Technical/economic/environmental analysis of biogas utilisation

Biogas may be utilised for Combined Heat and Power (CHP) production or for transport fuel production (CH₄-enriched biogas). When used to produce transport fuel either electricity is imported to power the plant or some of the biogas is used in a small CHP unit to meet electricity demand on site. The potential revenue from CH₄-enriched biogas when replacing petrol is higher than that for replacing diesel (Irish prices). Transport fuel production when replacing petrol requires the least gate fee. The production of greenhouse-gas is generated with cognisance of greenhouse-gas production with the scheme not in place; landfill of the Organic Fraction of Municipal Solid Waste (OFMSW) (20% of biomass) with and without combustion of landfill gas is investigated. The transport scenario with importation of brown electricity generates more greenhouse-gas than petrol or diesel, when the ‘do-nothing’ case involves combustion of landfill gas. The preferred solution involves transport fuel production with the production of CHP to meet electricity demand on site. A shortfall of this solution is that only 53% of biogas is available for export.     

Using landfill gas: A UK perspective

Landfill gas (LFG) is a flammable and potentially harmful mixture of methane, carbon dioxide and a large number of trace constituents produced when waste decays in landfills. The need to prevent harm from LFG emissions has been recognised since the 1970s, and is now enshrined in site regulations. Control measures such as gas extraction wells and multi-layered liners are now being implemented on a wide scale. Using LFG as a fuel or feed stock can complement the requirements of control for environmental protection, whilst providing an additional revenue stream and displacing conventional fuels. Use of LFG for power generation began in the UK in 1985 and government support for electricity from renewable sources has made this its dominant application. By the end of 1993 there were 49 power generation projects with a combined capacity of 80 MWe, generating 447 GWh of electricity in the year. In addition, the 12 direct use schemes using LFG as a fuel for kilns and boilers produced a further 9,200 GJ as heat. This paper reviews the processes of LFG formation and the technology and economics of generating electricity from it in the UK, and outlines the scope for further development.     

Economic analysis of renewable heat and electricity production by sewage sludge digestion—a case study

In this paper, we assess the total cost of energy recovery from sewage sludge through anaerobic digestion with biogas utilization in combined heat and power (CHP) system. The important advantage of anaerobic digestion process is the production of biogas, which can be used to generate electricity and heat as a source of renewable energy. From this study, it can be retained that the generated thermal energy from the anaerobic digestion process meets the needs of the wastewater treatment plant (WWTP) and guarantees its self‐sufficiency in heat. The surplus of renewable heat produced by CHP is not a primary factor to improve the economic viability of the process. Moreover, the sales of electricity output represent about 76% of the operating costs of anaerobic digestion process. Renewable energy production is not economically viable by its own, without considering the wastewater treatment function and the associated incomes. Nevertheless, sludge digestion helps to reduce the wastewater treatment costs mainly by giving a good source of revenue via electricity production. Copyright © 2014 John Wiley & Sons, Ltd.     

Insights into the production potential and trends of China's rural biogas

China, one of the countries in the world abundant in agricultural wastes, has a great potential for rural biogas production. As a strategy for building a new socialist countryside and sustainable agriculture in rural China, the development of biogas is an important means to convert agricultural wastes to clean and safe energy, thereby reducing the need for fossil fuel and alleviating environmental pollution. This study presents an assessment of the biogas production potential, its current development state, and perspectives of agricultural wastes in rural China. Estimated data show that annual biogas potential from agricultural wastes is approximately (3350.58 ± 669.28) × 10⁸ m³ (equal to 239.22 ± 47.78 million tons of equivalent standard coal); such potential has been underutilized in the past. By analyzing and summarizing the direction for future development and various benefits of rural biogas in China, we present burning questions and countermeasures for biogas development and recommend that the future development of rural biogas in China should focus on both household‐scale and large‐scale development, giving priority to the establishment of large‐scale biogas engineering and biogas plants, improvement of biogas comprehensive utilization level, and construction of a reticular model of systemized green agricultural engineering linked with biogas to solve completely the problem of agricultural waste accumulation and improve the living conditions in rural China. Copyright © 2015 John Wiley & Sons, Ltd.     

柴达木盆地第四系生物气资源量预测

针对柴达木盆地第四系生物气藏形成的特殊地质条件及相对较低的勘探程度,分别采用地质类比法、成因法和统计法对第四系生物气资源量进行预测,并运用蒙特卡罗法对预测的结果进行汇总,确定第四系生物气资源量为10 420×108m3,可采资源量为5 702×108m3.对相应的评价区带展开生物气潜力分析,确定近期第四系生物气勘探的重点为北斜坡和中央凹陷.根据该区第四系勘探认识程度及生物气剩余资源分布特征分析,认为在进行潜伏构造和岩性圈闭勘探的同时,寻找浅层气藏、低压水溶气藏也是今后第四系生物气勘探的主要目标.     

华南地区稻草的厌氧干发酵制取沼气研究

研究了经过C/N调节和白腐菌预处理后的稻草在不同温度条件下的干发酵瓶试实验,并根据瓶试实验结果以及华南地区的气候条件,进行了常温1m3罐试实验.瓶试实验结果表明在35℃条件下秸秆干发酵较为稳定,具有较高的产气率、产甲烷率及沼气质量.1m3罐试实验在常温条件下运行89d,累积产气量22.6m3,且前45d的累积产气量约占总产气量的80.4%.发酵原料产气率为570L/kgVS,产甲烷率为240L/kgVS,甲烷百分含量最高可达62%.从pH值、产气量和甲烷百分含量来看,整个发酵过程均为正常发酵.通过循环发酵液的罐试实验表明,发酵液的循环能有效避免酸中毒并提高产气率和产甲烷率,对稻草干发酵而言,循环发酵液是一种较好的搅拌方式.该工艺可为华南地区稻草秸秆的资源化利用提供依据.     

当前水污染治理的系统思考——建立城乡大循环 彻底根治水污染

提出治理水污染需要在现代农业背景下重建城乡之间物质循环系统,可通过"沼气推广工程"对农村污染源进行无害化处理,通过"沼气试点工程"对城市生活污水进行资源化利用,通过"沼气净化工程"对小城镇污水进行达标处理,通过"沼气回收工程"使企业有机污染物变废为宝,最后引进自然生态系统进化工程,使水体达到充分净化。