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Here is an informative article on the potential and challenges to biogas production in S. Africa. It provides additional details on the Harmony gold project including how much land will be dedicated to energy crops (GKG, sugar beets) in each phase. It really is not much. However, something is better than nothing and it could inspire similar applications of GKG in other locations.

Biogas power generation has huge potential for postmining land use

7th November 2014 By: Chantelle Kotze

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Leader of the Pack
Gold mining major Harmony Gold Mining Company’s (Harmony’s) novel approach to rehabilitating mining land entails following environmental best practice to reduce negative long-term operational impact, while also remaining cognisant of climate change, says CEO Graham Briggs.

Harmony has developed a long-term land rehabilitation strategy comprising two elements.

The first pertains to the creation of carbon sinks on mining-affected land, as the proper restoration of former mined land could capture large quantities of atmospheric carbon dioxide.

Instead of following standard rehabilitation practices, such as grassing, Harmony plants species – such as sweet sorghum, sugar beet and giant king grass – which are known for their high carbon sequestration potential.

Briggs says Harmony is finalising a plan to establish a carbon sink on the tailings. “Should the regulator accept this as a viable rehabilitation strategy, a vast amount of our landholding will be available for carbon sequestration.”

“In future, we might also use our sequestration projects to generate carbon credits, which could be used to offset South Africa’s proposed carbon tax,” he adds.

The second element of Harmony’s rehabilitation strategy is to plant energy crops on mine-impacted land that has zero economic value.

Once harvested, these crops will be converted into renewable energy, in the form of biogas, through an anaerobic digestion process. The biogas will be used to replace fossil fuels in Harmony’s metallurgical plants.

The implementation of the first phase of this R47-million bioenergy project, which was launched in September, can replace 71 000 GJ of fossil fuel, securing 11 permanent jobs.

The first phase, which is earthworks, is in the implementation stage and involves rehabilitating the surface of the land. This will be followed by soil conditioning for crop cultivation and the growth of the different crops, refurbishment of the plant equipment and installation of the anaerobic digester.

Once the plant is fully operational and the concept has been proven, Harmony will ramp up the plant to 185 000 GJ, at a cost of about R140-million, over an 18-month period. This phase could create about 200 direct and indirect jobs.

Harmony is planting energy crops on 100 ha of mine-impacted land, in the Free State, for the proof-of-concept project and an additional 250 ha for the ramp up of the plant.