been a contentious way of providing energy for society. Currently, about 435 commercial power-generating reactors are operating worldwide, 103 of them in the US. Collectively they produce 2658 TWh world-wide, and 806 TWh in the US. This represents 3 percent of world energy, and 8 percent of all energy in the US. [23]

All commercial reactors in the US are variants of light water reactors. Other designs have been subjects of research (see below).

Plus: Nuclear electricity is reliable and relatively cheap (2.9 cents per kW/h) once the reactor is in place and operating. In the US, while no new nuclear power plants have been built in many years, the amount of nuclear electricity provided has grown during the past decade due to the increased efficiency and reliability of existing reactors.

The nuclear cycle emits much less CO2 than the burning of coal to produce an equivalent amount of energy (though uranium mining and enrichment, and plant construction still entail carbon emissions). This has led some climate protection spokespeople to favor nuclear power, at least as a temporary bridge to an all-renewable energy future.

Minus: Uranium, the fuel for the nuclear cycle, is a non-renewable resource. The peak of production is likely to occur between 2040 and 2050 [24], which means that nuclear fuel is likely to become more scarce and expensive over the next few decades. Already, the average grade of uranium has declined substantially in recent years as the best reserves have been depleted. Recycling of fuel and the employment of alternative nuclear fuels are possible, but the technology has not been adequately developed.

Nuclear power plants are so costly to build that unsubsidized nuclear plants are not economically competitive with similar-sized fossil-fuel plants. Government subsidies in the US include: 1) those from the military nuclear industry, 2) non-military government subsidies, and 3) artificially low insurance costs.

The nuclear fuel cycle entails substantial environmental impacts, which may be greater during the mining and processing stages than during plant operation even when radiation-releasing accidents are taken into account. Mining entails ecosystem removal, dust, large amounts of tailings (equivalent to 100 to 1,000 times the amount of uranium extracted), and radiation-emitting particles leaching into groundwater. During plant operation, accidents causing small to large releases of radiation can impact the local environment or much larger geographic areas, potentially making land uninhabitable (as with Chernobyl).

Storage of radioactive waste is highly problematic. High-level waste (like spent fuel) is much more radioactive and difficult to deal with than low-level waste, and must be stored onsite for several years before transferal to a geological repository.

The best-known way to deal with waste, which can contain lethal doses of radiation for thousands of years, is to store it in a geological repository, deep underground. Yucca Mountain in Nevada, the only site being investigated as a repository in the US, will begin accepting waste in 2017. More repositories will be needed, especially if the use of nuclear power is expanded in the US. Even then, over tens of thousands of years waste could possibly leak into the water table. The issue is controversial even after extremely expensive and extensive analyses by the Department of Energy.

Nearly all commercial reactors use water as a coolant. Heat pollution from coolant water discharged into lakes, rivers or oceans can disrupt aquatic habitats. In recent years, a few reactors have had to be shut down due to water shortages, highlighting a future vulnerability of this technology in a world where fresh water is becoming increasingly scarce.

Reactors must not be sited in earthquake-prone regions due to the potential for radiation release in the event of a serious quake. Nuclear reactors are often cited as potential terrorist targets and as potential sources of radioactive materials for the production of terrorist "dirty bombs."

EROEI: A review of net energy studies of nuclear power that have been published to date by Hall et al. [25] found the information to be "disparate, widespread, idiosyncratic, prejudiced, and poorly documented." The largest issue is often what the appropriate boundaries of analysis should be. The review concluded that the most reliable EROEI information is quite old, while newer information is either highly optimistic 10:1 or more) or pessimistic (low or even negative).

Prospects: The nuclear power industry is growing, with ten to twenty new power plants being considered in the US alone. But the scale of growth is likely to be constrained mostly for reasons discussed above.

Hopes for a large-scale deployment of new nuclear plants rest on the development of new technologies: pebble-bed and modular reactors, fuel recycling, and the use of thorium as a fuel. The ultimate technological breakthrough for nuclear power would be the development of a commercial fusion reactor. However, each of these new technologies is problematic for some reason. Fusion is still decades away and will require much costly research. The technology to extract useful energy from thorium is highly promising, but will require many years and expensive research and development to commercialize. The only breeder reactors in existence are closed, soon to be closed, abandoned, or awaiting re-opening after serious accidents: BN-600 (Russia, end of life 2010); Clinch River Breeder Reactor (U.S., construction abandoned in 1982 because the US halted its spent-fuel reprocessing program and thus made breeders pointless); Monju (Japan, being brought online again after serious sodium leak and fire in 1995); Superphénix (France, closed 1998). Therefore, realistically, nuclear power plants constructed in the short and medium term can only be incrementally different from current designs.

In order for the nuclear industry to grow sufficiently so as to replace a significant portion of energy now derived from fossil fuels, scores if not hundreds of new plants would be required, and soon. Given the expense and long lead time entailed in plant construction, the industry may do well merely to build enough new plants to replace old ones that are nearing retirement and decommissioning.

Hall et al. end their review of nuclear power by stating: "In our opinion we need a very high-level series of analyses to review all of these issues. Even if this is done, it seems extremely likely that very strong opinions, both positive and negative, shall remain. There may be no resolution to the nuclear question that will be politically viable."

Hydropower is electric current produced from the kinetic energy of flowing water. Water’s gravitational energy is relatively easily captured, and relatively easily stored behind a dam. Hydro projects may be enormous (as with China’s Three Gorges Dam) or very small ("microhydro") in scale. Large projects typically involve a dam, a reservoir, tunnels, and turbines; small-scale projects usually simply employ the "run of the river," harnessing energy from a river’s natural flow, without water storage.

Hydropower currently provides 2894 TWh of electricity annually worldwide, and about 264 TWh in the US, which represents 6 percent of total energy globally and 3 percent nationally. Of all electrical energy, hydropower supplies 19 percent worldwide (with 15 percent coming from large hydropower), and 6.5 percent in the US.[26]

Plus: Unlike many other energy sources, for hydropower most energy and financial investment occurs during project construction, while very little is required for maintenance and operations. Therefore electricity from hydro is generally cheaper than electricity from other sources, which may cost two to three times as much to generate.

Minus: Energy analysts and environmentalists are divided on the environmental impacts of hydropower. Proponents of hydropower see it as a clean, renewable source of energy with only moderate environmental or social impacts. Detractors of hydropower see it as having environmental impacts as large as or larger than those of some conventional fossil fuels. Global effects include carbon emissions primarily during dam and reservoir construction. Regional effects result from reservoir creation, dam construction, water quality changes, and destruction of native habitat. The amount of carbon emissions produced is very site-specific and substantially lower than from fossil fuel sources. Much of the debate centers around hydropower’s effects on society and whether or not a constant supply of water for power, irrigation, or drinking justifies the relocation of millions of people. Large dam and reservoir construction nearly always requires major relocations, and about 40-80 million people have been relocated and otherwise impacted by various associated effects of hydro projects. Dam failure or collapse is a risk in some cases, especially in China.

EROEI: The EROEI of hydropower, which ranges roughly from 11.2:1 to 267:1, is very site-specific. Because hydropower is such a variable resource, used in many different geographical conditions and involving various technologies, one generalized EROEI ratio cannot describe all projects. The EROEI for favorable or even moderate sites can be extremely high, especially if the environmental or social impacts are not included in the analysis.

Prospects: Globally, there are many undeveloped dam sites with hydropower potential, though there are far fewer in the US, where most of the best sites have already been developed. Theoretically, hydropower at some level could be accessible to any population with a constant supply of flowing water. The International Hydropower Association estimates that only about one-third of the realistic potential of world hydropower has been developed. In practice, the low investment cost of fossil fuels, and the environmental and social costs of dams, has meant that fossil fuel-powered projects are much more common.

