Accounting rules. Tim Searchinger, a research scholar in the Princeton Environmental Institute and a fellow with the German Marshall Fund of the United States, is lead author of the “accounting” study. Michael Oppenheimer, director of the Program in Science, Technology and Environmental Policy and professor of geosciences and international affairs in the Wilson School of Public and International Affairs, is a co-author.

In a paper published in Science in February 2008, Searchinger and colleagues at Woods Hole Research Center and Iowa State University identified land use change—the conversion of rainforests, peatlands, savannas, or grasslands to produce food-based biofuels or to replace existing cropland diverted to biofuel crop production—as a major source of increased carbon dioxide emissions, far offsetting the presumed greenhouse gas benefits of using most current biofuels. (Earlier post.)

In new the study, “Fixing a Critical Climate Accounting Error,” the authors contend that across-the-board exemption of CO₂ emissions from bioenergy—the use of plant materials known as biomass for the production of renewable fuels—is improper in greenhouse gas regulations if emissions due to land-use changes also are not included. This, they assert, erroneously treats all uses of bioenergy as carbon-neutral, renewable energy regardless of the source of the biomass, and could create strong economic incentives for large-scale land conversion as countries around the world tighten carbon caps.

According to the researchers, the greenhouse gas consequences of using bioenergy vary greatly depending on the source of the biomass. For example, if plant growth increases to produce bioenergy, as when fast-growing trees or grasses are grown on degraded land, bioenergy reduces global warming because the plants absorb more carbon from the atmosphere, which offsets the CO₂ emitted by burning the bioenergy.

However, if bioenergy use results from burning wood chips from existing forests for electricity, or clearing rain forests to grow palm oil and other crops for biofuels, bioenergy does not reduce greenhouse gas emissions, and instead may increase them. Thus, the accounting rules in these legal measures mistakenly exempt the CO₂ emitted by bioenergy regardless of the source, according to the authors.

Neither the Kyoto Protocol, nor the existing or proposed climate legislation in Europe and the United States, currently applies limits to emissions from land use such as deforestation. Because of that, the exemption of the CO₂ actually emitted from the burning of biofuels and wood for electricity means all forms of bioenergy are treated as carbon neutral, which creates incentives to clear land.

The straightforward solution is to fix the accounting of bioenergy. That means tracing the actual flows of carbon and counting emissions from tailpipes and smokestacks whether from fossil energy or bioenergy. Instead of an assumption that all biomass offsets energy emissions, biomass should receive credit to the extent that its use results in additional carbon from enhanced plant growth or from the use of residues or biowastes. Under any crediting system, credits must reflect net changes in carbon stocks, emissions of non-CO2 greenhouse gases, and leakage emissions resulting from changes in land-use activities to replace crops or timber diverted to bioenergy.

Separately, Europe and the United States have established legal requirements for minimum use of biofuels, which assess greenhouse gas consequences based on life-cycle analyses that reflect some land-use effects. Such assessments vary widely in comprehensiveness, but none considers biofuels free from land-based emissions. Yet the carbon cap accounting ignores land-use emissions altogether, creating its own large, perverse incentives. Bioenergy can provide much energy and help meet greenhouse caps, but correct accounting must provide the right incentives.

—Searchinger et al. 2009

Indirect emissions from biofuels. In a separate paper published online in Science Express, a team of researchers led by Dr. Jerry Melillo, one of the co-authors on the new Searchinger paper, concludes that a global biofuels program will lead to intense pressures on land supply and can increase greenhouse gas emissions from land-use changes.

Using linked economic and terrestrial biogeochemistry models, they examined direct and indirect effects of possible land-use changes from an expanded global cellulosic bioenergy program on greenhouse gas emissions over the 21^st century. Their model predicts that indirect land use will be responsible for substantially more carbon loss (up to twice as much) than direct land use; however, because of predicted increases in fertilizer use, nitrous oxide emissions will be more important than carbon losses themselves in terms of warming potential.

They considered two cases to explore future land-use scenarios:

1. Conversion of natural areas to meet increased demand for land, as long as the conversion is profitable;

2. More intense use of existing managed land.

To identify the total effects of biofuels, they compared each of the cases to a scenario in which expanded biofuel use does not occur. In the scenarios with increased biofuels production, the direct effects such as changes in carbon storage and nitrous oxide (N₂O) emissions were estimated only in areas devoted to biofuels. Indirect effects are defined as the differences between the total effects and the direct effects.

One of the perplexing issues for policy analysts has been predicting the dynamics of the CI [carbon intensity. CI = GHG emissions per megajoule of energy produced] over different integration periods. If one integrates over a long enough period, biofuels show a substantial greenhouse gas advantage, but over a short period they have a higher CI than fossil fuel. Drawing on previous analyses, we argue that a solution need not be complex and can avoid valuing climate damages by using the immediate (annual) emissions (direct and indirect) for the CI calculation.

In other words, CI estimates should not integrate over multiple years, but rather simply consider the fuel offset for the policy time period (normally a single year). This becomes evident in Case 1, where despite the promise of eventual long-term economic benefits, a substantial penalty— in fact possibly worse than gasoline—in the first few decades may render the near term cost of the carbon debt difficult to overcome. In Case 2, where there is less willingness to convert land, the economics of biofuels would be favorable sooner.

