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The Science of Measuring Emissions
What Will it Mean for Ethanol?
by Kristin Brekke

“Indirect land use change” is a new phrase punctuating ethanol conversations this year, driven largely by two studies published by Science magazine in February. The national headlines that so eagerly followed – like “Study: Ethanol Worse for Climate than Gasoline,” “Biofuels Deemed a Greenhouse Threat” – propelled the topic to the spotlight and gave the researchers a chance to make their claims that U.S. ethanol production is somehow causing the destruction of environmentally sensitive land in countries like Brazil.

The “indirect land use change” argument has a second part: that the greenhouse gas emissions associated with this theoretical land clearing should count against biofuels in a total lifecycle analysis. And because a lifecycle analysis, or LCA, is a central part of so many policies – the Renewable Fuels Standard 2, a Low Carbon Fuels Standard, and potential cap-and-trade legislation – the treatment of biofuels under these regulations must be examined very closely.

If policy gets ahead of science, and regulations are based on theory instead of fact, biofuels could be unfairly penalized and their future jeopardized.

With scant scientific data available on this topic, the American Coalition for Ethanol commissioned a study on the implications of lifecycle analysis of the greenhouse gas emissions associated with biofuels.

The just-released research report, “Lifecycle Analysis of Greenhouse Gas Emissions Associated with Starch-Based Ethanol,” was conducted by leading consulting firm Global Insight, authored by John Kruse, PhD, with Stewart Ramsey and Tom Jackson. The full report is available on ACE’s website,


New policies use lifecycle analysis to evaluate fuels’ GHG footprint

The Renewable Fuels Standard of the Energy Independence & Security Act of 2007 (EISA) includes carve-outs for different types of biofuels and requirements that each type meet certain greenhouse gas emission reduction targets relative to gasoline. Corn-based ethanol from new facilities must achieve a 20 percent reduction in GHG emissions, and most other “new” biofuels must achieve a 50 percent reduction.

Among its many provisions, EISA says that its required lifecycle analysis (LCA) must include the indirect effects of clearing new lands for crop production, in the U.S. or elsewhere in the world. The Environmental Protection Agency is charged with quantifying these indirect effects.


What is lifecycle analysis?  The EPA defines lifecycle greenhouse gas emissions as:

“the aggregate quantity of greenhouse gas emissions (including direct emissions and significant indirect emissions such as significant emissions from land use changes), as determined by the Administrator, related to the full fuel lifecycle, including 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, where the mass values for all greenhouse gases are adjusted to account for the relative global warming potential."


Similarly, the State of California has passed and is implementing a Low Carbon Fuels Standard which also incorporates lifecycle analysis as the mechanism to assign a value to a fuel’s carbon footprint. The California Air Resources Board (CARB) released a draft of its policy framework in mid-October. Some elements, such as the quantification of carbon emissions from indirect land use change, are still being developed, but the initial methodology does not look promising for corn-based ethanol.

Previous studies have indicated that well-to-wheels GHG emissions from corn-based ethanol are approximately 22 percent lower than those of gasoline, without including any impacts from potential indirect land use change. However, CARB’s methodology includes the impacts of indirect land use change, which raises corn ethanol’s rating from 35 gCO2/MJ (emissions are measured in grams per CO2 equivalent per megajoule) up to 110 gCO2/MJ, which is 15 percent higher than those of gasoline.

“California is often a leader in environmental policies for the rest of the nation, so it’s important that we monitor how biofuels are treated in their proposed regulations and step in if needed to ensure that these regulations are done right,” Jennings said.

The draft results of CARB’s analysis do not look favorable to corn-based ethanol, but the agency’s presentation of the results does acknowledge some potential problems with the analysis, or at least areas that may be called into question. The Global Insight study evaluates some of these key questions as they relate to the treatment of biofuels under the lifecycle analysis.

Key findings of the Global Insight study

1) It is neither fair nor accurate to attribute all current and future land clearing to biofuels.

It is a fact that changes in the use of land are occurring. Changes in land use have always occurred. The changes are not new, nor are biofuels the primary driver behind them. Global population growth cannot be ignored as a major factor.

“It would be neither fair nor accurate to attribute all current and future land clearing to biofuels, considering the increases in world demand for crops for other purposes ,” the study states.

If some land use change is due to increased biofuels production, the overriding challenge is to quantify which changes can indeed be directly attributed to biofuels. And if the expansion of crop area is counted, the opposite should be looked at as well.

“Just as crop area is expanding in some countries, other countries such as China have experienced declining crop area,” Jennings noted. “If one is to account for increases in land use, one should also consider decreases in land use as well.”

Another issue raised by the report is that studies done so far tend to assume that patterns of future land conversion will follow past patterns, something the study say “neglects the possibility of policy initiatives to steer land development away from areas of greatest environmental impact, such as tropical rain forests.”

2) New technology is making both corn and ethanol production more efficient, more environmentally friendly

Yield improvements and increased efficiencies in the production of corn and of ethanol will impact the biofuels carbon footprint, and these improvements need to be reflected in any fair lifecycle analysis.

“When considering the lifecycle analysis of various fuels, it is important to recognize that corn ethanol is getting more and more efficient, while the production of gasoline from oil is getting not only more and more inefficient, but more harmful for the environment ,” Jennings said.

