Evaluation of process parameters and treatments of different raw materials for biogas production

Detta är en avhandling från Lund University

Sammanfattning: Popular Abstract in English In the age where there is a great demand of energy, raise in the prices of fossil fuels and increase of environmental concerns because of the greenhouse gas emissions, biogas production through anaerobic digestion, of different organic materials, provides a full or partial solution. There is a large number of cheap substrates as organic waste materials that can be utilized for the production of biogas. Biogas production not only generates an energy rich compound ‘methane’ but also is the technology for waste management. These wastes can, if not handled properly, cause emission of greenhouse gases as in the case of manure. Even though anaerobic digestion has been known from long ago, several processes were started in 1970s but due to the lack of proper knowledge, most of the processes failed. In order to make the anaerobic digestion process efficient enough to compete with traditional sources of energy, there is need of research. In this thesis we have studied the effect of different parameters on anaerobic digestion and evaluated the raw materials after different treatments to enhance the biogas production. For instance, sugarcane bagasse after different treatments was evaluated for production of biogas. Additional studies were carried out to evaluate the possible positive or negative effect of different substrate compositions and different sources of microorganisms (inoculum) on anaerobic digestion. Biochemical methane potential test is the procedure used to know how much methane can be produced from a given organic material. In this study we have used automatic and real time measurement of methane production during anaerobic digestion of organic biomass, which can run fifteen lab scale digesters in parallel. The effect of inoculum to substrate ratio was studied and the effect of this parameter was evaluated using different concentrations. In order to be able to produce biofuels from lignocellulosic materials (2nd generation biofuel), the lignocellulosic materials have to be pretreated. During different pretreatments toxic compounds are produced, which affect biotechnological processes like production of bioethanol using yeast. The effect of such toxic compounds at different concentrations and different combinations was studied on methane production. It was found that these compounds, at low concentrations, were not only non-inhibitory for the anaerobic digestion process but were also used as source for methane production. Globally millions of tons of methanol condensates are produced in pulp and paper mill. The methanol condensate contains up to 80 % methanol and has strong pungent smell. Because of impurities present in methanol condensate from pulp mill, it cannot be used for industrial application. The methanol condensate was anaerobically treated at different operating conditions. Methanol condensate was efficiently treated with the benefit of biogas production. As a bonus effect of the treatment, much of the smell of the feed was also eliminated. Additionally, enhancement of biogas production from different sludges from a pulp and paper mill using enzymes was evaluated.