我国生物质能源现代化应用前景展望(一)——生物质资源和供给

生物质能除了可以在改善世界一次能源结构、降低化石能源需求量方面做出重要贡献以外,还可在减少温室气体排放、保障能源供应安全、改善贸易平衡、促进农村发展和改进城市废弃物处理方式等方面发挥作用。目前全球每年一次能源消费总量为500EJ,生物质资源的年用量约占一次能源消费总量的10%左右,主要被用于传统的民用燃料和生产第一代生物燃料。第二代生物燃料技术预计将于2020年前后在一些国家实现工业化生产。IEA预测,2050年世界一次能源需求量为670EJ,生物质资源将占一次能源需求总量的20%左右。各方学者预测的2050年全球生物质资源量最低值基本在200~400EJ之间,最高值在400~1500EJ之间。中国的生物燃料产业尚处于起步阶段,不过应该说取得了良好的开端。我国生物质资源相对较少,且分布不均,发展生物质能产品需要依靠能源作物。只有通过合理开发、有效利用,才能在不与粮食和食用油争夺土地的前提下,在一定程度上提供生物运输燃料和生物质发电供热所需的原料,生物质能-农产品和/或生物质能-林产品联合生产系统应成为主要发展方向。美国生物燃料产业的发展模式对我国具有一定的借鉴意义。生物质最有效的利用方式是生产运输燃料,从长远来看,生物燃料可以与石油燃料竞争,尤其是喷气燃料和汽油更具替代优势,但受到生物质资源供应量的制约。     

Political,economic and environmental impacts of biomass-based hydrogen

The purpose of this study is to assess the political, economic and environmental impacts of producing hydrogen from biomass. Hydrogen is a promising renewable fuel for transportation and domestic applications. Hydrogen is a secondary form of energy that has to be manufactured like electricity. The promise of hydrogen as an energy carrier that can provide pollution-free, carbon-free power and fuels for buildings, industry, and transport makes it a potentially critical player in our energy future. Currently, most hydrogen is derived from non-renewable resources by steam reforming in which fossil fuels, primarily natural gas, but could in principle be generated from renewable resources such as biomass by gasification. Hydrogen production from fossil fuels is not renewable and produces at least the same amount of CO₂ as the direct combustion of the fossil fuel. The production of hydrogen from biomass has several advantages compared to that of fossil fuels. The major problem in utilization of hydrogen gas as a fuel is its unavailability in nature and the need for inexpensive production methods. Hydrogen production using steam reforming methane is the most economical method among the current commercial processes. These processes use non-renewable energy sources to produce hydrogen and are not sustainable. It is believed that in the future biomass can become an important sustainable source of hydrogen. Several studies have shown that the cost of producing hydrogen from biomass is strongly dependent on the cost of the feedstock. Biomass, in particular, could be a low-cost option for some countries. Therefore, a cost-effective energy-production process could be achieved in which agricultural wastes and various other biomasses are recycled to produce hydrogen economically. Policy interest in moving towards a hydrogen-based economy is rising, largely because converting hydrogen into useable energy can be more efficient than fossil fuels and has the virtue of only producing water as the by-product of the process. Achieving large-scale changes to develop a sustained hydrogen economy requires a large amount of planning and cooperation at national and international alike levels.     

Biomass energy potential in Turkey

Biomass energy includes fuelwood, agricultural residues, animal wastes, charcoal and other fuels derived from biological sources. It currently accounts for about 14% of world energy consumption. Biomass is the main source of energy for many developed and developing countries. In Turkey energy wood is available in the form of forest chips, fuelwood, wood waste, wood pellets, and it is also produced to a very limited extent from willow crops in short rotation forestry. The major part of wood harvested in the forest area (approximately 10 million ha) ends up as energy wood directly or indirectly after having been used for other purposes first. An overview of biomass potential and utilization in Turkey is presented. In 1999, the biomass share of the total energy consumption of the country is 10 percent. The level of fuelwood use together with that of other agricultural and animal wastes is compared with the commercial energy use within the country's global energy balance. The possibilities of increasing fuelwood production through afforestation programmes and substitution for commercial fuels are discussed. Biogas utilization in the rural regions is also reviewed, emphasizing its possible contribution.     

