我国生物质能源现代化应用前景展望(三)——生物质能源转化技术经济评估

秸秆、动植物油脂、微藻等生物质原料可以生产液体运输燃料,生物燃料的化学成分包括醇、酯、烃三类。燃料乙醇主要替代汽油,受到各国重视,其中纤维素乙醇技术发展较快。脂肪酸甲酯是第一代生物柴油的主要成分,价格主要受油脂原料价格的影响,由于和柴油相容性差,低温流动性不好,将逐渐被加氢生产的第二代生物柴油取代。相比醇、酯等含氧燃料,烃类生物燃料在使用性能上有很多优势。有多条技术路线可以生产烃类燃料,其中油脂加氢制喷气燃料已接近商业应用,热解油加氢可将木质生物质原料中的"木质素"组分转化为生物油,大型快速热解工厂可以和热电联产装置组成联合系统,从而提高工厂综合热效率,降低生物燃料生产成本。因此,快速热解生产汽柴油将成为主要的生物燃料生产路线。生物质与煤共气化技术通过提高气化温度,不仅可以提高生物质气化效率,减少焦油的生成,还可以解决生物质供给的季节性问题,为生物质的高效利用提供了一条新的技术途径。微藻高压液化生产柴油是最具发展潜力的第三代生物燃料技术,我国需要加强微藻养殖及加工技术攻关。     

烃类生物燃料加工技术

正烃类生物燃料加工技术中一些技术的突破可能加快产业化进程。专家预测,以烃类为主要成分的第二代生物柴油取代以脂肪酸甲酯为主要成分的第一代生物柴油是大势所趋。有多条技术路线以生物质为原料生产的烃类燃料可与传统燃料以任意比例调配。油脂加氢异构生产可再生柴油和喷气燃料将首先实现商业化,气化、热解转化木质生物质生产可再生柴油的技术已接近商用或者处于示范阶段,热解油加氢制烃燃料和CBGTL将成为主要的生物燃料生产路线。     

我国生物质能源现代化应用前景展望(四)——生物质能源转化生命周期分析

生物质种类不同,转化为运输燃料的途径也是多种多样,生命周期排放的温室气体和能耗也不相同。总结对比主要生物质转化途径的全生命周期分析(LCA)结果,有助于明确需要进一步改进的技术难题和方向。生物质转化为醇类燃料时,使用E85比使用传统汽油的碳排放明显下降,纤维素生化转化途径排放的二氧化碳当量值约为传统汽油的0.2~0.7倍,热化学途径约为传统汽油的0.6~0.9倍,玉米干法为传统汽油的0.8~1倍。油脂类生物质转化为酯类燃料时,生物柴油减排温室气体的效果,动物油脂地沟油、棕榈油豆油、椰子油菜籽油。动物油脂、地沟油生产生物柴油可减排温室气体70%~90%,以植物为原料的生物柴油可减排10%~90%。生物质转化为烃类燃料时,菜籽油基喷气燃料可减排温室气体13%~55%,F-T合成油比油脂加氢具有更好的减排效果,BTL通常可减排80%以上的温室气体,CBTL的减排效果与掺入生物质的比例有关,热解汽柴油的温室气体减排率为58%~70%。对于微藻生物燃料工艺过程,在微藻产率和含油量不太低的情况下,池子系统的温室气体排放低于石油柴油。     

石油炼厂加工纤维素/木质纤维素生物质原料的前景

生物质热解与生物油改质、生物质气化与合成气费-托转化工艺是正在研究开发的第二代生物燃料技术,前者利用快速热解工艺对生物质进行热解或热加氢改质生成热解油;后者用生物质直接合成或先转化为生物油后再生成合成气,合成气经改质和转化生产费-托合成烃。许多石油公司都在以纤维素/木质纤维素为原料,研究开发在石油炼厂内对生物质原料进行后续加工和应用的相关技术。在石油炼厂中引入生物质原料,其挑战是要找到源自非食用生物质或生物质废弃物的原料,而且这些原料应易于运输并易于在炼厂中进行处理,同时应尽可能使用现有的工艺和装置。虽然石油炼厂加工生物质原料尚存在一些问题,但近来开发势头十分强劲。从长远角度来看,任何能为炼厂提供原料,生命周期分析证明能减少CO2排放,并在经济上可行的技术均会在生物燃料开发竞争中成为赢家。     

由糠醛生产高附加值化学品和运输燃料的最新进展

糠醛由玉米芯等生物质经水解、脱水后得到,在合成树脂、医药等领域应用广泛。以可再生的糠醛作为原料替代化石资源,生产精细化学品和运输燃料对解决能源危机和环境问题具有重要意义。文章重点介绍了近几年以糠醛为原料生产精细化学品和运输燃料(生物汽油、生物柴油和航空燃料)的研究进展。     

