Welcome to my anaerobic digester series, if you would like to see the introduction post please click here.
Click here for Part II.
This is part 3 of my series.
[I made this figure myself]
Here is shown a typical in-ground AD. Biomass such as silage, crop residue, or manure is inserted into the influent chamber where it enters the main chamber where it begins to ferment creating biogas. The remaining solids left over after the process are then removed through the effluent chamber where they can be utilized as an organic fertilizer.
This post will cover some more background information on anaerobic digesting as well as some hazards of biogas usage. I will post the sources for the entire series in each post for reference.
Additional Background Information
Peura P. and T. Hyttinen (2011) found that even though the construction and implementation of AD systems on a small-scale are still in the infancy stages of technology, it is feasible economically.
They also state that rural communities who implement ADs have a high likelihood of becoming self-sufficient in the energy sector. It is estimated that by the year 2020, in order to meet global needs, 40% of the world energy have to come from renewable resources.
Studies have shown that biogas is a feasible contributor to this energy input into the grid, with wind and solar power as a supplement. It is estimated that in the near future a majority of countries will begin to implement biogas systems, in order to support the growing need of energy and diminishing availability of fossil fuels.
Hazards of Biogas
In many countries the treatment of wastewater consist of eliminating CO2 and CH4 through aerobic processes, which increases the emission of GHGs, as well as the energy needed to run fans during the treatment.
In order to reduce the emissions of GHGs during the treatment of wastewater, ADs are being considered by many nations; these programs already having been in use in some countries, such as India and Brazil.
While studies show that treating wastewater in ADs directly reduces the emissions of CO2 by saving energy and using the biogas as an alternative fuel, a recent German study found that the effluent from ADs, using waste water, contain Chemical Dissolved Oxygen (COD) and 10-20% of CODs were converted into CH4. Methane, the converted COD, is considered to have 21 times more an effect on global warming potential than CO2 in the atmosphere, it is equivalent to 40kg of CO2 per person per year.
However, it is also important to note that the combustion of biogas results in the emission of carbon aerosols, which can have negative effects on Earth’s atmospheric systems (Weichgrebe et al., 2008).
A study conducted by Naja et al. (2011) was done to determine the health risks of using biogas for cooking compared to when using natural gas.
The study focused primarily on biogas that had been purified before being injected into the natural gas lines and was held to current regulations and health risk assessments in Europe.
An important factor the study determined was that the quality of biogas was dependent on the source of solid waste, as well as the age of the waste being processed into biogas. It was determined that the health risk of cooking with the purified form of biogas was very low, as long as it followed the regulations set by European countries and was derived from non-hazardous waste.
The non-hazardous waste for production of biogas is defined as originating from household wastes, bio-wastes (based on presorting of wastes), assimilated wastes in landfills, and organic wastes (restaurants and agriculture).
Sources of Entire Thesis
Abu-Dahrieha J., A. Orozcob, E. Groomb, and D. Rooneya, 2011. Batch and continuous biogas production from grass silage liquor. Bioresource Technology, 102(23):10922-10928.
Arthur R., M. F. Baidooa, and E. Antwib, 2011. Biogas as a potential renewable energy source: A Ghanaian case study. Renewable Energy, 36(5):1510-1516.
Berglund M. and P. Borjesson, 2005. Assessment of energy performance in the life-cycle of biogas production. Biomass and Bioenergy, 30:254-266.
Energy Information Administration (EIA), 2009.
Emissions of greenhouse gases in the United States. Hazardous Waste Consultant, 29(5):1.5-1.20.
Gosens, J., Y. Lu, G. He, B. Bluemling, and T.A. Beckers, 2013. Sustainability effects of household-scale biogas in rural China. Decades of Diesel, 54:273–287.
Govasmark E., J. Stäb, B. Holen, D. Hoornstra, T. Nesbakk, and M. Salkinoja-Salonend, 2011. Chemical and microbiological hazards associated with recycling of anaerobic digested residue intended for agricultural use. Waste Management, 31(12):2577-2583.
Lansing S., R.B. Botero, J.F. Martina, 2007. Waste treatment and biogas quality in small-scale agricultural digesters. Bioresource Technology, 99(13):5881-5890.
Naja G.M., R. Alary, P. Bajeat, G. Bellenfant, J.J. Godon, J.P. Jaeg, G. Keck, A. Lattes, C. Leroux,
H. Modeloni, M. Moletta-Denatj, O. Ramalhoj, C. Roussellei, S. Wenischc, and I. Zdanevitchk, 2011. Assessment of biogas potential hazards. Renewable Energy, 36(12):3445-3451.
Odlare M., V. Arthurson, M. Pell, K. Svensson, E. Nehrenheim, and J. Abubaker, 2011. Land application of organic waste – Effects on the soil ecosystem. Applied Energy, 88(6):2210-2218.
Peura P. and T. Hyttinen, 2011. The potential and economics of bioenergy in Finland. Journal of Cleaner Production, 19:927-945.
Rennuit, C. and S.G. Sommer, 2013. Decision support for the construction of farm-scale biogas digesters in developing countries with cold seasons. Energies, 6(10):5314-5322.
Till J., A. Königb, and L. Eltropa, 2014. Bioenergy villages in Germany: Bringing a low carbon energy supply for rural areas into practice. Renewable Energy, 61:74-80.
Wang C.B. and L.X. Zhang, 2012. Life cycle assessment of carbon emission from a household biogas digester: Implications for policy. Procedia Environmental Sciences, 13:778 – 789.
Weichgrebe D., I. Urban, and K. Friedrich, 2008. Energy- and CO2-reduction potentials by anaerobic treatment of wastewater and organic kitchen wastes in consideration of different climatic conditions. Water and Science Technology, 58(2):379-384.
Zhang L.X., C.B. Wang, and B. Song, 2013. Carbon emission reduction potential of a typical household biogas system in rural China. Journal of Cleaner Production, 47:415-421.