Optimization of biogas production by anaerobic digestion for sustainable energy development in Zimbabwe

There is increasing international interest in developing low carbon renewable energy technologies. Biomass is increasingly being utilized as an energy source throughout the world. Several modern technologies have been developed that convert biomass to bioenergy. Anaerobic digestion is a mature energy technology for converting biomass to biogas, which is a renewable primary energy source. Biogas is a robust fuel that can be used to supply heat, electricity, process steam and methanol. There are vast biomass resources in Zimbabwe that have good potential for biogas production by anaerobic digestion. However, anaerobic digestion is not being optimally used as a biomass conversion technology in the country. This paper presents an overview of biogas production in Zimbabwe and outlines technical options that can be utilized to optimize biogas production by anaerobic digestion in the country.     

我国沼气技术的利用现状与前景展望

通过分析常用几种生物质能资源的发酵技术来阐述了我国对沼气的利用现状,并对沼气技术存在的问题提出了解决办法,对沼气技术的前景进行了展望。     

多元原料混合发酵制备沼气技术研究进展

目前,我国沼气的发酵原料主要是禽畜粪便和农作物秸秆,随着厌氧发酵技术的发展,更多种类废弃物也逐步受到人们的关注。有机废弃物沼气化利用在我国生态文明建设中有着重大意义。论文综述了我国生物质资源,如禽畜粪便、农作物秸秆、农产品加工废弃物、市政有机废弃物和能源作物的特性和作为沼气发酵原料的优缺点,比较了这些原料的沼气生产潜力,探讨了混合原料发酵技术及重要的几种沼气发酵外源添加剂。     

Overview of renewable energy sources in the Republic of the Sudan

Sudan is an agricultural country with fertile land, plenty of water resources, livestock, forestry resources and agricultural residues. An overview of the energy situation in Sudan is introduced with reference to the end uses and regional distribution. Energy sources are divided into two main types: conventional energy (biomass, petroleum products and electricity) and non-conventional energy (solar, wind, hydro, etc.). Sudan possesses a relatively high abundance of solar radiation, moderate wind speeds, hydro and biomass energy resources. Application of new and renewable sources of energy available in Sudan is now a major issue in strategic planning for alternatives to fossil fuels to provide part of local energy demand. Sudan is an important case study in the context of renewable energy. It has a long history of meeting its energy needs through renewables. Sudan’s renewables portfolio is broad and diverse, due in part to the country’s wide range of climates and landscapes. Like many of the African leaders in renewable energy utilisation, Sudan has a well-defined commitment to continue research, development and implementation of new technologies. Sustainable low-carbon energy scenarios for the new century emphasise the untapped potential of renewable resources. Rural areas of Sudan can benefit from this transition. The increased availability of reliable and efficient energy services stimulates new development alternatives. Renewable environmentally friendly energy must be encouraged, promoted, implemented and demonstrated, for use in the Republic of the Sudan.     

Socio-economic hurdles to widespread adoption of small-scale biogas digesters in Sub-Saharan Africa: A review

The unsustainable use of fossil fuels has led to increased awareness and widespread research on the accessibility of renewable energy resources such as biogas. Biogas is a methane rich gas that is produced by anaerobic fermentation of organic material. Despite its potential to replace biomass in Africa, where over 70% of the households use wood fuel and agricultural waste for cooking, biogas technology has not been adopted by Sub-Saharan African countries compared to their Asian counterparts. This paper examines the socioeconomic constraints to adoption of biogas in Sub-Saharan Africa and explores factors that could enhance adoption of the technology. These include standardization and quality control, as well as an approach of integrated farming using biogas and slurry. The article recommends mobilization of local and external funds to promote biogas, use of ready to use funds such as the Clean Development Mechanisms in overcoming the initial construction costs of biogas units, and formation of user and disseminator associations to reduce costs by joint procurement and linkage to finance. It further advocates the promotion of multiple uses of biogas for purposes other than cooking and lighting. It is expected that widespread adoption of the technology could lead to self-sufficiency in household energy provision for cooking. This would facilitate environmental management and economic development in Sub-Saharan Africa.     