Dams have the potential to produce a moderate amount of additional, high-quality electricity in less-industrialized countries, but are often associated with extremely high environmental and social costs. Many authors see "run-of-river" hydropower as the future, because it does away with massive relocation projects, minimizes the impacts on fish and wildlife, and does not release greenhouse gases (because there is generally no reservoir), while it retains the benefits of a clean, renewable, cheap source of energy. However, the relatively low power density of this approach limits its potential.

Wind. Wind power is one of the fastest-growing energy sources in the world, expanding more than five-fold between 2000 and 2007. However, it still accounts for less than one percent of the world’s electricity generation, and less than one percent of total energy. In the US, total production currently amounts to 32Twh, which is .77 percent of total electricity supplied, or 0.4 percent of total energy.

In the US, 35 percent of all the new electricity generation installed during 2007 (over 5,200 MW) was wind. In September 2008, the US surpassed Germany to become the world leader in wind energy production. US wind energy production has doubled in just two years. There is now more than 25,000 MW of generating capacity. (In discussing wind power, it is important to distinguish between nameplate production capacity—the amount of power that theoretically could be generated at full utilization—and the actual power produced: the former number is always much larger, because winds are intermittent and variable.) [27]

Wind turbine technology has advanced in recent years, with the capacity of the largest turbines growing from one MW in 1999 to up to 5 MW today. The nations currently leading in installed wind generation capacity are the United States, Germany, Spain, India, and China. Wind power currently accounts for about 19 percent of electricity produced in Denmark, 9 percent in Spain and Portugal, and 6 percent in Germany and the Republic of Ireland. In 2007-2008 wind became the fastest-growing energy source in Europe, in terms of quantity.

Plus: Wind power is a renewable source of energy, and there is enormous capacity for growth in wind generation: it has been estimated that developing 20 percent of the world’s wind-rich sites would produce seven times the current world electricity demand. [28] The cost of electricity from wind power, which is relatively low, has been declining in recent years. In the US as of 2006, the cost per unit of energy produced was estimated to be comparable to the cost of new generating capacity for coal and natural gas: wind cost was estimated at $55.80 per MWh, coal at $53.10/MWh and natural gas at $52.50.[29]

Minus: The uncontrolled, intermittent nature of wind reduces its value as compared to operator-controlled energy sources such as coal, gas, or nuclear power. For example, during January 2009 a high pressure system over Britain resulted in very low wind speeds combined with unusually low temperatures (and therefore higher than normal electricity demand). The only way for utility operators to prepare for such a situation is to build extra generation capacity from other energy sources. Therefore adding new wind generating capacity often does not substantially decrease the need for coal, gas, or nuclear power generation capacity; it merely enables those conventional power plants to be used less while the wind is blowing.

Since much of the wind resource base is in remote locations, getting the wind from the local point-of-generation to a potentially distant load center can be costly. The remoteness of the wind resource base also leads to increased costs for development in the case of land with difficult terrain or that is far from transportation infrastructure.

Being spread out over a significant land area, wind plants must compete with alternative uses of these land resources where multiple simultaneous usages are impossible.

The dramatic cost reductions in the manufacture of new wind turbines over the past two decades may slow as efficiencies are maximized and as materials costs increase.

EROEI: The average EROEI for all studies worldwide (operational and conceptual) was 24.6. The average EROEI for just the operational studies is 18.1. This compares favorably with conventional power generation technologies. [30]

In the US, existing wind power has a high EROEI (18:1), though problems with electricity storage may reduce this figure substantially as generating capacity grows. EROEI generally increases with the power rating of the turbine, because (1) smaller turbines represent older, less efficient technologies; (2) larger turbines have a greater rotor diameter and swept area, which is the most important determinant of a turbine’s potential to generate power, and (3) since the power available from wind increases by the cube of an increase in the wind speed, and larger turbines can extract energy from winds at greater heights, the wind speed and thus EROEI increase quickly.

The net energy ratio for wind power can range widely depending on the location of a turbine’s manufacture and installation, due to differences in the energy used for transportation of manufactured turbines between countries, the countries’ economic and energy structure, and recycling policies. For example, production and operation of an E-40 turbine in coastal Germany requires 1.39 times more energy than in Brazil.

Prospects: Wind is already a competitive source of power. For structural reasons (its long term cost of production is set by financing terms upon construction, and does not vary in the short term), it benefits from feed-in tariffs to protect it from short-term electricity price fluctuations, but overall it will be one of the cheapest sources of power as fossil fuels dwindle—and one with a price guaranteed not to increase over time. In the EU its penetration is already reaching 10 to 25 percent in several nations; prospects in the US are in some ways better, as growth is not limited by the geographical constraints and population density found in Europe.

Intermittency can be dealt with, as the European experience shows, by a combination of smart grid management and rare use of the existing fossil-fuel-fired capacity: even though a large amount of thermal power generation capacity will still be required, less coal and gas will need to be burned.

In the US, substantial further development of wind power will require significant investment in upgrading the national electricity grid.

Solar Photovoltaics (PV). Photovoltaic cells generate electricity directly from sunlight, with greater efficiency than photosynthesis does. PV solar cells most often use silicon as a semiconductor material. Since a huge amount of energy is transmitted to the earth’s surface in the form of solar radiation, tapping this source has great potential. If only 0.025 percent of this energy flow could be captured, it would be enough to satisfy world electricity demand. In 2006 and 2007, photovoltaic systems were the fastest growing energy technology in the world, increasing 50 percent annually.

The goals of PV research are to (1) increase the efficiency of the process of converting sunlight into electricity (the typical efficiency of an installed commercial single-crystalline silicon solar panel is 10 percent, while 24.7 percent efficiency has been achieved under laboratory conditions); and (2) decrease the cost of production (single-crystalline silicon panels average $3.00 per watt installed, while new photovoltaic materials and technologies, especially thin-film PV materials made by printing or spraying nano-chemicals onto an inexpensive plastic substrate, promise to reduce production costs dramatically, though usually at a loss of efficiency or durability). [31]

Plus: The solar energy captured by photovoltaic technology is renewable - and there is a lot of it. The cumulative average energy irradiating a square meter of earth’s surface for a year is approximately equal to the energy in a barrel of oil; if the sunlight could be captured at 10 percent efficiency, 3861 square miles of PV arrays would supply the energy of a billion barrels of oil. Covering the world’s estimated 360,000 square miles of building rooftops with PV arrays would generate the energy of 98 billion barrels of oil each year.

The price for new installed PV generating capacity has been declining steadily for many years. Unlike passive solar systems, PV cells can function on cloudy days.[32]

Minus: The functionality of PV power generation varies not only daily, but also seasonally with cloud cover, sun angle, and time of day. Thus, as with wind, the uncontrolled, intermittent nature of PV reduces its value as compared to operator-controlled energy sources such as coal, gas, or nuclear power. Sunlight is abundant, but diffuse: its area density is low. Thus efforts to harvest energy from sunlight are inevitably subject to costs and tradeoffs with scale.

Some of the environmental impacts of manufacturing PV systems have been analyzed by Alsema et al. and compared to the impacts of other energy technologies. [33] They have found energy pay-back times of 1.7 to 2.7 years and CO2 emissions which are greater than those found for wind energy systems, but only 5 percent of CO2 emissions from coal burning. Another potential impact is the loss of large amounts of wildlife habitat if really large industrial scale solar arrays are built, as they are likely to be, in undeveloped desert areas.

EROEI: Explicit net energy analysis of PV energy is scarce. However, using the time required for "energy pay back" and the lifetime of the system, it is possible to determine a rough EROEI. From a typical life-cycle analysis performed in 2005, Hall et al. calculated an EROEI of 3.75:1 to 10:1. [34]

Table: EROEI for various PV systems (ranging from commercially available to theoretical), calculated between 2000 and 2008. [35]

Some of these EROEI values are likely to change as research and development continue. If present conditions persist, EROEI may decline since sources of silicon for the industry are limited.

