能源植物甜高粱种质资源和分子生物学研究进展

世界能源危机和全球生态环境日益恶化迫使人们急需开发可再生能源。生物质能源作为一种清洁的可再生能源已受到世界各国的高度重视。发展生物质能源的瓶颈之一是生物质原料不足。甜高粱的生物学产量和含糖量极高,同时兼有耐旱、耐涝、耐贫瘠和耐盐碱等诸多优良特性,被认为是最具开发潜力的能源植物之一。该文从甜高粱的分类学、生物学特点、种质资源评价、功能基因以及基因组信息等方面综述了甜高粱的最新研究进展和存在的问题,并展望了甜高粱作为能源植物的研发前景。     

甜高粱在生物能源产业发展中的前景

为了应对全球能源危机和温室气体排放引起的全球气候迅速变化所带来的不利影响,世界上许多国家的科学家们都在致力于探索、开发和利用清洁的可再生能源。同时为了国家的粮食安全,发展能源植物不得不选择能生长在边际性贫瘠土壤的非粮作物。甜高粱之所以成为目前公认的最具有应用前景的可再生能源作物之一,是由于其具有很多独特的优势:甜高粱含糖量和甘蔗相当,其生物量大、生长周期短、抗旱、耐盐碱和耐贫瘠等特性,使得其在燃料乙醇原料中所占的比例越来越大,很多国家把它作为甘蔗的互补作物甚至替代作物。在未来生物能源发展中,甜高粱必然凭借其自身优势发挥重要作用。     

聚焦生物质能源

<正>资源短缺、能源危机和环境污染己成为全球关注的严重问题。开发利用可再生的生物质资源对于解决人类发展面临的资源与环境危机具有重要意义。目前,以生物质能源为主的生物质开发利用备受世界各国政府和科学家的关注。生物质能源开发与利用是把能源植物和农业废弃物等生物质原料利用     

基于文献计量学的能源植物国际研究趋势与发展格局

随着环境的不断恶化与化石资源的急剧消耗,世界各国都在加快可再生能源(尤其是生物质能源)的研发进程,以保障国家能源安全,应对全球气候变化。其中,能源植物的开发利用是提供生物质原料的重要途径之一。分析能源植物的国内外研究进展,把握其发展趋势,结合我国的特点和需求,有助于支持基础研究,促进源头创新。以ISI Web of Science数据库为数据来源,Thomson Data Analyzer为工具,从文献计量学的角度分析能源植物的国际发展态势。     

应用固定化酵母流化床反应器发酵甜高粱茎秆汁液制取燃料酒精的研究

应用固定化酵母细胞流化床生物反应器发酵甜高粱茎秆汁液制取燃料酒精的研究是辽宁省科委下达的重点课题。由中科院林土所和沈阳农业大学完成。能源是世界各国所关注的问题。一些先进国家和地区能源的紧张状况,严重地影响着工农业生产和人们的生活。为了缓解石油、煤和天然气等能源供应的紧张状况,必需寻觅新的能源、开发非传统的和可再生的能源,“绿色能源”引起了世界各国的普遍重视,其中最受重视的途径之一是生产被称为“绿色石油”的燃料酒精。     

生物燃料发展概况

近几年来,国际油价不断上涨,不可再生能源资源日益减少,石油能源危机即将来到。面对即将到来的能源危机,全世界都认识到必须采取开源节流的战略,即一方面节约能源,另一方面开发新能源。全球正在大力开发生物质能,太阳能、水能、风能和地热能等可再生能源并开始逐步替代矿物能源。其中,以生物质能发展最为迅速,将成为发展的重点。生物质能源的开发与利用主要包括两方面：生物质能源发电和制备生物液体燃料如生物乙醇,生物丁醇、生物柴油等。生物质液体燃料作为液体交通燃料的唯一可再生替代能源,得到了迅猛发展。[编者按]     

微藻生物炼制研究现状及发展策略

前言 资源短缺和环境污染问题已成为制约世界经济可持续发展的瓶颈.以可再生且环境友好的生物质资源替代化石资源已成为解决资源和环境问题的主要途径之一①,Henry R.Bungay②在1982年针对生物质资源开发与利用提出了生物炼制(Bio-Refinery)这一概念.美国国家可再生能源实验室(U.S.NREL)将生物炼制定义为将生物质原料转化为燃料、电热能和化学产品的生物质转化工艺与设备的集成.生物炼制的原料主要有:含纤维素的生物质和废弃物、谷类或玉米、青草、苜蓿、微藻等.其中微藻是一类在海洋、湖泊等水体中广泛分布的微型植物,能够利用光能固定CO2实现自养,其细胞中含有丰富的油脂、色素、蛋白质、维生素等成分.微藻生物炼制是以微藻为原料,生产各种化学品、燃料、生物基材料和食品等产品的工艺与设备的集成.     

