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21 Dec 2012 00:00
As Eskom's electricity prices increase, the viability of biogas (and other sustainable energy) projects obviously increases. (Samantha Reinders, M&G)
There are a number of different biogas technologies, but generally it is produced from decaying organic material in an anaerobic environment. The combination of gases produced and piped off includes methane and carbon dioxide.
An effluent by-product of biogas systems is generally excellent plant fertiliser.
The technologies are not new and they are low-tech.
Internationally, biogas projects vary from household (normally farm household) installations to 500MW installations (the latter being about a sixth of the size of an average South African power station).
Until a few years ago, Eskom was supplying among the world's cheapest (coal-based) electricity, which was available at the flick of a switch. The production of electricity from sustainable energy projects generally still costs two or three times Eskom's tariffs. As Eskom's electricity prices increase, the viability of biogas (and other sustainable energy) projects obviously increases.
Also, a highly attractive combination of Eskom and government incentives for this kind of project has recently become available.
Biogas projects could now often yield an internal rate of return of 35% to 40% a year, resulting in a maximum of a four-year payback period – compared with 10 to 15 years for photovoltaic (solar) systems, said Ryan Dearlove of BiogasSA, a local biogas technology supply company.
Biogas projects have other major advantages over solar and wind technologies: they can generate electricity 24 hours a day and biogas can be stored much more easily and cheaply than electricity.
Major rebates or incentives that now enhance the potential viability of alternative energy projects are:
Of course, applying for these incentives involves a thicket of bureaucracy. This will take much longer than the actual construction of biogas digesters, which normally takes only a few months.
Anyone with a strong flow of organic waste in slurry form (or waste water to combine with solid waste) can consider installing a biodigester. For the average urban household, installing one is not an option because the household is unlikely to produce enough waste – primarily sewage, although garden waste can in certain circumstances be added to sewage.
Small farmers can consider small projects (to supply household appliances such as biogas stoves and lamps) because of the addition of the waste (faeces and urine) from their livestock. Likewise, viability is possible with small businesses such as restaurants and food-processing concerns.
Most initial private sector projects will be among large agricultural concerns, including dairy farms, abattoirs and feedlots.
In the public sector, biogas projects for processing municipal sewage waste were a "no-brainer", said Dearlove, and all municipalities should be setting them up.
There are an increasing number of South African biogas technology suppliers – probably about 10 indigenous companies and a number of overseas companies. Nonetheless, for smaller units it was generally easier and cheaper for a buyer in Africa to order a containerised biogas unit from China, said Dearlove.
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