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.     

淮安市生活污水净化沼气池技术应用效益分析

从对生活污水处理效果、资金投入等方面的计算，比较了建设净化沼气池、普通化粪池与污水处理厂集中处理3种方法的优劣，介绍了淮安市生活污水净化沼气池推广应用情况，重点对淮安市净化沼气池推广效益进行了分析。     

厌氧技术处理生活污水及其效果分析

厌氧生活污水分散处理技术具有投资少、能耗低、运行费用小和处理效率高等优点，已成为分散处理城镇生活污水的主要技术，应用前景十分广阔；文章分析和讨论了该技术的原理、设计、工艺和运行效果，结果表明，出水能够达到国家二级排放标准。     

Innovative financing models for low carbon transitions: Exploring the case for revolving funds for domestic energy efficiency programmes

The IEA has estimated that over the next four decades US$31 trillion will be required to promote energy efficiency in buildings. However, the opportunities to make such investments are often constrained, particularly in contexts of austerity. We consider the potential of revolving funds as an innovative financing mechanism that could reduce investment requirements and enhance investment impacts by recovering and reinvesting some of the savings generated by early investments. Such funds have been created in various contexts, but there has never been a formal academic evaluation of their potential to contribute to low carbon transitions. To address this, we propose a generic revolving fund model and apply it using data on the costs and benefits of domestic sector retrofit in the UK. We find that a revolving fund could reduce the costs of domestic sector retrofit in the UK by 26%, or £9 billion, whilst also making such a scheme cost-neutral, albeit with significant up-front investments that would only pay for themselves over an extended period of time. We conclude that revolving funds could enable countries with limited resources to invest more heavily and more effectively in low carbon development, even in contexts of austerity.     

The emerging liquid biofuel market in Argentina: Implications for domestic demand and international trade

While the world's transport energy matrix is still strongly linked to limited and heavily polluting fossil fuels, new markets are appearing for the production and use of alternative transport fuels, such as liquid biofuels. Due to an interconnected global economy, such markets today are developing on a global scale with actors looking to meet local as well as potential international demand. The aim of this paper is to describe and evaluate the emergence of markets for liquid biofuels in Argentina. It reveals that biodiesel production for international supply is likely to emerge in the short run (up to 2010), giving the opportunity to be switched back to local supply in the medium run (post-2010). It also suggests that a bioethanol market (demand and supply) does not seem to be likely in the short run, and it is highly uncertain in the medium run as the most influential actors oppose its development. On the other hand, the current constellations of the biodiesel market appear to leave many uncertainties regarding its sustainability, especially in regard to a limited role of small and medium sized enterprises, and a suitable and diversified biodiesel feedstock. Currently, the focus lies solely on (very) large-scale production of biodiesel derived from soybean oil for the export market.     

Solar assisted biogas plant IIA: Experimental validation of the mathematical models for floating drum type biogas plant

The theoretical predictions presented in an earlier paper for the performance of solar assisted biogas plants are compared with experimental measurements made on four separate systems. There is good agreement between the results and the theoretical predictions.     

Solar assisted biogas plants IV: Optimum area for blackening and double glazing over a fixed-dome biogas plant

The paper presents the economic analysis of a fixed-dome biogas plant of rated capacity 8 m³, above which a part of the ground is blackened and doubly glazed in the cold climate of Srinagar. Blackening and glazing of the ground cannot alone maintain the slurry temperature at 35°C, which is the optimum temperature in the mesophilic range for the anaerobic digestion of cattle dung, and so a part of the biogas must be burnt. The electrical simulation experiments have been performed to determine the loss or gain of heat from the underground biodigestor to the ambient atmosphere through the ground if a part of the ground above is blackened and double glazed. Economic analysis of the system shows that the optimum area to be blackened and glazed would have a radius 1.5 times that of the biodigestor.     

