Methane (CH4) is a greenhouse gas (GHG) that contributes to the global warming. One of the largest sources of methane is livestock, preferably ruminants which alone counted for 30% of the total agricultural anthropogenic methane emissions in the year of 2000. The reason to why ruminants are such large contributors of methane are that the gas is produced in the rumen by enteric formation and leaves the animals by belching, exhaling or by the excreta.Diets high in concentrates can result in a lower emission of methane. Also diets with a high content of starch, such as alfalfa-grass, have a methane-decreasing. It is profitable to reduce enteric methane formation since that form of methane is unavoidably lost.

The quantity of methane emissions from sheep depend on several factors, for example, the composition of the diet, feed quality, the age of the animals, time of the day and maybe also breed and sex. A comprising literature review was made about which factors that affect the size of emissions. In addition, a questionnaire was sent to two farms, one with a more intensive production system and another with a more extensive system. Inventories of the two farms were made; the rest of the data needed to conduct the study was taken from literature and other sources. Meat produced at the more intensive farm caused emissions of 0.4 kg of methane per kg of bone free meat and the more extensive farm caused emissions of 0.9 kg methane per kg of bone free meat.

A growing population together with a change in food habits to a more diverse diet containing more animal products such as meat and milk makes the possibility to produce and sell products of cattle a growing market. And at the same time there is an ongoing debate about global warming, where raising cattle is questioned due to their high production of enteric methane. To be able to raise animals in a more environmental friendly way and at the same time improve productivity in a developing country such as Vietnam would be favorable. The use of feed additives with high electron affinity could decrease the Methane production and at the same time improve the gross energy digested. Nitrate and Sulfur are both good electron acceptors, but due to its toxic effects the use of nitrate in feed has been neglected.

In developing countries such as Vietnam the population consumes more animal products for example milk and meat than before which requires greater livestock production. Ruminants contributes to more methane emission which creates a dilemma between food production and its environmental impact. By feeding ruminants with nutritive crops which humans can not assimilate the animal performance will increase in terms of better growth and milk production without inpinging on food that can be consumed directly by humans. Increasing animal performance reduces methane emission in terms of amount of methane in kg-1 milk and meat which today is much greater in developing countries than developed countries. The aim of the study was to investigate tropical tannin-rich legumes for their potential as a feed supplement for ruminants made in vitro.

Deposited waste material degrades within a short period in anaerobic environments. The methane gas that is formed provides a harmful contribute to the greenhouse effect, 23 times larger impact than carbon dioxide. It is therefore desirable to minimize the emissions of methane gas from landfills. This may be achieved by drain the landfill of gas. In this thesis the amount of produced methane gas at the landfill at Örebro has been calculated. Estimations have also been made of the amount of methane gas that might be produced in the landfill in the future.

This thesis aims to examine the viability of various techniques for increased electricity generation in CHP plants and the effect of electricity price fluctuations on the profitability.The techniques examined are fuel dryer, pellet production, Methane production, combined methane- and pellet production, seasonal heating storages in caverns and pit heat storages and condensing tail. Using Excel and Matlab, the prerequisites for investment costs, revenues and expenses were calculated.What affects the price of electricity is a combination of economic and technological development, energy prices, economic structure, population changes and weather. Different scenarios for the electricity price were therefore examined. In the base case, the electricity price was given by the Nord Pool electricity price statistics of area three in 2011. Thereafter, WiMo was used to design the electricity scenarios for 2030, which was then applied to the data to obtain the viability of various scenarios. The techniques examined were found to give greater profits to the CHP plant by increasing and optimizing the production of electricity.

In this thesis the methane gas potential of three different substrates, two algaes Saccharina latissima and Laminaria digitata and biosludge mixed with paper fiber was studied. This was done by batch experiments in a laboratory environment to examine the gas production and composition of the produced gas.Biogas production is a complex anaerobic digestion process in which various microorganisms decompose the substrate in steps and at the end produce biogas and a residue. Many factors affect the production of gas, for example the substrate content, temperature and pH in the digester.The analysis of methane potential were divided into two experiments. In experiment 1 substrates were digested along with inoculum from Växjö waste water treatment plant in a temperature of about 37 ?C.

