Food scraps are an unlikely ally in any battle – except in the one we cannot afford to lose. Two military bases in Limpopo are proving that the war to save the planet can be won one kitchen at a time.
A man on a military base who talks and even sings to what is in essence a high-tech compost heap is not an every-day sight – unless you find yourself on the outskirts of Louis Trichardt in Limpopo. There, on South Africa’s most northern air force base, civilian military member Morris Rathumbu has forged a close relationship with the biodigester he has made his own over the past two years.
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 fertilizer.
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.”
When Surridge says the biodigester must be kept alive, she means it literally. Biodigesting is an organic and biological process driven by the same bacteria that keep the human digestive system healthy. These live organisms are the reason that every biodigester is unique, with its own preferences and quirks. And that is why they require such care.
“I know that my biodigester likes more water on Wednesdays and the time it takes me to sing Happy Birthday twice gets enough water into the digester’s daily diet,” says Rathumbu. “I love this technology because it is like having a family. Learning about it has broadened my horizons.”