Comment

456 © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd

Perhaps

the greatest

challenge that

remains is the

cost of the

feedstock

Affordable feedstocks for biorefi neries

In 2014, biorefi neries producing a mix of materials, chemicals, fuels, and energy are tantalizingly close, but commercial success remains elusive. It is clear that success in this area will involve reducing process costs – new

enzymes and micro-organisms are being brought to bear which will help with this challenge. It is also evident that the markets for new, benefi cial products must be developed – a process which takes time and oft en requires signifi cant support from governments. Perhaps the greatest challenge that remains is the cost of feedstock. Accessing inexpensive feedstocks, in the short to mid-term, is most likely done by gathering residues from agricultural and forest har-vests; signifi cant eff orts to develop these supply chains are underway. Serious questions have been raised about the environmental footprint of biorefi nery products, however, which jeopardize future government programs for the biorefi nery and which could limit the market for biorefi nery products.  

Th e use of residual feedstocks from agriculture or forestry has created per-haps the most controversy. Recently the case for cellulosic ethanol derived from crop residues has been challenged by a number of high-profi le studies. In the USA, a paper by Liska et al.1 published in Nature Climate Change found that corn stover removal would signifi cantly impact soil carbon, adding as much as 90 g CO 2 per megajoule of biofuel, rendering the product unable to meet requirements for greenhouse gas (GHG) reduction compared to gasoline. While other studies suggest that stover recovery at lower rates does not seri-ously change soil emissions,2 the suitability of this feedstock has been called into question.

Confusing the issue is the fact that the successful biorefi nery will address product needs across multiple markets. Th e combined benefi t of developing these products – and off setting non-renewable requirements – would change

Warren Mabee, Queen’s University, CanadaContact: warren.mabee@queensu.ca

Comment W Mabee

457 © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 8:456–457 (2014); DOI: 10.1002/bbb

the relative environmental impacts of residue recovery. Th ere is a need for clarity in conducting life cycle assessment of emerging biorefi neries.

Th e science of life cycle assessment is at a stage where it is not unusual to see a range of results, linked to the assumptions and system boundaries used by the modeler. In the European Union, the BioGrace project highlighted the need to harmonize the calculation of life cycle impacts.3 Th is project calls for legislative action to create a level playing fi eld for advanced biofuels in the European context. It is high time that the USA and Canada consider similar action, to clarify the benefi ts of biorefi nery products and to better focus future research eff orts.

References1. Liska AJ, Yang H, Milner M, Goddard S, Blanco-Canqui H, Pelton MP et al., Biofuels from crop residue can reduce soil carbon and

increase CO2 emissions. Nature Climate Change 4:398–401 (2014).

2. Jin VL, Baker JM, Johnson JM-F, Karlen DL, Lehman RM, Osborne SL et al., Soil greenhouse gas emissions in response to corn stover removal and tillage management across the US corn belt. Bioenerg Res 7:517–527 (2014).

3. Hennecke AM, Faist M, Reinhardt J, Junquera V, Neeft J and Fehrenbach H. Biofuel greenhouse gas calculations under the European Renewable Energy Directive – A comparison of the BioGrace tool vs. the tool of the Roundtable on Sustainable Biofuels. Applied Energy 102(2):55–62 (2014).

Warren Mabee, Queen’s University, Canada

DOI: 10.1002/bbb.1507