Biomass energy and the environmental impacts associated with its production and utilization

Biomass is the first-ever fuel used by humankind and is also the fuel which was the mainstay of the global fuel economy till the middle of the 18th century. Then fossil fuels took over because fossil fuels were not only more abundant and denser in their energy content, but also generated less pollution when burnt, in comparison to biomass. In recent years there is a resurgence of interest in biomass energy because biomass is perceived as a carbon-neutral source of energy unlike net carbon-emitting fossil fuels of which copious use has led to global warming and ocean acidification.The paper takes stock of the various sources of biomass and the possible ways in which it can be utilized for generating energy. It then examines the environmental impacts, including impact vis a vis greenhouse gas emissions, of different biomass energy generation–utilization options.     

Sustainable energy: A review of gasification technologies

Biomass has been widely recognized as a clean and renewable energy source, with increasing potential to replace conventional fossil fuels in the energy market. The abundance of biomass ranks it as the third energy resource after oil and coal. The reduction of imported forms of energy, and the conservation of the limited supply of fossil fuels, depends upon the utilization of all other available fuel energy sources. Energy conversion systems based on the use of biomass are of particular interest to scientists because of their potential to reduce global CO₂ emissions. With these considerations, gasification methods come to the forefront of biomass-to-energy conversions for a number of reasons. Primarily, gasification is more advantageous because of the conversion of biomass into a combustible gas, making it a more efficient process than other thermochemical processes. Biomass gasification has been studied widely as an efficient and sustainable technology for the generation of heat, production of hydrogen and ethanol, and power generation. Renewable energy can have a significant positive impact for developing countries. In rural areas, particularly in remote locations, transmission and distribution of energy generated from fossil fuels can be difficult and expensive, a challenge that renewable energy can attempt to correct by facilitating economic and social development in communities. This paper aims to take stock of the latest technologies for gasification.     

An advanced integrated biomass gasification and molten fuel cell power system

Biomass has recently received considerable attention as a potential substitute for fossil fuels in electric power production. Renewable biomass crops, industrial wood residues, and municipal wastes as fuels for production of electricity allow substantial reduction of environmental impact. High reactivity of biomass makes it relatively easy to convert solid feedstocks into gaseous fuel for subsequent use in a power cycle.So far most of the studies were focused on investigating performance and economics of biomass gasifiction–gas turbine systems. A general conclusion resulting from these studies is that the combination of biomass gasifiers, hot gas cleanup systems, and advanced gas turbines is promising for cost competitive electric power generation[1, 2]. In this paper another concept of biomass fueled power systems is considered, namely biomass gasification with a molten carbonate fuel cell (MCFC). Comparison between two concepts is made in terms of efficiency, feasibility, and process requirements. As an example of such a system, a highly efficient novel power cycle consisting of the Battelle gasification process, a molten carbonate fuel cell, and a steam turbine is introduced. The calculated efficiency is around 53%, which exceeds efficiencies of traditional designs[1, 3] considerably. Finally, an economic analysis and electricity cost projection are performed for a power plant consuming 2000 tons of biomass per day. Results are compared with those for more traditional integrated biomass gasification/gas turbine systems and for coal fueled cycles.     

