Although this may seem to be a big investment for this amount of electricity produced, the plant will serve several purposes in addition to power generation. "Emphasis on the project has been to truly make this a demonstration plant for South Africans and a research facility," said Robin Carlisle, minister for Transport and Public Works in a response to questions from the George Herald.
The plant will feature a biogas digester that will produce methane biogas which will be used to generate electricity. Cow dung from the farm’s 320 cows will be fed to the digester. It will be harvested daily from the hard surfaces of the dairy. Calculations indicate that the plant should be able to produce a constant 8 to 12 kW. The gas can also be stored, which will enable variable power supply and peaks in excess of 12 kW.
"The plant includes many periphery expenditures which are not related to the biogas digester. The cost includes a pilot plant model that will demonstrate the larger plant, which can be used at other sites as well. In addition, there are many measuring and monitoring devices which would not normally be included in a biogas digester, but would be used for experimental purposes by the farm staff and researchers," said Carlisle.
Fertiliser to be sold
"We want to make better use of the treatment of waste cow manure in waste stabilisation ponds and we intend to sell the treated manure to the public as fertiliser as well as produce treated effluent water quality that complies with the Department of Water and Environment effluent standards for irrigation purposes."
Asked if the amount of power generated could be upped at a later stage, he said it may be difficult to increase the quantity of biogas produced at this particular farm. "This is due to the cows being farmed in pastures where it makes it difficult to capture the cow manure.
"Other methods of milk farming will definitely be able to produce more biogas per cow. Biogas can also be produced from chickens, pigs, abattoir waste, wineries, and just about any agricultural process. The purpose of the project is not just to demonstrate the production of electricity from cow manure, but the general principle."
Cheaper for farmers
Should a farmer wish to erect a similar biogas digester, it could cost anything from R250 000 to R1-million. "The unit cost of the energy produced becomes cheaper as more cows are involved. At current electricity rates, payback periods would be in the order of five to 10 years," said Carlisle.
In a country such as Austria, where electricity is more expensive than here, more than 340 biogas plants were operational five years ago already, many of which on farms.
According to Carlisle, a 1 MW digester using manure from Friesland cows is being constructed by Faircape in Cape Town. Other companies that have constructed a number of these plants locally are CAE and Agama. "This is not a new technology and the processes are well developed, docu-mented and available for commercial use."
The Department of Transport and Public Works (implementing agent) is running the project in co-operation with the Department of Agriculture (as the user client).
Two and a half years of planning and research have gone into the project. It is foreseen that the plant will be completed and commissioned in March 2012.
Power generated from animal and human waste has other uses. A British company, GENeco, has devised a way to run a car on human waste. GENeco teamed up with Volkswagen on the "Bio-Bug," a poop-powered ride that can reach 183 km/h.
ARTICLE: ALIDA DE BEER, GEORGE HERALD REPORTER