Prospects: Despite the enormous growth of PV energy, in recent years the annual increase in oil, gas, or coal production has usually exceeded total existing photovoltaic energy production. Therefore if PV is to become a primary energy source the rate of increase in capacity will need to be much greater than is currently the case.

Because of its high up-front cost, a substantial proportion of installed PV has been distributed on home roofs and in remote off-grid villages. Commercial utility-scale PV installations are now appearing in several nations, partly due to the lower price of newer thin-film PV materials and changing government policies. [36]

The current economic crisis has lowered the rate of PV expansion substantially, but that situation could be reversed if government efforts to revive the economy focus on investment in renewable energy.

However, if very large and rapid growth in the PV industry were to occur, the problem of materials shortages would have to be addressed in order to avert dramatic increases in cost. Materials in question—copper, cadmium-telluride (CdTe), and copper-indium-gallium-diselenide (CIGS)—are crucial to some of the thin-film PV materials to which the future growth of the industry (based on lowering of production costs) is often linked. With time, PV production may be constrained by lack of available materials, the rate at which materials can be recovered or recycled, or possibly by competition with other industries for those scarce materials. The only long-term solution will rest in the development of new PV materials that are common and cheap.

Active (concentrating) solar thermal. This technology typically consists of installations of mirrors to focus sunlight, creating very high temperatures heating a liquid that turns a turbine, producing electricity. The same power plant technology that is used with fossil fuels can be used with solar thermal since the focusing collectors can heat liquid to temperatures from 300°C to 1000°C. Fossil fuel can be used as a backup at night or when sunshine is intermittent.

There is a great deal of interest and research in solar thermal and a second generation of plants is now being designed and built, mostly in Spain. Worldwide capacity will soon reach 3000 MW.

Plus: Like PV energy, active solar thermal is renewable and there is enormous potential for growth. In the best locations, cost per watt of installed capacity is competitive with fossil-fuel power sources. Solar thermal benefits from using already mature power plant technology and needs less land than a photovoltaic array of the same generating capacity.

Minus: Again like PV, concentrating solar thermal power is intermittent and seasonal. Some environmental impacts are to be expected on the land area covered by mirror arrays and during the construction of transmission lines to mostly desert areas where this technology works best.

EROEI: The energy balance of this technology is highly variable depending on location, thus few studies have been done. In the best locations (areas with many sunny days per year), EROEI is likely to be quite high.

Prospects: There is considerable potential for utility-scale deployment of concentrating solar thermal power. Some energy writers have suggested that all of the world’s energy needs could be filled with electrical power generated by this technology. This would require the covering of large areas of desert in the southwestern US, northern Africa, central Asia, and central Australia with mirrors, as well as the construction of high-power transmission lines from these desert sites to places where electricity demand is highest. Such a project is possible in principle, but the logistical hurdles and financial costs would be daunting. Moreover, some intermittency problems would remain even if the sunniest sites were chosen.

Leaving aside such grandiose plans, nevertheless for nations that lie sufficiently close to the equator, this appears to be one of the most promising alternative sources of energy available. [37] Rising fossil fuel prices, renewable portfolio standards (RPSs) coming into effect in many states and an American public that is becoming increasingly interested in renewable energy sources are making it an attractive technology in the U.S.

Passive solar consists of capturing and optimizing heat and light from the sun within living spaces without the use of any collectors, pumps, or mechanical parts so as to reduce or eliminate the need for powered heating or lighting. Buildings are responsible for a large percentage of total energy usage in most countries, and so passive solar technologies are capable of offsetting a substantial portion of energy production and consumption that might otherwise come from fossil fuels. A passive solar building is designed 1) to maintain a comfortable average temperature, and 2) to minimize temperature fluctuations. It usually takes more time, money, and design effort to build, with extra costs made up in energy savings over time.

Chart: historical timeline of passive solar energy, 5th century to 2006. [38]

Passive solar buildings utilize seven main construction elements, and passive solar heating takes three dominant forms: direct gain, trombe walls, and insulated gain. Other uses of natural energy in buildings include passive solar cooling and daylighting.

Plus: Depending on the study, passive solar homes cost less than, the same as, or around 3-5 percent more than other custom homes. The extra cost will eventually pay for itself in energy savings. A solar home can only generate heat for its occupants and not extra electricity, but if used on all new houses, the system could go a long way toward replacing other fuels.

Incorporating a passive solar system into the design of a new home is generally cheaper than fitting it onto an existing home. A solar home "decreases cooling loads and reduces electricity consumption, which leads to significant decline in the use of fossil fuels." [39] Passive solar buildings, in contrast to buildings with artificial lighting, may provide a healthier, more productive work environment.

Minus: Limitations of passive solar heating include geographic location (clouds and colder regions make solar heating less effective), and sealing the house envelope to reduce air leaks means increasing the chance of pollutants becoming trapped inside. The heat-collecting equator-facing side of the house needs good sun exposure in the winter, which may require spacing houses farther apart and using more land than other types of housing.

EROEI: Passive solar design is extremely site-specific, and architects rarely get quantitative feedback on the system, so determining the EROEI is very difficult. However, if the system is built into the house from the beginning, then large energy gains can be obtained with few or no further investments.

Energy savings can range from 30 to 70 percent, so EROEI varies vastly from case to case. For example, if the payback period is five years and the house lasts for 50, then the EROI would be 10:1.

Table 1: energy savings at various locations (with date, type and size of building indicated) for the daylighting technique. [40]

Table 2: energy savings at various locations (with date, techniques, monetary savings, and cost indicated) for the passive solar heating technique.[41]

Prospects: Designing buildings from the start to take advantage of natural heating and lighting, and to use more insulation and solar mass, has tremendous potential to reduce energy demand. In many cases, new high-efficiency buildings require more energy for construction. Until now, this assumed requirement for a higher up-front investment has discouraged mass-scale construction of passive solar buildings in most countries.

Higher energy prices will no doubt gradually alter this situation, but quicker results could be obtained through shifts in building regulations and standards, as has been shown in Germany. There, the development of the voluntary Passivhaus standard has stimulated construction and retrofitting of more than 20,000 passive houses in northern Europe. [43] The Passivhaus is designed to use very little energy for heating. Passive solar provides space heating and superinsulation and air-tight construction to stop the heat from leaking out.

Buildings in the industrialized nations have generally become more efficient in recent years, however declines in averaged energy use per square foot have generally been more than offset by population growth and the overbuilding of real estate, so that the total amount of energy used in buildings has continued to increase. Thus population and economic growth patterns need to be part of the "green building" agenda. [42]

Geothermal energy is derived from the heat within the earth, which can be ‘mined’ by extracting hot water or steam, either to run a turbine for electricity generation or for direct use of the heat itself. Geothermal power can be generated in regions where tectonic plates meet and volcanic and seismic activity are common. Lower temperature geothermal direct heat can be tapped anywhere on earth by digging a few meters down and installing a tube system connected to a heat pump.

Currently, the only places being exploited for geothermal electrical power are where hydrothermal resources exist in the form of hot water or steam reservoirs. In these locations, hot groundwater is pumped to the surface from 2-3 km deep wells and used to drive turbines. Power can also be generated from hot dry rocks by pumping turbine fluid into them through 3 to 10 km deep bore holes. This method, called Enhanced Geothermal System (EGS) generation, is the subject of a great deal of research, but no power has been generated commercially using EGS.

In 2006, world geothermal power capacity was about 10 GW. [44] There is no consensus on potential resource base estimates for power generation. Hydrothermal areas that have both heat and water are rare, so the utility of most geothermal resources depends on whether EGS and other developing technologies will prove to be commercially viable. For example, a 2006 MIT report estimated U.S. hydrothermal resources at 2400 to 9600 EJ, while dry heat geothermal resources were estimated to be as much as 13 million EJ. [45]

Annual growth of geothermal power capacity worldwide has slowed from 9 percent in 1997 to 2.5 percent in 2004. However the use of direct heat using heat pumps or piped hot water has been growing 30 to 40 percent annually, particularly in Europe, Asia and Canada. [46]

Plus: Geothermal power plants produce much lower emissions and use less land area compared to fossil fuel plants. They run constantly, unlike other renewable sources such as wind and solar. Geothermal direct heat is available everywhere, although it becomes less cost-effective in temperate climates. Countries rich in geothermal resources will become less dependent on foreign energy.