Progress and recent trends in biofuels

In this paper, the modern biomass-based transportation fuels such as fuels from Fischer–Tropsch synthesis, bioethanol, fatty acid (m)ethylester, biomethanol, and biohydrogen are briefly reviewed. Here, the term biofuel is referred to as liquid or gaseous fuels for the transport sector that are predominantly produced from biomass. There are several reasons for bio-fuels to be considered as relevant technologies by both developing and industrialized countries. They include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues related to the rural sector. The term modern biomass is generally used to describe the traditional biomass use through the efficient and clean combustion technologies and sustained supply of biomass resources, environmentally sound and competitive fuels, heat and electricity using modern conversion technologies. Modern biomass can be used for the generation of electricity and heat. Bioethanol and biodiesel as well as diesel produced from biomass by Fischer–Tropsch synthesis are the most modern biomass-based transportation fuels. Bio-ethanol is a petrol additive/substitute. It is possible that wood, straw and even household wastes may be economically converted to bio-ethanol. Bio-ethanol is derived from alcoholic fermentation of sucrose or simple sugars, which are produced from biomass by hydrolysis process. Currently crops generating starch, sugar or oil are the basis for transport fuel production. There has been renewed interest in the use of vegetable oils for making biodiesel due to its less polluting and renewable nature as against the conventional petroleum diesel fuel. Biodiesel is a renewable replacement to petroleum-based diesel. Biomass energy conversion facilities are important for obtaining bio-oil. Pyrolysis is the most important process among the thermal conversion processes of biomass. Brief summaries of the basic concepts involved in the thermochemical conversions of biomass fuels are presented. The percentage share of biomass was 62.1% of the total renewable energy sources in 1995. The reduction of greenhouse gases pollution is the main advantage of utilizing biomass energy.     

Bio‐oil,solid and gaseous biofuels from biomass pyrolysis processes—An overview

As the global demand for energy rapidly increases and fossil fuels will be soon exhausted, bio‐energy has become one of the key options for shorter and medium term substitution for fossil fuels and the mitigation of greenhouse gas emissions. Biomass currently supplies 14% of the world's energy needs. Biomass pyrolysis has a long history and substantial future potential—driven by increased interest in renewable energy. This article presents the state‐of‐the‐art of biomass pyrolysis systems, which have been—or are expected to be—commercialized. Performance levels, technological status, market penetration of new technologies and the costs of modern forms of biomass energy are discussed. Advanced methods have been developed in the last two decades for the direct thermal conversion of biomass to liquid fuels, charcoals and various chemicals in higher yields than those obtained by traditional pyrolysis processes. The most important reactor configurations are fluidized beds, rotating cones, vacuum and ablative pyrolysis reactors. Fluidized beds and rotating cones are easier for scaling and possibly more cost effective. Slow pyrolysis is being used for the production of charcoal, which can also be gasified to obtain hydrogen‐rich gas. The short residence time pyrolysis of biomass (flash pyrolysis), at moderate temperatures, is being used to obtain a high yield of liquid products (up to 70% wt), particularly interesting as energetic vectors. Bio‐oil can substitute for fuel oil—or diesel fuel—in many static applications including boilers, furnaces, engines and turbines for electricity generation. While commercial biocrudes can easily substitute for heavy fuel oils, it is necessary to improve the quality in order to consider biocrudes as a replacement for light fuel oils. For transportation fuels, high severity chemical/catalytic processes are needed. An attractive future transportation fuel can be hydrogen, produced by steam reforming of the whole oil, or its carbohydrate‐derived fraction. Pyrolysis gas—containing significant amount of carbon dioxide, along with methane—might be used as a fuel for industrial combustion. Presently, heat applications are most economically competitive, followed by combined heat and power applications; electric applications are generally not competitive. Copyright © 2011 John Wiley & Sons, Ltd.     

Meeting U.S. liquid transport fuel needs with a nuclear hydrogen biomass system

The two major energy challenges for the United States are replacing crude oil in our transportation system and eliminating greenhouse gas emissions. A domestic-source greenhouse-gas-neutral nuclear hydrogen biomass system to replace oil in the transportation sector is described. Some parts of the transportation system can be electrified with electricity supplied by nuclear energy sources that do not emit significant quantities of greenhouse gases. Other components of the transportation system require liquid fuels. Biomass can be converted to greenhouse-gas-neutral liquid fuels; however, the conversion of biomass-to-liquid fuels is energy intensive. There is insufficient biomass to meet U.S. liquid fuel demands and provide the energy required to process the biomass-to-liquid fuels. With the use of nuclear energy to provide heat, electricity, and hydrogen for the processing of biomass-to-liquid fuels, the liquid fuel production per unit of biomass is dramatically increased, and the available biomass could meet U.S. liquid fuel requirements.     

