Latest News on biogas production : Apr 2022

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Biogas production: current state and perspectives

Anaerobic digestion of energy crops, residues, and wastes is of increasing interest in order to reduce the greenhouse gas emissions and to facilitate a sustainable development of energy supply. Production of biogas provides a versatile carrier of renewable energy, as methane can be used for replacement of fossil fuels in both heat and power generation and as a vehicle fuel. For biogas production, various process types are applied which can be classified in wet and dry fermentation systems. Most often applied are wet digester systems using vertical stirred tank digester with different stirrer types dependent on the origin of the feedstock. Biogas is mainly utilized in engine-based combined heat and power plants, whereas microgas turbines and fuel cells are expensive alternatives which need further development work for reducing the costs and increasing their reliability. Gas upgrading and utilization as renewable vehicle fuel or injection into the natural gas grid is of increasing interest because the gas can be used in a more efficient way. The digestate from anaerobic fermentation is a valuable fertilizer due to the increased availability of nitrogen and the better short-term fertilization effect. Anaerobic treatment minimizes the survival of pathogens which is important for using the digested residue as fertilizer. This paper reviews the current state and perspectives of biogas production, including the biochemical parameters and feedstocks which influence the efficiency and reliability of the microbial conversion and gas yield.[1]

Trace compounds of biogas from different biogas production plants

Biogas composition and variation in three different biogas production plants were studied to provide information pertaining to its potential use as biofuel. Methane, carbon dioxide, oxygen, nitrogen, volatile organic compounds (VOCs) and sulphur compounds were measured in samples of biogases from a landfill, sewage treatment plant sludge digester and farm biogas plant. Methane content ranged from 48% to 65%, carbon dioxide from 36% to 41% and nitrogen from <1% to 17%. Oxygen content in all three gases was <1%. The highest methane content occurred in the gas from the sewage digester while the lowest methane and highest nitrogen contents were found in the landfill gas during winter. The amount of total volatile organic compounds (TVOCs) varied from 5 to 268 mg m−3, and was lowest in the biogas from the farm biogas plant. Hydrogen sulphide and other sulphur compounds occurred in landfill gas and farm biogas and in smaller amounts in the sewage digester gas. Organic silicon compounds were also found in the landfill and sewage digester gases. To conclude, the biogases in the different production plants varied, especially in trace compound content. This should be taken into account when planning uses for biogas.[2]

Biogas: Production and utilization

Among the aspects of biogas production and utilization covered are: (1) the microbiology and biochemistry of the acid and methane production stages in the anaerobic process; (2) factors affecting the process, such as temperature, acidity and alkalinity, nutrients, and cations; (3) denitrification processes and systems; and (4) the process kinetics of suspended growth systems, packed columns, and fluidized beds. Also considered are such issues in the application of this technology as the digestion of municipal treatment plant sludges, animal wastes, food processing wastes and energy crops. Attention is in addition given to anaerobic digester design, offgas measurement of anaerobic digesters, and sludge treatment through soil conditioning and composting.[3]

State of Development of Biogas Production in Europe

The share of renewable energies in electricity production is still low in Europe but there is a political will to increase it in the future by the development of solar and wind energies but also by the development of electricity production from biogas. Biogas production from solid waste is developing in Europe but with important differences between countries. Germany is from far the country where biogas industry is the most developed with 62% of the European biogas plants. However, the latest support schemes implemented in Germany (2012 and 2014) have strongly slowed down the German biogas market. Italy is number two for the number of anaerobic plants. Biogas industry developed very rapidly till 2013 when Italy had the highest feed-in tariff in Europe. However Italy has revised its support scheme to redirect the biogas market towards small size plants based on animal and agricultural waste. The development of biogas in France started significantly at the end of the years 2000 with the implementation of the first support scheme. However, the biogas market is developing rather slowly due to the rather low feed-in tariffs implemented in France. The example of Germany shows clearly that biogas market dynamism is directly linked to the support schemes and the feed-in tariffs implemented. Indeed, biogas industry in Europe was performing rather well since recently, but negative changes or cuts in the support schemes in some countries during the last two years, particularly in Germany and Italy, have slowed down a lot the biogas market, phenomenon which should last in the coming years though some countries like UK or France are maintaining their policies in favor of biogas.However, several factors could favor the development of the biogas market: The acceptance of digestate as a fertilizer, the possible ban of land-filling and the limitation of incineration of organic waste.[4]

Enhancement of biogas production from solid substrates using different techniques––a review

Biogas, a clean and renewable form of energy could very well substitute (especially in the rural sector) for conventional sources of energy (fossil fuels, oil, etc.) which are causing ecological–environmental problems and at the same time depleting at a faster rate. Despite its numerous advantages, the potential of biogas technology could not be fully harnessed or tapped as certain constraints are also associated with it. Most common among these are: the large hydraulic retention time of 30–50 days, low gas production in winter, etc. Therefore, efforts are needed to remove its various limitations so as to popularize this technology in the rural areas. Researchers have tried different techniques to enhance gas production. This paper reviews the various techniques, which could be used to enhance the gas production rate from solid substrates.[5]

Reference

[1] Weiland, P., 2010. Biogas production: current state and perspectives. Applied microbiology and biotechnology, 85(4), pp.849-860.

[2] Rasi, S., Veijanen, A. and Rintala, J., 2007. Trace compounds of biogas from different biogas production plants. Energy, 32(8), pp.1375-1380.

[3] Price, E.C. and Cheremisinoff, P.N., 1981. Biogas: production and utilization. Ann Arbor.

[4] Torrijos, M., 2016. State of development of biogas production in Europe. Procedia Environmental Sciences, 35, pp.881-889.

[5] Sreekrishnan, T.R., Kohli, S. and Rana, V., 2004. Enhancement of biogas production from solid substrates using different techniques––a review. Bioresource technology, 95(1), pp.1-10.

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