Biogas as a potential renewable energy source: A Ghanaian case study

The associated harmful environmental, health and social effects with the use of traditional biomass and fossil fuel has enhanced the growing interest in the search for alternate cleaner source of energy globally. Ghana, a developing country depends heavy on woodfuel as a source of fuel contributing about 72% of the primary energy supply with crude oil and hydro making up the rest. Biogas generation has simply been seen as a by-product of anaerobic digestion of organic waste. Having proven to be a practicable and promising technology, it has been very successful and a very reliable and clean source of energy when proper management programmes are followed. There are vast biomass resources including organic waste in Ghana that have the potential for use as feedstock for biogas production to reduce the over reliance of woodfuel and fossil fuel, and to help reduce the it would reduce greenhouse gas emissions which may be affecting climate change. Ghana having the technical potential of constructing about 278,000 biogas plants, only a little over 100 biogas plants has so far been established. This paper presents the energy situation and the status of the biogas technology and utilization in Ghana. It also presents the potential benefits, prospects and challenges of the biogas technology.     

生物质气化发电技术

随着人们对能源需求的日益增长，作为人类目前主要能源来源的化石燃料却迅速减少，而生物质能是一种重要的可再生能源，它分布广泛，数量巨大。但由于它能量密度低，又分散，收集和运输困难，所以难以大规模集中处理。另一方面随着经济的发展，我国电力供应日益紧张，对电力需求很大，电价居高不下，在这种环境下，通过气化发电技术，把生物质转化为电力，既能大规模处理生物质废料，又能为生产提供电力，具有明显的社会和经济效益。本文主要讲述生物质的气化技术，生物质气净化处理技术及生物质气用于内燃机的发电技术。     

Pretreatment of lignocellulosic biomass for enhanced biogas production

Lignocellulosic biomass is an abundant organic material that can be used for sustainable production of bioenergy and biofuels such as biogas (about 50–75% CH₄ and 25–50% CO₂). Out of all bioconversion technologies for biofuel and bioenergy production, anaerobic digestion (AD) is a most cost-effective bioconversion technology that has been implemented worldwide for commercial production of electricity, heat, and compressed natural gas (CNG) from organic materials. However, the utilization of lignocellulosic biomass for biogas production via anaerobic digestion has not been widely adopted because the complicated structure of the plant cell wall makes it resistant to microbial attack. Pretreatment of recalcitrant lignocellulosic biomass is essential to achieve high biogas yield in the AD process. A number of different pretreatment techniques involving physical, chemical, and biological approaches have been investigated over the past few decades, but there is no report that systematically compares the performance of these pretreatment methods for application on lignocellulosic biomass for biogas production. This paper reviews the methods that have been studied for pretreatment of lignocellulosic biomass for conversion to biogas. It describes the AD process, structural and compositional properties of lignocellulosic biomass, and various pretreatment techniques, including the pretreatment process, parameters, performance, and advantages vs. drawbacks. This paper concludes with the current status and future research perspectives of pretreatment.     

生物质气化发电技术

随着人们对能源需求的日益增长,作为人类目前主要能源来源的化石燃料却迅速减少,而生物质能是一种重要的可再生能源,它分布广泛,数量巨大。但由于它能量密度低,又分散,收集和运输困难,所以难以大规模集中处理。另一方面随着经济的发展,我国电力供应日益紧张,对电力需求很大,电价居高不下,在这种环境下,通过气化发电技术,把生物质转化为电力,既能大规模处理生物质废料,又能为生产提供电力,具有明显的社会和经济效益。本文主要讲述生物质的气化技术,生物质气净化处理技术及生物质气用于内燃机的发电技术。     

