Evaluation of energy efficiency of various biogas production and utilization pathways

The energy efficiency of different biogas systems, including single and co-digestion of multiple feedstock, different biogas utilization pathways, and waste-stream management strategies was evaluated. The input data were derived from assessment of existing biogas systems, present knowledge on anaerobic digestion process management and technologies for biogas system operating conditions in Germany. The energy balance was evaluated as Primary Energy Input to Output (PEIO) ratio, to assess the process energy efficiency, hence, the potential sustainability. Results indicate that the PEIO correspond to 10.5–64.0% and 34.1–55.0% for single feedstock digestion and feedstock co-digestion, respectively. Energy balance was assessed to be negative for feedstock transportation distances in excess of 22 km and 425 km for cattle manure and for Municipal Solid Waste, respectively, which defines the operational limits for respective feedstock transportation. Energy input was highly influenced by the characteristics of feedstock used. For example, agricultural waste, in most part, did not require pre-treatment. Energy crop feedstock required the respect cultivation energy inputs, and processing of industrial waste streams included energy-demanding pre-treatment processes to meet stipulated hygiene standards. Energy balance depended on biogas yield, the utilization efficiency, and energy value of intended fossil fuel substitution. For example, obtained results suggests that, whereas the upgrading of biogas to biomethane for injection into natural gas network potentially increased the primary energy input for biogas utilization by up to 100%; the energy efficiency of the biogas system improved by up to 65% when natural gas was substituted instead of electricity. It was also found that, system energy efficiency could be further enhanced by 5.1–6.1% through recovery of residual biogas from enclosed digestate storage units. Overall, this study provides bases for more detailed assessment of environmental compatibility of energy efficiency pathways in biogas production and utilization, including management of spent digestate.     

Planning land use for biogas energy crop production: The potential of cutaway peat production lands

Each year, thousands of hectares of peatland that had been harvested are being released in Finland, which can offer an opportunity to increase energy crops and attain the bioenergy targets for non-agriculture lands. In this study, the Geographic Information System (GIS) method was used to improve the assessment of decentralized renewable energy resources. The amount of peat production lands and future cutaway areas for energy crop production was calculated as a case study by using ArcGIS and the Finnish Topographic database. There are almost 1000 km² of peat production lands in Finland, and theoretically, approximately 300 km² of cutaway peatlands could be used for energy crops after 30 years. The dry biomass yield of reed canary grass (Phalaris arundinacea) or timothy-fescue grass (mix of Phleum pratense and Festuca pratensis) could be higher than 100 Gg a⁻¹ in these lands indicating methane potential of approximately 300 GWh. The exhausted peat production areas in the western region of Finland have significant potential for use for energy crops; North and South Ostrobothnia account for almost 45% of the total peat production land. A future goal could be to use the cutaway peat production lands more efficiently for bioenergy to mitigate climate change. Since the use of wastelands (including peatlands) are being considered in Europe as a way to avoid competition with food production, the GIS method used in the study to identify suitable peat lands could be applicable to biomass resource studies being conducted in many countries.     

Potential biomass supply for agro-pellet production from agricultural crop residue in Nepal

Nepal, a country rich in biomass, still does not have any commercial pellet production plants and is wasting large amounts of agricultural crop residue. The current study showed that about 5.61 million tonnes (Mt) of biomass in the form of pellets are potentially available from agricultural crop residues. The brick and cement industries could use these agro-pellets. Co-firing of pellets in such industries could play an important role in reducing the import volume of coal and minimize the related environmental loadings.     

生物质能的转化和利用技术研究

能源短缺成为影响中国未来发展的主要问题之一。生物质能的应用有助于解决我国能源短缺的问题，同时能够减小化石燃料使用带来的负面影响。文章主要介绍了生物质能的概念、生物质能利用的意义及生物质能的转化和利用技术，而且还提出实际利用过程中需要解决的问题以及未来的发展方向——以生物质为核心的多联产系统。     

秸秆类生物质隧道式沼气发酵技术与装置研究

传统隧道式沼气池由于工艺落后、产气率低,已很难适应现代沼气事业的发展。通过对传统隧道式沼气池中发酵原料的存在状态与运行方式,原料、沼气菌、水三者之间的接触方式以及发酵特点的分析,指出了传统隧道式沼气池存在的问题。针对存在的问题,研究出一种新型隧道式沼气发酵装置,发酵原料在新型隧道式沼气发酵装置中的存在状态由原来的混乱、自然分层、堆集变成了可控、有序排列、悬浮,沼气池的容积率、产气率和原料利用率变得更高,原料适应范围更广,管理更简单,使定量管理沼气发酵成为可能。     

