Waste Not, Want Not: Turning Harvest Waste Into Electricity

Johnnie McMillan

 Gorge farm utilises local organic crop waste as feedstock for an innovative two-stage Anaerobic Digestive plant that is consistently up to 30% more efficient than conventional single-stage plants. The waste is digested by micro-organisms feeding in the absence of oxygen to produce biogas... “Through biogas and solar, we want to displace expensive and imported generation fuels – like diesel and heavy fuel oil – from Kenya’s distributed power mix" - Johnnie McMillan, Managing Director, Tropical Power.

Across Africa countries are committed to scaling up renewable energy production to meet their growing energy needs. However, this will require bold thinking and innovation to deliver affordable and reliable power solutions that can be rapidly deployed. When even waste material can be used to produce energy, it’s a win-win situation all round.

Africa’s first grid-connected anaerobic digester plant on Gorge Farm in Kenya was developed by Tropical Power and is operated by independent power producer Biojoule. The Gorge Farm Energy Park, launched in August 2015, uses organic waste and sunshine to produce renewable power, both of which are plentiful on the 800ha vegetable farm.

Currently only 23 per cent of Kenya’s population have access to electricity, says the World Bank, yet access to energy is a key imperative for economic development. Gorge Farm Energy Park has an installed capacity of 2.8MW, with a net output of 2.2 MW bringing much-needed power into the grid at a time when Kenya’s energy needs are steadily rising.

The plant is powered by GE’s J420 Jenbacher engines, which are able to operate smoothly at 2,000 meters above sea level. This was the first time that Jenbacher engines were deployed on a renewable energy project in East Africa. As the largest biodigester of its type in East Africa, Gorge Farm Park is seen as a trailblazer for renewable energy development in the region.

The project cost US$6.5 million to build and was developed in under 12 months, with a projected payback period of less than six years.

“Through the Gorge Farm Energy Park we aim to displace the expensive and imported generation fuels – like diesel and heavy fuel oil – from Kenya’s distributed power mix. The Gorge Farm AD Plant is proof that locally produced feedstock can generate clean and cost effective distributed power,” says Mike Mason, chairman of Tropical Power.

“This was the first anaerobic digester project for GE in sub-Saharan Africa. It is a big win for Kenya and Africa in general, demonstrating that waste to power projects are feasible in this market” says Oluwatoyin Abegunde, GE’s distributed power leader for Africa.

Beyond producing power, the plant has multiple environmental benefits. These include the development of a rich natural fertiliser, which is a by-product of the power production process. Once fed back into the land this helps to improve crop health and reduces the need for synthetic fertilisers. Further by displacing oil-fired generation from the grid, the plant reduces carbon emissions by 7,000 tons a year.

“The Gorge Farm Energy Park is a showcase project for Nakuru County, Kenya and the African continent. Distributed power projects are vital to our energy security, reliability and efficiency. And the Park will be using local crop waste and the sun to generate clean, renewable power close to the point of use,” said Nakuru County Governor Kinuthia Mbugua.