Kitchen waste converted to gas used for cooking at air force and army base in South Africa

  • Two military bases in Limpopo, South Africa, are proving that the war to save the planet can be won one kitchen at a time.

Air Force Base Makhado and the 523 Squadron (SQN) army base in the town of Louis Trichardt, were selected as the pilot sites for the Department of Defence’s biodigester project in partnership with the South African National Energy Development Institute (SANEDI). In 2021, this saw the installation of a pre-cast biodigester on each base to turn kitchen food waste that is normally sent to landfill into biogas that is used for cooking.

The biogas plants consist of large, sealed anaerobic digesters in which waste material is decomposed to produce methane gas. These were installed underground at the bases to make them unobtrusive and to prevent any unpleasant sights or smells around them. In addition to gas for cooking, the digesters produce an organic by-product, called the digestate, which is an excellent organic fertiliser.

A relatively simple solution to the twin problems of waste management and energy costs makes perfect sense. There is, however, a critical success factor that often scuppers biogas projects and that, says SANEDI’s Dr Karen Surridge, is people. “Biodigesters are the most labour-intensive renewable energy technology. I always say it’s like having a baby, and people don’t believe it until they have a biodigester to look after and keep alive.”

The upshot of the digester’s happiness is that it produces enough gas for the stove-top cooking required to provide breakfast and supper for 220 people every day, thus saving a predicted amount of around 116 MWh of electricity over the combined system’s lifetime. Based on this performance, it will be possible to add two more biodigesters in parallel on this system to power additional cooking burners and a water heater in the kitchen.

Over the past two years, Surridge collected performance data from both biodigesters: to date 17,5 MWh of electricity has been saved, 6,5 tons of CO2 emissions avoided and 30 tons of kitchen waste diverted from landfill.

Author: Bryan Groenendaal

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