Life cycle energy and greenhouse gas emissions for an ethanol production process based on blue-green algae

Ethanol can be produced via an intracellular photosynthetic process in cyanobacteria (blue-green algae), excreted through the cell walls, collected from closed photobioreactors as a dilute ethanol-in-water solution, and purified to fuel grade ethanol. This sequence forms the basis for a biofuel production process that is currently being examined for its commercial potential. In this paper, we calculate the life cycle energy and greenhouse gas emissions for three different system scenarios for this proposed ethanol production process, using process simulations and thermodynamic calculations. The energy required for ethanol separation increases rapidly for low initial concentrations of ethanol, and, unlike other biofuel systems, there is little waste biomass available to provide process heat and electricity to offset those energy requirements. The ethanol purification process is a major consumer of energy and a significant contributor to the carbon footprint. With a lead scenario based on a natural-gas-fueled combined heat and power system to provide process electricity and extra heat and conservative assumptions around the ethanol separation process, the net life cycle energy consumption, excluding photosynthesis, ranges from 0.55 MJ/MJ(EtOH) down to 0.20 MJ/ MJ(EtOH), and the net life cycle greenhouse gas emissions range from 29.8 g CO?e/MJ(EtOH) down to 12.3 g CO?e/MJ(EtOH) for initial ethanol concentrations from 0.5 wt % to 5 wt %. In comparison to gasoline, these predicted values represent 67% and 87% reductions in the carbon footprint for this ethanol fuel on a energy equivalent basis. Energy consumption and greenhouse gas emissions can be further reduced via employment of higher efficiency heat exchangers in ethanol purification and/ or with use of solar thermal for some of the process heat.     

木薯燃料乙醇生产过程能量综合利用模式探讨

分析了现有木薯燃料乙醇生产工艺,重点介绍了降低木薯燃料乙醇生产过程中能耗的途径,并提出了木薯燃料乙醇生产过程中能量综合利用模式。     

四川燃料乙醇产业发展综述

随着能源供应日趋紧张和生态环境不断恶化,以燃料乙醇为代表的生物质液体燃料开发利用受到各国重视,得以迅速发展。我国以消化“陈化粮”为主要目标的燃料乙醇发展已历时多年,具备一定的产业规模和应用基础。出于对粮食安全的重视,国家鼓励利用边际性土地种植木薯、甘薯、甘蔗和甜高粱等非粮食类作物发展燃料乙醇。本课题历时3年的研究,收集了大量数据,通过对原料、规模、布局、市场、政策等方面研究,对四川省燃料乙醇产业发展提出可操作的建议,有关内容正在实施中。     

木薯燃料乙醇产业发展状况和趋势

通过回顾中粮集团木薯燃料乙醇项目的进程,重点介绍了木薯燃料乙醇产业发展现状和中粮木薯燃料乙醇装置技术特点。提出了在低碳经济的背景下,木薯燃料乙醇产业发展趋势。     

Selection and Characterization of Endomycopsis fibuligera Strains for One-step Fermentation of Starch to Ethanol

In a step-wise systematic selection, a strain of Endomycopsis fibuligera NRRL 76 was found to be better than the other strains tested in the production of α-amylase and glucoamylase as well as ethanol directly from sugary and starchy substrates. Comparatively, the strain tolerated more ethanol. converted more starch to ethanol, produced less biomass and did not assimilate ethanol. There was an interrelationship between qualitative and quantitative production of amylases and ethanol production in batch fermentation with various strains. The constitutive nature of glucoamylase produced. Us lack of catabo-lite repression and resistance to ethanol inhibition as well as the nature of starch hydrolytic products obtained, appeared to be important characteristic features in the strain for efficient conversion of starch directly to ethanol. Among a wide range of starchy substrates used in ethanol production by the yeast strains, cassava starch and waxy rice were found to be more suitable. When the strain NRRL 76 was grown optimally at pH 6.0 and 30C for 1 d under aeration followed by 3d without aeration, the maximum ethanol concentration was 92.0g/L and 73.5 g/L in media containing 300g/L and 200g/L of cassava starch respectively as compared to 73.5g/L and 77.3g/L of ethanol by another promising strain of Schwanniomyces castellii ATCC 26077, under similar set of conditions. This process of NRRL 76 was compared with other one step processes reported in literature and found to be better than the others. The strain also converted high concentrations of cassava starch (up to 400g/L) and also waxy rice (250g/L) to ethanol satisfactorily.     

