Compounded Climate Accounting Errors

Timothy Searchinger, visiting scholar at Princeton University, Dan Kammen of the University of California Berkeley, David Tilman of the University of Minnesota and other authors from the Environmental Defense Fund published an interesting new proposal in the Policy Forum section of Science magazine today. The argument put forward is that “Replacing fossil fuels with bioenergy does not by itself reduce carbon emissions, because the CO2 released by tailpipes and smokestacks is roughly the same per unit of energy regardless of the source.”

The premise behind this proposal is that the world is facing such a great need to reduce carbon emissions that future sources of energy and biofuels cannot make use of any currently sequestered carbon. Maybe… but there’s a perverse consequence of using this logic. Fossil fuels are a source of sequestered carbon. If you then say that all existing biomass is an untouchable source of sequestered carbon, you are essentially counting that sequestration as a benefit of having used fossil fuels for the past 150 years.

The logic is particularly tortured when a foregone sequestration penalty is attributed to biofuels when none is counted for petroleum.

There is much in the paper to agree with — particularly in recognizing carbon sequestration benefits from improved land management practices and energy crops. And certainly, the challenge of climate change is so great that implementing best practices for carbon sequestration is a necessity.

But a proposal that attributes carbon sequestration in trees as a plus in the accounting of fossil fuel use is counterproductive.

Environmentalists Want to “Stick” It to Farmers

Jason Hill of the University of Minnesota’s Institute on the Environment wrote recently in the St. Paul Pioneer Press, asking why the Waxman-Markey climate change bill should treat agricultural emissions differently from energy and transportation emissions, with a “carrot-and-stick approach, one in which fossil fuels suffer the stick while agriculture feasts upon the carrot.” Hill’s primary objection to the bill is the amendments added by Rep. Collin Peterson (D-Minn.), which exempt agriculture and forestry from carbon caps but provide credits for carbon sequestration that farmers can trade on the market. They also would postpone implementation of the EPA’s analysis of international land use change.

Writes Hill, “Peterson’s amendment is essentially nothing more than a slick accounting trick, one meant to portray biofuels produced in this nation in a better light while making the carbon footprint of agriculture in developing countries look worse.”

This is a bizarre statement, turning even the theory of indirect land use change on its ear. The original calculation of indirect land use change put forward by Searchinger et al held that “when farmers use today’s good cropland to produce food, they help to avert greenhouse gasses from land use change.” Further, in the context of international negotiations for a climate change treaty to replace the Kyoto Protocol, the ILUC theory is clearly an attempt to shift accounting of carbon emissions in developing countries onto U.S. biofuels.

Calculations of land use change by current models are completely contradicted by agricultural trade and production numbers, making the models appear to be nothing more than accounting tricks. The model projections look nothing like real outcomes because they rely on several false premises and double count certain sources of emissions. The greatest fallacy of the ILUC theory is that worldwide agricultural productivity has already reached a natural limit and cannot respond to increased demand in any other way than clearing of rainforests. The main premise of the theory – that biofuels have been introduced into a static worldwide agricultural system and therefore are the primary cause of shifting agricultural production – is an assumption that can’t be supported by data.

Using USDA’s modest assumption for growth in yields of U.S. corn over the life of the Renewable Fuel Standard, a simple calculation shows that corn productivity can keep up with demand to produce the conventional biofuel portion of the RFS. This assumes continuation of 2016 to 2018 USDA projections for 2022 – constant total planted acreage of 90.5 million acres, increase of 75 million bushels per year for fuel ethanol, and increase of 1.8 bushel per acre per year yield improvement:

Overall harvested acreage for corn production is projected to remain stable due to continued yield productivity gains

In fact, USDA currently projects a corn yield of 159.5 bushels per acre for this year. And USDA projections from January 2009 show that inclusion of biofuels will stabilize land use, in terms of the acres planted to the eight major crops:

U.S. land planted to eight major crops.

Beyond this, and despite a report) that deforestation in Brazil increased in June, the deforestation rate in Brazil continues to decline. Responding to the Agence France-Presse report, Mongabay noted, “Deforestation in the Brazilian Amazon typically peaks during the June-August dry season when ranchers and farmers burn forest to clear land for development.”

A group of scholars – that includes Hill – recently called for a focus on real solutions to climate change. The world needs economic growth, energy and food. We should not premise our search for solutions on the false notion that these three necessities are in direct competition with each other.

New Biofuels Manifesto

University of Minnesota Professor David Tilman, Princeton University Visiting Scholar Tim Searchinger, Dartmouth Professor Lee Lynd and others involved in the debate over the environmental and social impacts of biofuels have published in Science magazine what amounts to a new manifesto on how biofuels can be done right.

The authors list five biofuel feedstocks that are the best in terms of sustainability — “lower life-cycle greenhouse-gas emissions than traditional fossil fuels and with little or no competition with food products.”

The authors conclude:

Three steps should be taken: meaningful science-based environmental safeguards should be adopted, a robust biofuels industry should be enabled, and those who have invested in first-generation biofuels should have a viable path forward.

The EPA’s proposed rule on the Renewable Fuel Standard was intended to outline a viable path forward for first-generation biofuels. The Best Case Natural Gas Dry Mill, the Biomass Dry Mill, and the Biomass Dry Mill with Combined Heat and Power scenarios outlined in the “EPA Lifecycle Analysis of Greenhouse Gas Emissions from Renewable Fuels” all produce reductions in greenhouse gases that come close to or exceed the 20 percent standard in the RFS. The EPA’s definition of the Best Case is: “Best case plants produce wet distillers grain co-product and include the following technologies: combined heat and power (CHP), fractionation, membrane separation and raw starch hydrolysis.”

