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

根据可再生运输燃料义务(RTFO)的条款，英国承诺在2010年12月之前用生物衍生燃料取代5.75%的汽油消费。预计未来这种需求将会增加，特别是为了应对对气候变化和燃料安全的担忧。目前，英国的生物燃料发电量微不足道，需求由从巴西等国进口的生物乙醇来满足。生物乙醇主要由以高非结构性碳水化合物含量为特征的“第一代”作物(如玉米、小麦、甜菜和甘蔗)生产。所涉及的技术简单明了，生产已变得更具价格竞争力。在英国，用这种作物生产生物燃料的可行性有限，因为需要耕地，而耕地主要用于粮食生产，而且涉及的能源投入很高。从草类等“第二代”木质纤维作物中生产生物燃料提供了一种潜在的替代方案。草地占英国农业用地的70%，大大超过了种植粮食作物的面积。多年生黑麦草的生物量产量与用于生产生物燃料的其他木质纤维作物相似。与其他候选木质纤维作物相比，这种作物具有许多可发酵原料所需的特征，包括容易获得的高水溶性糖含量、高纤维消化率和低木质素含量。多年生草本植物的年投入需求较低，有助于乡村景观，维持生物多样性和对环境敏感的景观，这些景观对旅游业具有主要吸引力。英国农民拥有管理这些草所需的专业知识，这些草可以在漫长的季节收获，并在冬季储存。我们认为，多年生黑麦草可以为生产生物乙醇提供一种在环境和经济上可行的原料，现有的生物材料和技术可以很容易地实现这一点。本方案将解决发展可持续的、低投入的草本植物转化为生物乙醇工艺的主要挑战。这将包括降低主要运营成本，最大限度地提高产量和碳成本效率。将利用Iger的大量黑麦草种质资源来选择合适的品种，特别是具有高消化率(低木质素)的高糖多年生牧草。这种豆科植物，白三叶，将被种植在草地上，以提供氮素，并最大限度地减少与人造肥料相关的温室气体排放。这项计划将测试农场榨汁生产两种不同原料的可行性；一种富含水溶性碳酸盐(果聚糖)的液体组分和一种高干物质稳定的木质纤维组分。将评估处理、保存/稳定和运输这些原料的程序。一个主要目标是最大限度地利用多年生黑麦草中的所有糖类发酵生产乙醇。这将通过使用适当的预处理、酶、酵母和产生酒精的嗜热微生物的组合来实现，利用TMO可再生能源的开创性方法从几乎任何类型的生物质中生产乙醇。将优化发酵条件，以最大限度地提高黑麦草原料在实验室和中试规模上的乙醇产量。将对这些过程的碳和能源平衡以及经济可行性进行评估。该方案产生的数据将为准确比较生物乙醇生产中使用的其他作物提供有价值的信息。

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.