In the densely populated township of Khayelitsha in the Western Cape where finding fresh and healthy food can be difficult, backyard gardeners are turning to biochar to boost their soil and improve plant growth.
Local growers say this simple yet powerful tool boosts yields in a community often overlooked for agricultural activities.
Capetonian Freda Burden, a sustainability practitioner now residing in Berlin, Germany, is the brain behind this movement.
Burden holds a BSc in biochemistry, genetics, and English from the University of Cape Town (UCT), and a postgraduate diploma in sustainable development from Stellenbosch University.
A gardening breakthrough
In late 2023, she led an agricultural project on the Cape Flats to test biochar to see if it could boost yields in backyard and community food gardens. The study was conducted across ten gardens and the results were promising.
The project began when Carl Wesselink, director of SouthSouthNorth (SSN), reached out for assistance in designing experiments to test the effects of biochar-based soil amendments on food gardens in Kuyasa, Khayelitsha.
“SSN had donated 30kg of activated biochar to the Abalimi Bezekhaya Garden Centre,” she explains.
Activated biochar is like dry charcoal, made by burning organic materials slowly. To make it more useful for gardening, it needs to soak up nutrients and water. This can happen naturally from rain or by treating it with things like livestock urine or manure, which helps it improve the soil.
Biochar takes root
Thembisa Kulana, a gardener from Kuyasa, has been experimenting with biochar. In her small backyard, Kulana set up a few trials. She sprinkled biochar into three different garden sections: one with only soil, one with sheep manure, and a third with her usual mix of manure and soil. The results were clear.
“The biochar section produced larger and higher-quality vegetables,” she says.
Asiphe Mntuyedwa, a field worker for Abalimi Bezekhaya, also witnessed the magic of biochar. She noted that the best results came when biochar was mixed with well-composted sheep manure.
‘We found that biochar works best when mixed with sheep manure. The results were much better when biochar was combined with manure than any other tests.”
Asiphe Mntuyedwa
She notes that growing food on the sandy soil common on the Cape Flats can be challenging, so the soil needs to be well-composted before using biochar for it to be effective.
“Overall, biochar works best on soil that has been well-prepared, especially when properly composted beforehand,” she adds.
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Fighting climate change, one garden at a time
Burden explains that using the donated biochar in Kuyasa’s soil shows the potential to significantly boost crop yields. A mix of biochar and composted sheep manure increased yields even more.
“Biochar has the potential to positively impact soil health, thereby increasing the agricultural productivity of soils and bolstering food security,” she explains.
Burden adds that the biochar production process traps carbon in stable structures that can remain in the soil for thousands of years. By doing so, biochar helps combat climate change by capturing carbon and lowering greenhouse gas emissions from the soil.
Although this research project was a pilot study, it succeeded in identifying ways in which future iterations could be improved and township gardeners are better off knowing the benefits of biochar.
Burden says although they identified two limitations and made suggestions on how to address them in the future, she’s excited to share the knowledge with as many people as possible.
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