生物质气化技术面临的挑战及技术选择

生物质气化可实现低品位生物质能的深层次利用,不同地区、不同行业有不同的能源需求和产业结构,应合理选择生物质气化技术。固定床气化技术针对的是中小规模应用,该技术存在的问题包括焦油含量高、规模小、机械化和自动化程度较低、发电效率低等。流化床气化技术针对的是中等及以上规模应用,目前需要解决的问题是热效率低,发电效率低,需要开发高气化效率和无焦油的燃气型气化炉、低热值燃气轮机、高效燃气净化系统,以便采用BIGCC技术。沼气技术是一项生物质综合高效清洁利用的多联产工艺,目前急需开发高效高浓度厌氧消化的沼气发酵工艺和配套的集成设备,培育和筛选高效沼气发酵微生物菌群,简化沼气净化工序,解决沼液、沼渣的利用难题等。生物质快速热解技术是一种高温处理过程,其最大的优点是产物生物油易于储存运输,不存在产品规模和消费的地域限制问题。从工艺特点、经济效益和规模化生产来看,沼气技术更适合处理高含水的养殖业粪便,快速热解技术更适合农作物秸秆的规模化转化,燃气型气化技术更适合社区生活垃圾和农林产品加工废弃物的处理。     

The environmental benefits of domestic biogas technology in rural Ethiopia

This study examined the diverse environmental impacts of domestic biogas technology in rural Ethiopia. It employed a cross-sectional survey approach involving a total of 358 sample biogas-user and non-user households. The results of the analyses showed that the substitution of traditional biomass fuels and kerosene with biogas energy enabled the biogas-user households to reduce greenhouse gas (GHG) emissions on average by about 1.9 t of CO₂ equivalents per digester per year. The reduced use of chemical fertilizer also assisted GHG emission reductions. Moreover, the technology helped in reducing depletion of woody biomass through improving efficiency of energy use and energy substitutions. It assisted in improving the fertility of soil via reducing biomass removals as fuel and the direct use of nutrient enriched bio-slurry. Furthermore, the reduced biomass removals contributed to carbon sequestration. To further enhance the diverse environmental benefits of the technology, proper and uninterrupted operation and utilization of the biogas technology should be ensured; skillful and standby biogas technicians should be present at reasonable distances to provide maintenance and aftersales services. An operational platform for joint stakeholders' actions should also be in place to assist in exploiting its full potential, and seeking and realizing the carbon reduction financial incentive for the households.     

Intensification of biogas production using various technologies: A review

Anaerobic digestion (AD) is an organic matter conversion technology which offers a wide range of options for production of biogas from organic biomass, providing an excellent opportunity to convert abundant bioresources into safe, eco-friendly, renewable energy. Important factors in the process of AD are the biodiversity of microorganisms, chemical load of oxygen demand, and content of water and total solids. A challenge for the future is to find technologies that will maximally enhance biogas production and to find pathways for biogas to supersede well-established technologies and practices in the contemporary heavily fossil fuel-based energy system. Current studies on technologies of biogas production indicate a number of possibilities of using appropriate biological and physicochemical additives, like added enzymes or fruit pomace, as well as immobilizing microorganisms on biofilters. Anaerobic biorefinery is an emerging concept that generates not only bioenergy but also high-value biochemical products from the same feedstock. This study is a review of articles describing the intensification of biogas production by using various technologies.     

水合物技术在沼气配送中的应用

我国沼气资源丰富,但是大量中小沼气工程受规模限制未能得到充分有效的利用,可通过高效收集方式将沼气集中后进行高值利用。文章介绍了一种可用于沼气配送的新方法——水合物配送技术,该技术具有储气能力强、安全性高、经济性和灵活性好等诸多优点,不但可以用于沼气配送,而且能对沼气进行分离提纯。通过对气体水合物技术基本原理、储运与提纯发展状况的分析,论述了该技术在我国沼气配送和提纯应用中的优势,并针对我国沼气分散、气量小的特点提出了沼气水合物特色配送路线。     