Environmental,social, and economic assessment of energy utilization of crop residue in China

This paper aims to discuss an environmental, social, and economic analysis of energy utilization of crop residues from life cycle perspectives in China. The methodologies employed to achieve this objective are environmental life cycle assessment (E-LCA), life cycle cost (LCC), and social life cycle assessment (S-LCA). Five scenarios are developed based on the conversion technologies and final bioenergy products. The system boundaries include crop residue collection, transportation, pre-treatment, and conversion process. The replaced amounts of energy are also taken into account in the E-LCA analysis. The functional unit is defined as 1 MJ of energy produced. Eight impact categories are considered besides climate change in E-LCA. The investment capital cost and salary cost are collected and compared in the life cycle of the scenarios. Three stakeholders and several subcategories are considered in the S-LCA analysis defined by UNEP/SETAS guidelines. The results show that the energy utilization of crop residue has carbon emission factors of 0.09–0.18 kg (CO₂ eq per 1 MJ), and presents a net carbon emissions reduction of 0.03–0.15 kg (CO₂ eq per 1 MJ) compared with the convectional electricity or petrol, but the other impacts should be paid attention to in the biomass energy scenarios. The energy utilization of crop residues can bring economic benefit to local communities and the society, but the working conditions of local workers need to be improved in future biomass energy development.     

Potential of biomass residues for energy production and utilization in a region of Portugal

This article concentrates on the evaluation of the potential of biomass residues, both forest and agricultural residues, for energy production and utilization in a region of Portugal (Marvão). Marvão has been identified as an excellent region for the installation of small-scale biomass plants for heating purposes given the relatively high potential of biomass residues that it presents. The assessment of the potential of the biomass residues was carried out using Geographical Information Systems (GIS) database and statistical analysis. It was concluded that the annual biomass residues potential for Marvão is about 10,600 tonnes, which corresponds to an energy production potential of about 106,000 GJ per annum. In addition, to illustrate the potential of biomass residues for energy utilization in the region of Marvão, the heating system of a hotel located in Marvão village has been analyzed as a case study. It was concluded that the conversion of the existing fossil fuel-based heating system to a biomass-based system would have economical and environmental advantages for local investors.     

生物质能利用技术现状及进展

在阐述生物质能源开发利用意义的基础上,针对现有的生物质能利用技术的发展现状进行了综合分析,主要介绍了生物质燃烧技术、生物质气化技术和生物质液化技术以及生物化学转化过程,指出了在目前形势下,大力发展生物质能利用技术具有广阔的前景.     

生物的能源利用和生物质气化

生物质可泛指有机物质.从能源利用角度来说是指储存太阳能又可释放热能的植物.自从人类发现并发明对火的应用,生物质能的燃烧热利用伴随着人类文明的进步,在漫长的历史进程中,曾成为人类赖以生存的能量之源.从实用角度,这里的生物质能是指林业和农业生产加工剩余物,如枝条、秸秆、树皮、锯末屑、灌木条、谷果壳等.     

Reed canary grass biomass yield and energy use efficiency in Northern European pedoclimatic conditions

Reed canary grass is a potential bio-energy crop in Northern Europe. As plantation biomass production depends on local pedoclimatic conditions, it is important to evaluate yield in the context of soil-specific characteristics. The current study used regression models to evaluate reed canary grass yield variability in the context of soil nitrogen (N) content and in applied mineral N fertilisers. Reed canary grass bio-energy potential was evaluated in a soil-specific manner to calculate the production and energy use efficiency. Soils with low N content produce yields of almost 1 Mg ha⁻¹ in years with unsuitable weather conditions for plant growth. The average dry matter yield of 6-7 Mg ha⁻¹ is achievable within limited years on soils with N contents of more than 0.6%. Fertilisation increases the yield and decreases yield variability in humus-poor soils, but on soils with high N content, production risks increase with increasing N fertiliser applications. Energy use efficiency decreases with increasing input on Histosols; increasing the input from 6 to 31 GJ ha⁻¹ results in energy use efficiency decreasing from 9 to 2 GJ GJ⁻¹. As a consequence of energy use efficiency, a diminishing return occurs on Haplic Albeluvisol, as optimum efficiency peaks at 5.2 GJ GJ⁻¹ using 198 kg N ha⁻¹. The current study integrated the developed models in the soil Geographic Information System and calculated the energy use efficiency of selected areas. This approach enables researchers to evaluate production risks in the region and provides a framework for knowledge-based bio-energy production.     