Minus: In addition to geography and technology, high capital cost and low fossil fuel costs are major limiting factors for geothermal development. Technological improvements are necessary for the geothermal industry to continue to grow. Water can also be a limiting factor, since both hydrothermal and dry rock systems consume water.

The sustainability of geothermal power generating systems is a cause of concern. Geothermal resources are only renewable if heat removal is balanced by natural replenishment of the heat source. Some geothermal plants have seen declines in temperature, most probably because the plant was oversized for the local heat source.

There is likely to be some air, water, thermal and noise pollution from the building and operation of a geothermal plant, as well as solid waste buildup and the possibility of induced seismic activity nearby it.

EROEI: The net energy for electricity generation from hydrothermal resources has ranged, depending on the researcher, from 2:1 to 13:1. This discrepancy represents both the lack of a unified methodology for EROEI analysis and disagreements about system boundaries, quality-correction, and future expectation. [47]

There are no calculations of EROEI values for geothermal direct use, though for various reasons it is assumed that they are higher than those of hydrothermal resources. As a starting point, it has been calculated that heat pumps move 3 to 5 times the energy in heat that they consume in electricity.

Prospects: The limited hydrothermal resources are unlikely to become a silver bullet solution to meet increasing global energy needs, but could continue to be important regionally. If non-hydrothermal resources were to become economically feasible, much larger, less-depletable geothermal resources would be opened up worldwide, potentially increasing EROEI, geographic relevance, long-term sustainability and production of geothermal power. Geothermal heat pumps already seem to be generating net thermal energy on small scales and are nearly limitless geographically. They are most useful in regions with cold winters and hot summers since they provide both heating and cooling.

Tidal Power generation from tidal forces is geographically limited to places where there is a large movement of water as the tide flows in and out, such as estuaries, bays, headlands, or channels connecting two bodies of water.

The oldest tidal power technology, dating back to the Middle Ages when it was used to grind grain, consists of building a barrage or dam which blocks off all or most of a tidal passage. The difference in the height of water on the two sides of the barrage is used to run turbines. A newer technology, which is still in the development stage, places underwater turbines called tidal stream generators directly in a tidal current or stream.

Globally, there is about 0.3 GW of installed capacity of tidal power [48], most of it produced by the barrage built in 1966 in France across the estuary of the Rance River. One estimate of the size of the global annual potential for tidal power is 450 TWh, much of it located on the coasts of Asia, North America, and the United Kingdom. [49]

Plus: Once a tidal generating system is in place, it has low operating costs and produces reliable, although not constant, carbon-free power.

Minus: Sites for large barrages are limited to a few places around the world. They require large amounts of capital to build, and have a significant negative impact on the ecosystem of the dammed river or bay.

EROEI: No calculations have been done for tidal power EROEI as yet. For tidal stream generators this figure is likely to be close to that of wind power (an average EROEI of 18:1) since the turbine technology for wind and water is so similar that tidal stream generators have been described as "underwater windmills." Construction of barrage systems may be similar to that of dams (EROEI ~ 11.2:1 to 267:1), but they will have a somewhat lower EROEI since they only generate power for part of the tidal cycle.

Prospects: Many new barrage systems have been proposed and new sites identified, but the initial cost is a difficulty. There is often strong local opposition as with the proposed barrage for the mouth of the River Severn in the U.K. Tidal stream generators need less capital investment and if designed and sited well may have very little environmental impact. Prototype turbines and commercial tidal stream generating systems are being tested around the world.

Wave Power Electricity can be generated from wind-driven ocean waves. Some wave energy devices are designed to work offshore in deeper water, harvesting the up and down motion of the waves. Onshore systems use the force of breaking waves or the rise and fall of water to run pumps or turbines.

The commonly quoted estimate of potential global wave power generation is about 2 TW [50], distributed mostly on the western coasts of the Americas, Europe, southern Africa and Australia where wind-driven waves reach the shore after accumulating energy over long distances. For current designs of wave generators the economically exploitable resource is likely to be from 140 – 750 TWh per year. [51] The only operating commercial system is the 2.25 MW Agucadora Wave Park off the coast of Portugal.

Research in wave energy has been funded by both governments and small engineering companies and there are many prototype designs. Once the development stage is over and the price and siting problems of wave energy systems are better understood, there may be more investment in them. In order for costs to decrease, problems with resistance to corrosion and storm damage must be solved.

Plus: Once installed, wave energy devices emit negligible greenhouse gases and should be cheap to run. Since the majority of the world’s population lives near the coast, wave energy is convenient for providing electricity to many and it may also turn out to be an expensive but sustainable way to desalinate water.

Minus: In addition to high construction costs, there are concerns about the environmental impact of some designs. They may interfere with fishing grounds and navigation or cause erosion. Wave energy fluctuates seasonally as well as daily since winds are stronger in the winter, making it a somewhat intermittent energy source.

EROEI: The net energy of wave energy devices has not been thoroughly analyzed. One rough estimate of EROEI for the Portuguese Pelamis device is 15:1. [52]

Prospects: Wave power generation will need more research and development and infrastructure building before it can become widespread. More needs to be understood about the environmental impacts of wave energy farms so that destructive siting can be avoided. The best devices will need to be identified and improved, and production of wave devices will need to become much cheaper.

Biomass Wood and other kinds of traditional biomass still account annually for about 13 percent of the world’s total energy consumption and are used by up to 3 billion people for cooking and heating. [53] Nontraditional ‘new’ biomass uses generally involve converting biomass into liquid fuel, using it to generate electricity, or using it to co-generate heat and electricity. World electric power generation from biomass was about 183 TWh in 2005 from an installed capacity of 40GW, with 27 percent of this coming from biogas and municipal solid waste. [54]

Biogas is created by the biological process of decay in the absence of oxygen. Biogas emission occurs naturally in places where anaerobic decay is concentrated, like swamps, landfills, or cows’ digestive systems. Industrial manufacture of biogas uses bacteria to ferment or anaerobically digest biodegradable material, producing a combustible mixture of 50 – 75 percent methane and other gases. [55] Biogas can be used like natural gas and burned as fuel in anything from a small cookstove to an electrical plant. Small-scale biogas is utilized all over the world, both in households and for industry.

Wood fuels presently account for 60 percent of global forest production and along with agricultural residues contribute 220 GWth for cooking and heating energy. [56] Forests are a huge resource, covering 7 percent of the earth’s surface, but net deforestation is occurring around the globe, especially in South America, Indonesia and Africa. Deforestation is caused mostly by commercial logging and clearing land for large-scale agriculture, not by traditional wood gathering, which is often sustainably practiced. However in many areas, wood use and population pressure are leading to deforestation and even desertification.