Building capacity for low-carbon communities: The role of grassroots initiatives

Grassroots initiatives for change rely on people with limited power, limited resources and limited ability to influence others. From this position, people acting from the bottom up can change their own actions, seek to influence others around them and seek to change the social structures that they inhabit. These acts are invariably conceived, initiated and enacted within communities, and there is an emerging interest from practitioner, policy and academic circles in the importance of community as a space for realising pro-environmental change. In this paper, we ask what role grassroots initiatives can have in creating low-carbon communities. Using a theoretical framework from work on community-based practice change initiatives, we discuss the interplay between grassroots action and community capacity. We then present two cases of grassroots low-carbon community initiatives in light of this theoretical work. We conclude by discussing key themes emerging from the cases, including the potential for grassroots initiatives to build community capacity for low-carbon practices, and the importance of locally crafted solutions according to the structures specific to place.     

Internalizing externalities of electricity generation: An analysis with MESSAGE-MACRO

This paper examines the global impacts of a policy that internalizes the external costs (related to air pollution damage, excluding climate costs) of electricity generation using a combined energy systems and macroeconomic model. Starting point are estimates of the monetary damage costs for SO₂, NO_X, and PM per kWh electricity generated, taking into account the fuel type, sulfur content, removal technology, generation efficiency, and population density. Internalizing these externalities implies that clean and advanced technologies increase their share in global electricity production. Particularly, advanced coal power plants, natural gas combined cycles, natural gas fuel cells, wind and biomass technologies gain significant market shares at the expense of traditional coal- and gas-fired plants. Global carbon dioxide emissions are lowered by 3% to 5%. Sulfur dioxide emissions drop significantly below the already low level. The policy increases the costs of electricity production by 0.2 (in 2050) to 1.2 € cent/kWh (in 2010). Gross domestic product losses are between 0.6% and 1.1%. They are comparatively high during the initial phase of the policy, pointing to the need for a gradual phasing of the policy.     

Techniques for transformation of biogas to biomethane

Biogas from anaerobic digestion and landfills consists primarily of CH₄ and CO₂. Trace components that are often present in biogas are water vapor, hydrogen sulfide, siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide and nitrogen. In order to transfer biogas into biomethane, two major steps are performed: (1) a cleaning process to remove the trace components and (2) an upgrading process to adjust the calorific value. Upgrading is generally performed in order to meet the standards for use as vehicle fuel or for injection in the natural gas grid.Different methods for biogas cleaning and upgrading are used. They differ in functioning, the necessary quality conditions of the incoming gas, the efficiency and their operational bottlenecks. Condensation methods (demisters, cyclone separators or moisture traps) and drying methods (adsorption or absorption) are used to remove water in combination with foam and dust.A number of techniques have been developed to remove H₂S from biogas. Air dosing to the biogas and addition of iron chloride into the digester tank are two procedures that remove H₂S during digestion. Techniques such as adsorption on iron oxide pellets and absorption in liquids remove H₂S after digestion.Subsequently, trace components like siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide and nitrogen can require extra removal steps, if not sufficiently removed by other treatment steps.Finally, CH₄ must be separated from CO₂ using pressure swing adsorption, membrane separation, physical or chemical CO₂-absorption.     

沼气湿法脱硫新工艺

沼气作为一种生物质能源,已广泛用于内燃机电站发电。但是,沼气中的H2S对内燃机的腐蚀,严重制约了内燃机的可靠使用。文章采用湿法脱硫技术对某养殖场沼气进行处理,并对脱硫前后的内燃机部件损耗进行了比较,证明了该方法的有效性和可行性。脱硫后的沼气中硫化氢浓度低于200 mg/m3,对沼气内燃机的应用具有良好的保护作用。     

Energy taxes: A method for financing national health insurance

The research shows that an energy tax could be used to finance a national health care program. The tax would generate sufficient revenues for the plan, reduce imports, and reduce pollution. The tax could be altered to decrease its regressive nature and still maintain sufficient revenues.     

