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.     

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.     

Technical–economical analysis of the Saveh biogas power plant

The resource limitation of fossil fuels and the problems arising from their combustion has led to widespread research on the accessibility of new and renewable energy resources. Solar, wind, thermal and hydro sources, and finally biogas are among these renewable energy resources. But what makes biogas distinct from other renewable energies is its importance in controlling and collecting organic waste material and at the same time producing fertilizer and water for use in agricultural irrigation. Unlike other forms of renewable energy, biogas neither has any geographical limitations and required technology for producing energy and nor is it complex or monopolistic. Considering the ever increasing amount of different types of organic waste materials (about 15 million tonnes) in Iran, working on the control of waste material and biogas production becomes inevitable.In this paper, biogas and the benefits from its production are discussed, as is the technical-economic analysis of the Saveh biogas power plant as a case study.     

Biogas as a sustainable energy source in Nepal: Present status and future challenges

Cattle manure, human excreta and agriculture residues are used in anaerobic bioreactors in many parts of the world to produce methane gas, which is used for the purpose of cooking and lighting. Since such waste materials are readily available in farms, rural people of many developing countries have been benefited from this technology. Besides, this technology is cheaper and simpler, thus, gaining popularity throughout the world. Nepal is one of the least developed countries with the vast majority of people involved in subsistence agriculture. The use of biogas technology in Nepal has benefited the country in improving health, environment, economy and energy conservation. In this paper, we present the state of the biogas sector in Nepal.     

The potential of a renewable energy technology for rural electrification in Nepal: A case study from Tangting

Nepal, one of the least developed countries, is characterized by low per capita energy consumption and hugely dominated by traditional energy sources. Despite having enormous potential of hydro-electricity, only 50% of the total population has access to grid electricity. Firewood is the primary energy source for domestic purposes in rural environments. Due to geographical remoteness, a scattered consumer, higher costs of supply and maintenance, low consumption and low level of households’ income linking the rural areas to national electricity grid is difficult and implausible. In order to solve the energy problem in rural areas, Nepal’s government has initiated the production and distribution of several renewable energy technologies. Among several renewable technologies, micro-hydropower has been one of the most promising and widely adopted decentralized technologies to distribute electricity in rural areas. This article begins with a general overview of energy situation in Nepal. Present status and perspective of micro-hydro plants have also been discussed. Similarly, the dynamics of the relationship between electricity and socio-economic development has been analyzed by means of a typical rural electrification project in Tangting, Nepal by assessing the impacts of electricity on health, education, environment, and income in the village. The community has greatly benefitted from the arrival of environment friendly and affordable electricity. It has been concluded that the task of providing electricity to more remote and isolated villages is still challenging in Nepal. More systematic and comprehensive study supported by research and development is required to extend micro-hydro based electricity in more remote and poor communities of Nepal.     

Use of waste for heat,electricity and transport—Challenges when performing energy system analysis

This paper presents a comparative energy system analysis of different technologies utilising organic waste for heat and power production as well as fuel for transport. Technologies included in the analysis are second-generation biofuel production, gasification, fermentation (biogas production) and improved incineration. It is argued that energy technologies should be assessed together with the energy systems of which they form part and influence. The energy system analysis is performed by use of the EnergyPLAN model, which simulates the Danish energy system hour by hour. The analysis shows that most fossil fuel is saved by gasifying the organic waste and using the syngas for combined heat and power production. On the other hand, least greenhouse gases are emitted if biogas is produced from organic waste and used for combined heat and power production; assuming that the use of organic waste for biogas production facilitates the use of manure for biogas production. The technology which provides the cheapest CO₂ reduction is gasification of waste with the subsequent conversion of gas into transport fuel.     

Scaling-up bio-hydrogen production from food waste: Feasibilities and challenges

Hydrogen has potential as a renewable energy source due to its outstanding clean energy content. The production of hydrogen from food waste by dark fermentation gains attention from researchers across the world as it requires lower energy and chemicals compared to other chemical routes, not to mention that the use of food waste as raw material could help lessen the global waste dumping crisis. Currently, the knowledge of hydrogen production from food waste by dark fermentation is still limited in a laboratory scale. This article intends to provide up-to-date status quo on this technology. Factors affecting production potential, appropriate condition of production, feasibility of scaled-up production and economic value analysis of such technology is summarized and analyzed.     