Cogeneration or Combined Heat and Power (CHP) plants can burn fossil fuels or biomass to make electricity and are configured so that the heat from this process is not wasted but used for space or water heating. Biomass CHP is more efficient at producing heat than electricity, but can be practical if there is a local source of excess biomass and a community or industrial demand nearby for heat and electricity. Biomass plants are being built in the U.S., in northern Europe, and also in Brazil where they are associated with the sugar processing industry. The rate of growth of biopower has been around 5 percent per year over the last decade. [57] Biomass power plants are only half as efficient as natural gas plants and are limited in size by a fuelshed of around 100 miles, but they provide a good source of rural jobs and reliable baseload power. [58]

Another bioenergy source is biogas from waste materials, but it is difficult to find estimates of the possible size of this resource. The National Grid in the U.K. has suggested that waste methane can be collected, cleaned and added to the existing natural gas pipeline system. They estimate that if all the country’s sewage, food, agriculture and manufacturing biowastes were used, half of all U.K. residential gas needs could be met. Burning biogas for heat and cooking offers 90 percent energy conversion efficiency, while using biogas to generate electricity is only 30 percent efficient. [59]

Plus: Biomass is distributed widely where people live. This makes it well-suited for use in small-scale, region-appropriate applications where using local biomass is sustainable. In Europe there has been steady growth in biomass CHP plants in which scrap materials from wood processing or agriculture are burned, while in developing countries CHP’s are often run on coconut or rice husks. In California, dairy farms are using methane from cow manure to run their dairy operations. Biogas is used extensively in China for industry, and 25 million households worldwide use biogas for cooking and lighting. [60]

Burning biomass and biogas is considered to be carbon neutral, since unlike fossil fuels they operate within the biospheric carbon cycle. Biomass contains carbon that would be released naturally by decomposition or burning to the atmosphere over a short period of time. Using waste sources of biogas like cow manure or landfill gas reduces emissions of methane, a greenhouse gas twenty-three times more potent than carbon dioxide.

Minus: Biomass is a renewable resource but not a particularly expandable one. Often available biomass is a waste product of other human activities, such as crop residues from agriculture, wood chips, sawdust and black liquor from wood products industries and solid waste from municipal trash and sewage. In a future, less energy-intensive agricultural system, crop residues may be needed to replenish soil fertility and won’t be available for power generation. There may also be more competition for waste products as manufacturing from recycled materials increases.

Using biomass for cooking food has contributed to deforestation in many parts of the world and it is associated with poor health and shortened lifespans, especially for women who cook with wood or charcoal in unvented spaces. Finding a substitute fuel or increasing the efficiency of cooking with wood is the goal of programs in India, China and Africa. [61] In order to reduce greenhouse gas emissions, it is more desirable to re-forest than to plan to use more wood as fuel.

EROEI estimates for biomass are extremely variable. Biomass is generally more efficiently used for heat than for electricity, but electricity generation from biomass can be energetically favorable if the source is harvested sustainably or is a waste product. Biogas is usually made from waste materials and utilizes decomposition, which is a low energy-input process, so it is inherently efficient.

Prospects: Wood, charcoal and agricultural residues will continue to be used around the world for cooking and heating. There is a declining amount of biomass-derived materials entering the waste stream because of increased recycling, so the prospect of expanding landfill methane capture is declining. Use of other kinds of biogas is a potential growth area. Policies that support biogas expansion exist in India and especially in China, where there is a target of increasing the number of household-scale biogas digesters from an estimated 1 million in 2006 to 45 million by 2020.

Ethanol is an alcohol made from plant material that is first broken down into sugars and then fermented. It has had a long history of use as a transportation fuel beginning with the Model T Ford. In 2007, 13.1 billion gallons of ethanol were produced globally. Thirty-eight percent of it was produced from sugar cane in Brazil, while another 50 percent was manufactured from corn in the U.S.[62] There has been a high rate of growth in the industry, with a 15 percent annual increase in world production between 2000 and 2006. Ethanol can be substituted for gasoline, but the total quantity produced is still only a tiny fraction of the 142 trillion gallons of gasoline consumed in the U.S. each year. [63]

Ethanol can be blended with gasoline and used in existing cars in concentrations of up to 10 percent. For percentages higher than this modifications are needed since ethanol is more corrosive than gasoline. New cars are already being manufactured that run on 100 percent ethanol, on the 25/75 ethanol/gasoline ‘gasohol’ blend used in Brazil, or the 85/15 E85 blend found in the U.S.

In the U.S., corn ethanol has become controversial because of the problems associated with using a staple food plant like corn as a fuel and because ethanol plants run on fossil fuels. However there is also interest in making ethanol from non-food plant materials like corn fiber, wheat chaff or pine trees. An especially interesting potential feedstock is the native prairie plant switchgrass, which requires less fossil fuel input than corn and can yield 3 to 5 times as many gallons of ethanol per acre. However, making cellulosic ethanol out of these non-food feedstocks is a technology in its infancy and not yet commercial.

Potential ethanol resources are limited by the amount of land available to grow feedstock. According to the Union of Concerned Scientists (UCS), using all of the corn grown in the U.S. with nothing left for food or animal feed would only displace perhaps 15 percent of U.S. gasoline demand by 2025. [64] Large-scale growing of switchgrass or another new cellulose crop would require finding very large acreages to cultivate them.

Plus: Ethanol has the portability and flexibility of oil and can be used in small amounts blended with gasoline in existing vehicles. The distribution infrastructure for gasoline could be gradually switched over to ethanol with very little disruption as new cars that run on higher ethanol concentrations are phased in.

Cellulosic ethanol is promising in terms of net energy return since it can be broken down using enzymes rather than needing to be heated using coal or natural gas as is the case with corn. It also has potentially less environmental impact with respect to land use and lifecycle greenhouse gas emissions. The UCS reports that it has the potential to reduce greenhouse gas emissions by 80-90 percent compared to gasoline. [65] However there are still technical problems with producing cellulosic ethanol on a commercial scale that have not yet been solved.

Minus: There are approximately 45 MJ per kilogram contained in both the finished gasoline and crude oil, while ethanol has an energy density of about 26 MJ per kilogram and corn has only 16 MJ per kilogram. In general, this means that large amounts of corn must be grown and harvested to equal even a small portion of our gasoline consumption on an energy equivalent level, which will undoubtedly expand the land area that is impacted by the production process of corn-based ethanol.

Increases in corn ethanol production may have helped to drive up the price of corn around the world in 2007, contributing to a 400 percent rise in the price of tortillas in Mexico. [66] Ethanol and other biofuels now consume 17 percent of the world’s grain harvest.

There are climate change implications to corn ethanol production as well. If food crops are used for making transportation fuel rather than food, more land will have to go into food production somewhere else. When natural ecosystems are cleared for food or ethanol production, the result will be a ’carbon debt’ which will release 17 to 420 times more CO2 than is saved by displacing fossil fuels. [67] Corn-based ethanol, since fossil fuels are necessary for growing corn and converting it, is estimated to offer only a 10-25 percent reduction in greenhouse gas emissions compared to gasoline. [68] Corn ethanol also uses three to six gallons of water for every gallon of ethanol produced and has been shown to emit more air pollutants than gasoline.

EROEI: There is a range of estimates of this number for ethanol since EROEI depends on widely ranging variables such as the energy input required to get the feedstock, (high for corn and low for switchgrass and cellulose waste materials) and which process is used to convert it to alcohol.

There is even a geographic difference in energy input depending on how well suited the feedstock crop is to the region in which it is grown. For example, it has been reported on The Oil Drum (www.theoildrum.com) that there is a definite hierarchy of corn productivity by state. For example, in 2005, 173 bushels per acre (10859 kg/ha) were harvested in Iowa, while only 113 bushels per acre were harvested in Texas (7093 kg/ha). This is consistent with the general principle of gradient analysis in ecology, which states that individual plant species grow best near the middle of their gradient space; that is near the center of their range in environmental conditions such as temperature and soil moisture. The climatic conditions in Iowa are clearly at the center of corn’s gradient space. What is understood less is that corn production is also less energy-intensive at or near the center of corn’s gradient space. [69]

These results show diminishing returns for EROEI as the distance from Iowa increases, meaning that the geographic expansion of corn production will produce lower yields at higher costs. Ethanol production in Iowa and Texas yield very different energy balances, so that in Iowa the production of a bushel of corn costs 43 MJ, while in Texas it costs 71 MJ. Calculated EROEI’s for corn ethanol range from 1.8:1 to 1.14:1.