Greater measures to protect forests could make the economics and CI of biofuels even more favorable because improved management on low quality or degraded land can lead to carbon accumulation in the soil, rather than a carbon loss. Interestingly, our results suggest tropical regions that are currently suffering significant amounts of deforestation may also be the most competitive producers of biofuels. Our suggested strategy of not integrating over future fuel offsets increases the near-term CI of biofuels unless forested lands globally are better protected. Success in avoiding deforestation will be reflected in lower estimates of indirect emissions, and a lower carbon penalty in carbon control areas for their use.

—Melillo et al. 2009

Biofuels industry reaction. Reaction from biofuel associations to the new Searchinger paper was fairly swift. The Renewable Fuels Association noted that the release of CO₂ from recently living organisms has no overall effect on atmospheric CO₂ levels—and is therefore carbon neutral—because atmospheric CO₂ decreases when a plant photosynthesizes, then increases back to its initial level when that carbon (in the form of a biofuel) is burned and returned to the atmosphere. In this way, RFA said, biofuels “recycle” organic carbon.

Conversely, the RFA said, accepted carbon accounting for fossil fuels such as petroleum does include tailpipe emissions from combustion. This is because the carbon in fossil fuels has been sequestered underground for millions of years rather than recently sequestered by growing organisms and cannot be naturally offset by feedstock uptake.

There is undeniable evidence that the climate concerns we face have been caused in large measure by the reckless use of finite fossil fuel resources. Developing a host of renewable alternatives, including from biomass feedstocks, should be a central goal. While recognizing that all carbon-based energy has associated carbon emissions, we must look for the least carbon-intensive alternatives and favor approaches that ‘recycle’ above-ground carbon. Based on a fair apples-to-apples comparison with petroleum, biofuels clearly offer society a lower-carbon path forward.

The real issue is not accounting tactics, but whether biofuels reduce GHG emissions compared to continued petroleum use. There is clear and substantial evidence that they do. The biogenic emissions resulting from the use of biofuels are recycled during the plant’s growth via the photosynthesis process. This stands in stark contrast to petroleum, which when combusted releases carbon that has been stored underground for millions of years.

RFA strongly agrees with the authors that natural ecosystems with high carbon storage—such as rainforest, peat soils, and other native lands—absolutely should not be converted to produce biofuel feedstocks. Those who directly convert these land types for biofuel crop production or any other purpose should be severely penalized and every effort should be taken locally to prevent this type of direct action.

However, there is no credible evidence that positively links US biofuels expansion to the conversion of these land types. There are ample supplies of agricultural land available, together with improvements in agricultural technology, to meet the energy and food demands of a growing population.

—Statement from the RFA

The Biotechnology Industry Organization (BIO) said that treating renewable energy the same as fossil energy thwarts the goal of reducing climate change.

Biofuels and biomass energy recycle atmospheric carbon, while fossil energy takes carbon that has been stored for millions of years in the earth and releases it into the atmosphere. The policy proposed today distorts this simple fact. It also fails to take into account that well-managed biomass production can sequester more carbon in the soil than is released into the atmosphere through combustion of biofuels and bioenergy. Biomass carbon can also be sequestered in production of biobased products.

The US Environmental Protection Agency’s analysis earlier this year shows that well-managed cellulosic sources of biomass can actually take more CO₂ from the air, and sequester it in the soil, than is released through combustion in automobiles.

The proposal put forward today, similar to a previous proposal for accounting of lifecycle emissions from biofuels, would hold US production of renewable energy and biomass accountable for emissions in other countries, limiting the ability of the United States to reduce its own emissions. This is a misguided policy proposal to protect foreign habitats by penalizing American farmers and biofuels producers who may be having no impact on land use practices in developing nations.

Renewable energy should not be treated in the same manner as fossil fuels under any climate change cap and trade legislation or treaty. Rather, biofuels should be recognized for their unique role in helping attain a low carbon future. To date, climate change legislation being considered by Congress has focused primarily on limiting emissions from stationary sources such as power plants and factories. But we cannot have a low-carbon future without low-carbon transportation fuels. Congress should not be penalizing low-carbon biofuels, but instead should be rewarding their production since they can help reduce the carbon footprint of the transportation sector.

—Brent Erickson, executive vice president of BIO’s Industrial & Environmental Section

Resources

• Timothy D. Searchinger, Steven P. Hamburg, Jerry Melillo, William Chameides, Petr Havlik, Daniel M. Kammen, Gene E. Likens, Ruben N. Lubowski, Michael Obersteiner, Michael Oppenheimer, G. Philip Robertson, William H. Schlesinger, G. David Tilman (2009) Fixing a Critical Climate Accounting Error. Science Vol. 326. no. 5952, pp. 527 - 528 doi: 10.1126/science.1178797

• Jerry M. Melillo, John M. Reilly, David W. Kicklighter, Angelo C. Gurgel, Timothy W. Cronin, Sergey Paltsev, Benjamin S. Felzer, Xiaodong Wang, Andrei P. Sokolov, C. Adam Schlosser (2009) Indirect Emissions from Biofuels: How Important? Science Express doi: 10.1126/science.1180251