燃烧式生物质发电技术介绍

利用生物质可再生能源发电是解决能源短缺的途径之一,开发"绿色能源"已成为当今世界工业化国家开源节流、化害为利和保护环境的重要手段。根据国家发改委最新制定的《可再生能源中长期发展规划》,到2020年,我国生物质能发电装机20000MW。     

合成生物学在生物燃料上的应用趋势及展望

近年来,世界各国都面临着化石能源日益枯竭、人口增长、温室气体排放增加、环境日益恶化等危机,寻找可再生的清洁替代能源已成为人类最紧迫的任务之一,燃料乙醇、生物柴油等可再生的生物质能源成为世界各国研究的重点。尽管近年来生物燃料的研发已经取得了很多进展,但其商业化发展仍然面临着转化效率低、生产成本高等难题。     

利用木质纤维素生产丁醇的研究进展

随着化石燃料的逐年减少,以生物质为原料的生物能源研究近年来成为能源领域的研究热点,充分利用可再生生物质为发展经济的生物燃料生产工艺提供了一个极好的机会。与燃料乙醇和生物柴油相比,生物丁醇更具有优越性,以可再生木质纤维素生物质为原料进行发酵生产丁醇在近年来被广泛的研究。对于利用可再生生物质为原料生产丁醇,需要解决原料的选择、产品收率低、抑制物对生产菌株毒性等问题。本文对以木质纤维素生物质为原料进行生物丁醇发酵过程中的原料预处理、抑制物对丁醇生产菌的影响,以及水解液的脱毒和耐抑制物菌株的选育等方面进行综述,并对以木质纤维素生产燃料丁醇所面临的机遇与问题进行了简要评述。     

Legacy effects of individual crops affect N2O emissions accounting within crop rotations

Uruguay is pursuing renewable energy production pathways using feedstocks from its agricultural sector to supply transportation fuels, among them ethanol produced from commercial technologies that use sweet and grain sorghum. However, the environmental performance of the fuel is not known. We investigate the life cycle environmental and cost performance of these two major agricultural crops used to produce ethanol that have begun commercial production and are poised to grow to meet national energy targets for replacing gasoline. Using both attributional and consequential life cycle assessment (LCA) frameworks for system boundaries to quantify the carbon intensity, and engineering cost analysis to estimate the unit production cost of ethanol from grain and sweet sorghum, we determined abatement costs. We found 1) an accounting error in estimating N₂O emissions for a specific crop in multiple crop rotations when using Intergovernmental Panel on Climate Change(IPCC) Tier 1 methods within an attributional LCA framework, due to N legacy effects; 2) choice of baseline and crop identity in multiple crop rotations evaluated within the consequential LCA framework both affect the global warming intensity (GWI) of ethanol; and 3) although abatement costs for ethanol from grain sorghum are positive and from sweet sorghum they are negative, both grain and sweet sorghum pathways have a high potential for reducing transport fuel GWI by more than 50% relative to gasoline, and are within the ranges targeted by the US renewable transportation fuel policies.     

Impact of Storage Time on the Juice and Sugars Extracted from Chopped and Whole Stalk Sweet Pearl Millet and Sweet Sorghum Biomass

Since they have a high concentrations of fermentable sugars, sweet pearl millet and sweet sorghum are two interesting crops for bioethanol production. However, if the juice is not extracted from the biomass immediately after harvest, the biomass has to be transported and stored for further juice extraction. This delay could affect the amount of juice extracted and its sugar concentration. This paper presents the results of 3 years of experiments where different storage modes (chopped and whole stalks) and various storage time (0 to 14 days) were applied on two different crop species (sweet pearl millet and sweet sorghum). Storing sweet pearl millet as whole stalks for 2 weeks resulted in a water-soluble carbohydrate (WSC) concentration decrease of 52 %, while no significant decrease of the WSC concentration was observed for sweet sorghum. Whole stalks storage is much more efficient than storing the biomass chopped to avoid a rapid sugar loss. However, more juice can be extracted from stored chopped biomass than from stored whole stalks biomass. If the juice cannot be extracted quickly after the harvest, the biomass can be stored as whole stalks to avoid rapid sugar deterioration, especially for sweet sorghum.     