燃料乙醇炼制系统优化与碳减排研究进展

生物质是丰富可再生的碳源,以糖、淀粉、秸秆纤维素或其他生物质原料高效生产燃料乙醇,可减少化石能源的需求,其中以木质纤维素为原料的第二代燃料乙醇具有广阔的发展前景。与化石能源相比,燃料乙醇具有环保、经济、可再生的优势,但其在生产工艺技术、经济效益和环境影响等方面仍需要深入研究。近年来,通过开展燃料乙醇炼制系统优化及全生命周期分析研究,有力地促进了燃料乙醇技术进步,推动了燃料乙醇碳减排相关研究。文章主要论述了近年来燃料乙醇生产技术的发展,重点对燃料乙醇系统的模拟优化和碳减排研究进展进行了总结,并对燃料乙醇发展趋势进行了展望,以期为燃料乙醇的可持续发展提供参考。     

国外可再生能源文献信息

用无催化剂的SCF法生产生物柴油和生物柴油的燃料特性；用新鲜或废植物油生产的柴油及其粘稠度；生物柴油中挥发性有机化合物的吸收：用预留空间气相色谱法测定无限稀释活性系数；风能、压缩空气储能和生物质气化联合系统的技术、环境和社会特性；一种基于生物质气化制氢的综合工艺的能源效率问题；橄榄饼：一种可利用的生物质燃料；用高效等离子燃料电池（IPFC）把矿物燃料和生物质燃料转换为电力和运输燃料；乙醇汽车燃料中硫酸酯的分光光度测定法；燃料电池制氢时的乙醇蒸汽重整；地热储中冷水锋运动的分析模型；日本西南部阿苏山西侧地热储三维特征的大地电磁电阻率仿真。[编者按]     

现代生物能源第二波研发和产业化浪潮

液态和气态生物燃料一直是生物能源研发的"重中之重"。纤维素乙醇这种所谓的"第二代生物燃料"的开发热持续了近10年,但始终未能突破商业化生产的技术、经济瓶颈。物料预处理成本和酶成本过高,是木质纤维素乙醇产业化的两大根本性障碍,同时还存在着其他不确定性。而基于热化学平台和糖平台的新型液体生物燃料正在走上世界能源舞台。近年来生物质气化-合成油、生物质裂解提质油、EL类生物燃油、生物MTG油、CBGTL油、藻类油/燃气、生物质气化-合成天然气等各种新型的生物燃料不断涌现,而且研发和产业化速度很快,若干品种的研发已处于产业化的前夜,有望在今后2~4年内实现商业化。它们不但符合"先进生物燃料"关于碳减排的要求,而且还是所谓的"可直接使用生物燃料",即能以任何比例与常规汽柴油调合,或完全单独用于现有的发动机,无需像燃料乙醇那样必须有专用的储运设施。液态和气态生物能源正在迎接研发和产业化的第二波浪潮,中国在其中也占有了一席之地。在这样的大背景下,上述新型生物燃料的主要原料木质纤维素类物料的重要性将愈发凸显。     

我国生物质能源现代化应用前景展望(二)——生物质制备液体燃料的转化途径

利用可再生生物质资源转化制备液体燃料已成为全球关注的热点。常见的生物质能源原料主要有草本植物、木本植物、微藻和脂肪类生物质资源,丰富的生物质资源为生物质液体燃料的生产提供了广泛的原料来源,也为生物质能源的多样性发展提供了坚实的物质基础。不同的生物质原料种类和转化方式可生产出性能各异的多种液体燃料,主要包括醇类燃料(乙醇、丁醇等)、烃类燃料和生物柴油等,由此构建出生物质转化制备液体燃料的转化途径网络。醇类燃料的生物质转化途径主要包括生物质直接发酵、生物质合成气发酵、生物质合成气化学合成等;烃类燃料的生物质转化途径主要有生物质液化加氢、微藻热化学途径、生物质合成气费托合成、生物质发酵脂肪酸加氢及油脂类加氢途径等;生物柴油的转化途径主要有油脂酯交换和微藻萃取酯交换。在这些液体燃料的转化途径中,只有生物质发酵制乙醇途径和油脂酯交换途径基本实现了商业化应用,其他大部分转化途径仍处于开发阶段。     

