For four days in June, the European biofuel industry gathered in Milan, Italy, for the 20th European Biomass Conference and Exhibition. The event attracted more than 1,500 participants, including researchers, engineers and technologists, as well as people from standards organizations and financing institutions.
A key day-long workshop during the event considered the European Multilevel Integrated Biorefinery Design for Sustainable Biomass Processing (EuroBioRef) project. Launched two years ago, EuroBioRef deals with the entire biomass transformation process, from non-edible crops production to final commercial products. It involves 29 partners — both corporate and academic — from 14 different countries in a highly collaborative network focused on topics such as crop production; biomass pretreatment; fermentation, enzymatic, catalytic and thermochemical processes; assessment by a lifecycle analysis (LCA); and an economic evaluation of the value chain.
For all the process challenges that lie ahead, it was the LCA and economic evaluation that really came under close scrutiny. This follows the June 8 publication of "Crop-based biofuels and associated environmental concerns," a commentary in GCB Bioenergy — a journal that promotes understanding of the interface between biological sciences and the production of fuels directly from plants, algae and waste — that challenges how emissions from bioenergy production are calculated.
Authors Keith A. Smith of the School of GeoSciences, University of Edinburgh, Scotland, and Timothy D. Searchinger of the Princeton Environmental Institute and Woodrow Wilson School, Princeton, N.J., argue that calculations of greenhouse gas (GHG) emissions from bioenergy production are neglecting crucial information — and this has led to overestimating the benefits of biofuels compared to fossil fuels.
The authors conclude that LCAs exaggerate the positive aspects of biofuel use versus fossil fuel use by omitting carbon dioxide emission from vehicles that use ethanol and biodiesel — even when there's no valid justification for doing so.
Supporters of bioenergy traditionally have argued that this carbon dioxide should be ignored because plants grown for biofuel absorb and therefore offset the same amount of carbon that's emitted by refining and combusting the fuel.
Not so, say Smith and Searchinger, who contend that this double counts the carbon absorbed by plants when the bioenergy crops are grown on land that's either already used for crop production or already growing other plants, because the bioenergy doesn't necessarily result in additional carbon absorption.
The authors point out that biofuels can only reduce GHGs if they result in additional plant growth or if they, in effect, generate additional usable biomass by capturing waste material that would otherwise decompose anyway.
Even worse, this overestimation of bioenergy LCAs becomes increasingly magnified when the omission of carbon dioxide is combined with the underestimation of nitrogen emissions from fertilizer application.
LCA results for biofuels from cereals and rapeseed depend heavily on how they estimate nitrous oxide emissions from fertilizer use. Applying biochemically reactive nitrogen to agricultural soils emits GHG byproduct nitrous oxide into the atmosphere. While the scale of this emission is relatively small in comparison to nitrogen fertilizer that's leaching in drainage water or by ultimate microbial reduction to dinitrogen, it's nevertheless of vital environmental importance, say the authors.
"Emissions of nitrous oxide from the soil make a large contribution to the global warming associated with crop production because each kilogram of it emitted to the atmosphere has about the same effect as 300 kg of carbon dioxide," says Smith. He notes that several current LCAs underestimate the percentage of nitrogen fertilizer application that's actually emitted to the atmosphere as a GHG. The authors claim that the observed increase in atmospheric nitrous oxide shows that this percentage is in reality nearly double the values used in the LCAs, which greatly changes their outcome. They quote research which demonstrates that, when nitrous oxide emissions are properly taken into account, first-generation biofuels can actually increase global warming, not mitigate it.
Because results of the LCAs have been widely utilized, Searchinger and Smith conclude that the overall development and research of alternative fuels has been heading in the wrong direction. "The best opportunity to make beneficial biofuels is to use waste material or to focus on relatively wet, but highly degraded land," notes Smith. If bioenergy crops are produced on degraded land, less GHGs will be emitted and more will be stored. And there are additional benefits as this method will not compete with crop production for food, textiles, and other products.
SEÁN OTTEWELL is Chemical Processing's Editor at Large. You can e-mail him at [email protected].