Feedstock Crop Production Costs and Biofuel Feedstock Input Costs Associated with the Production of Energy Cane and Sweet Sorghum in the Southeastern USA

Concentration of biofuel feedstock crop production in specific regions of the USA is dependent on the relative comparative advantage of production in a specific region based on several agronomic and economic factors. For the southeastern region of the USA, energy cane and sweet sorghum have been identified as two feedstock crops with the greatest potential for further development of production. This study utilized field trial data from yield studies in Louisiana to develop estimates of feedstock crop production costs and biofuel feedstock input costs for these two crops. Results indicated that feedstock production costs on a harvest yield basis, as well as the related dry matter basis, were heavily dependent on yield level. Economic research from this study indicated that energy cane had a slight cost advantage compared with sweet sorghum, although production of sorghum in certain periods during the growing season was very cost competitive with energy cane.     

Agronomic Considerations for Sweet Sorghum Biofuel Production in the South-Central USA

Sweet sorghum (Sorghum bicolor (L.) Moench) is currently recognized throughout the world as a highly promising biomass energy crop. Production systems and management practices for sweet sorghum have not been fully developed for the USA, although sporadic research efforts during recent decades have provided some insights into production of sweet sorghum primarily for fermentable sugar production. Field plot experiments were conducted at sites across Louisiana to assess biomass and sugar yield responses to N fertilizer, plant density, and selected cultivars. Although linear increases in stem biomass production and fermentable sugar yield were obtained with increasing N fertilizer rate under irrigated conditions, most of the increase was from the initial 45 kg N ha⁻¹ increment. Nitrogen fertilization increased stem biomass production but not fermentable sugar yield in some non-irrigated environments. Increased plant density contributed to fermentable sugar yield only under growth-limiting conditions, particularly under limited soil moisture. Location effects indicate that sweet sorghum may not be suitable for some sub-optimal cropland and pasture environments in Louisiana. During the primary growing season, cultivar did not affect fermentable sugar yields, although Dale was consistently high in sugar concentration during this period. Nitrogen fertilizer increased fermentable sugar yields only when moisture was not limiting. Overall results indicate that in environments where soil moisture limits plant growth, sugar yield responses are likely from increased plant density and not from increased N fertilization.     

Assessment of Sugarcane Billet Harvester on Recovery of Sweet Sorghum Biomass for Ethanol Production

Sweet sorghum (Sorghum bicolor L. Moench) is a promising bioenergy crop for the production of ethanol and bio-based products. Sugarcane billet harvesters can be used to harvest sweet sorghum. Multiple extractor fan speed settings of these harvesters allow for separating the extraneous matter in the feedstock, which has been associated with increased milling throughput and better juice quality at the processing facility. This removal is not completely selective, and some stalk material is also lost. These losses can be higher for sweet sorghum than sugarcane due its lower weight. This paper presents an assessment of how the speed of the primary extractor fan of a sugarcane billet combine used for harvesting sweet sorghum affects the biomass yield, biomass losses, and quality at delivery for the production of ethanol from extracted juice and fiber. Three primary extractor fan speeds (0, 800, and 1100 rpm) were evaluated. Higher fan speeds decreased fresh biomass yields by up to 28.3 Mg ha^?1. Juice quality was not significantly different among treatments. Ethanol yield calculated from sweet sorghum harvested at 0 rpm was 6075 L ha^?1. This value decreased by about half for material harvested at 1100 rpm due to the differences in biomass yield.     

Techno-Economic Evaluation of Cellulosic Ethanol Production Based on Pilot Biorefinery Data: a Case Study of Sweet Sorghum Bagasse Processed via L+SScF

Replacing fossil fuels with renewable fuels derived from lignocellulosic biomass can contribute to the mitigation of global warming and the economic development of rural communities. This will require lignocellulosic biofuels to become price competitive with fossil fuels. Techno-economic analyses can provide insights into which parts of the biofuel production process need to be optimized to reduce cost or energy use. We used data obtained from a pilot biorefinery to model a commercial-scale biorefinery that processes lignocellulosic biomass to ethanol, with a focus on the minimum ethanol selling price (MESP). The process utilizes a phosphoric acid-catalyzed pre-treatment of sweet sorghum bagasse followed by liquefaction and simultaneous saccharification and co-fermentation (L+SScF) of hexose and pentose sugars by an engineered Escherichia coli strain. After validating a techno-economic model developed with the SuperPro Designer software for the conversion of sugarcane bagasse to ethanol by comparing it to a published Aspen Plus model, six different scenarios were modeled for sweet sorghum bagasse Under the most optimistic scenario, the ethanol can be produced at a cost close to the energy-equivalent price of gasoline. Aside from an increase in the price of gasoline, the gap between ethanol and gasoline prices could also be bridged by either a decrease in the cost of cellulolytic enzymes or development of value-added products from lignin.     