生物质应用于制液体和气体燃料而不是用于发电

我国能源结构从长期看仍将以煤为主,缺油少气。从我国能源结构来讲,生物质利用的最好方式不是发电．因生物质可以生产液体和气体燃料,而风能、太阳能、水能却只能发电。我国秸杆综合利用取得明显成效．在农业和畜牧业的利用领域还可能进一步拓宽,作为燃料利用的量还可能进一步缩减。从我国还在进行的第一次能源大转换来看,我国生物质使用量已大大减少,但还有相当的数量。要减少作为能源使用的生物质传统利用量,把它用于饲料、肥料和工业原料等还有发展前景的用途。在一次能源消费以化石能源为主的时期,中国存在液体燃料和气体燃料短缺的问题,以后进入第三次能源转换时期,新能源和可再生能源替代化石能源之后,液体燃料和气体燃料短缺的问题将会更加突出。因此,生物质应用于生产液体燃料和气体燃料,而不是用于发电。而且生物质发电厂投资高、燃料成本不断上涨,使发电成本高＋生物质发电将长期缺乏竞争力。我国发展生物质液体燃料已具备一定的条件．前几年中石油、中石化和中海油已开始种植可提炼生物液体燃料的能源林。我国非粮生物质液体燃料生产基地正在积极建设之中。我国发展生物质气体燃料也具有一定优势,在沼气、气化和城镇有机废物处理方面都积累了一定的经验。总之生物质生产液体燃料和气体燃料是一种既适应我国当前、又适应未来能源需求的有效措施。     

The characteristics of air pollutants from the combustion of biomass pellets

Biomass is renewable clean energy. The aim of this study is to explore the combustion properties and emission characteristics of NO_X, SO₂, PM, and HCl in the combustion process of biomass pellet fuels. In this study, three kinds of fuels (pine sawdust, mixed wood, and corn straw) were selected to be studied by using a tube furnace to simulate industrial boiler. Experiments were conducted under different combustion conditions (combustion temperature and air flow). The results show that pollutant emissions were related to fuel type, combustion temperature, and air flow. The emissions of NO_X were contingent on N content in the fuel and the peak emissions of NO_X appeared in the range of 50~600 mg/m³ at 4 L/min and 700℃. The emissions of SO₂ were related to combustion condition and close to zero under the condition of sufficient combustion. The emissions of HCl and particulate matter (PM) increase with the rise of temperature, but the emission of PM was minimal at 800℃. Average HCl emission was 0.2~0.5 mg/g under steady-state conditions (4 L/min and 700℃). All in all, the pollutant emissions of biomass pellet fuels during combustion are lower than those of the traditional fuel, and the combustion efficiency is relatively higher.     

Upgrading of Candelilla biocrude to hydrocarbon fuels by fluid catalytic cracking

Biomass has been recognized as a major world renewable energy source to supplement declining fossil fuel sources of energy. Biomass derived transportation fuels have not only the potential to replace conventional fuels but can also be utilized as blending components for improving the quality of these fuels. The biocrude obtained from Euphorbia antisyphilitica, identified as the most potential petrocrop was investigated as a potential source for liquid fuels. The feed was studied for yield conversion data under different catalyst to feed ratio at various temperatures. Maximum middle distillates selectivity was observed at catalyst/oil ratio 4 and 6 and reaction temperature 500 °C. The main constituents of the gaseous products are C₃, C₄ and C₅. The liquid fuels are highly aromatic with low olefinic content.     

