Food and bioenergy: reviewing the potential of dual-purpose wheat crops

Abstract

Within the bioenergy debate, the ‘food vs. fuel’ controversy quickly replaced enthusiasm for biofuels derived from first-generation feedstocks. Second-generation biofuels offer an opportunity to produce fuels from dedicated energy crops, waste materials or coproducts such as cereal straw. Wheat represents one of the most widely grown arable crops around the world, with wheat straw, a potential source of biofuel feedstock. Wheat straw currently has limited economic value; hence, wheat cultivars have been bred for increased grain yield; however, with the development of second-generation biofuel production, utilization of straw biomass provides the potential for ‘food and fuel’. Reviewing the evidence for the development of dual-purpose wheat cultivars optimized for food grain and straw biomass production, we present a holistic assessment of a potential ideotype for a dual-purpose cultivar (DPC). An ideal DPC would be characterized by high grain and straw yields, high straw digestibility (i.e. biofuel yield potential) and good lodging resistance. Considerable variation in these traits exists among current wheat cultivars, facilitating the selection of improved individual traits; however, increasing straw yield and digestibility could potentially have negative trade-off impacts on grain yield and lodging resistance, reducing the feasibility of a single ideotype. Adoption of alternative management practices could potentially increase straw yield and digestibility, albeit these practices are also associated with potential trade-offs among cultivar traits. Benefits from using DPCs include reduced logistics costs along the biofuel feedstock supply chain, but practical barriers to differential pricing for straw digestibility traits are likely to reduce the financial incentive to farmers for growing higher ‘biofuel-quality’ straw cultivars. Further research is required to explore the relationships among the ideotype traits to quantify potential DPC benefits; this will help to determine whether stakeholders along the bioenergy feedstock supply chain will invest in the development of DPCs that provide food and fuel potential.