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Bringing Anaerobic Digestion to Africa


Tropical Power, based out of Nairobi, Kenya, opened Africa's first grid-connect anarobic digestion power plant in August in Naivasha, Kenya. The $7.5 million project took nearly a year to complete and the plant is expected to use approximately 50,000 metric of organic crop waste each year and produce at least 35,000 metric tons of nitrogen-rich byproduct.

Energy experts agree that the Gorge Farm AD Plant is a pioneering power project for Kenya. Distributed power projects, which generate electricity close to the point of use, are vital to Kenya’s energy security, reliability and efficiency. “Government ministries, departments and agencies are working together to encourage the private sector to develop high-quality distributed renewable power assets, like the Gorge Farm Energy Park,” says engineer Joseph Njoroge, principal secretary for the Ministry of Energy and Petroleum. “Kenya is open for business for investors and developers interested in clean, renewable and bankable energy projects. The biogas technology at this cutting-edge project will provide Kenyans with more clean, reliable and cost-effective electricity in their homes and businesses.”

Getting Off the Ground
Tropical Power is a joint venture between Mike Mason, a British entrepreneur, and the owners of Vegpro, an agricultural company in Kenya. Mason wanted to generate renewable power from biomass and Vegpro wanted to reduce its carbon footprint and be more resource-efficient, so the two teamed with ClimateCare in taking its 2.8-MW biogas digester plant in Naivasha, Kenya, through the voluntary gold standard. “The aim of the company is to make efficient use of locally available renewable energy feedstocks, such as harvest waste on the farms where we operate,” says Tom Morton, director of ClimateCare’s Nairobi office, and a key member of the Tropical Power team. “We use this to generate cost-effective renewable energy, to displace fossil fuels and, where possible, use the byproducts as a fertilizer.”

Getting the project off the ground wasn’t easy. There were few engineers in Kenya and certainly not enough to get the job done. ClimateCare and Vegpro both provided help from other facilities around the world and helped train more than 50 Kenyans in the jobs necessary to get it done. “Vegpro has operations in Kenya,” Morton says. “When investing in a project, we seek partners that control the feedstock, have capital to coinvest and have an energy demand. It therefore made sense to work on one of Vegpro’s farms initially, before rolling the model out with third parties.”

The facility is set up as a two-stage AD plant to use local, organic crop waste as feedstock, which is expected to be more than 30 percent more efficient than conventional single-stage plants. According to Morton, the waste is then digested by microorganisms feeding in the absence of oxygen to produce biogas, which is combusted in gas engines to produce electricity and heat. “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,” says Johnnie McMillian, Tropical Power’s managing director. “The Gorge Farm AD Plant is physical proof that locally produced feedstock can be used to generate clean and cost-effective distributed power for all Kenyans.”

The plant has an effective life of 25 years and the project is expected to have a six-year payback period due to the combination of grid sales and higher-tariff energy supply to Gorge Farm.
“The biology of the microbes that make the gas and the feedstocks that provide the source of energy are unique from site to site, and require time and expertise to understand,” Mason says. “Tropical Power has been supported in this with extensive help from the Universities of Oxford and Southampton.”

Other companies who had a hand in the success include Snow Leopard Projects GmbH, providing Tropical Power’s exclusive development license; GE, which deployed two Jenbacher J420 gas engines, provided by Clarke Energy; IET Siemens for switchgear and transformers, SAR GMBH for instrumentation and control systems, and Paulmichel for agitators and stirring equipment.
The Gorge Farm AD Plant will be owned and managed by Biojoule Kenya, an independent power producer.

Morton feels there is great potential for other biogas power projects in certain parts of Africa. “While we are focusing on large-scale opportunities, such as Gorge Farm Energy Park to begin with, we are also doing R&D on reducing the scale of the operations so that they can be applicable in areas with less feedstock and lower electricity demand,” he says. “This is the first AD plant, and we also have a small plant in Kenya that uses rose waste to displace kerosene in a rose propagation unit.”

Looking to the Future
Tropical Power has a 5-MW biogas project in development in Ghana at the Kpong Farm Energy Park, but Morton says it’s still in the planning stages and there isn’t much he can share. He does reveal that next year, Tropical Power will begin construction on a further 10 MW of solar generation capacity at the plant that will be colocated with the AD plant in Naivasha and will feed directly to the grid.“The key thing for the AD is to have ownership of the feedstock, to coinvest and to have an electricity demand,” he says. “We also need a grid connection to sell the surplus power. Ideally, there would also be a set for the waste heat from the engines and we are exploring possibilities for this in Naivasha.”

Article cited from: http://goo.gl/pt3e1q