Effective renewable energy activities in Bangladesh

Bangladesh is endowed with plentiful supply of renewable sources of energy. Out of the various renewable sources, solar and biomass and to a limited extend, wind and hydro-power are effectively used. This paper, discusses the effective applications of these resources. Bangladesh receives an average daily solar radiation of 4–6.5 kWh/m². Solar photovoltaic (PV) are gaining acceptance for providing electricity to households and small business enterprises in grid remote rural areas. Under the ‘Rural Electrification and Renewable Energy Development (RERED) Programme’ a total of 64,000 SHSs will be installed by 2007. So far, a total of 37,000 SHSs with a capacity of about 2.5 MWp have been installed in the country.The next effective source of renewable energy is biomass. Under this category improved stoves, bio-gas plant and bio-mass briquitting are note worthy. The Institute of Fuel Research and Development (IFRD) has developed a number of improved stoves. These stoves save 50–70% fuel as compared to the traditional ones. So far, more than 100,000 stoves have been installed in the users kitchens. The potential of biogas technology is immense. According to an official estimates there is a cattle population of 24 million and poultry population of 75 million. This can produce about 3 billion m³ biogas. The Local Government Engineering Department (LGED) and IFRD are working to install the biogas plants in the rural areas. So far, a total of 19,596 biogas plants have been installed. Khulna University of Engineering and Technology (KUET) has successfully under took a research and development work on biomass briquitting technology with a grant from SIDA. By now, this technology has transferred to private entrepreneurs. Currently, about 60 small private enterprises are producing briquettes from rice husk and saw dust.Because the country is flat, hydropower is not abundant. At present, 230 MW is harnessed from the Kaptai dam. Besides, in the southeastern hilly regions a few micro-hydro sites have been identified. Very recently, one 10 kW micro-hydro plant has been installed by LGED at Bamerchara in Chittagong.Wind energy potential is not encouraging except in the coastal areas of Bangladesh. A few wind turbines have been installed as demonstration units. A project is going on for wind mapping of the country by LGED     

The role of renewable and sustainable energy in the energy mix of Malaysia: a review

Energy consumption has risen in Malaysia because of developing strategies and increasing rate of population. Depletion of fossil fuel resources, fluctuation in the crude oil prices, and emersion of new environmental problems due to greenhouse gasses effects of fossil fuel combustion have convinced governments to invest in development of power generation based on renewable and sustainable energy (RSE) resources. Recently, power generation from RSE resources has been taken into account in the energy mix of every country to supply the annual electricity demand. In this paper, the scenario of the energy mix of Malaysia and the role of RSE resources in power generation are studied. Major RSE sources, namely biomass and biogas, hydro‐electricity, solar energy, and wind energy, are discussed, focusing more toward the electrical energy demand for electrification. It is found that power generation based on biomass and biogas utilization, solar power generation, and hydropower has enough spaces for more development in Malaysia. Moreover, minihydropower and wind power generation could be effective for rural regions of Malaysia. Copyright © 2014 John Wiley & Sons, Ltd.     

沼气重整制合成气技术可行性探讨

论述了沼气的组成和利用现状,通过天然气蒸汽重整中的加碳技术说明了沼气中二氧化碳的利用价值。借鉴天然气重整工业经验和模拟沼气重整的实验室研究,探讨了沼气重整制合成气技术的可行性,初步提出了沼气重整制合成气的试验方案。分析认为,沼气通过脱硫、脱氧、与水蒸气混合加热进行重整制合成气是提高沼气综合利用率的有效途径,为沼气重整制合成气工业研究提供了参考依据。     

生态村分布式供能系统分析

针对广大农村沼气和太阳能利用率低的问题,提出了一种生物质能与太阳能互补综合利用的生态村分布式供能系统。该系统将太阳能光伏发电、太阳能光热转换、生物质气化与常规燃气发电整合,实现生物质能与太阳能的供电、供暖、制冷、供燃气和供热水五联产,可有效缓解新农村含碳能源利用带来的环境和安全性问题,有效解决生物质利用效率低和太阳能利用不稳定等技术瓶颈问题。以唐山市沙河驿镇唐庄子村为例,优化生态村分布式供能系统方案,其研究结果可为生态村的建设提供技术支撑。     