An experimental study on air gasification of biomass micron fuel (BMF) in a cyclone gasifier

Biomass micron fuel (BMF) produced from feedstock (energy crops, agricultural wastes, forestry residues and so on) through an efficient crushing process is a kind of powdery biomass fuel with particle size of less than 250 μm. Based on the properties of BMF, a cyclone gasifier concept has been considered in our laboratory for biomass gasification. The concept combines and integrates partial oxidation, fast pyrolysis, gasification, and tar cracking, as well as a shift reaction, with the purpose of producing a high quality of gas. In this paper, characteristics of BMF air gasification were studied in the gasifier. Without outer heat energy input, the whole process is supplied with energy produced by partial combustion of BMF in the gasifier using a hypostoichiometric amount of air. The effects of equivalence ratio (ER) and biomass particle size on gasification temperature, gas composition, gas yield, low-heating value (LHV), carbon conversion and gasification efficiency were studied. The results showed that higher ER led to higher gasification temperature and contributed to high H₂-content, but too high ER lowered fuel gas content and degraded fuel gas quality. A smaller particle was more favorable for higher gas yield, LHV, carbon conversion and gasification efficiency. And the BMF air gasification in the cyclone gasifier with the energy self-sufficiency is reliable.     

Present and prospective role of bioenergy in regional energy system

Bioenergy is the energy released from the reaction of organic carbon material with oxygen. The organic material derived from plants and animals is also referred to as biomass. Biomass is a flexible feedstock capable of conversion into solid, liquid and gaseous fuels by chemical and biological processes. These intermediate biofuels (such as methane gas, ethanol, charcoal) can be substituted for fossil based fuels. Wood and charcoal are important as household fuels and for small scale industries such as brick making, cashew processing etc. The scarcity of biofuels has far reaching implications on the environment. Hence, expansion of bioenergy systems could be influential in bettering both the socio-economic condition and the environment of the region. This paper examines the present role of biomass in the region’s (Uttara Kannada District, Karnataka State, India) energy supply and calculates the potential for future biomass provision and scope for conversion to both modern and traditional fuels. Based on the detailed investigation of biomass resource availability and demand, we can categorise the Uttara Kannada District into two zones (a) Biomass surplus zone consisting of Taluks mainly from hilly area (b) Biomass deficit zone, consisting of thickly populated coastal Taluks such as Bhatkal, Kumta, Ankola, Honnavar and Karwar. Fuel wood is mainly used for cooking and horticulture residues from coconut, arecanut trees are used for water heating purposes. Most of the households in this region still use traditional stoves where efficiency is less than 10%. The present inefficient fuel consumption could be brought down by the usage of fuel efficient stoves (a saving of the order of 27%). Availability of animal residues for biogas generation in Sirsi, Siddapur, Yellapur Taluks gives a viable alternative for cooking, lighting fuel and a useful fertiliser. However to support the present livestock population, fodder from agricultural residues is insufficient in these Taluks. There is a need to supplement the fodder availability with fodder crops as successfully tried in Banavasi village by some progressive farmers.     

Biomass Energy and Biochemical Conversion Processing for Fuels and Chemicals

Biomass, mainly in the form of wood, is the oldest form of energy used by humans. Biomass is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles, and providing process heat for industrial facilities. Biomass potential includes wood and animal and plant wastes. Biomass, mainly now represents only 3% of primary energy consumption in industrialized countries. World production of biomass is estimated at 146 billion metric tons a year, mostly wild plant growth. Energy from biomass fuels is used in the electric utility, lumber and wood products, and pulp and paper industries. Biomass conversion may be conducted on two broad pathways: chemical decomposition and biological digestion. The conversion technologies for utilizing biomass can be separated into four basic categories: direct combustion processes, thermochemical processes, biochemical processes, and agrochemical processes. Biological processes are essentially microbic digestion and fermentation.     

