In the search for alternative energy sources, biofuels like ethanol and biodiesel were once heralded as the energy solution of the future. Plant-based, renewable and “clean,” fuels from crops like corn and sugar cane garnered a lot of attention along with significant government backing.
But the ethanol dream hasn’t panned out quite as expected, as the environmental footprint from turning corn into gasoline has been found to be in some cases greater than that for petroleum.
Now, new research from the University of Pittsburgh promises to breathe new life into the beleaguered biofuel industry, by arguing that second-generation biofuels can be an environmentally sustainable energy source.
Since the mid-2000s, governments in both Canada and the United States have put their support behind the biofuel sector in hopes that both countries could grow their way out of the fossil fuel problem. Global production of biofuels has jumped over the past decade and in 2005, the US became the world’s largest producer of ethanol.
But the trend is mired in controversy. Using up valuable farmland to grow crops for ethanol only makes sense, the claim goes, if the total impact on the environment is less from creating and burning biofuels than from extracting and burning fossil fuels. It’s not.
“Although some forms of bioenergy can play a helpful role, dedicating land specifically for generating bioenergy is unwise,” says Andrew Steer and Craig Hanson of the World Resources Institute, to the Guardian. “It uses land needed for food production and carbon storage, it requires large areas to generate just a small amount of fuel, and it won’t typically cut greenhouse gas emissions.”
Indeed, Steer and Hanson quote research that suggests that just to account for 20 per cent of the world’s energy needs by the year 2050 would require using up all of the world’s annual crop harvests, plant residues, timber and grass for livestock.
Yet, one avenue still seems to hold promise in the biofuel dream, and that’s second generation or advanced biofuels, derived from plant and animal sources not being used for food, and thus are not taking valuable resources out of the food chain but making use of energy sources that might otherwise go to waste.
"Second-generation biofuels differ from first generation biofuels because they don't come directly from food crops like corn and soy," said Vikas Khanna, assistant professor of civil and environmental engineering at the University of Pittsburgh and co-author of a new study, in a press release."They include woody crops, perennial grasses, agricultural and forest residues, and industrial wastes."
Khanna and colleagues conducted a full life cycle assessment (an analysis of environmental impact throughout all stages of a product’s life and use) of one version of a second generation biofuel sourced from short-rotation woody crops and converted to bio-oil.
Researchers used a common metric for looking at fuel efficiency, the Energy Return on Investment (EROI) ratio, where anything higher than a ratio 1:1 is considered a promising energy source (crude petroleum, for example, has a very high EROI at 11:1).
The results showed that for multistage second generation biofuel systems, the EROI ranges from 1.32:1 to as high as 3.76:1. The researchers argue that by using a lower temperature system of pyrolysis, the process of creating biofuel by heating biomass to high temperatures in the absence of oxygen, more biofuel can be created and the energy output of the system can improve.
“These results are compelling and indicate that multistage systems exhibit comparatively higher gasoline/diesel-range fuel yield relative to current technology,” say the study’s authors, whose research is published in the journal Energy & Environmental Science.