生物质能利用技术的经济性分析

对国内生物质能利用技术的现状进行了简要介绍和分类，以经济评价为基础，对生物质直接燃烧、户用沼气池、生物质气化发电、大中型养殖场沼气工程和垃圾发电等生物质能技术进行了综合分析，提出了根据地方实际，发展不同生物质能技术的建议。     

A critical review on global trends in biogas scenario with its up-gradation techniques for fuel cell and future perspectives

Renewable biogas production technology is an excellent method for eradication of greenhouse gas emission and thereby reducing global warming. This review discusses extensively on global biomass potential, energy need and method of satisfying the energy demand through sustainable techniques. One of the best alternative technological developments for the conversion of waste into useful energy is anaerobic digestion to produce biogas. It is recognized as one among leading green energy to manage the environmental and meet the current energy tasks to tackle globally. Generally, biogas can be utilized for cooking, heat and electricity generation. In order to extend the scope of application, traces of carbon dioxide, hydrogen sulphide has to be removed by several upgrading technologies to produce high purity methane (90%). This study discusses on biogas up-gradation using physical and chemical absorption, membrane separation, cryogenic separation, hybrid technology etc. Among the various up-gradation techniques, hybrid technology yields methane purity of 97%. In addition, this work reviews about benefits and problems in anaerobic integrated Solid Oxide Fuel Cell (SOFC) with latest real-world achievement in SOFC. Several SOFC systems with dynamic model development were reviewed based on efficiency of power generation. SOFC generates 45% more electricity than generator with heat engine. This review extends the scope for further research in biogas upgradation and global warming mitigation potential with carbon credits.     

Contrastive study between the biomass energy utilization structure and the ecotype energy utilization structure in rural residences — A case in Hunan province,China

The purposes of this study are to look into the actuality of rural residential energy consumption in Hunan province, China, to improve rural residential energy utilization structures, and to protect the environment. An investigation on rural residential energy consumption was carried out in the villages of Xintian and Jiangwan in the spring and summer of 2005. Biomass energy is used in Xintian while biogas is popularized in Jiangwan. A questionnaire survey covered basic information of residences in the two villages, and energy consumption data of each family in the spring and summer were also recorded continuously. The characteristics of energy utilization structures of the two villages, the one with biomass energy utilization structure and the other with the ecotype energy utilization structure, are contrasted, and seasonal variance characteristics of energy consumption in spring and summer are analyzed. Sequentially, influence factors of rural residential energy consumption are further discussed qualitatively and quantificationally. Environmental benefit is assessed finally when biogas substitutes biomass energy. Conclusions are summarized as follows: In Xintian, a complicated energy structure is still dominant, where biomass energy accounts for a significant proportion and manifold energy resources exist simultaneously; the energy consumption is high; categories of energy resources used by households vary between spring and summer. The energy structure is definitely better in Jiangwan, where the ratios of commercial energy and ecotype energy used are both higher than those in Xintian and the ratio of biomass energy is smaller. Categories of used energy resources are also more constant in spring and summer. The total energy use amount of each season in Xintian is larger than that in Jiangwan respectively, while there is little difference in the efficiency energy use amount of each season between the two villages. Qualitative and quantitative analyses show that the accessibility of local energy resources, the domestic economical level, governmental energy policies, and consumption conceptions of farmers affect energy utilization structures definitely, while the efficiency of cookers, the number of family members, and annual income have effect on energy consumption amounts. Environmental analysis shows that the usage of biogas makes a great contribution in optimizing the energy consumption structure, reducing energy consumption, discharging less harmful gases and keeping the ecosystem in balance. The comparison between biomass energy and ecotype energy provides instructions for future development of rural residential energy consumption in China.