August 19, 2007

A four-star idea for rating biofuels

Any greenhouse gas cap and trade system for ethanol and other biofuels will be dependent upon an accurate assessment of its carbon footprint - not only the amount of carbon emitted to the atmosphere during usage but also the the carbon lifecycle of the fuel's production.

If coal is the fuel, the carbon emitted is not already part of the above ground carbon cycle and is therefore carbon positive. Plus it takes energy to mine, process, and deliver coal. At the other end of the spectrum, if hybrid poplars are the feedstock, not only are the emissions carbon neutral but the growing trees are effectively sequestering carbon dioxide (with a highly valued carbon negative impact). There are benefits to crops that do not need to be tilled, are perennial, or do not require fertilizers. There are benefits to conversion processes that do not require the use of fossil fuels or electricity.

Various groups are engaged in the task of coming up with a "green biofuels" rating system that incorporates the "global warming intensity" (GWI) of the fuel, a rating for the kind of feedstock being converted, and the use of fossil fuels in the conversion or refinery process. An excellent article written by Susanne Retka Schill for Ethanol Producer magazine reports on some of the more promising efforts to come up with a system sophisticated and reliable enough to provide industry benchmarks for setting caps and for trading credits. Concurrently, it must be simple enough for commercial and residental consumers to make informed buying decisions. The more comprehensive and comprehensible the system, the better the incentives will be to motivate change to renewable fuels.

Here is a small taste of what is contained in the published article...

Developing a Biofuels Rating System

Producing four-star biofuels may give producers a leg up when the United States develops a carbon cap-and-trade system. Methods to quantify greenhouse gas emissions and rate biofuels are being proposed and tested in an attempt to incorporate the multiple facets of cropping systems, conversion processes and industry and consumer needs.
By Susanne Retka Schill

The chart shows how a Green Biofuels Index might work for different cropping scenarios and biofuels technologies. GWI is global warming intensity. The formula shown in the middle column generates the number value. One star is awarded for each 40 value units.

All biofuels are not created equal. Renewable fuels have different carbon footprints, depending on the feedstock that's used to produce it, how that feedstock was grown, how far it was transported and how it was converted to ethanol. Before ethanol producers can join cap-and-trade programs or sell offset credits on the Chicago Climate Exchange, the hurdle to quantify and express greenhouse gas performance must be cleared. Although there are several systems and models being developed, EPM talked to researchers involved in two projects that are tackling the challenge from different angles. One is focused on a biofuels rating system, the other models a life cycle assessment of biofuels to provide a glimpse of what the future may hold for biofuels marketing.

In the end, the winners in the greenhouse gas reduction comparisons aren't surprising, but the numerical values are interesting. Switchgrass and hybrid poplar energy crops transformed into biofuels provide the most greenhouse gas reductions when compared with gasoline and diesel, at about a 115 percent reduction, in the long term when soil carbon levels are at equilibrium and no longer sequestering additional amounts. Reed canary grass reduced greenhouse gas emissions by 85 percent. The different rotations and tillage systems for corn and soybean rotations reduced greenhouse gas emissions around 40 percent. These numbers compare with current analyses of the corn-to-ethanol production process showing a 20 percent greenhouse gas reduction, Adler says.

The greatest impact on reducing the amount of greenhouse gases associated with energy use by switching to biofuels came from eliminating the life cycle greenhouse gases from fossil fuel use, followed by the storage of carbon in the soil from perennial crops. People most often think of carbon when considering greenhouse gases, but agricultural systems release methane from the soil, which is 23 times more active than carbon dioxide as a greenhouse gas, and nitrous oxide, which is 300 times more powerful, Parton explains. Plus, the carbon sequestration effect of no-till or perennial crops has a relatively short-term positive effect on greenhouse gas emissions. "It's a positive for 20 years, then you reach a new equilibrium," Parton says.

Susanne Retka Schill is an Ethanol Producer Magazine staff writer. Reach her at or (701) 746-8385.

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