上海积极开发可再生能源

7t堆积于田间地头的秸秆经过水解、发酵、蒸馏，就能变成1t汽车燃料；无需复杂的工艺，1t餐厨剩余的泔脚油又将以0．9t生物柴油的形式重获新生。一座以纤维素废弃物为原料、年产600t乙醇的中试示范生产线己在奉贤投入运行．一座年产2万t生物柴油的示范线不久也将落户奉贤。上海目前年产生活垃圾600万t．其中30％属于生物质，是一口不可小觑的“油井”。     

Economic feasibility of algal biodiesel under alternative public policies

The motivation for this research was to determine the influence of public policies on economic feasibility of producing algal biodiesel in a system that produced all its energy needs internally. To achieve this, a steady-state mass balance/unit operation system was modeled first. Open raceway technology was assumed for the production of algal feedstock, and the residual biomass after oil extraction was assumed fermented to produce ethanol for the transesterification process. The project assumed the production of 50 million gallons of biodiesel per year and using about 14% of the diesel output to supplement internal energy requirements. It sold the remainder biodiesel and ethanol as pure biofuels to maximize the rents from the renewable fuel standards quota system. Assuming a peak daily yield of 500 kg algal biomass (dry basis)/ha, the results show that production of algal biodiesel under the foregoing constraints is only economically feasible with direct and indirect public policy intervention. For example, the renewable fuel standards' tracking RIN (Renewable fuel Identification Number) system provides a treasury-neutral value for biofuel producers as does the reinstatement of the renewable fuel tax credit. Additionally, the capital costs of an integrated system are such that some form of capital cost grant from the government would support the economic feasibility of the algal biodiesel production.     

A comprehensive review on lignocellulosic biomass biorefinery for sustainable biofuel production

The increasingly severe environmental pollution and energy shortage issues have demanded the production of renewable and sustainable biofuels to replace conventional fossil fuels. Lignocellulosic (LC) biomass as an abundant feedstock for second-generation biofuel production can help overcome the shortcomings of first-generation biofuels related to the “food versus fuel” debate and feedstock availability. Embracing the “circular bioeconomy” concept, an integrated biorefinery platform of LC biomass can be performed by employing different conversion technologies to obtain multiple valuable products. This review provides an overview of the principles and applications of thermochemical processes (pyrolysis, torrefaction, hydrothermal liquefaction, and gasification) and biochemical processes (pretreatment technologies, enzyme hydrolysis, biochemical conversion processes) involved in LC biomass biorefinery for potential biofuel applications. The engineering perspective of LC biofuel production on separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP) were also discussed.     

Role of energy policy in renewable energy accomplishment: The case of second-generation bioethanol

Renewable energy has been in the limelight ever since the price of crude petroleum oil increases to the unprecedented height of US$96 per barrel recently. This is due to the diminishing oil reserves in the world and political instabilities in some oil-exporting countries. The advantages of renewable energy compared to fossil fuels are enormous in terms of environment and availability. Biofuels like bioethanol and biodiesel are currently being produced from agricultural products such as sugarcane and rapeseed oil, respectively. Collectively, these biofuels from food sources are known as first-generation biofuels. Although first-generation biofuels have the potential to replace fossil fuels as the main source of energy supply, its production is surrounded by certain issues like tropical forests’ destruction. Instead, second-generation bioethanol, which utilizes non-edible sources such as lignocellulose biomass to produce ethanol, has been shown to be more suitable as the source of renewable energy. However, there are challenges and obstacles such as cost, technology and environmental issues that need to be overcome. Hence, the introduction of energy policy is crucial in promoting and implementing second-generation bioethanol effectively and subsequently become a major source of renewable energy.     

Biofuel production: Prospects,challenges and feedstock in Australia

The growing demands for energy coupled with ever increasing environmental concerns have allowed the global production of biofuels to rise significantly in recent years. Many countries across the world have begun utilising biofuels on a national scale, while many more are in the process of planning and implementing similar steps. While Australia has an abundance of fossil fuels in the form of coal, natural gas, and oil, and currently employs a variety of alternative energy sources, the technology to produce and implement biofuels in Australia is in its embryonic stage. Today, Australia is using first generation feedstock as the main source for the production of biofuel, but is progressively broadening into second-generation biofuel production technology. Australia has an enormous amount of biomass available in the form of agricultural and forestry residues, bagasse and feedstock currently unused for the production of biofuels. The technology for the conversion of lignocellulosic biomass into biofuels warrants further research to maximise yield to the point of industrial feasibility. This review discusses the current state of ethanol production in Australia, the key technological challenges involved in the production of second-generation biofuel and the availability of various kinds of lignocellulosic biomass for biofuel production.     

