Despite the biogas sector being a well developed industry globally, ongoing research continues to further develop and strengthen the industry in South Africa, highlights the South African Biogas Industry Association.
The association notes that a variety of biogas applications have been focused on in South Africa as biogas is only one of the many types of competing biofuels, which include solid, liquid or gaseous fuels from biomass.
Based on a research report titled ‘Biogas Technology Matrix’ conducted by German solutions provider Giz and the South African-German Energy Programme in July, specific approaches with a high relevance for the South African market and its special conditions have been considered.
The selection criteria that are considered when deciding whether to produce a biofuel include: the availability of resources in South Africa, how these resources can be processed and used, and the availability and use of the relevant technology considering the local availability of the substrates and residues in questions.
In conjunction with the selection criteria, South Africa’s conventional substrates with a high potential for biogas production and the conditions for use of those materials have been considered. In this regard, agricultural by-products (products from crop farming and animal husbandry), agro-industrial residues from the food and beverage industry, as well as substrates from animal processing, have been considered.
The report indicates that agriculture can, through the provision of biomass, add value to the production of energy. Agricultural by-products such as manure, fodder remains and plant residues – which would otherwise not be used – provide particular economic and ecological benefits to biogas generation.
Giz highlights that, as South Africa is one of the largest crop producers in Africa, digestate evolving from crop farming residues are widely produced. Digestate is the material remaining after the anaerobic digestion of a biodegradable feedstock. Anaerobic digestion produces two main products: digestate and biogas.
“Taking into account political support, adequate merchandise and trade, these substrates could be accessible as renewable-energy sources,” states Giz.
In addition, energy crop purposely cropped for use in a biogas plant could also be grown. This is the main base for biogas production in Germany, where cropping of energy plants was subsidised until July 2014.
Energy crop, mostly maize, is ensiled, that is preserved inside a silo, to provide substrate throughout the year. Giz highlights that applying an energy crop as a feedstock could be attractive for South Africa in order to substitute substrates evolving only during a certain time of the year, while still guaranteeing constant capacity use and to increase
the system’s biogas yield.
However, the issue of food production solely for the purposes of biogas production is
controversial, given the fact that food security is one of the top priorities for the South African government.
Manure is used as a basic substrate in most biogas plants, as its composition has stabilising characteristics and can balance deviations of the biological process. As a result of the high numbers of livestock in South Africa, significant amounts of liquid and solid manure are produced.
The report highlights that these manures can be easily transformed into biogas respectively, and are an accessible and often necessary cosubstrate for biogas plants operating on other substrates.
These manures often contaminate ground and surface waters and are a large methane emitter, owing to the fact that they are not generally treated adequately and are
disposed of into the environment. Treatment in biogas plants could remediate these negative environmental impacts.
Additionally, municipal solid waste is a mixture of solid waste originating from households and businesses.
South Africa is changing its perception towards refusal of municipal solid waste by moving away from landfill disposal. The 2011 National Waste Management Strategy of the Department of Environmental Affairs motivated for municipal bylaws to set service standards for separating, compacting and storing solid waste, managing and directing solid waste disposal, and controlling litter.
Anaerobic digestion (the breakdown of biodegradable material) of municipal biowaste can contribute largely towards organic waste management. This municipal solid waste can be used as a substrate for biogas production, however, Giz states that few plants use this substrate source, owing to a lack of well-established waste separation techniques, which make it difficult to remove impurities.
Giz indicates that, in South Africa, there are numerous grocery market chains and restaurants where the concept can be applied. However, there could be a trade-off between offtaking
of the substrate for application for animal feeding purposes at farming facilities and biogas application.
Benefits of Biogas Technology
All biofuels are produced from renewable sources and are included as a subset of renewable-energy sources. Well-functioning biogas systems can yield a range of benefits for their users, society and the environment in general.
For example, transformation of organic waste into high-quality fertiliser, environmental advantages through the protection of soil, water and air, reducing pressure on landfill sites, additional income for farmers through energy and fertiliser production, macroeconomic benefits through decentralised energy generation and environmental protection.