The study notes that with the technology coming online in corn and ethanol production, the carbon footprint is set to improve significantly in the next ten years. Jennings notes that yield improvements in crop production translate in to lower land use requirements, and these need to be taken into consideration.

Assumptions about corn production are key to the LCA and must reflect the steady increases in corn yield per acre. U.S. average corn yields have doubled between 1970 and today, and some industry leaders are predicting even faster yield increases in the next decades, possibly achieving 300 bushels per acre within 20 years. In addition, nitrogen fertilizer use per acre peaked in 1985 and has been trending lower since.

“The combination of these trends suggest significant improvement in GHG emissions per bushel since 1970,” the report states.

The energy efficiency of the ethanol production process is also advancing, leading to reduced GHG emissions. A related study found that between 2004 and 2007, ethanol plants reduced their BTU usage by between 14 and 21 percent. Since 2002, U.S. ethanol producers have achieved an average 22 percent drop in energy demand.

New technology being developed and adopted by ethanol producers will mean further reductions in energy requirements, such as a “no cook” process which reduces natural gas usage by up to 15 percent and fractionation, which separates the corn kernel in to the endosperm, germ, and bran. Fractionation, which is expected to be more widely adopted in the next two to three years, offers higher ethanol yields and opportunities for additional food and feed products to come from America’s ethanol plants. Some ethanol producers are also adding alternative fuel sources to reduce natural gas usage, such as biomass gasifiers which can utilize wood chips or corn stover as a source of fuel for the process.

Ethanol yields continue to improve, growing from 2.795 gallons per bushel of corn in 2004 to 2.802 gallons in 2007, according to one survey. These yields are higher than the 2.65 to 2.72 gallons per bushel assumed in the USDA’s GREET model, which is often used as a benchmark for other analyses.

“In addition, the technology is in the pipeline to further increase ethanol yields per bushel with yields approaching 3.0 to 3.1 gallons per bushel in the next 10 years, with a yield potential of 3.3 gallons per bushel,” the study finds.

3) Oil is becoming less efficient and more harmful to the environment

“ With the technology coming online in corn and ethanol production, the carbon footprint is only set to improve significantly in the next ten years, where as feedstock sources for the petroleum industry, such as oil sands, will further degrade petroleum’s carbon footprint ,” the study states.

Looking ahead to future biofuels production finds even more efficient and environmentally sound results, but the opposite is true for petroleum. While tomorrow’s gallon of ethanol will be from low-carbon sources like switchgrass, tomorrow’s gallon of oil will come from carbon-intense sources like tar sands or coal.

“High oil prices incentivize the production of crude oil from sources such as tar sands and coal which have considerably higher GHG emissions than biofuels. Depending upon the energy source used in the mining of tar sands, well-to-pump GHG emissions can be over 300 percent of conventional crude oil as demonstrated by GREET,” the study states.

The EPA is comparing the lifecycle analysis of biofuels to that of petroleum in 2005, not a fair comparison since the carbon footprint of oil will degrade significantly in these post-2005 years when new oil sources like the Canadian tar sands are tapped.

The study also raises the question of whether the LCA are including the indirect emissions associated with petroleum as they are with biofuels.

“No directive has been given to EPA, nor does there appear to be any research by EPA, on the indirect GHG emissions associated with petroleum production. Yet several research centers, including the Congressional Research Service, Securing America’s Future Energy, and the International Center for Technology Assessment, have noted the indirect military costs associated with securing petroleum from foreign sources,” the study notes.

CRS, for example, performed a literature review on indirect military costs in 1992 and found impacts ranging from billion to billion.


The policies appear to be ahead of the science on indirect land use change

“The argument in favor of including indirect land use change may have some intuitive appeal, but there are some major impediments to its inclusion in a lifecycle analysis, especially one to be conducted in the near future,” according to the study.

One of those major impediments – large margins of error in a small existing data pool.

“ Lifecycle analysis is being used to actually quantify GHG emissions, and the scientific literature shows a huge variation in estimates of carbon release from land clearing in general, on the order of 50 percent plus or minus – a huge margin of error ,” the study states. “In addition, the clearing of different types of land will generate different amounts of carbon release. Further, it is questionable whether the necessary data are available to determine what types of land are being cleared for agricultural use and by which methods.”

The research acknowledges that increased use of biofuels could certainly lead to unintended consequences such as the clearing of land to make up for the volume of crops being used as feedstocks for fuels, and the issue does warrant further study. “However, as pointed out in a letter recently signed by dozens of scientists involved in the issue of alternative energy, sound policy decisions need to be based on solid empirical evidence utilizing reliable data and models created specifically to incorporate the relevant issues… For now, the issue of indirect land use certainly appears to lack some of the data necessary to conduct robust analyses.”

The study concludes:

“Considering the changing world policy and agricultural environment, the sparse and unreliable data on land use change, the multiple drivers of land use change, and the considerable ambiguity in measuring GHG emissions associated with land use change, any assignment of GHG emissions from indirect land use change would be suspect at best. While EPA is under a directive to measure indirect land use change effects from biofuels production, in this case, the policy appears to be ahead of the science in regulating what science cannot yet measure with any degree of certainty.”


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The American Coalition for Ethanol publishes Ethanol Today magazine each month to cover the biofuels industryís hot topics, including cellulosic ethanol, E85, corn ethanol, food versus fuel, ethanolís carbon footprint, E10, E15, and mid-range ethanol blends.
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