KIAMBU, Kenya (AFP) — In 35 years working the land, Kenyan farmer Josphat Muchiri Njonge has never seen his coffee shrubs burst with so much fruit on his verdant hillside plot outside bustling Nairobi.
Same too goes for the banana and avocado trees swaying on his 2-acre family farm in Kiambu. The plot is also lush with kale, spinach, maize and the cereal amaranth.
His secret weapon lies underground.
There, in a brick tank, dung from his 10 dairy cows is quietly transformed into a rich, organic fertiliser that he says has supercharged the soil and harvests.
It isn't the only benefit Njonge, and tens of thousands of other smallholder farmers across Africa derive from "biodigesters."
These tanks, either made of masonry or modern plastics, act like a magical mechanical stomach.
In the darkness, natural micro-organisms break down manure in the absence of oxygen to create compost and biogas, a clean, renewable energy source.
Kenya boasts more biodigesters than anywhere else in Africa -- a "poo power" that is being used to run everything from cooking stoves to farm equipment, phone chargers and shower heaters.
It is a smart use of land, something that the UN's top scientific panel for climate change says will be crucial for keeping global temperatures at safer levels while feeding a growing population.
In a special report this week, the Intergovernmental Panel on Climate Change detailed how intensive farming has degraded the environment — a crisis that requires a major rethink about how food is produced and land used wisely.
Agriculture and deforestation produces almost a quarter of greenhouse gas emissions, with methane from livestock a major contributor to a warming planet.
Biogas is essentially carbon neutral, and helps reduce fossil fuel emissions by replacing the firewood and charcoal traditionally burned in kitchens in Africa.
Enormous demand for these cheap sources of wood has ravaged Kenya's forests and degraded its soils.
Their fumes also kill, with 15,000 deaths a year from indoor air pollution, according to government figures.
"It's very convenient for me. I've been using firewood, charcoal, but I don't anymore," said Anne Mburu, a farmer in Kiambu, who used to spend $20 a month on firewood before installing a modern, prefabricated digester alongside her cow shed.
Future energy
Biogas is filling a gap in East Africa, where developing economies are fast growing but power is costly, unreliable or non-existent.