Importance of policy support and feedstock prices on economic feasibility of bioethanol production from wheat straw in the UK

The economic feasibility of producing bioethanol from wheat straw in the UK using various state-of-the-art pretreatment technologies (steam explosion with and without acid catalyst, liquid hot water, dilute acid and wet oxidation) is assessed in this study. Under the current-technology base-case modeled using high enzyme loadings demonstrated at the laboratory-scale, wet oxidation pretreatment had the lowest minimum ethanol selling price (MESP) of £0.347/L ($2.032/gal). A contribution analysis showed feedstock price and enzyme cost were the two greatest contributors to the MESP, which led to a prospective case study and sensitivity analysis for assessing the effects of these two factors on the potential for economically competitive wheat straw-to-bioethanol UK supply chains. Prospective case studies modeled with a reduced enzyme loading and cost, demonstrated that although pretreatment scenarios with liquid hot water and steam explosion without acid catalyst were the closest to petrol pump prices, policy support in the form of tax exemptions could significantly enhance competitiveness of bioethanol with conventional fuel. A sensitivity analysis of feedstock prices also demonstrated that access to wheat straw prices of £35/t or lower would allow bioethanol production to be competitive with petrol under the best case scenario.