Anaerobic digestion – or AD – may sound like a strange concept to some. Put simply, it’s what happens when organic materials – such as food waste – are broken down by microorganisms, producing biogas as a by-product.
In Kenya, the Gorge Farm Energy Park is looking to harness the power of AD on a large scale. Its crops feed an AD plant, which is referred to by one team member as a “big mechanical cow.”
The farm’s plant is operated by Biojoule, an associate company of engineering, procurement and construction business Tropical Power.
“You feed it biomass on one end, it gives you ‘manure’ and liquid fertilizer on the other end, and in the process gives you biogas,” Christopher Macharia, lead project engineer, told CNBC’s Sustainable Energy.
“Once we’ve got the biogas, we need to turn the biogas to electricity and the way we do this is using… a gas engine generator,” Macharia went on to add. “Essentially this is just like an engine in a car, a normal vehicle. The only difference is that instead of using petrol, diesel, you use biogas to run it.”
The potential for AD appears to be significant. “Recent research shows that we could speed up the process of digestion by up to perhaps thirty times,” Mike Mason, chairman of Tropical Power, said.
“Do that, and we change the whole relationship between agricultural waste and energy, and every farm, every farmer, becomes an energy supplier as well as a food grower,” Mason added.
While the potential is there, challenges remain.
“This type of technology has a lot of potential, but of course there are also challenges and barriers that need to be overcome, and this is again where the importance of (a) long term, stable, enabling environment comes into the picture,” the Food and Agriculture Organisation’s Andrea Rossi told Sustainable Energy.
“Some of these limitations include artificially low energy prices due to fossil fuel subsidies, the high up-front investment required for the installation of the technology – and its purchase of course – combined with high costs of capital and in some cases problems accessing credit that can be faced by investors in developing countries.”