According to the Knowledge Product (KP) studies commissioned by the Department of Environmental Affairs (DEA), anaerobic digestion (AD) of organic waste is the biological degradation of biodegradable wastes by anaerobic microbes under controlled conditions in the absence of oxygen. This produces gas that is mainly composed of methane (CH4) and carbon dioxide (CO2), otherwise known as biogas. Use was made of the manual provided by GreenCape and approved by the Western Cape Department of Economic Development and Tourism, ‘Towards integrated municipal waste management: technical guide for technology identification and screening for integrated waste management planning’.
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Read more () The Bio2Watt biogas plant in Bronkhorstspruit is located on the premises of one of South Africa’s larger feedlots (Beefcor) in an agricultural area of Gauteng. The Bronkhorstspruit Biogas Project (BBP) is the first large scale animal waste-to-energy project in South Africa, addressing clean energy needs while resolving waste issues. It will process approximately 60,000 tonnes of organic waste per annum, mainly cattle manure but also chicken abattoir waste, food waste and paper sludge. Through an anaerobic digestion process, biogas is collected and then burnt in a combined heat and power (CHP) engine to produce electricity and heat. This development has been made possible through agreements with the City of Tshwane and Eskom for the wheeling of the power between the project developer (Bio2Watt) and the power purchaser (BMW South Africa). The City of Tshwane is also a key supplier of waste to the project, diverting some of its organic waste, such as food waste, from landfills to the biogas plant. The location provides the project with proximity to key fuel supplies; grid access and sufficient water supplied by Beefcor’s storm water collection dams. The full case study provides background to the project and technology used, describes the business model and wheeling agreement, and highlights key challenges, enablers and lessons learnt.
Bild © Howling Hound Photography
Read more (www.sairec.org.za/wp-content/uploads/2015/09/factsheet-Elgin_reduced.pdf) Elgin Fruit Juices has an anaerobic digester that converts wastes into methane gas through combined heat and power (CHP) and generates heat and electricity. The generated heat is converted into 10 bar steam. This project’s construction phase started in June 2013. The project was completed and the Elgin Fruit Juices Anaerobic Digester was commissioned in December 2013. The electricity and heat being produced are currently used on-site to offset electricity and coal consumption.
Elgin Fruit Juices Fruit Waste to Biogas to 0.5 MWe anaerobic digester
Read more (http://www.biothermenergy.com/content/petrosa-biogas-project) In October 2007, BioTherm commissioned its 4.2 MW Biogas Project at the state-owned PetroSA refinery in Mossel Bay in the Western Cape Province. This project was the first non-recourse project financed independent power producer (IPP) deal to be concluded in South Africa. It was also the first project to successfully register for certified emission reductions (CERs) carbon credits and is also the first project to monetise CERs in South Africa. The biogas-to-electricity project was registered with the international Clean Development Mechanism (CDM) Executive Board on 29 September 2006 and took 11 months to construct. PetroSA operates the gas-to-liquids (GTL) refinery at Duinzicht, about 12 km from Mossel Bay. The production process at the PetroSA GTL refinery incorporates waste process water that is treated and returned to the GTL process by passing it through anaerobic digesters. The anaerobic digestion is a continuous process, critical for the successful operation of the PetroSA plant and produces a methane-rich biogas as a by-product. Prior to the MethCap plant being put into commercial operation, the biogas was flared to achieve full methane destruction. It is estimated that the equivalent of at least 1,300 GWh of gross heat value has been wasted in this manner over the lifetime of the plant. The MethCap plant uses the waste biogas to generate electricity that is used on-site by PetroSA, making the refinery less reliant on electricity supplied from the national grid. The biogas is piped to three gas engine generator sets, each with a capability to generate a maximum of 1,412 kW at full load. The environmental benefits of the project are a reduction in greenhouse-gas emissions by the national grid and the more efficient use of energy and resources.
South Africa MethCap process effluent PetroSA 4 MWe Biogas Anaerobic Digesters
Read More (http://zorg-biogas.com/biogas-plants/dry fermentation, http://zorg-biogas.com/biogas-plants/dry_fermentation?lang=en ) Until now, biogas technology has mainly concentrated on ‘wet fermentation’ of agricultural waste. Processability of materials with a high dry matter content solid waste was limited. The recently developed dry fermentation process allows methane yields from stackable organic matter with a high dry matter content, requiring no conversion into a pumpable liquid substrate. This method renders fermentation of biowaste possible with up to 50% dry matter content. Biowaste is inoculated with substratum that has already been fermented. It is then filled into the tank and fermented under airtight conditions. Continuous inoculation with bacterial matter occurs per recirculation of percolation liquid, which is sprayed over the organic matter in the digester. During the fermentation process, no further mixing, pumping or stirring is necessary inside the digester, nor is further material added. Excess percolation liquid is collected in a drainage system, temporarily stored in the percolation tank, and then re-sprayed over the biomass in the digester.
Munich, Germany: Dry Digester of MBT-sorted organic, highly-degradable urban solid waste to yield Biogas converted to 1 MWe and digestate dried as compost.
Read More (http://wtert.in/wp-content/uploads/2015/02/Kompogas-presentation-for-Webinar-Hyderabad-30-Jan2015.pdf) These units were originally designed to process animal dung and other agricultural wastes to produce biogas and power. The process has been extended to handle highly biodegradable urban solid wastes such as food wastes. The digestate is dried and used on land as a soil conditioner.
Doha, Qatar: Plug flow digester processing food waste to produce 1 MWe and digestate used as a soil ameliorant.
Read More (http://www.sciencedirect.com/science/article/pii/S1364032114009691) Waste to energy analysis of a large-scale sugar industry plant was performed. The biogas power plant of ShakarGanj Sugar mills generates electricity from biogas produced by the waste (spent wash). The analysis of the spent wash indicates that it contains a high chemical oxygen demand (95,000 mg/l) which reduces to 18,000 mg/l during biogas production. Biogas is produced from anaerobic digestion of the spent wash. The biogas is passed through desulphurisation and dehumidification units which lower the sulphur content from 30,000 ppm to 250 ppm. The results indicate that the total biogas production from 0.5 million m3 of spent wash was 20.34 million m3 during October and September. The total electricity production was 37.7 million kWh and the total steam (28,260 t) generated was used by the mill. The electricity production efficiency using new biogas boilers was 92%. The estimated CO2 emission reduction for the year was 28,032 (tCO2e). According to the CDM the emission factor was zero. The total revenue generated from the utilisation of sugar industrial waste during the study period was USD 3.56 million.
ShakarGanj Sugar Mill, Pakistan
According to the Knowledge Product (KP) studies commissioned by the Department of Environmental Affa...