[Press release] Study shines new light on estimated yields for cellulosic bioenergy crops
For immediate release: 28 February 2014
Assumptions concerning potential energy crop yields in some research studies may overstate those yields by as much as 100%.
One key factor in developing a sustainable biofuels policy is to realistically estimate the amount of biomass that can on average be grown on a given amount of land to produce cellulosic biofuel. A new study suggests that estimates for potential energy crop yields from some widely cited research studies may overstate those yields by as much as 100%. The findings could have significant implications for long-term renewable energy targets.
The study, published by researchers from the International Council on Clean Transportation in the peer-reviewed journal Biomass and Bioenergy, examined reported yields of five important energy crops (Miscanthus, switchgrass, poplar, willow, and Eucalyptus). The authors found that the highest predicted yields, and associated expectations of how much biomass could be grown for energy, could not be supported by an overview of studies in this field.
A handful of studies on biomass production report very high yields, but the ICCT found that these were all extrapolated from very small experimental plots, intensively irrigated and weeded, and carefully hand-harvested. These are conditions that would not be replicable at commercial scale. Studies that grew energy crops over larger areas and used conventional harvesting techniques have shown much more modest results, but these more realistic experiments are not always the ones highlighted by bioenergy researchers.
Not only are commercial-scale energy crop yields lower than often thought, but they are not likely to improve rapidly over time. The ICCT note that agricultural practices and achievements in plant breeding or genetic modifications that have increased yields of food crops over the past several decades, like intensive fertilization and increasing the ratio of grain to straw, generally do not work on energy crops. Miscanthus, for example, often considered a top candidate for large-scale biomass production, is a hybrid between two types of plants and cannot reproduce by seed, which significantly slows down research.
But the authors stressed that their findings should not be interpreted to mean that policies supporting cellulosic biofuel are misplaced. “We need more, not less, support for cellulosic biofuels right now to get the industry going,” said Stephanie Searle, the study’s lead author. “There is an important place for cellulosic biofuel in reducing greenhouse gas emissions from transportation, but that makes it all the more important to be realistic about how much biomass can be produced.”
Read a synopsis of the paper at www.theicct.org/blogs/staff/high-importance-lower-expectations-energy-crop-yields-edition.
Download the paper at Science Direct.
The International Council on Clean Transportation is an independent research organization working on behalf of transportation air quality and energy eﬃciency regulators worldwide. It was founded in 2001 to provide reliable, independent technical expertise on vehicles and fuels to the public sector. The ICCT participants’ council comprises high-level civil servants, academic researchers, and independent transportation and environmental policy experts, who come together at regular intervals to collaborate as individuals on setting a global agenda for clean transportation. The ICCT maintains offices in Berlin, Brussels, China, and London, as well as in the U.S. It is funded principally by private foundations, such as the Hewlett Foundation and ClimateWorks in the United States and Stiftung Mercator in Europe.
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