Kenyan farmers turn to bugs as fertiliser costs rise

Kenyan farmers are using redworms and black soldier fly larvae to turn waste into organic fertiliser as soil degradation, higher fertiliser costs and demand for organic food push some growers to look for alternatives.

At his farm in Lari, about 50 kilometres from Nairobi, George Muturi uses redworms to make vermicompost from food waste, crop waste and cow dung. He said the switch away from chemical fertilisers had improved his soil and helped his vegetables grow during dry periods.

Muturi has about 70 worm beds, each holding at least 5,000 redworms. The worms break down the waste over about six weeks into a nutrient-rich compost. Multiple studies have shown that vermicompost can improve soil structure, organic matter and water retention.

A 2025 soil report by the Heinrich Boll Foundation, a German think tank, found that more than 40 percent of east Africa's soils were degraded, partly because of overuse of chemical fertilisers. The report estimated the loss in productivity at more than $65 billion a year and classified 32 percent of Kenya's cropland as strongly acidic.

In Nakuru County, Robert Mwangi uses black soldier fly larvae to break down food waste from the city’s main market. The larvae produce frass, which is used as organic fertiliser, while mature larvae are dried for animal feed.

Mwangi said he processes about 10 tonnes of food waste a week and sells compost to farmers around Kenya. He said demand has exceeded what he can produce.

Muturi said vermicompost is still far from industrial-scale use because large amounts are needed to match synthetic fertilisers, but both farmers described the approach as a way to improve soil and reduce waste.