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Turning waste into energy a possible solution
Biogas is probably the best-kept secret in the renewable-energy industry and organic waste is one of the largest untapped sources of natural energy avail- able today, asserts Ubuntu Energy Solutions MD Jonathan de Magalhães.
“It is a simple solution that can be deployed in a short time, but people do not know too much about it,” he adds.
Biogas is produced through the biological breakdown of organic matter.
“Organic waste, such as dead plant matter, animal manure and kitchen waste, can easily be converted into biogas in a simple biogas digester. Biogas consists mainly of methane (CH4) and carbon dioxide,” explains De Magalhães, who will be attending this year’s Africa Energy Indaba as a consultant.
Biogas provides a clean, easily controlled source of renewable energy from available organic waste with little labour input, replacing firewood or fossil fuels, which are becoming more expensive as demand outweighs supply, he adds.
While biogas is used all over the world – India, for example, has more than 4.5- million digesters – harnessing biogas energy in South Africa is practically unknown.
“Only a small number of digesters have been built successfully and commissioned to date – a loss to the renewables industry sector in the country, since biogas fulfils environmental sustainability criteria, requires a relatively low technological input and is cost effective to implement,” says De Magalhães.
Additionally, a biogas digester treats the organic waste and prevents it from taking up precious space in landfills or overburdened sewage plants.
In South Africa, the waste disposed of in landfills produces unwanted landfill gas, such as CH4 and leachate emissions.
Further, there is pressure on the country’s aging sewerage system.
Easy disposal and treatment of organic waste, such as black water or sewage treatment, which involves feeding the sewage into the biogas digester along with additional organic waste and water, will increase the yield of biogas from the digester daily.
Additionally, in environments that would normally require a septic tank system, the cost saving of not needing the septic tank can be used to offset the costs of the biogas system.
Grass cuttings, animal manure, kitchen waste and almost any other type of similar waste can be used to generate a usable form of energy.
As the biogas digester is a closed system, there is no leakage of the organic waste into the surrounding environment. This can significantly reduce, or even eliminate, the need for an environmental-impact study. De Magalhães notes that, with this solution, there is also the advantage of a reduction of associated energy costs. The biogas generated by the digester system can be used for water heating, space heating, cooking, lighting or running a biogas generator for electricity generation or any combination of these.
By using biogas instead of traditional resources, such as electricity or gas, to provide this functionality, energy costs can be significantly reduced, providing a quick return on investment for biogas solutions,” says De Magalhães. In addition to the cost savings, the use of biogas can also provide a passive income, he says. As the process of biogas generation uses the bacteria in the organic waste, the organic slurry at the end of the process can be easily managed and all organic smells are contained within the closed digester system.
This organic slurry can be used as a natural fertiliser for almost all agricultural applications, reducing any costs associated with buying traditional fertilisers.
This 100% natural organic fertiliser can also be sold to agricultural farms and nurseries, either in its liquid form or predried and pelletised, providing an addi- tional form of income from the biogas digester.
Biogas digesters are used all over the world and the technologies have made significant advances, especially over the last three years.
The first biogas system was installed in India in 1859. These digesters are also widely used in Brazil to produce biogas.
According to De Magalhães, generating biogas offers a better return on investment than solar or wind systems.
“It is easy to install and deploy, and is very low in maintenance, probably only requiring some attention once every five to seven years. For these reasons, biogas digesters would work well in rural villages, farming communities and at game lodges,” says De Magalhães.
But even the average family in Johan- nesburg could use their organic household waste in a biogas system.
“As long as you have enough feedstock to put into the biogas system, such as black water, grass cuttings, and a reasonable amount of kitchen waste, you can generate your own biogas.
“If you combine a small digester system with some solar panels and an intelligent inverter system, you can generate up to 80% [of your electricity needs] off the grid,” he says.
Nevertheless, despite the many advantages, De Magalhães says there have been no government initiatives in South Africa to assist those wishing to deploy biogas systems.
Source: engineeringnews.co.za
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