The global energy demand is increasing rapidly in recent years. On the other hand the fossil fuel reserves are slowing down. The energy supply is one of the major challenges facing the world now and in the future. Furthermore, effects of global warming cannot be neglected anymore. Alternative energy sources such as biogas production should be developed. The biomass can have a large amount of biogas potential, but the main problem is the shortage of arable land. The objective of this study was to determine the biogas yields of JUNCAO alone and other different substrates for biogas production. The feasibility of using JUNCAO and other energy crops or residues in methane production through anaerobic digestion was evaluated in this thesis paper, and screened out for its suitability for biogas production. Anaerobic digestion is a biochemical process where the microbes convert organic materials, substrate in a neutral pH and temperature controlled environment anaerobically, for producing methane gas, which consists of primarily methane (CH4) and carbon dioxide (CO2). The samples used in these experiments were obtained from the JUNCAO Research Institute of Fujian Agriculture and Forestry University during summer 2013. In the screening experiments, all the substrate materials were taken to the laboratory and chopped into smaller pieces between 1.5 to 2.0 cm with scissors or knife. The main substrate material in this study was JUNCAO, (Arundo donax L). The other substrate materials that were used include, residues of different mushroom species such as Pleurotus eryngii, Tremella fuciformis and Agrocybe cylindraceae, sugarcane straw, and wheat seed shells and the biogas slurry was used for the inoculation of the simple anaerobic digesters.
In this study, the biogas production and composition from different substrates in mesophilic digester (37??C) conditions during 30 days of fermentation were measured and compared. The daily biogas production was cumulated over the period of the anaerobic digestion, to determine the total volume of biogas, in litres (L) after which the microbiology and nutrients analysis were carried out. The calculations were made in a system consisting of 24ml plastic digester bottles of 550ml capacity with rubber stoppers at one end.Energy is regarded as one of the most important tool of the socio-economic developments in modern society, primarily in the rural areas of developing countries. Despite improvements in technology however, some three billion people in the world, continue to meet their energy needs for cooking through traditional means, by burning biomass resources (i.e. firewood, crop residues and cow dung). These practices are known to be the source of significant environmental, social economic and public health issues. To achieve sustainable development for these regions, it is imperative that access to clean and affordable renewable energy like biogas from anaerobic digestion is made available. In spite of its significant potential to serve developing nations, however, the high costs and lack of expertise in installation and maintenance of biogas technology have created more problems especially the isolated communities.
The production of biogas through anaerobic digestion of organic materials provides a renewable energy that can be used to replace some fossil fuels, and contribute to cutting down the emissions of greenhouse gases (GHG). Furthermore, the dependence on fossil fuels as primary energy source has led to global climate change, environmental degradation, and human health problems. Anaerobic digestion is a multiple-stage process, to improve biogas yield from biomass fermentation, it can be generated from a large numbers of raw materials, and the microbial community composition and metabolic processes carried out by microbes residing in biogas reactors is very important. The microbial species are capable of digesting the organic materials and convert them to produce biogas. The energy source is the material that the organism uses to get energy for both its growth and function. The other energy sources for a microorganism can be the nutrients derived from the substrate, and solar energy derived from the sun.
Biogas can be used for cooking, lighting, electricity generation, also as a vehicle fuel while the residues can be used to enrich the soil for crops production. Biogas is consisting of mainly 50-70% methane (CH4), and 30-50% carbon dioxide (CO2), and small amounts of trace elements. Biogas production depends on various parameters that affect the yields of the gas from different substrates, such as pH of slurry, temperature and more importantly, the carbon to nitrogen ratio that controls the pH value of the slurry creating a better environment for microbes. The total solids, volatile matter, mineral concentrations are also among the factors affecting biogas yields.
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