Biomass and biomass water use efficiency in oilseed crop (Brassica juncea L.) under semi-arid microenvironments

Biomass production in arid and semi-arid regions requires a special attention owing to spatiotemporal scarcity of irrigation water wherein improved water use efficiency (WUE) of the crop is targeted. Under field conditions, the crop undergoes dynamic changes in near ground or within-canopy microenvironments. This changed microclimatic condition may have an impact on phenological response of the oilseed crop which in turn would affect biomass productivity, economic seed yield and water use efficiency of the crop. Henceforth, quantification of biomass production and its WUE of oilseed Brassica crop is essentially required owing to have better understanding of the crop water requirement under the era of climate change. Following a 2 years field experiment, it was revealed that the changes in leaf area index were explained by about 68–74%. The best fit polynomial third order regression analysis indicated >93% prediction in biomass production as a function of time factor. Improved biomass partitioning into economic sinks was also observed. Small scale change in near ground microenvironment may reduce the prediction of biomass variability to the extent of 3%. The mean ET variations were observed as 2.4, 1.5 and 3.2 mm day⁻¹ during the critical phenological stages. Mean seed yield, biomass WUE and seed yield WUE ranged between 2.71 and 2.87 Mg ha⁻¹, 11.4 and 13.1 g m⁻² mm⁻¹ and 19.3 and 22.9 kg ha⁻¹ mm⁻¹ respectively. Variations in both biomass and seed yield water use efficiencies due to small scale change in near ground microclimates were revealed.     

An analysis of energy use efficiency of canola production in Turkey

In this study, a survey and economic analysis regarding the use of input have been performed with canola farmers in the Trakya region of Turkey; survey data were obtained from 100 farmers, face-to-face. The average energy use efficiency is 4.68 and this value increases as farm size increases; according to the results of this study, energy is used more efficiently in large farms. The difference between average input and output energy is 67259.36 (MJ ha⁻¹). The specific energies of small, medium, and large farms are 62584.37, 69836.21, and 74405.43 respectively. The ratio of direct and indirect energy sources are 24.69%, and 75.31% respectively, and the benefit–cost ratio of canola production is 2.09.     

An overview of biomass energy utilization in Vojvodina

The Autonomous Province of Vojvodina is an autonomous province in Serbia. It is located in the northern part of the country, in the Pannonia plain. Vojvodina is an energy-deficient province. Energy plays a pivotal role in socio-economic development by raising the standard of living. Biomass has been used by mankind as an energy source for thousands of years. Traditional fuels like firewood, dung and crop residues currently contribute a major share in meeting the everyday energy requirements of rural and low-income urban households in Vojvodina. Contribution of the renewable energy sources in the total consumption of energy in Vojvidina is less than 1%, i.e. it amounts to 280 KWh/year. Production of biodiesel in the year 2008 was 0.07 million tons, what is for 133% higher with respect to the production in the year 2007 (0.03 million tons). In Vojvodina, as the raw materials for bioethanol production are seen primarily sugar beet, corn, wheat surpluses, potato surpluses and waste potato, as well as the raw materials intended for these purposes grown on the uncultivated soils, such as hybrid broomcorn, Jerusalem artichoke and triticale. With introduction of new technologies for cultivation and collecting of biomass production of the electrical energy could be raised to 6.4 GWh/m² year, what, with retention of the contemporary consumption, would represent the significant 9% of the total consumption in the province. According to programme of realisation of energy strategy of Vojvodina/Serbia in the field of the renewable energy sources for to period till the year 2010 and its completion, till the year 2015, in Vojvodina could be created conditions for the employment of about 24,000 workers, i.e. 4000 employed for maintenance of the newly constructed plants, 17,000 employed on designing and manufacturing of plants and 3000 employed in auxiliary activities.     

