The potential of biomass as a feed for energy products in South Africa is limited due to arable land, rainfall and food security constraints. The best candidate feedstocks are urban organic waste and lignocellulose (comprising a mix of agricultural and forestry residue, and harvested invasive alien plants). It may be possible, with government assistance, to develop a sizeable energy crop industry for biodiesel manufacture based on subsistence farmland.
Bioenergy in South Africa has limited potential on account of relatively low primary productivity, largely constrained by rainfall and exacerbated by significant inter-annual variability. These factors, together with an inevitable focus on food security, combine to limit the attractiveness of energy derived from biomass.
Despite these constraints, some potential does exist. Technoeconomic assessment of options for biomass conversion to energy, and considerations such as job creation, impact on rural economies, greenhouse gas (GHG) mitigation and likely subsidies required to make energy products cost-competitive, were evaluated and resulted in the following set of feasible options for biomass utilisation:
The option requires intervention from government in respect of policy, accelerated permit processing for wastewater and solid waste facilities, and sponsoring of research and development of standardised large-scale digester and biogas upgrading technology. Some local authorities may elect to use wastewater biogas for in-situ electricity generation. Estimated contribution from feasible project options: up to 1 400MWe (electrical output of a power plant in megawatts).
1To benefit GHG emissions (greenhouse gas emissions), the eradicated biomass will have to be replaced. Options include managed Category 2 invasive plants (such as Eucalyptus) or restoration of indigenous vegetation.
2Sugar cane and sweet sorghum are attractive as energy crops due to high yields and large areas suitable for cultivation. Ethanol for E10 blends (5-10% ethanol added to petrol) needs to be near anhydrous (containing no water) and is expensive to produce, making it uncompetitive. E100 (95% ethanol and 5% water), as used in Brazil, is less expensive to produce but was not considered since it does not form part of the current Biofuels Strategy.
A number of project options for a variety of feedstock and processing combinations were evaluated. Not all of these combinations are feasible, generally since smaller facilities do not have the requisite economy of scale, or the combined feedstock and transport costs are too high. The feasible options identified generally minimise the cost of production based on feedstock input, transport costs and economy of scale, but in practice the logistics of supply and local variations in density and accessibility of feedstock might limit the size of such a facility.
Impacts of the most feasible options, as described above, were also assessed in terms of environmental considerations (GHG emission mitigation, invasive alien plant eradication, better utilisation of degraded land), and socioeconomic benefits (job creation, contribution to regional economy, and access to clean energy). It is clear from the assessment of these impacts that, in general, the following holds true:
-improve water availability through eradication of invasive alien plants;
-revitalise subsistence farming areas;
-create jobs in extraction, harvesting and processing of biomass;
-provide access to clean energy in some cases; and
– develop the rural economy.
To conclude, bioenergy is feasible in South Africa at a relatively small scale, involving mostly processing of organic waste, residues from forestry and agriculture, and eradication of invasive alien plants.
Feasible project options depend on the cost of feedstock, processing costs and transport costs. These factors are subject to economy of scale considerations. Furthermore, current low oil prices make bioenergy in general, and biofuel in particular, less attractive, with purposely cultivated crops being affected the most.
Despite this, it is possible to determine short-, medium- and long-term strategies for bioenergy generation, which, in total, may be able to contribute approximately 3 500MW of electricity equivalent to the national energy mix over the planning horizon of 20 years.Should accessible and sufficiently dense invasive alien plants be successfully eradicated over the planning horizon, it will have a significant impact on woody biomass availability and eventually reduce capacity by approximately 1 000 MWe. Negative greenhouse gas benefits ensue should the eradicated invasive alien plants not be replaced by more or less equally productive alternatives — either as managed short-rotation coppicing stands of Category 2 plants (such as Eucalyptus), or with indigenous species.