大中型沼气工程高压水洗提纯工艺的模拟

沼气高压水洗提纯工艺在我国尚处于起步阶段。针对国外水洗工艺规模适用于250 m3/h以上超大型工程,而我国大中型沼气工程在50 m3/h左右,缺乏合适水洗工艺的现状,文章基于CH4-CO2-H2S-H2O体系ELECNRTL热力学模型,构建了高压水洗全工艺流程,并对工艺关键参数,包括沼气处理量、补水量、沼气中甲烷浓度和H2S含量等对工艺的影响进行分析,在此基础上给出了水洗吸收塔和解吸塔参数。为发展我国沼气高压水洗工艺奠定了理论基础。     

Evaluating livestock manures for biogas production: a GIS based method

The Animals (data)Base for Energy Potential Estimation (ABEPE), presented in this paper, is a GIS based biomass resource assessment application using a relational database management system to estimate biogas production from livestock manures. Energy and biogas potential of livestock residues of all major groups of stock-raising animals (cattle, pigs, sheep/goats, poultry, etc.) were evaluated. The calculations were based on geographical and time-depending data of Greece. Typical input data included population of animal groupings, by-product factors, availability factors, energy factors, etc. for the period 1970–1998. Output included manure production, available energy and biogas quantities. Furthermore, ‘ABEPE’ can perform time-depending prediction of all types of output, based on past and present trends. As a case example, the prediction results for the year 2010 are herein presented. The possibility of biogas upgrading in order to be distributed through the national natural gas network is also discussed.     

Solar assisted biogas plants IV A: Experimental validation of a numerical model for slurry temperature in a glazed fixed-dome biogas plant

The paper presents a comparison between the theoretical and experimental temperatures of digester slurry in a glazed fixed-dome biogas plants. The agreement is within ±2.6°C except for an instance of 4.2°C in the month of April 1988.     

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.     

A study of a greenhouse concept on conventional biogas systems for enhancing biogas yield in winter months

A new concept is introduced of using a greenhouse for enhancing the biogas yield from a conventional biogas system in the winter months. If a conventional biogas system is glazed, the trapped solar energy can be used to raise the temperature of the slurry which normally goes low enough to reduce the gas yield appreciably. Numerical calculations have been performed corresponding to the meteorological data on a typical winter day, i.e. 19 January 1981, at New Delhi (India). A comparative study of the performances of conventional and solar-assisted biogas plants using the concept of a greenhouse indicates that the ambient temperature of the slurry can be raised from 18°C to about 37°C, the optimal temperature for anaerobic fermentation.     

Prospects for expanded utilization of biogas in Germany

The prospects for expanded utilization of biogas systems in German was analysed, by identifying the operational and policy factors affecting the complete chain of processes from implementation process for biogas plants, through to biogas production and utilization. It was found that the Renewable Energies Act (EEG) and energy tax reliefs provide bases for the support of expanded utilization. Upgrading of biogas to natural gas quality for utilization in the transportation sector was arguably the most promising technology that could support rapid utilization expansion. Sustainable deployment of biogas systems in light of the unstable feedstock prices and availability, and the need for subsidy-free operation in the long term requires; enhancement of feedstock flexibility and quality characteristics to maximise gas yield, and optimisation of the anaerobic digestion process management. Assessment of energy balance and potential environmental impacts of the integrated process chain provides a holistic assessment of sustainability. The results also support the development and foster of policies and framework for development of biogas as environmentally friendly energy resource, among a mix of renewable energy sources, hence, compete favourably with fossil fuels to enhance the prospects for expanded utilization.     

Investigation of scale economies for African biogas installations

Biogas technology can serve as a means to overcome energy poverty, which poses a constant barrier to economic development in Africa. This technology can be built on a wide range of scales, and conventional financial wisdom is that larger installations have advantages resulting from economies of scale. This study analyses the statistical evidence bearing on the existence of economies of scale in the small to medium scale production and use of biogas to support faster estimation (at the order of magnitude level) of investment costs for different plant sizes. Investment cost data were gathered for 21 biogas plants in the 4–100 m³ range built since 1999 in eight African countries. Statistical regression indicates diseconomies of scale in the size range of the biogas industry investigated with a cost capacity factor (n) of 1.20 (R² = 0.90). The cost capacity factor obtained is notably greater than the conventionally used 0.6 factor rule. The result illustrates that the average cost size relationship is statistically significant with ±40% average estimating error.