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，英国承诺到2010年12月将其5.75%的汽油消费用生物衍生燃料替代。预计未来这一需求将增加，特别是为了应对对气候变化和燃料安全的关切。目前，英国的生物燃料发电量可以忽略不计，需求由巴西等国家的生物乙醇进口来满足。生物乙醇主要由“第一代”作物（如玉米、小麦、甜菜和甘蔗）生产，这些作物的特点是非结构性碳水化合物含量高。所涉及的技术很简单，生产也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是有限的，因为需要耕地，而耕地主要用于粮食生产，而且所涉及的能源投入很高。从“第二代”木质纤维素作物（如草）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%，大大超过了粮食作物的种植面积。多年生黑麦草的生物量产量与用于生物燃料生产的其他木质纤维素作物相似。与其它候选木质纤维素作物相比，这种作物具有许多在可发酵原料中所需的特性，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。多年生牧草每年的投入要求低，有助于农村景观，保持生物多样性和环境敏感的景观，对旅游业有重要的吸引力。英国农民拥有管理这些草的必要专业知识，这些草可以在很长一段时间内收获，并在冬季储存。我们建议，多年生黑麦草可以提供一个环境和经济上可行的原料生产生物乙醇和现有的生物材料和技术可以很容易地适应实现这一目标。该方案将解决开发可持续的低投入工艺，将草转化为生物乙醇的主要挑战。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。IGER的大量选择的黑麦草种质将被用来选择合适的品种，特别是高糖多年生草具有高消化率（低木质素）。豆科植物，白色三叶草，将被包括在草地，以提供氮和尽量减少与人造肥料相关的绿色房屋气体排放。该计划将测试农场榨汁的可行性，以产生两种单独的原料;富含水溶性碳水化合物（果聚糖）的液体部分和高干物质稳定的木质纤维素部分。将评估处理、保存/稳定和运输这些原料的程序。一个主要的目标是最大限度地利用多年生黑麦草中的各种糖发酵成乙醇。这将通过使用预处理，酶，酵母和乙醇生产嗜热微生物的适当组合来实现，利用TMO Renewables开创性的方法从几乎任何类型的生物质生产乙醇。发酵条件将被优化，以最大限度地提高乙醇生产从黑麦草原料在实验室和中试规模。将评估这些工艺的碳和能量平衡以及经济可行性。该方案产生的数据将为与生物乙醇生产中使用的其他作物进行准确比较提供有价值的信息。

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.