Role of renewable energy technologies in rural communities' adaptation to climate change in Nepal

The aim of this paper is to analyze the role of renewable energy technologies (RETs) such as biogas, improved cooking stoves (ICSs), micro hydro (MH) and solar power (SP) in helping rural communities in Nepal to adapt to climate change. The analysis considers the energy efficiency of different RETs as well as their socio-economic and environmental impacts. The efficient use of biomass in new technology, such as biogas and ICSs for cooking, has increased energy security and reduced the negative effects of traditional biomass usage. MH and SP systems are replacing candles and kerosene lamps, and are the most promising RET models for electricity generation in rural Nepal. The improved illumination from these technologies also produces better education, health, environments, and social harmony in rural communities. This study uses the Long-range Energy Alternatives Planning model (LEAP) model to develop a plan for long-term RETs use in Nepal, and specifically focuses on household energy use in rural areas. It assesses the role of biogas and ICSs in rural communities and climate change adaptation in Nepal, along with the potential role of MH and SP technologies. According to the LEAP analysis, the planned implementation of MH for 20-year long-term will result in the reduction of 2.553 million tons of CO₂ emissions. Similarly SP, biogas, and ICSs will result in a reduction in CO₂ emissions of 5.214 million tons, 35.880 million tons, and 7.452 million tons, respectively.     

Biogas plants in Denmark: technological and economic developments

Biogas plants are one of the important elements in the Danish energy-policy of having reduced CO₂ emissions by 20% by 2005. Since 1984, development efforts concerning centralised biogas plants in Denmark have been carried out, and Denmark now has approximately 20 large centralised biogas plants. All Danish biogas plants have increased gas production as a result of admixing industrial organic wastes with manure. This is predominantly regarded as a great advantage for both biogas plants and waste suppliers. The paper will describe the technological development of this renewable energy source in terms of biogas production prices. The price has dropped dramatically during the last 15 years. Based on this analysis, the paper discusses the socio-economic costs of technology development including state budget and employment effects. Also the paper refers to socio-economic feasibility studies from the early 1990s, when biogas production prices were much higher than natural gas. Still, employment effects made the development feasible in socio-economic terms.     

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。     

Green waste to biogas: Renewable energy possibilities for Thailand's green markets

Today, the production of energy from waste is not a new process; however, its implementation and application continue to be a challenge in developing countries. Despite the abundance of valuable waste in the urban markets of these countries, practices aiming at renewable energy generation are missing. In Thailand, so-called green markets are replete with renewable energy potential, but the practical implementation of this potential is rare. Therefore, the main purpose of this study is to show that the conversion of green waste into renewable energy is not only environmentally beneficial but also financially rewarding. This is demonstrated by exploring the energy potential of the market and conducting a benefit–cost analysis under two scenarios. The results illustrate that for the selected market, converting organic waste into biogas is advantageous both environmentally as well as financially; further, the benefit–cost ratio is three times higher after conversion, compared to before. Additionally, there is a huge margin of conversion and production of biogas. The policy makers and planners of Talaad Thai (Thailand's largest green market) should invest greater effort in initiating plans, and set an example for other markets in Thailand, in order to make this planet clean and green.     

Biogas derived from municipal solid waste to generate electrical power through solid oxide fuel cells