Prospects and challenges for green hydrogen production and utilization in the Philippines

The Philippines is exploring different alternative sources of energy to make the country less dependent on imported fossil fuels and to reduce significantly the country's CO₂ emissions. Given the abundance of renewable energy potential in the country, green hydrogen from renewables is a promising fuel because it can be utilized as an energy carrier and can provide a source of clean and sustainable energy with no emissions. This paper aims to review the prospects and challenges for the potential use of green hydrogen in several production and utilization pathways in the Philippines. The study identified green hydrogen production routes from available renewable energy sources in the country, including geothermal, hydropower, wind, solar, biomass, and ocean. Opportunities for several utilization pathways include transportation, industry, utility, and energy storage. From the analysis, this study proposes a roadmap for a green hydrogen economy in the country by 2050, divided into three phases: I–green hydrogen as industrial feedstock, II–green hydrogen as fuel cell technology, and III–commercialization of green hydrogen. On the other hand, the analysis identified several challenges, including technical, economic, and social aspects, as well as the corresponding policy implications for the realization of a green hydrogen economy that can be applied in the Philippines and other developing countries.     

An evaluation of biomass co-firing in Europe

Reduction of the emissions of greenhouses gases, increasing the share of renewable energy sources (RES) in the energy balance, increasing electricity production from renewable energy sources and decreasing energy dependency represent the main goals of all current strategies in Europe. Biomass co-firing in large coal-based thermal power plants provides a considerable opportunity to increase the share of RES in the primary energy balance and the share of electricity from RES in gross electricity consumption in a country. Biomass-coal co-firing means reducing CO₂ and SO₂, emissions and it may also reduce NO_x emissions, and also represents a near-term, low-risk, low-cost and sustainable energy development. Biomass-coal co-firing is the most effective measure to reduce CO₂ emissions, because it substitutes coal, which has the most intensive CO₂ emissions per kWh electricity production, by biomass, with a zero net emission of CO₂. Biomass co-firing experience worldwide are reviewed in this paper. Biomass co-firing has been successfully demonstrated in over 150 installations worldwide for most combinations of fuels and boiler types in the range of 50–700 MWe, although a number of very small plants have also been involved. More than a hundred of these have been in Europe. A key indicator for the assessment of biomass co-firing is intrduced and used to evaluate all available biomass co-firing technologies.     

The pollutant discharge improvement by introducing HHO gas into biomass boiler

Biomass fuel has been widely concerned because its net CO₂ emission is close to zero. Biomass boilers are known to have lower pollutant emissions than fossil fuel boilers, but in some applications, they also release high-level CO and NO. We developed a medium-sized hydrogen and oxygen (HHO) generator, with high energy conversion rate and adjustable output gas. The HHO gas was then introduced into a biomass hot air generator for mixed combustion. The experimental results showed that based on the electricity consumption of gas production and biomass fuel price, the total cost during preheating reduced. In addition, the average concentrations of CO, NO and smoke decreased by 93.0%, 22.5% and 80%, respectively. Integration of biomass fuel and HHO gas can effectively reduce pollutant emissions and save fuel, especially in areas rich in renewable energy.     

A review on process modeling and design of biohydrogen

The current energy supply depends on fossil fuels which have increased carbon dioxide emissions leading to global warming and depleted non-renewable fossil fuels resources. Hydrogen (H₂) fuel could be an eco-friendly alternative since H₂ consumption only produces water. However, the overall impacts of the H₂ economy depend on feedstock types, production technologies, and process routes. The existing process technologies for H₂ production used fossil fuels encounter the escalation of fossil fuel prices and long-term sustainability challenges. Therefore, biohydrogen production from renewable resources like biomass wastes and wastewaters has become the focal development of a sustainable global energy supply. Different from other biohydrogen production studies, this paper emphasizes biohydrogen fermentation processes using different renewable sources and microorganisms. Moreover, it gives an overview of the latest advancing research in different biohydrogen process designs, modeling, and optimization. It also presents the biohydrogen production routes and kinetic modeling for biohydrogenation.     

我国生物质能利用现状与展望

生物质能是重要的可再生能源资源,具有广阔的开发利用前景。介绍了我国生物质能的发展现状,包括固态生物质燃料、液态生物质燃料（燃料乙醇、生物柴油）、气态生物质燃料的开发利用和技术进展。对我国发展生物质能提出了建议,包括生物质能原料的利用和开发,生物质能开发利用的路线与技术,以及开展国际合作与交流,引进吸收国外先进的技术和设备等。