Ethanol from sugar cane in Brazil is calculated to have an EROEI of 8:1 to 10:1, but when made from Louisiana sugar cane in the U.S., where growing conditions are worse, the EROEI is closer to 1:1. [70] Estimates for the net energy of cellulose ethanol vary widely, from 2:1 to 36:1. [71]

Prospects: Ethanol’s future as a major transport fuel is probably dim except perhaps in Brazil, where sugar cane supplies the world’s only economically competitive ethanol industry. The political power of the corn lobby in the U.S. has kept corn ethanol subsidized and investment flowing, but its poor net energy ratio will eventually cause it to be uneconomic. The technical problems of processing cellulose for ethanol may be overcome, but land use considerations will be likely to limit the size of production.

Biodiesel. Biodiesel is a non-petroleum-based diesel fuel made by transesterification of vegetable oil or animal fat (tallow). It can be used (alone, or blended with conventional petrodiesel) in unmodified diesel-engine vehicles. Biodiesel is distinguished from the straight vegetable oil (SVO), sometimes referred to as "waste vegetable oil" (WVO), "used vegetable oil."(UVO), or "pure plant oil" (PPO). Vegetable oil can itself be used as a fuel either alone in some converted diesel vehicles, or blended with biodiesel or other fuels.

The vegetable oil used as motor fuel or in the manufacture of biodiesel is typically made from soy, rape seed ("canola"), palm, or sunflower; considerable research has been devoted to producing oil for this purpose from algae, with varying reports of success (more below). The process for making biodiesel consists of a chemical treatment of vegetable oil (transesterification) to remove glycerine, leaving long-chain alkyl (methyl, propyl or ethyl) esters.

Global biodiesel production reached about 8.2 million tons (230 million gallons) in 2006, with approximately 85 percent of biodiesel production coming from the European Union, but with rapid expansion occurring in Malaysia and Indonesia. [72]

In the United States, average retail (at the pump) prices, including Federal and state fuel taxes, of B2/B5 are lower than petroleum diesel by about 12 cents, and B20 blends are the same as petrodiesel.[73] B99 and B100 generally cost more than petrodiesel except where local governments provide a subsidy.

Plus: Biodiesel has some more favorable environmental characteristics than petroleum diesel. Through its lifecycle, biodiesel emits one fifth the CO2 of petroleum diesel, contains less sulfur and leads to longer engine life. [74] When biodiesel is made from waste materials like used vegetable oil, many of the environmental tradeoffs entailed in the production of other biofuels become non-issues.

Minus: The most negative impact of expanding biodiesel production is the need for large amounts of land to grow oil crops. Palm oil is the most fruitful oil crop, producing 13 times the amount of oil as soybeans, the most-used biodiesel feedstock in the U.S. In Malaysia and Indonesia, rainforest is being cut to plant palm oil plantations and it has been estimated that it will take 100 years for the climate benefits of biodiesel production from each acre of land to make up for the CO2 emissions from losing the rainforest. [75] Palm oil production (for food as well as fuel) is driving deforestation across Southeast Asia and reducing rainforest habitat to the point where larger species, such as the orangutan, are threatened with extinction. [76] Soybean farming in Brazil is already putting pressure on Amazon rainforests. If soybeans begin to be used extensively for biofuels this pressure will increase.

EROEI: The first comprehensive analysis of the full life cycles of soybean biodiesel and corn grain ethanol shows that biodiesel has much less of an impact on the environment and a much higher net energy benefit than corn ethanol, but that neither can do much to meet U.S. energy demand. [77]

The researchers tracked all the energy used for growing corn and soybeans and converting the crops into biofuels. They also looked at how much fertilizer and pesticide corn and soybeans required and how much greenhouse gases and nitrogen, phosphorus, and pesticide pollutants each released into the environment.

"Quantifying the benefits and costs of biofuels throughout their life cycles allows us not only to make sound choices today but also to identify better biofuels for the future," said Jason Hill, a postdoctoral researcher in the department of ecology, evolution, and behavior and the department of applied economics and lead author of the study. [78]

The study showed that both corn grain ethanol and soybean biodiesel produce more energy than is needed to grow the crops and convert them into biofuels. This finding refutes other studies claiming that these biofuels require more energy to produce than they provide. The amount of energy each returns differs greatly, however. Soybean biodiesel returns 93 percent more energy than is used to produce it, (1.93:1) while corn grain ethanol currently provides only 25 percent more energy. Other researchers have claimed that the net energy of soybean biodiesel has improved over the last decade because of increased efficiencies in farming, and calculated net energy at 3.5:1. [79] Palm oil biodiesel has the highest net energy, perhaps as high as 9:1. [80]

Prospects: Biodiesel can also be made from algae, which in turn can be grown on waste carbon sources, like the CO2 scrubbed from coal-burning power plants or sewage sludge. This is an intriguing possibility, but is still in a developmental stage. Limiting factors may be the need for large tanks, water, sunshine and thermal protection in cold climates. Saltwater rather than freshwater can be used to grow the algae, and there is optimism that this technology can be used to produce significant amounts of fuel. [81]

There are concerns, as with ethanol, that biodiesel crops will begin to compete with food crops for land in developing countries and raise the price of food. The need for land is the main limitation on expansion of biodiesel production and is likely to limit the scale of the industry. Biodiesel from waste oil and fats will continue to be a small and local source of fuel, while algae-growing shows promise as a sustainable, large-scale biodiesel technology.

It would be impossible to address all possible sources of energy in an overview of this nature. Some potential sources that have been discussed elsewhere in the energy literature include: Ocean thermal, "zero-point" and other "free energy" sources, space-orbiting solar collectors, He4 from the Moon, and methane hydrates. Of these, only methane hydrates has any prospect of yielding commercial amounts of energy in the foreseeable future, and that will depend upon significant technological developments to enable the harvesting of this fragile material. Methanol and Butanol are not discussed here because their properties and prospects differ little from those of other biofuels.

Thus over the course of the next decade or two, society’s energy almost certainly must come from some combination of the 17 sources above.


13. Energy Information Administration, Voluntary Reporting of Greenhouse Gases Program http://www.eia.doe.gov/oiaf/1605/coefficients.html

14. Michael T. Klare, Resource Wars: The New Landscape of Global Conflict (New York: Owl Books, 2002).

15. Energy Information Administration (EIA), World Proved Reserves of Oil and Natural Gas, Most Recent Estimates http://www.eia.doe.gov/emeu/international/reserves.html

16. Alternative Fuels Dilemma (reference incomplete; will be updated at final publication)

17. EIA, International Energy Annual 2006, Net Generation by Energy Source (2007), U.S . Energy Consumption by Energy Source (2006) http://www.eia.doe.gov/

18. Alternative Fuels Dilemma

19. Ibid.

20. M. C. Herweyer, A. Gupta, "Unconventional Oil: Tar Sands and Shale Oil", Appendix D, The Oil Drum, 2008, www.theoildrum.com/node/3839

21. World Energy Council (WEC), 2007 Survey of Energy Resources, 93, http://www.worldenergy.org/publications/survey_of_energy_resources_2007/...

22. A. R. Brandt, "Net energy and greenhouse gas emissions analysis of synthetic crude oil produced from Green River oil shale," Energy and Resources Group Working Paper, (University of California, Berkeley, 2006).

23. WEC, 2007 Survey of Energy Resources, 235; EIA, U.S. Nuclear Generation of Electricity, 2007; Renewable Energy Policy Network for the 21st Century (REN21), "Renewables 2007: Global Status Report," 9, http://www.ren21.net/

24. EnergyWatch Group, Uranium Resources and Nuclear Energy, 2006.

25. Robert Powers, "The Energy Return of Nuclear Power," Appendix F, The Oil Drum, 2008, http://www.theoildrum.com/node/3877

26. WEC 2007 Survey of Energy Resources, 272;REN21, "Renewables 2007: Global Status Report," EIA, World Net Generation of Electricity by Type, 2005.

