Now they're under assault by the Swiss Federal Laboratories for Materials Science and Technology (EMPA), who've made the blunt assessment that "most biofuels are not green."
The researchers there say studied the full life-cycle impact of biofuels – looking at what the fuels consume, what they produce and what they cause, a concept Europeans call "ecobalance" – and found "only a few biofuels (have) an overall better ecobalance than petrol."
The problems are manifold and not unfamiliar: fertilizers used to grow the crops end up in lakes and rivers; soil acidities rise. "Most biofuels … just deflect the environmental impact: fewer greenhouse gases, thus more growth-related pollution for land used for agriculture," researcher Rainer Zah says in a statement.
Biogas from "residues and waste materials" fare best in this study, an update and expansion on a 2007 report by EMPA, done in collaboration with Agroscope Reckenholz-Tankion and the Paul Scherrer Institute. Depending on the precise source material, biogas can have about half the impact on the environment that petrol does, the researchers say.
Ethanol-based fuels (corn and sugar cane are the most common inputs) generally have a better ecobalance than do oil-based fuels (think: soybean or palm oil), EMPA says. This is in line with European Commission data that came out earlier this year, which showed palm oil and soybean-derived fuels having a carbon footprint nearly as large as the notorious tar sands oil.
The worst-case biofuel scenario is when rain forests are felled to make way for crops that get channeled to making fuel. Biofuels produced from these lands are the ones that "usually emit more greenhouse gases than fossil fuels," according to the researchers.
This can happen even when the deforested land doesn't move directly to biofuel crop production; using existing ag land to grow crops for biofuels can lead to other forested areas being cleared to make up for the lost food production. That's the pernicious indirect land use change phenomenon.
The researchers aren't without any hope for biofuels, however. They don't really endorse them, but they do allow that thoughtful management can make a valuable difference. For example, even palm oil cultivation, if done on unused grazing land in Columbia, can increase the carbon content of soil. This points to how highly variable the ecobalance calculation can be, depending on precise locations and practices.
The biofuels industry, as you might imagine, sees things rather differently than EMPA. The key indirect land use change argument is largely dismissed by the industry. For instance, the group Growth Energy, which promotes ethanol, calls it a theory that is "flawed, speculative and withstands no credible scrutiny."
The group notes: "According to the National Institute of Space Research, deforestation in the Amazon has declined sharply just as American biofuels production doubled. In 2004, 10,588 square miles of the Amazon was deforested and in 2009/10, that number dropped to 2,490.7 square miles. Meanwhile, U.S. ethanol production has gone from approximately 3 billion gallons in 2004 to approximately 13.23 billion gallons in 2010."