Production, transportation and milling costs of sweet sorghum as a feedstock for centralized bioethanol production in the upper Midwest

Sweet sorghum has been identified as a possible ethanol feedstock because of its biomass yield and high concentration of readily fermentable sugars. It has found limited use, however, because of poor post-harvest storage characteristics and short harvest window in cooler climates. Previous research (Bennett, A.S., Anex, R.P., 2008. Farm-gate production costs of sweet sorghum as a bioethanol feedstock. Transactions of the ASABE 51(2), 603-613) indicates that fermentable carbohydrates (FC) can be produced at less expense from sweet sorghum than from corn grain. Previous research, however, did not include costs associated with off-farm transportation, storage, or capital costs associated with milling and energy recovery equipment that are required to provide FC suitable for biological conversion. This study includes these additional costs and reevaluates sweet sorghum as a biocommodity feedstock. A total of eight harvest-transport-processing options are modeled, including 4-row self-propelled and 2-row tractor-pulled forage harvesters, two different modes of in-field transport, fresh processing, on-farm ensilage and at-plant ensilage. Monte Carlo simulation and sensitivity analysis are used to account for system variability and compare scenarios. Transportation costs are found to be significant ranging from $33 to $71 Mg (-1) FC, with highest costs associated with at-plant ensilage scenarios. Economies of scale benefit larger milling equipment and boiler systems reducing FC costs by more than 50% when increasing annual plant capacity from 37.9 to 379 million liters. Ensiled storage of high moisture sweet sorghum in bunkers can lead to significant losses of FC (>20%) and result in systems with net FC costs well above those of corn-derived FC. Despite relatively high transport costs, seasonal, fresh processed sweet sorghum is found to produce FC at costs competitive with corn grain derived FC.     

The production‐ecological sustainability of cassava,sugarcane and sweet sorghum cultivation for bioethanol in Mozambique

We present an approach for providing quantitative insight into the production‐ecological sustainability of biofuel feedstock production systems. The approach is based on a simple crop‐soil model and was used for assessing feedstock from current and improved production systems of cassava for bioethanol. Assessments were performed for a study area in Mozambique, a country considered promising for biomass production. Our focus is on the potential role of smallholders in the production of feedstock for biofuels. We take cassava as the crop for this purpose and compare it with feedstock production on plantations using sugarcane, sweet sorghum and cassava as benchmarks. Production‐ecological sustainability was defined by seven indicators related to resource‐use efficiency, soil quality, net energy production and greenhouse gas (GHG) emissions. Results indicate that of the assessed systems, sugarcane performed better than cassava, although it requires substantial water for irrigation. Targeted use of nutrient inputs improved sustainability of smallholder cassava. Cassava production systems on more fertile soils were more sustainable than those on less fertile soils; the latter required more external inputs for achieving the same output, affecting most indicators negatively and reducing the feasibility for smallholders. Cassava and sweet sorghum performed similarly. Cassava production requires much more labour per hectare than production of sugarcane or sweet sorghum. Production of bioethanol feedstock on cultivated lands was more sustainable and had potential for carbon sequestration, avoiding GHG emissions from clearing natural vegetation if new land is opened.     

Ethanol production potential of sweet sorghum assessed using forage fiber analysis procedures

Sweet sorghum (Sorghum bicolor (L.) Moench) is widely recognized as a highly promising biomass energy crop with particular potential to complement sugarcane production in diversified cropping systems. Agronomic assessments have led to identification of four cultivars well suited for such sugarcane‐based production systems in southern Louisiana. Sweet sorghum biofuel production systems are currently being developed, and research producing large sample numbers requiring ethanol yield assessment is anticipated. Fiber analysis approaches developed for forage evaluation appear to be useful for screening such large numbers of samples for relative ethanol yield. Chemical composition, forage fiber characteristics, digestibility, and ethanol production of sweet sorghum bagasse from the four cultivars were assessed. Measures of detergent fiber, lignin, and digestibility were highly correlated with ethanol production (P < 0.01). The best linear regression models accounted for about 80% of the variation among cultivars in ethanol production. Bagasse from the cultivar Dale produced more ethanol per gram of material than any of the other cultivars. This superior ethanol production was apparently associated with less lignin in stems of Dale. Forage evaluation measures including detergent fiber analyses, in vitro digestibility, and an in vitro gas production technique successfully identified the cultivar superior in ethanol yield indicating their usefulness for screening sweet sorghum samples for potential ethanol production in research programs generating large sample numbers from evaluations of germ plasm or agronomic treatments. These screening procedures reduce time and expense of alternatives such as hexose sugar assessment for calculating theoretical ethanol yield.