Käppala wastewater treatment plant situated on the island of Lidingö northeast of Stockholm is running a project during 2004 and 2005 with the purpose to map out the capacity of anaerobic digestion in the digesters that treat primary and excess sludge. The purpose of this thesis work, which is part of that project, was to characterize the present anaerobic digestion process and to investigate its capacity to treat other organic wastes such as restaurant waste and waste from water works. To decide the potential of both methane and biogas production from different substrates batch laboratory tests were carried out. To imitate the anaerobic digestion process at Käppala continuous tests with small scale reactors were carried out. These reactors were later fed with restaurant waste.The batch laboratory tests showed that primary sludge had a potential biogas and Methane production of 0,62 and 0,35 Ndm3/g VS respectively after 40 days of digestion.

The world?s growing need for energy together with a desire to ward off the worst consequences of global climate change has resulted in a never seen desire to invest resources in renewable energy sources. Biogas production through anaerobic digestion is one of those growing energy sources. In Sweden there are over two hundred plants that uses this biological process to break down organic substances while producing carbon dioxide and the energy-rich gas methane.This master?s thesis has focused on development of the mixture of different organic substances that is treated at a specific plant, namely Mosserud biogas plant.

The aim of the study was to investigate if methane emission in a constructed wetland changed in a diurnal pattern correlating to temperature, humidity or light conditions. The gas measurements were carried out with a static chamber technique. The wetland (in Nykvarn outside of Linköping, Sweden) takes care of wastewater to reduce the nitrogen loads. Measurements were carried out at three different occasions in the summer of 1998 on two sites in the wetland. One site was close to the inflow, inhabited by Lemnaceae, and another site was located further downstream inhabited by the emergent macrophyte Typha latifolia.

Värmekollektor in Sunne is a company whose main occupation is to collect the gas produced inlandfills. The gas contains about 50 % of Methane which is a greenhouse gas 20 times worse than CO2and should therefore not be allowed to leak into the atmosphere. The Methane is in as large amount aspossible used in different plants for example heating of households. But there are occasions when aflare is needed to burn the excess gas at standstills or testing of new landfills. The Flare only burns themethane to reduce the hazarder?s effect of the environment, it does not take advantage of the energy inthe gasThe goal of this master thesis was for me to create a foundation for an in-house production offlares for Värmekollektor.

Until 2020, 49% of Sweden's use of energy must derive from renewable sources. Greenhouse gases must as well decline with 40% compared to 1990 as a part of Sweden's 16 environmental objectives. Biogas is part of the effort to achieve these objectives, but as the demand for biogas increases, more substrates are needed to meet the demand. The purpose is to investigate the conditions for pea residue as substrate by performing lab-scale mesophilic digestion with different fractions and notch lengths and then to summarize pea residue as a substrate for biogas production. During anaerobic digestion, 1000 ml bottles were used as reactors for digestion.

A growing interest for the climate and the environment has led to an increased interest forenvironmentally friendly and renewable energy sources, such as biogas. Planning new biogasplants requires a decision basis including facts about approximate amounts of biogas possibleto produce at the plant. The purpose of this thesis is to develop a model that calculates theapproximate biogas and digestate production from a planned or existing biogas plant.Developing the model required a literature review and studies of calculations concerningbiogas and digestate production performed by WSP Sweden AB. As a complement to themodel development, facts about substrates for biogas production were compiled through aliterature review. In addition the methane potential from selected materials was determined bybatch experiments.

The Swedish production of biogas was 1,5 TWh 2011. About half of the production was used as vehicle fuels. The cost for upgrading biogas depends on the size of the biogas plant and its gas production. If the gas flow is low the cost will be high. However, further development of existing upgrading technologies or development of new ones, have good potential to decrease the upgrading cost for small scale biogas plants.

Because of the increasing trends in energy consumption and increased environmental awareness, greater focus has been placed on improvement and development of renewable energy sources. An already proven and accepted method is biogas production from anaerobic digestion at municipal wastewater treatment plants.In the waste water treatment process solid material and dissolved pollutants are separated from the water, forming a sludge. The sludge is separated from the process and stabilized during anaerobic digestion or aerobic aeration. Most often, mesophilic anaerobic digestion is used. Because of degradation by microorganisms, biogas with a high content of methane is formed during the digestion.