The question will be whether anyone invests in these technologies or in additional biofuel production at all, given the current economic and social climate in which biofuel companies are operating. One possible factor in choosing the best biofuels ought to be how soon they can become a reality and whether they can be improved from there.

Life Cycle Analysis, International Land Use Change and Uncertainty

Bruce Dale, University Distinguished Professor of Chemical Engineering at Michigan State University, shared this presentation that he gave during a webinar hosted by the North Central Bioeconomy Consortium. In it, he highlights the number of factors in Life Cycle Analysis and Indirect Land Use Change (ILUC) models that produce uncertainty – in other words, if the assumptions or data for these factors change, how much do the results change.

Dale is primarily examining the “carbon debt” concept that was introduced in the February 2008 Science papers by Searchinger and Fargione/Tilman. Dale argues that those papers failed to take into account how land converted to crop production might be managed. Dale recently submitted a paper to Environmental Science and Technology, testing the effect on land use change emissions if crop production is managed in a sustainable manner:

Sustainable cropping management practices (no-till and no-till plus cover crops) reduce the payback period to 2 years for the grassland conversion case and to 14 years for the forest conversion case. It is significant that no-till and cover crop practices also yield higher soil organic carbon (SOC) levels in corn fields derived from former grasslands or forests than the SOC levels that result if these grasslands or forests are allowed to continue undisturbed.”

Aside from assumptions about land management, life cycle analysis can be affected dramatically by changes in the amount and kinds of energy used in the biorefinery. American Fuels recently posted a note about some forthcoming research on the energy balance of biofuel production:

University of Nebraska at Lincoln researcher Kenneth Cassman concluded in a upcoming study that ethanol production has become more energy efficient.
‘Recent research conducted at the University of Nebraska clearly shows that estimates for the energy balance of corn-based ethanol are much more favorable – in fact two to three times more favorable, than previous estimates.'”

Since energy inputs are such a large factor in biofuel production, improvements in efficiency will significantly reduce the life cycle greenhouse gas emissions of biofuels when compared to gasoline.

Tilman clarifies study

Much of the media coverage of the recent Science Magazine studies made it clear that many hadn’t actually read the studies before they reported on them. Some interpreted the studies as condemning corn ethanol production now, not as the worst case scenario of what could happen in the future.

University of Minnesota professor David Tilman, an author of one study, clarified it today in an interview with Minnesota Daily:

Tilman, who is currently on sabbatical from the University, said he feels the study is misunderstood by others in the industry.

“The goal of our paper was to point out if we do certain things, that those things would give us fuels that didn’t have very much environmental benefit,” he said.

Tilman said the paper didn’t say the problems were happening now, but instead that they could happen in the future.

The challenge to the biofuels industry, and one it’s willing to undertake, is to make sure that future growth continues in a responsible way so that biofuels can continue to improve the environment.

Biofuels and Carbon Debt

The Energy Independence and Security Act of 2007 establishes an ambitious renewable fuel standard that increases biofuel production and use to 36 billion gallons by 2022. The standard also mandates that renewable fuels produced in new facilities constructed after enactment of the Act, which occurred in December 2007, “achieve at least a 20 percent reduction in lifecycle greenhouse gas emissions compared to baseline lifecycle greenhouse gas emissions.” The Act does not specify a specific instrument for measuring lifecycle greenhouse gas emissions, but it does define lifecycle greenhouse gas emissions as “including direct emissions and significant indirect emissions such as significant emissions from land use changes and all stages of fuel and feedstock production and distribution, from feedstock generation or extraction through the distribution and delivery and use of the finished fuel to the ultimate consumer.”

Recently, two teams of researchers proposed a modification of the GREET model (see Biofuels and GHG Lifecycle) to include greenhouse gas emissions from land use change, as mentioned in the Act, and their work was published in Science on Feb. 8, 2008. David Tilman of the University of Minnesota and colleagues proposed a “carbon debt” for biofuel feedstocks as a corollary to their carbon capture.This debt is defined as “the amount of CO2 released during the first 50 years” of the process of clearing land for production of biofuel feedstocks. The carbon debt is repaid primarily by the uptake of carbon dioxide by the feedstocks. Tilman et al. conclude that “If biofuels are to mitigate global climate change, our results suggest that they need to be produced with little reduction of the storehouses of organic carbon in the soils and vegetation of natural and managed ecosystems. Tilman et al. allow that “improvements in biofuel production could reduce payback times” though these improvements are not calculated in the present paper.

Searchinger and colleagues go further than Tilman in calculating this “carbon debt,” by including indirect increases in carbon emissions such as the loss of future storage of carbon in converted land.  They also calculate an expected increase in croplands in Central and South America — at the expense of rainforests and grasslands — due to population growth and increased demand for food in these regions. They claim that diversion of U.S. crops to biofuels must carry a “carbon debt” for this phenomenon.

As the EPA considers implementation of the lifecycle reduction of greenhouse gases required in the new Energy Security Act, they should include a full accounting of the carbon balance of land use including possible beneficial changes. Better agronomic practices can increase carbon sequestration in cropland while allowing for collection of crop wastes for biofuel production.