Depleting fossil fuels and the pollution resulting from their consumption indicate an urgent need for clean and dependable alternatives such as renewable energies. Biomass is a free and abundant source of renewable energy. Municipal solid waste (MSW) as one of the main categories of biomass has always been an issue for metropolitan cities. It has, however, a high potential for biogas production. In this study, the technical and economic aspects of generating electrical power through solid oxide fuel cells (SOFCs) powered by injecting biogas derived from Tehran's MSW, as a case study, are investigated. The main objectives of the current study are to identify the power generation capability of the process and find out if it can result in a competitive energy resource. The total amount of obtainable methane through anaerobic digestion of MSW and then the achievable power generation capacity by using the obtained biogas are computed using the electrochemical relations inside the SOFC. The economic calculations are carried out to estimate the final price of the generated electricity, taking into account the major capital and ongoing costs of the required equipment. The effect of variations of MSW composition on the power generation capability and final electricity price is also studied. Moreover, the application of a gas turbine (GT) with the SOFC as a hybrid SOFC–GT system to recover the produced heat by SOFC and its effect on the power generation capability and the final electricity price are investigated. Results indicate that around 997.3 tons day^?1 biomethane can be generated using Tehran's MSW. By using the SOFC, the produced biogas can generate 300 MW_AC electrical power with a final cost of Depleting fossil fuels and the pollution resulting from their consumption indicate an urgent need for clean and dependable alternatives such as renewable energies. Biomass is a free and abundant source of renewable energy. Municipal solid waste (MSW) as one of the main categories of biomass has always been an issue for metropolitan cities. It has, however, a high potential for biogas production. In this study, the technical and economic aspects of generating electrical power through solid oxide fuel cells (SOFCs) powered by injecting biogas derived from Tehran's MSW, as a case study, are investigated. The main objectives of the current study are to identify the power generation capability of the process and find out if it can result in a competitive energy resource. The total amount of obtainable methane through anaerobic digestion of MSW and then the achievable power generation capacity by using the obtained biogas are computed using the electrochemical relations inside the SOFC. The economic calculations are carried out to estimate the final price of the generated electricity, taking into account the major capital and ongoing costs of the required equipment. The effect of variations of MSW composition on the power generation capability and final electricity price is also studied. Moreover, the application of a gas turbine (GT) with the SOFC as a hybrid SOFC–GT system to recover the produced heat by SOFC and its effect on the power generation capability and the final electricity price are investigated. Results indicate that around 997.3 tons day^?1 biomethane can be generated using Tehran's MSW. By using the SOFC, the produced biogas can generate 300 MW_AC electrical power with a final cost of $0.178 kWh^?1. By using the hybrid SOFC–GT, the electrical power capacity is increased to 525 MW_AC, and the final electricity cost drops to $0.11 kWh^?1, which indicates its competitiveness with other common energy resources in the near future, especially by considering different governmental subsidy policies that support renewable energy resources. The considerable environmental benefits of the proposed procedure, from both MSW management and CO₂ emission reduction points of view, make it a promising sustainable energy resource for the future. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Techno‐economic assessment for energy generation using bagasse: case study

Bagasse is selected as the biomass source that is studied because of its annual significant rate production in Iran and potential for energy generation. Bagasse has been as an energy source for the production of energy required to run the sugar factory. The energy needed by factories was supplied by burning bagasse directly inside furnaces, which had an exceptionally low output. To this end, today, a secondary use for this waste product is in combined heat and power plants where its use as a fuel source provides both heat and power. In addition, low efficiency of traditional methods was caused to increase the use of modern methods such as anaerobic digestion, gasification and pyrolysis for the production of bio‐fuels. In this paper, the energy conversion technologies are compared and ranked for the first time in Iran. Therefore, the most fundamental innovation of this research is the choice of the best energy conversion technology for the fuel production with a higher efficiency. To assess the feasibility application and economic benefit of biogas CHP plant, a design for a typical biogas unit is programmed. The results show the acceptable payback period; therefore, economically and technically, biogas CHP plant appears to be an attractive proposition in Iran. Copyright © 2012 John Wiley & Sons, Ltd.     

Macro-level integrated renewable energy production schemes for sustainable development

The production of renewable clean energy is a prime necessity for the sustainable future existence of our planet. However, because of the resource-intensive nature, and other challenges associated with these new generation renewable energy sources, novel industrial frameworks need to be co-developed. Integrated renewable energy production schemes with foundations on resource sharing, carbon neutrality, energy-efficient design, source reduction, green processing plan, anthropogenic use of waste resources for the production green energy along with the production of raw material for allied food and chemical industries is imperative for the sustainable development of this sector especially in an emission-constrained future industrial scenario. To attain these objectives, the scope of hybrid renewable production systems and integrated renewable energy industrial ecology is briefly described. Further, the principles of Integrated Renewable Energy Park (IREP) approach, an example for macro-level energy production, and its benefits and global applications are also explored.     