27. WEC 2007 Survey of Energy Resources, 479; Joe Provey, "Wind: Embracing America’s Fastest-Growing Form of Renewable Energy," www.alternet.org/environment/118047/wind:_embracing_america's_fastest-growing_form_of_renewable_energy/

28. Christina L. Archer, Mark Z. Jacobson, "Evaluation of Global Wind Power," J. Geophysical Research: Atmospheres, 2005, http://www.stanford.edu/group/efmh/winds/global_winds.html

29. EIA, "Technology Choices for New U.S. Generating Capacity: Levelized Cost Calculations." International Energy Outlook 2006, http://www.eia.doe.gov/oiaf/archive/ieo06/special_topics.html

30. Ida Kubisewski and Cutler Cleveland, "Energy from Wind: A Discussion of the EROI Research," The Oil Drum, http://www.theoildrum.com/node/1863

31. WEC 2007 Survey of Energy Resources, 381, Ken Zweibel, James Mason and Vasilis Fthenakis, "A Solar Grand Plan", Scientific American, December 2007, http://www.sciam.com/article.cfm?id=a-solar-grand-plan

32. European Photovoltaic Technology Platform, http://www.eupvplatform.org/index.php?id=47

33. Erik A. Alsema and Mariska J. de Wild-Scholten, "Environmental Impacts of Crystalline Silicon Photovoltaic Module Production," 13th CIRP Intern. Conf. on Life Cycle Engineering, 2006, http://www.ecn.nl/docs/library/report/2006/rx06041.pdf

34. Charles A.S. Hall, "The Energy Return of (Industrial) Solar – Passive Solar, PV, Wind and Hydro," Appendix G-2: Photovoltaics, The Oil Drum, http://www.theoildrum.com/node/3910

35. Ibid., Table: EROEI for various PV systems (ranging from commercially available to theoretical), calculated between 2000 and 2008.

36. Graham Jesmer, "The US Utility-scale Solar Picture," Renewable Energy World.com, http://www.renewableenergyworld.com/rea/news/article/2009/02/the-us-util...

37. Ibid.; Tom Standing, "Arizona Solar Power Project Calculations," The Oil Drum, http://www.theoildrum.com/node/4911#more

38. Kallistia Giermek, "The Energy Return of (Industrial) Solar – Passive Solar, PV, Wind and Hydro," Appendix G-1: Passive Solar, Chart: historical timeline of passive solar energy, 5th century to 2006, The Oil Drum, http://www.theoildrum.com/node/3910

39. Ibid.

40. Ibid., Table 1: energy savings at various locations (with date, type and size of building indicated) for the daylighting technique.

41. Ibid.,Table 2: energy savings at various locations (with date, techniques, monetary savings, and cost indicated) for the passive solar heating technique.

42. Ibid.

43. UK Timber Frame Association, "Timber Frame takes the Passivhaus tour," Buildingtalk.com, http://www.buildingtalk.com/news/tim/tim140.html

44. REN21, "Renewables 2007: Global Status Report," http://www.ren21.net

45. Massachusetts Institute of Technology, The Future of Geothermal Energy (Idaho National Laboratory, 2006), http://geothermal.inel.gov/publications/future_of_geothermal_energy.pdf

46. Patrick Hughes, Geothermal (Ground-Source) Heat Pumps: Market Status, Barriers to Adoption and Actions to Overcome Barriers (Oak Ridge National Laboratory ORNL-232, 2008)

47. Daniel Halloran, Geothermal (SUNY-ESF, Syracuse NY), online 2008 http://www.theoildrum.com/node/3949)

48. REN21, "Renewables 2007: Global Status Report," http://www.ren21.net

49. "Energy Source: Tidal Power," The Pembina Institute, http://re.pembina.org/sources/tidal

50. World Energy Council, 1993.

51. WEC 2007 Survey of Energy Resources, 543.

52. Daniel Halloran, Wave Energy: Potential, EROI, and Social and Environmental Impacts (SUNY-ESF, Syracuse NY), online 2008. http://www.theoildrum.com/node/3949)

53. WEC 2007 Survey of Energy Resources, 333.

54. REN21, "Renewables 2007: Global Status Report," http://www.ren21.net

55. "Energy from Biomass," bioenergie.de, http://www.bio-energie.de/cms35/Biomass.393.0.html

56. "FAO Facts & Figures," Food and Agriculture Association of the United Nations, http://www.fao.org/forestry/30515/en/

57. WEC 2007 Survey of Energy Resources, 333.

58. "Net Greenhouse Gas Emissions from Biomass and Other Renewable Generators, USA Biomass, http://www.usabiomass.org/

59. David Ehrlich,"Putting Biogas into the Pipelines," earth2tech.com, http://earth2tech.com/2009/02/03/putting-biogas-into-the-pipelines/, "’Gone Green’ a Scenario for 2020", nationalgrid.com, http://www.nationalgrid.com/NR/rdonlyres/554D4B87-75E2-4AC7-B222-6B40836...

60. REN21, "Renewables 2007: Global Status Report," http://www.ren21.net

61. Ibid.

62. Statistics, Renewable Fuels Association, http://www.ethanolrfa.org/industry/statistics/

63. EIA, Petroleum Basic Statistics, http://www.eia.doe.gov/basics/quickoil.html

64. "The Truth about Ethanol," Union of Concerned Scientists, http://www.ucsusa.org/clean_vehicles/technologies_and_fuels/biofuels/the...

65. Ibid.

66. "Mexicans stage tortilla protest," BBC News online, http://news.bbc.co.uk/2/hi/americas/6319093.stm

67. Joseph Fargione, Jason Hill, David Tilman, Stephen Polasky and Peter Hawthorne, "Land Clearing and the Biofuel Debt," Science, February 7, 2008, http://www.sciencemag.org/cgi/content/abstract/1152747

68. Richard Lance Christie, "The Renewable Deal: Chapter 5: Biofuels," Earth Restoration Portal, 2008, http://www.manyone.net/EarthRestorationPortal/articles/view/131998/?topi...

69. "The Effect of NaturalGradients on the Net Energy Profits from Corn Ethanol", The Oil Drum, http://netenergy.theoildrum.com/node/4910#more

70. Charles A.S. Hall, in comments on "Provisional Results from EROEI Assessments," The Oil Drum, http://www.theoildrum.com/node/3810

71. "Biofuels for Transportation," Worldwatch Institute, 2006, http://www.worldwatch.org/system/files/EBF008_1.pdf

72. REN21, "Renewables 2007: Global Status Report," http://www.ren21.net

73. Cost for biodiesel: reference incomplete; will be updated for final publication.

74. Richard Lance Christie, "The Renewable Deal: Chapter 5: Biofuels," Earth Restoration Portal, 2008, http://www.manyone.net/EarthRestorationPortal/articles/view/131998/?topi...

75. Ibid.

76. Rhett A. Butler, "Orangutan should become symbol of palm-oil opposition," Mongabay.com, http://news.mongabay.com/2008/0102-palm_oil.html

77. Jason Hill, Erik Nelson, David Tilman, Stephen Polasky and Douglas Tiffany, "Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels," Proceedings of the National Academy of Sciences, July 25, 2006, Vol 103. http://www.pnas.org/content/103/30/11206.abstract?

78. "Soybean biodiesel has higher net energy benefit than corn ethanol—study," Mongabay.com, http://news.mongabay.com/2006/0711-umn.html

79. "Biodiesel proven to have a significantly positive net energy ratio," Biodiesel Now, http://www.biodieselnow.com/blogs/general_biodiesel/archive/2008/02/07/b...

80. "Biofuels for Transportation: Global Potential and Implications for Sustainable Agriculture and Energy in the 21st Century," Worldwatch Institute, 2006.

81. Michael Briggs, "Widespread Biodiesel Production from Algae," UNH Biodiesel Group (University of New Hampshire, 2004), http://www.unh.edu/p2/biodiesel/article_alge.html

The author wishes to acknowledge the contributions of Suzanne Doyle to research and the contribution of some writing, to Alina Xu of International Forum on Globalization who compiled a previous summary of data of which this is an expansion, and to Dr. Charles Hall and his students (principally David Murphy) at SUNY-Syracuse, whose work on net energy was the inspiration for this document.

