Raining on Cellulosic Ethanol’s Parade

Writer Alyssa Danigelis posted an item of interest on Discovery News last month detailing the latest supposed “blow” to the biofuel industry. The writer highlights a new study in Agronomy Journal in which Kansas State University Assistant Professor Humberto Blanco-Canqui concludes, “Only a small fraction (about 25%) of residue might be available for removal, depending on soil type and climate. This small amount of crop residues is not economically feasible nor logistically possible.”

Matt Merritt of POET and Professor Bruce Dale of Michigan State University have posted responses to Blanco-Canqui’s conclusion. What they drive at is that the fraction of agricultural residue that can be removed from a field depends greatly on the geography and management of that field. Jim Hettenhaus of CEA Inc. has helped lead a study in Imperial, Neb., to determine optimum stover removal and storage practices based on local variables in soil type and weather, and he was kind enough to share preliminary results (See Stover Value Review). And several years ago, BIO published a study, Achieving Sustainable Production of Agricultural Biomass for Biorefinery Feedstock, that indicates the amount of residue removed from a field can be increased through adoption of no-till soil management.

The economic feasibility of harvesting crop residues for cellulosic biofuel production, of course, is highly dependent on the individual farmer. Aside from its value in managing organic carbon in tilled soil, crop residues are also currently used as animal bedding and other things. Individual farmers are thus faced with a decision whether the biofuel market for crop residues is attractive enought to induce them to change their field management practices, buy new harvesting equipment, and forego current uses of residues to instead transport them to a collection or storage facility. The same economic question faces any farmer who considers growing switchgrass or short-rotation woody crops, which are favored by Blanco-Canqui. And for the most part, biofuel production does not yet provide a compelling market for farmers, although POET and others have begun contracting directly with farmers to harvest and deliver small, easily harvested amounts of residues to pilot production plants.

Perhaps the most pernicious assumption behind many academic and press articles is that cellulosic ethanol “proposes turning waste into something useful.” Considering the costs of trash removal for most cities, even trash won’t be considered “waste” if it becomes a valuable feedstock for biofuels. Just as pernicious, perhaps, is the industry’s assumption that an apparently abundant resource is naturally a cheap resource. Inevitably, these assumptions have led everyone to search for the perfect energy source – one that doesn’t compete with food production, doesn’t require petroleum fertilizers, and doesn’t come with the dreaded “unintended consequences.” A far better plan would be to seek sources that best fit a local area, and then look for ways to manage them in economically and environmentally sound ways.