Access to energy in Mid/Far west region-Nepal from the perspective of energy poverty

Energy Access to satisfy the basic needs is a big challenge in Nepal due to presence of geographical variations, poor transportability, fragmented settlements, illusive energy development strategy, and lack of sufficient capital. In this situation, Energy Poverty can be referred to absence of access to convenient, reliable, efficient and modern energy technologies to satisfy the basic needs that can support for human and economic development. The article illustrate about the energy poverty situation of Nepal, which has been defined in terms of efficiency of energy end-use devices and minimum energy requirement, basically in the residential sector of the country. Mid and Far west Development Region of the country has given focus to provide overview on energy poverty situation and measures required to reduce the poverty by 50% by 2015/16. For outlining the energy technology interventions for reducing energy poverty situation, more efforts have been given on the role of renewable energy technologies in the Mid and Far West Region of the country.     

Potential of renewable hydrogen production for energy supply in Hong Kong

Hong Kong is highly vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. The combustion of fossil fuels also causes serious environmental pollution. Therefore, it is important to explore the opportunities for clean renewable energy for long-term energy supply. Hong Kong has the potential to develop clean renewable hydrogen energy to improve the environmental performance. This paper reviews the recent development of hydrogen production technologies, followed by an overview of the renewable energy sources and a discussion about potential applications for renewable hydrogen production in Hong Kong. The results show that although renewable energy resources cannot entirely satisfy the energy demand in Hong Kong, solar energy, wind power, and biomass are available renewable sources for significant hydrogen production. A system consisting of wind turbines and photovoltaic (PV) panels coupled with electrolyzers is a promising design to produce hydrogen. Biomass, especially organic waste, offers an economical, environmental-friendly way for renewable hydrogen production. The achievable hydrogen energy output would be as much as 40% of the total energy consumption in transportation.     

Biogas production and its application in compressed gas

Nowadays, the world is facing critical problem of energy deficit, global warming, and deterioration of the environment. Under the current scenario, the biogas energy source is the most challenging one to cope up with the scarcity of energy. Biogas is a renewable energy source which can be obtained by fermentation of organic matter also known as biomass. The biomass includes livestock waste (cow dung, manure, and uneaten food), food waste, and residues from meat, fish and dairy processing. The present study is to explore the potential of biogas production from cow dung and its usage through compressed form in a cylinder. This stored biogas can be put in use to the extent where it is required and it also reduces transportation costs, which is a major hurdle in the biogas usage. This paper summarizes an idea that can be carried out for effective biogas production, scrubbing, compression, and bottling process.     

On the wind energy in Turkey

Increase in negative effects of fossil fuels on the environment has forced many countries, including Turkey, to use renewable energy sources. Today, clean, domestic and renewable energy is commonly accepted as the key for future life, not only for Turkey but also for the world. As wind energy is an alternative clean energy source compared to the fossil fuels that pollute the atmosphere, systems that convert wind energy to electricity have developed rapidly. Turkey is an energy importing country, more than half of the energy requirement has been supplied by imports. Turkey's domestic fossil fuel resources are extremely limited. In addition, Turkey's geographical location has several advantages for extensive use of wind power. In this context, renewable energy resources appear to be one of the most efficient and effective solutions for sustainable energy development and environmental pollution prevention in Turkey. Since wind energy will be used more and more in the future, its current potential, usage, and assessment in Turkey is the focus of the present study. The paper not only presents a review of the potential and utilization of the wind power in Turkey but also provides some guidelines for policy makers.     

Renewable energy in India: Historical developments and prospects

Promoting renewable energy in India has assumed great importance in recent years in view of high growth rate of energy consumption, high share of coal in domestic energy demand, heavy dependence on imports for meeting demands for petroleum fuels and volatility of world oil market. A number of renewable energy technologies (RETs) are now well established in the country. The technology that has achieved the most dramatic growth rate and success is wind energy; India ranks fourth in the world in terms of total installed capacity. India hosts the world's largest small gasifier programme and second largest biogas programme. After many years of slow growth, demand for solar water heaters appears to be gaining momentum. Small hydro has been growing in India at a slow but steady pace. Installation of some of the technologies appears to have slowed down in recent years; these include improved cooking stoves (ICSs) and solar photovoltaic (PV) systems. In spite of many successes, the overall growth of renewable energy in India has remained rather slow. A number of factors are likely to boost the future prospects of renewable energy in the country; these include global pressure and voluntary targets for greenhouse gas emission reduction, a possible future oil crisis, intensification of rural electrification program, and import of hydropower from neighbouring countries.