木薯燃料乙醇的原料储藏

木薯收获期集中,不适应车用燃料乙醇企业的连续生产要求,因此进行木薯原料的储藏十分必要。安全的原料储藏水分、符合要求的仓储设施、科学合理的储藏方法、及时正确的问题防治保证了木薯燃料乙醇原料的长期储藏,从而有效解决了“原料集中供应”和“企业连续生产”之间的矛盾。     

Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production

The implications for greenhouse gas emissions of optimizing a slow pyrolysis-based bioenergy system for biochar and energy production rather than solely for energy production were assessed. Scenarios for feedstock production were examined using a life-cycle approach. We considered both purpose grown bioenergy crops (BEC) and the use of crop wastes (CW) as feedstocks. The BEC scenarios involved a change from growing winter wheat to purpose grown miscanthus, switchgrass, and corn as bioenergy crops. The CW scenarios consider both corn stover and winter wheat straw as feedstocks. Our findings show that the avoided emissions are between 2 and 5 times greater when biochar is applied to agricultural land (2--19 Mg CO2 ha(-1) y(-1)) than used solely for fossil energy offsets. 41--64% of these emission reductions are related to the retention of C in biochar, the rest to offsetting fossil fuel use for energy, fertilizer savings, and avoided soil emissions other than CO2. Despite a reduction in energy output of approximately 30% where the slow pyrolysis technology is optimized to produce biochar for land application, the energy produced per unit energy input at 2--7 MJ/MJ is greater than that of comparable technologies such as ethanol from corn. The C emissions per MWh of electricity production range from 91-360 kg CO2 MWh(-1), before accounting for C offset due to the use of biochar are considerably below the lifecycle emissions associated with fossil fuel use for electricity generation (600-900 kg CO2 MWh(-1)). Low-temperature slow pyrolysis offers an energetically efficient strategy for bioenergy production, and the land application of biochar reduces greenhouse emissions to a greater extent than when the biochar is used to offset fossil fuel emissions.     

木薯非粮燃料乙醇生产技术进展

对我国木薯非粮食作物生产燃料乙醇生产技术的发展现状及存在的问题进行了综述,并对木薯非粮燃料乙醇产业的健康发展提出了建议。     

酿酒活性干酵母生理特性的研究

建立一种酿酒活性干酵母生理活性的简易评价方法,比较并筛选一株适合以木薯粉水解液发酵发酵生产燃料酒精的活性干酵母。优化2株酿酒活性干酵母的活化条件、生长温度和生长pH值,以木薯粉水解液为发酵液,在最适生长条件下比较两株酵母的生长曲线、发酵强度、耐糖能力、耐温能力和耐酒精能力。选择酿酒活性干酵母Ⅰ作为木薯粉水解液发酵酵母,该酵母在前36h发酵强度高于1g(/L.h),36h后发酵强度迅速下降;耐糖能力为20%,耐受温度是55℃以及耐酒精浓度是7%。     

木薯作为我国燃料乙醇原料的潜力分析

从光合作用、单位面积酒精产量、耐旱、耐贫瘠等方面分析了木薯作为非粮燃料乙醇原料的优势,根据我国对非粮燃料乙醇的需求,分析了我国木薯作为非粮燃料乙醇的潜力,并对发展非粮燃料乙醇木薯原料进行了展望。     

The chemical composition and true metabolisable energy content of cassava root meal imported into Northern Ireland

The chemical composition and true metabolisable energy (TME) content of 10 samples of cassava root meal imported into Northern Ireland were measured. There were no major significant differences in the chemical composition of the native and pelleted cassava. Traces of HCN were found in all the samples and the four mycotoxins for which examinations were carried out were absent. The true metabolisable energy content of the meal was 13.46 MJ kg^?1 as fed, i.e. 15.13 MJ kg^?1 in the dry matter.     

“酒精沼气双发酵耦联工艺”中硫化物对酒精发酵的影响

"酒精沼气双发酵耦联工艺"中硫化物会对酒精发酵产生抑制,不利于工艺的稳定运行。与对照相比,pH 4.0,24 mmol/L的硫化物使酒精发酵时间从48 h延长至318 h,酒精产量由90.73 g/L下降至82.28 g/L,酵母数量由3.78×108/mL下降至2.20×108/mL,甘油产量由6.99 g/L上升至11.02 g/L。甘油产量上升是硫化物存在时酒精产量下降的原因之一。硫化物对酒精发酵的抑制性随添加时间的推迟而减弱,这是因为在酒精发酵过程中,硫化物会以H2S的形式随着CO2一起从发酵液逸出。pH 4.0时,硫化物对酒精发酵的临界抑制浓度为1.2 mmol/L。     

耐热葡萄糖苷酶在木薯原料处理中的应用

木薯是理想的经济作物,可以用来生产木薯淀粉、燃料乙醇、木薯酒等,副产物木薯渣、木薯酒精糟是良好的饲料。但木薯原料中含有有毒物质生氰糖苷,限制了其应用。利用耐热葡萄糖苷酶对木薯原料进行处理,能够有效降低其毒性。     

我国燃料乙醇产业管理体制和运行机制初探

燃料乙醇作为一种绿色可再生能源,在我国石油资源紧缺、环境压力日益加剧的今天,正迎来新一轮发展高潮。本文介绍了我国燃料乙醇现有管理体制和运行机制,初步探讨管理体制和运行机制存在的问题,并从国家和企业两个角度提出了解决问题的相关建议。     

薯类原料生物转化燃料乙醇研究进展

对我国红薯、木薯和马铃薯转化燃料乙醇的发展现状及存在的问题进行了综述.论述了3种原料的生物学特性、种植情况及其燃料乙醇的生产工艺进展,比较了3种原料生产燃料乙醇的经济参数,对当前我国燃料乙醇产业发展提出了建议并展望了薯类乙醇发展的未来.对我国燃料乙醇产业的发展有一定指导意义.     