Current status and future forecasting of biofuels technology development

Over the last few decades, the significant increase in energy demand followed by increasing fossil fuels depletion convinced countries authority to choose renewable energy to satisfy demand. Therefore, global enthusiasm in renewable energy such as bioenergy technology is increased. Is biofuels technology ready to address the global demand for energy? Investigating in technology development can answer. In this paper, the current statuses of biofuel technologies are determined. Regarding patent codes, seven technologies are identified, which are CHP turbines for biofeed, gas turbine for biofeed, biodiesel, grain bioethanol, bio‐pyrolysis, torrefaction of biomass, and cellulosic bioethanol. The results of patent investigating show that the biodiesel technology is in the mature status and its technology trend is going to go downward. The others six technologies are in the growth stage. Analysis of 57 619 patents in biofuel technologies for technology forecasting has been done by technology life cycle. The torrefication of biomass technology has started its growth stages and will become mature in 2061. In this research, the S‐curves of all biofuel groups are plotted and maturity phases are forecasted.     

Second generation biofuels: Economics and policies

This study reviews economics of production of second generation biofuels from various feedstocks, including crop and wood/forestry residues, lignocellulosic energy crops, jatropha, and algae. The study indicates that while second generation biofuels could significantly contribute to the future energy supply mix, cost is a major barrier to its commercial production in the near to medium term. Depending upon type of biofuels, feedstock prices and conversion costs, the cost of cellulosic ethanol is found to be two to three times higher than the current price of gasoline on an energy equivalent basis. The median cost (across the studies reviewed) of biodiesel produced from microalgae, a prospective feedstock, is seven times higher than the current price of diesel, although much higher cost estimates have been reported. As compared with the case of first generation biofuels, in which feedstock can account for over two-thirds of the total costs, the share of feedstock in the total costs is relatively lower (30–50%) in the case of second generation biofuels. While significant cost reductions are needed for both types of second generation biofuels, the critical barriers are at different steps of the production process. For cellulosic ethanol, the biomass conversion costs needs to be reduced. On the other hand, feedstock cost is the main issue for biodiesel. At present, policy instruments, such as fiscal incentives and consumption mandates have in general not differentiated between the first and second generation biofuels except in the cases of the US and EU. The policy regime should be revised to account for the relative merits of different types of biofuels.     

Biomethane in the transport sector—An appraisal of the forgotten option

The last 20 years efforts to find a long-term and large-scale biofuel alternative to petrol and diesel for the transport sector have been intensified with a focus on liquid biofuels, such as ethanol, methanol and Fischer–Tropsh diesel derived from wood. The large-scale production of biomethane has so far largely been overlooked in comparative studies that focus on the long-term renewable options. The aim of this article fills this gap and to provide a broad and systematic assessment of the future potential of biomethane compared to other biofuels. In order to become a large-scale option, biomethane production from woody biomass via gasification needs to be developed and commercialized. However, biomethane exhibits a clear development path with relatively low financial and technical risks starting with local solutions utilizing wet biomass resources towards medium and eventually large-scale gasification with economics similar to liquid second generation biofuels. The disadvantage of being a gaseous fuel is not insurmountable and can furthermore be relaxed by the integration and dual-use of the existing distribution system for natural gas. This assessment concludes that more emphasize should be given to biomethane as a large-scale option given the opportunity to use woody biomass from gasification.     

Lifecycle economic analysis of biofuels: Accounting for economic substitution in policy assessment

This paper develops a lifecycle economic analysis (LCEA) model that integrates endogenous input substitution into the standard lifecycle analysis (LCA) of biofuel that typically assumes fixed-proportions production. We use the LCEA model to examine impacts of a pure carbon tax and a revenue-neutral tax-subsidy policy on lifecycle greenhouse gas emissions from cellulosic ethanol using forest residues as feedstock in Washington State. In a model allowing for input substitution in the cellulosic ethanol feedstock, conversion, and transportation process, we consider energy source substitution (woody biomass for coal in the cellulosic ethanol conversion plant and biodiesel for diesel in feedstock production and feedstock and ethanol transportation) as well as substitution of capital and labor for energy in all stages of the lifecycle. We find that ignoring endogenous input substitution by using standard LCA leads to substantial underestimation of the impact of carbon tax policies on carbon emissions. Both tax policies can substantially reduce carbon emissions by inducing substitution among inputs. The revenue-neutral tax-subsidy policy reduces emissions more effectively than the carbon tax policy for carbon tax rates currently in place throughout most of the world. It stimulates substitution of woody biomass for coal and biodiesel for diesel at much lower tax rates when accompanied by corresponding subsidies for reduced emissions from renewable sources.