Next month: Combining energy sources; Conclusions: The Case for Conservation.

gyrogearloose's picture
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Re: Heinberg: Prospects for Alternative Energies to Replace ...
Chris Kresser wrote:

Richard Heinberg's Museletter: The Conservation Imperative: Energy Limits to Growth and the Path to Sustainability - Part 2
by Richard Heinberg

Download printable pdf version here (PDF, 248 KB); Read onlind version with charts/graphics here.

While this report is focused on the prospects for alternative energy sources to replace fossil fuels, it is useful to apply the above criteria first to oil, coal, and gas so that comparisons can be made with their potential replacements.

About 750 kilojoules of energy are required to lift 15kg of oil 5 meters—an absolute minimum energy investment for pumping oil that no longer flows out of the ground under pressure. But energy is expended also in exploration, drilling, refining, and so on.

Bold underlined mine ( from near start of article )

Not a good start, very basic error of 3 orders of magnitude 

E = Mass (Kg ) * G ( gravitational constant ) * Height ( meters )

E = 15 * 9.8 * 5

E = 735 J

Most positive displacement pumps are over 80% efficient

E= 735 / 0.8 = 918 J

Even if he just made a "typo"  it  was such a glaring error he would appear to have no real basic instinctive grasp of the subject.

Brings the rest of the article into question, as where he only provides conclusions, and not the math behind the conclusion, as his maths ability is questionable.


Richard Heinberg's newsletter wrote:

Some of the environmental impacts of manufacturing PV systems have been analyzed by Alsema et al. and compared to the impacts of other energy technologies. [33] They have found energy pay-back times of 1.7 to 2.7 years

EROEI: The net energy for electricity generation from hydrothermal resources has ranged, depending on the researcher, from 2:1 to 13:1. This discrepancy represents both the lack of a unified methodology for EROEI analysis and disagreements about system boundaries, quality-correction, and future expectation. [47]




Never  questions the ( in my and others opinion ) dubiously high EROEI of solar claimed, but does so for hydrothermal specifically pointing out disagreement over methodology.

Some estimates of energy payback for PV come out at 0

A start on an overview of various energy sources BUT

Days of work for me to straighten it out completely, 

Very definitely needs to be taken with a grain of salt, as to those without a solid engineering background could easily come away with the wrong impression about aspects of the situation.


Cheers Hamish


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Re: Heinberg: Prospects for Alternative Energies to Replace ...

Another problem is that oil wells are seldom 5 meters deep.  How about 5 kilometers?  Not far off for drilling deep deposits on the outer continental shelf. I got out my physics text just to double check this. It's the only way Heinberg's numbers make sense.

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Re: Heinberg: Prospects for Alternative Energies to Replace ...

Which is why I suggested the possability of a typo.

But the problem of an aparent lack of instinctive understanding still stands.


Cheers Hamish


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Re: Heinberg: Prospects for Alternative Energies to Replace ...

Have you read any of Heinberg's other material?  I'd hesitate to make a judgment based on one passage in an article, which may have been a typo as you pointed out.  Heinberg is a highly respected writer and commentator on these issues.  He's a senior fellow at the Post Carbon Institute, an organization that has made a huge contribution to awareness of peak oil, resource depletion and climate change.  Heinberg is an acknowledged expert within the peak oil community, and is held in high esteem by Chris M. and many other people on this site.  I'd give him the benefit of the doubt.

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Re: Heinberg: Prospects for Alternative Energies to Replace ...

I've read three of Heinberg's books including The Party's Over, Peak Everything, and The Depletion Protocol.  I follow him on the web with his website and a regular search of his latest videos.  He seems to be one of the most level headed of the Peak Oil observers.  If we met, I'm sure we'd be close personal friends.  Seriously folks, Heinberg is where I start any investigation on Peak Oil and its consequences.  Of course, Karl Marx, Noam Chomsky, Michael Parenti, Howard Zinn, Jarred Diamond, Gore Vidal, et al, are also key in understanding what I uncover.

I should also add a shout out to Dale Allen Pfeiffer.  His book The End of the Oil Age was my first contact with Peak Oil.  After reading that book, it took me months to recover.  Reading and rereading it was a constant Holy Sh#t! experience.  That led me to Heinberg, Kunstler, Ruppert, Campbell, Carolyn Baker, Dmitry Orlov, and a list of others too long to name.

I've taken the red pill.  :^)

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Re: Heinberg: Prospects for Alternative Energies to Replace ...

Richard Heinberg dismisses Nuclear Breeder reactors as a failed
cause.This is borne out by several failed examples. However I believe
this is still our best choice as the Liquid Flouride Thorium Reactor as
described by Dr. Joe Bonmetti at  http://neinuclearnotes.blogspot.com/2008/11/thorium-at-googles-tech-talk.html 
Unfortunately this type of breeder reactor has not been pursued.

LFTRs are a proven technology, research was terminated in 1975. New
advances with better heat exchangers and the Brayton cycle turbines
make this a highly desirable option. LFTRs can burn our stockpile of
radio-active waste from existing nuclear power plants. LFTRs produce
little long term radio active waste, or products suitable for making
bombs. The radio-active waste produced has a short half life and
requires only 300 years of storage as compared to the uranium waste
which has to be stored for 10,000 years. There is also much less
radio-active waste, 0.3% for equivalent power from uranium. Thorium is
plentiful, there is enough in coal ash and mine tailings to power the
world for 100 years, and a million years supply can be dug out of the
earth. See http://www.energyfromthorium.com/ and click on “Energy from
Thorium” and read. We should build a factory to build these in a size
small enough to ship on trucks (200MW) and an assembly line will bring
down costs. These could be set up all over the world (no worries about
nuclear proliferation) and first locations should be to replace coal
and oil fired electrical generating plants, because there is already
power distribution set up at these locations. Pollution from these
sources will be terminated.

At least one study for corn based Ethanol had an EROEI of less than 1.This is because it included cost of fertilizer and environmental damage by pesticides not included in other assessments.

Aside from these two caveats I think this it a pretty good assessment of current energy status.

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Re: Heinberg: Prospects for Alternative Energies to Replace ...
Roy wrote:

Richard Heinberg dismisses Nuclear Breeder reactors as a failed cause.This is borne out by several failed examples. However I believe this is still our best choice as the Liquid Flouride Thorium Reactor as described by Dr. Joe Bonmetti at  http://neinuclearnotes.blogspot.com/2008/11/thorium-at-googles-tech-talk.html  Unfortunately this type of breeder reactor has not been pursued.


Well then, why?  It seems fairly certain that a centralized energy source that requires big capital and returns big profits would be a shoo-in.  There has to be some factor either technical, regulatory, or financial.  Billions have been poured into fusion despite the solution to the containment issue that always seem just 30 years away.  Perhaps the technology is scalable in both directions so that people could put them in their basements or build them as multimegawatt generators.  Decentralized power generation is a no-no in the big capital world.

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Re: Heinberg: Prospects for Alternative Energies to Replace ...

I seem to recall that certain types of reactors were "frowned upon" by the US govt as an intermediary fission product was plutonium.....

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Re: Heinberg: Prospects for Alternative Energies to Replace ...

I don't know why the LFTR got sidelined. If you follow the links, there is some debate on this and it seems to get down to timing, and secrecy. The project was initially secret and therefore not well known and the Anti-Nuclear activists were in full swing, this was about the time the last light water nuclear reactors were built. The political feeling at the time was the Reduce, Re-use and Recycle philosophy and more power simply wasn't required. Later Fusion got the limelight and seemed to be the way of the future.The really weird part is that newer breeder designers didn't seem to know anything about the LFTR and actually produced inferior designs. Now the LFTR is no longer secret and appears to be a clear winner.

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