Energiebedarf und Energiefluß in einer Kartoffelstärkefabrik

Energy Use and Energy Flow in a Potato Starch Plant . The aim of the study was to determine in a potato starch plant the energy flow and energy use to produce various products. The plant requires natural gas and electricity as energy carriers which are converted to steam heat (46.4%), heating gas (17.2%) and electricity (18.7%). The conversion losses amount to 17.3% in total. The end energy is used in large amount for the drying of starch (15.9%) and its modification (24.2%) as well as for the production of potato protein (18.2%) and the evaporation of the remaining potato juice (12.4%). The accumulated specific energy demand shows that the wet starch is the least energy intensive product (10 120 MJ/t d. s.). In comparison dried starch (12 120 MJ/t d. s.), starch derivates (17 840 or 20 900 MJ/t d. s.) and potato protein (41 900 MJ/t d. s.) have a significant higher energy intensity.     

木薯燃料乙醇全生命周期CO_2排放分析——以循环经济为基础

缓解能源紧张、减少CO2温室气体排放保护环境是发展新能源的主要目的。在燃料乙醇项目的前期研究过程中,以循环经济"减量化、再利用、资源化"为指导,优化木薯燃料乙醇全生命周期的生产工艺,减少使用外来碳源,资源化再利用从种植到生产过程中产生的废弃物,做到木薯原料中碳的"吃干榨尽",生产环节实现碳的闭路循环。资源化再利用废弃物可替代原有生产工艺中化石能源的使用,以减少CO2的排放。     

耐高温乙醇酵母的研究现状及进展

乙醇是一种重要的工业原料,同时,乙醇作为一种清洁的可再生能源,可用作液体燃料替代或者部分替代汽油。应用微生物发酵技术将甘蔗、玉米、木薯和纤维类废弃物等转化为燃料乙醇,已成为解决世界能源危机的一条理想途径。本文总结了应用高温驯化、杂交育种、诱变育种、原生质体融合和基因工程等技术选育耐高温酵母的进展,并重点介绍了离子柬生物工程技术的原理及其在选育耐高温酵母应用中的优势。离子柬生物工程技术与传统微生物育种技术、现代生物技术相结合,将大大提高耐高温乙醇酵母菌种的选育效率。     

Policy implications of uncertainty in modeled life-cycle greenhouse gas emissions of biofuels

Biofuels have received legislative support recently in California's Low-Carbon Fuel Standard and the Federal Energy Independence and Security Act. Both present new fuel types, but neither provides methodological guidelines for dealing with the inherent uncertainty in evaluating their potential life-cycle greenhouse gas emissions. Emissions reductions are based on point estimates only. This work demonstrates the use of Monte Carlo simulation to estimate life-cycle emissions distributions from ethanol and butanol from corn or switchgrass. Life-cycle emissions distributions for each feedstock and fuel pairing modeled span an order of magnitude or more. Using a streamlined life-cycle assessment, corn ethanol emissions range from 50 to 250 g CO(2)e/MJ, for example, and each feedstock-fuel pathway studied shows some probability of greater emissions than a distribution for gasoline. Potential GHG emissions reductions from displacing fossil fuels with biofuels are difficult to forecast given this high degree of uncertainty in life-cycle emissions. This uncertainty is driven by the importance and uncertainty of indirect land use change emissions. Incorporating uncertainty in the decision making process can illuminate the risks of policy failure (e.g., increased emissions), and a calculated risk of failure due to uncertainty can be used to inform more appropriate reduction targets in future biofuel policies.     

糖型与淀粉型木薯后代块根品质与发酵特性

为了研究糖型与淀粉型木薯后代块根品质与发酵特性,测定了28个木薯品系块根的干物质、淀粉、总糖、还原糖、粗蛋白和灰分等主要品质性状。结果表明,淀粉型木薯后代块根的淀粉（14.52%）、总糖（27.48%）、干物质（41.24%）、粗蛋白（1.67%）和灰分（0.25%）含量,总体上比糖型木薯后代块根高;糖型木薯后代块根还原糖含量（2.01%）显著高于淀粉型木薯后代块根（0.61%）（P＜0.05）,而其淀粉含量仅6.62%。相关分析表明,还原糖与淀粉、总糖、干物质和粗蛋白等性状均呈显著负相关（P＜0.05）。通过杂交改良克服负相关,新品系SM03块根的乙醇转化率达到53.7 mL/100 g干质量,产酒精34.73 L/hm2。SM03和SC16只糖化、不经过糊化预处理,酵母发酵分别产酒精31.13 L/hm2、27.80 L/hm2,均是很有推广价值的能源木薯新品种。