A study commissioned by the SA National Energy Development Institute (Sanedi) and conducted by the University of Johannesburg’s Process, Energy, Environmental and Technology Station (UJ Peets) has found that the biogas sector has the potential to reduce rural energy poverty, reduce urban organic waste on landfill sites, and boost employment and business opportunities through the use of micro-digester technology.
Sanedi renewable energy manager Dr Karen Surridge says micro-digesters operate like rubbish disposal systems where biogas, including methane gas, is produced through the decomposition of organic waste.
The methane gas can be used to drive turbines to generate electricity, to power vehicles, or utilised in households, commerce and industry.
“We’re hoping to reduce the costs for primary energy,” says Surridge.
The research conducted by UJ Peets concluded that micro-digesters provide alternative energy sources for cooking, further enabling households to move away from firewood and the expense of purchasing paraffin.
Potential as an alternative source of energy
The report by UJ Peets says the development of micro-digester technology can provide government with an alternative in its energy mix while achieving the objective of skills development, economic transformation and job creation.
“Biogas reportedly has the potential to generate 2.5MW of electricity in South Africa with a market potential of R10 billion,” it says.
Sanedi says the potential size of the sector is estimated to be 21 000 units, with the potential to increase to 54 000 units. Based on this, the entity says the sector has potential to create at least 17 000 jobs and up to 150MW of daily capacity diverted from “less clean” and green energy sources, including firewood and charcoal.
SANDF’s biogas plants
In August 2021, the South African National Defence Force (SANDF) and Sanedi announced their partnership in installing biogas plants at two military bases.
Sanedi installed the plants and trained personnel to maintain them at the air force base and the 523 Electronic Warfare Squadron base in Makhado, northern Limpopo.
The power provided by the plants has been used in the preparation of meals three times a day for up to 200 people at the air force base, and 20 people at the electronic warfare squadron base, since since February and the end of March respectively.
Surridge says the biogas digesters have provided an alternative to much of the electricity previously used in the kitchens, and will save the base an estimated R250 000 in electricity costs over the 20-year lifetime period of the plant.
“The choice of a base with a small kitchen and one with a large kitchen was partly made to demonstrate that biogas plants can be tailored to specific needs and provide a wide range of solutions,” says Surridge.
The large digesters were installed underground to make them unobtrusive. This, according to Sanedi, shields the environment from any unpleasant odours that might escape.
The drawback of the technology is that it is labour-intensive, requires constant attention and is difficult to get off the ground once installed.
“Daily maintenance is absolutely essential, so the process is quite labour-intensive,” says Surridge. “Once installed, a biogas system can take as long as six months to start producing gas optimally. The initial process is like feeding a baby. Waste material must be added regularly throughout the system’s lifetime and the gas must be used soon after it is produced, otherwise it dissipates. It can’t be stored or bottled.”
Sanedi says it hopes to introduce micro-digesters into the public sector, starting with correctional services.
A solution to organic waste and landfill issues
According to Statistics SA’s 2019 General Household Survey, demand for consumer goods has led to a huge increase in domestic waste, which is having a negative effect on the environment.
“Cities are rapidly running out of appropriate dumping sites and recycling of waste materials is globally becoming a vital component of strategies to preserve nature and limit the demand for raw material.”
The 2019 survey shows that 90% of households in rural areas discarded refuse themselves, compared with only 19.7% in urban areas and 15.6% in metropolitan areas.
The South African State of Waste Report, published by the Department of Environmental Affairs in 2020, found that in 2017 South Africa generated 54.2 million tons of general waste of which 56.3% was organic waste, predominantly from sugar mills, sawmills and the paper and pulp industry.
The report also indicated that the country generated 66.9 million tons of hazardous waste, with only 6% being recycled and the remainder (94%) landfilled.
The Organics Recycling Association of SA and the City of Cape Town have appealed to large organic waste generators to register with the city and submit their integrated waste management plans in order to comply with the Western Cape’s 50% organics landfill ban at the end of 2022.
Surridge believes widespread use of the technology can reduce air and soil pollution, decrease health risks associated with hazardous rotting food, and mitigate the issue of landfill.
However, the study shows that South Africa’s uptake of the technology is low compared with other countries. The total number of small-scale biogas digesters installed in the country is around 350. This differs significantly from Kenya with 14 000, and Uganda and Ethiopia with 11 000 each.
Nondumiso Lehutso is a Moneyweb intern.