Conversion of high sugar grasses to alcohol based transport fuel (GRASSOHOL)

Under the terms of the Renewable Transport Fuel Obligation (RTFO), the UK is committed to substituting 5.75% of its gasoline consumption with bio-derived fuels by December 2010. This demand is predicted to increase in the future, particularly in response to concerns about climate change and fuel security. Current, biofuel generation in the UK is negligible and demands are met by bioethanol imports from countries such as Brazil. Bioethanol is mainly produced from 'first generation' crops (e.g. maize, wheat, sugar beet and sugar cane) which are characterised by a high non-structural carbohydrate content. The technology involved is straightforward and production has become more price competitive. The feasibility of producing biofuel from such crops in the UK is limited because of the requirement for arable land which is primarily used for food production and the high energy input involved. Production of biofuel from 'second generation' lignocellulosic crops such as grasses offers a potential alternative. Grasslands comprise up to 70% of UK agricultural land greatly exceeding the area used for food crops. Perennial ryegrass achieves similar biomass yields to other lignocellulosic crops used for biofuel production. This crop has a number of traits which are desirable in a fermentable feedstock including a readily available high water-soluble sugar content, high fibre digestibility and a low lignin content in comparison with other candidate lignocellulosic crops. Perennial grasses have low annual input requirements and contribute to the rural landscape, maintaining biodiversity and environmentally sensitive landscapes which have major attractants for the tourist industry. UK farmers have the necessary expertise involved in management of these grasses which can be harvested over a long season and stored over winter. We propose that perennial ryegrass can provide an environmentally and economically viable feedstock for the production of bioethanol and that existing biological material and technologies can be readily adapted to achieve this. The main challenges for development of a sustainable, low input process, for conversion of grasses to bioethanol will be addressed in this programme. This will include reducing the major operating costs, maximising yield and carbon cost efficiency. IGER's large selection of ryegrass germplasm will be exploited to select for appropriate varieties, in particular, high sugar perennial grasses with high digestibility (low lignin). The legume, white clover, will be included in grass swards to provide nitrogen and minimise green house gas emissions associated with artificial fertilizer. This programme will test the feasiblility of juicing on-farm to generate two separate feedstocks; a water soluble carbohdyrate (fructan) rich liquid fraction and a high dry-matter stable lignocellulosic fraction. Procedures for handling, preserving/stabilising and transporting these feedstocks will be assessed. A major aim is to maximise utilisation of the full range of sugars in perennial ryegrass for fermentation to ethanol. This will be achieved by using an appropriate combination of pre-treatments, enzymes, yeast and an ethanol producing thermophilic micro-organsim, taking advantage of TMO Renewables groundbreaking method for producing ethanol from almost any type of biomass. Fermentation conditions will be optimised to maximise ethanol production from ryegrass feedstock both at laboratory and pilot scale. The carbon and energy balance as well as the economic viability of these processes will be evaluated. Data generated by this programme will provide valuable information for accurate comparisons with other crops used in bioethanol production.

Current biofuel generation in the UK will not meet the UK's Renewable Transport Fuel Obligation. The production of bioethanol from 'first generation' crops (e.g. maize, wheat, etc.) in the UK is limited by the requirement for arable land (primarily used for food production) and high energy inputs. Grasses, which comprise up to 70% of UK agricultural land, offer a potential alternative. Perennial ryegrass, which can achieve similar biomass yields to other lignocellulosic biofuel crops, contains high quantities of readily available water-soluble sugars, has high fibre digestibility, low lignin content, low annual input requirements while contributing to the rural landscape, maintaining biodiversity and environmentally sensitive landscapes. Our objective is to provide an environmentally and economically viable feedstock for the production of bioethanol using IBER's large collection of ryegrass germplasm. The legume, white clover, will be included in grass swards to provide nitrogen and minimize green house gas emissions associated with artificial fertilizer. From the grass, two separate feedstocks will be produced; a water soluble carbohydrate rich liquid fraction and a high dry-matter stable lignocellulosic fraction. Procedures for handling, preserving/stabilizing and transporting these feedstocks will be assessed. The utilization of the full range of sugars for fermentation to ethanol will be achieved by using an appropriate combination of pre-treatments, enzymes, yeast and an ethanol producing thermophilic micro-organism which can ferment a wide range of C5 and C6 sugars. Fermentation conditions will be optimized to maximize ethanol production both at laboratory and pilot scale. The carbon and energy balance as well as the economic viability of these processes will be evaluated. Data generated by this programme will provide information for accurate comparisons with other crops used in bioethanol production.