"South Africa definitely has exploitable bio-energy potential," stated Council for Scientific and Industrial Research principal engineer Crescent Mushwana at the launch of the South Africa Bio-energy Atlas in Pretoria on Friday. "Bio-energy is feasible from organic waste, residues from forestry and agriculture [lignocellulose], and eradication of alien invasive plants." These all amount to 'low-hanging fruits'. "The economic viability of biofuels from purposely cultivated crops is currently negatively affected by the low price of oil."

However, most agricultural residues are already allocated to other uses, he cautioned, such as soil and nutrient regeneration. On the other hand, there is a lot that can be done in urban areas.

"Biomass potential is always closely correlated with population density," he highlighted. And areas of dense population tend to have good infrastructure, making it easier and cheaper to deploy biomass as an energy source. "Organic waste is largely concentrated in big urban areas."

Organic wastes are turned into biogas using simple devices called digesters. Basically, these are air-tight containers in which a biological process called anaerobic digestion takes place. Ideally, the temperature has to be controlled for optimal efficiency. The result is a mixture of methane (the major part) and carbon dioxide gas. The methane can be used as fuel to generate electricity. The residues can be used as fertiliser. "Organic waste looks like a [low-cost] winner in all cases."

"Lignocellulose is a very important factor we should look at," he points out. "In the short term there is potential for what can be done with existing operations." This could include co-located electricity generation at sawmills and sugar mills.

"Compared to renewable energy programmes, there is space for these [bio-energy] technologies to play. Definitely for lignocellulose and biogas from digesters," assures Mushwana. These two technologies are both cost-competitive. "Definitely, there is potential."

The goal of the atlas is to act as a "decision support tool" to help the government in planning, investment and deployment decisions regarding bio-energy technologies, for heating, transport fuels as well as power generation.