生物质能利用技术比较与分析

生物质能的开发利用可同时解决环境污染和能源短缺问题。分析了生物质能源的特点及其利用现状，并对国内外生物质能利用技术进行了分析与比较，为生物质能利用技术的发展提供参考。     

牛粪与蘑菇渣厌氧混合发酵产沼气研究

文章以牛粪和蘑菇渣为研究对象,进行了牛粪和蘑菇渣厌氧混合发酵的批次实验,并对厌氧混合发酵过程的累积甲烷产量进行了模型拟合。研究结果表明:蘑菇渣和牛粪的质量比为1∶3时,发酵系统的产甲烷效果和稳定性最好;但是,相对于单一牛粪发酵而言,混合发酵的产气量并没有表现出更多的优势;Gompertz模型更适合于牛粪和蘑菇渣厌氧混合发酵实验组累积甲烷产量的预测和分析。     

Hydrogen production from Chlamydomonas reinhardtii biomass using a two-step conversion process: Anaerobic conversion and photosynthetic fermentation

Chlamydomonas reinhardtii UTEX 90 accumulated 1.45 g dry cell weight and 0.77 g starch/L during photosynthetic growth using TAP media at 25 ^°C${}^{°}\mathrm{C}$ in presence of 2% _CO2${\mathrm{CO}}_2$ for 3 days. C. reinhardtii biomass was concentrated and then converted into hydrogen and organic acids by anaerobic fermentation with Clostridium butyricum. Organic acids in the fermentate of algal biomass were consecutively photo-dissimilated to hydrogen by Rhodobacter sphaeroides KD131. In the concentrated algal biomass 52% of the starch was hydrolyzed to 37.1 mmol _H2${\mathrm{H}}_2$/L-concentrated algal biomass and 13.6, 25.5, 7.4 and 493 mM of formate, acetate, propionate, and butyrate, respectively by C. butyricum. R. sphaeroides KD131 evolved 5.72 mmol _H2${\mathrm{H}}_2$ per ml-fermentate of algal biomass under illumination of 8 klux at 30 ^°C${}^{°}\mathrm{C}$. Only 80% of the organic acids, mainly butyrate, were hydrolyzed during photo-incubation. During anaerobic conversion, 2.58 mol _H2/mol${\mathrm{H}}_2/\mathrm{mol}$ starch–glucose was evolved using C. butyricum and then 5.72 mol _H2/L${\mathrm{H}}_2/\mathrm{L}$-anaerobic fermentate was produced by R. sphaeroides KD131. Thus, the two-step conversion process produced 8.30 mol _H2${\mathrm{H}}_2$ from 1 mol starch–glucose equivalent algal biomass via organic acids.     

大气环境和能源利用技术

本文介绍了世界的现状和今后十余年对能源需求的预测,能量消费和大气环境的关系。不同能量消费对环境影响的程度以及在能量消费不断增长的情况下改善大气环境的措施。同时得意介绍了寿命周期和环境影响评价的方法。     

Birch production and utilization for energy

Natural birch stands represent a significant biomass resource since birches are one of the most common deciduous genera in cool temperate regions, even in places ranging up to the forest line. Many characteristics of birch make it highly suited for short rotation forestry. However, growing birch in very short rotations (less than 10 years) in northern climates is not worthwhile on the basis of biomass production and economics. Rotations of 15 to 20 years may give good results everywhere. The intensive culture of birch plantations has largely remained untested, but it is very likely that the yield levels can be increased significantly by using cloned material as well as improved silvicultural treatments, fertilization and pest control. Birch feedstock, compared to material of many other tree species, is of even quality. Moisture content is low and basic density high. Branches and bark are also suitable for energy use. Birch plays an important part in the energy budget of entire nations, particularly of Finland and Sweden     

Estimation of potential biomass resource and biogas production from aquatic plants in Argentina

It is expected that the future construction of the Paraná Medio Hydroelectric Project on the middle Paraná River in Argentina will lead to the accumulation of floating hydrophytes, mainly water hyacinth. Several problems are related to aquatic plants, and steps for efficient control of the vegetation should be taken. If mechanical control is used, the biomass must be processed, preferably in a useful way. Water hyacinth growth in the middle Paraná River has been measured and its bioconversion to methane by anaerobic fermentation determined. It is estimated that gross methane production may be between 1.0 and 4.1 × 10 m³/yr. The fermentation residue production, with a potential value as soil condition, may represent between 54.9 and 221.4 × 10³ t nitrogen/year, i.e., between 2 and 8 times the present nitrogen fertilizer demand in Argentina.     

Analysis of the energy efficiency of solar aided biomass gasification for pure hydrogen production

This paper presents a simulative analysis of the energy efficiency of solar aided biomass gasification for pure hydrogen production. Solar heat has been considered as available at 250 °C in three gasification processes: i) gasification reactor followed by two water gas shift reactors and a pressure swing adsorber; ii) gasification reactor followed by an integrated membrane water gas shift reactor; iii) supercritical gasification reactor followed by two flash separators and a pressure swing adsorber.