Assessing the feasibility of a biogas and wastewater treatment plant at Rio Fish LTD fish farm and processing facility

Background Information

The fish industry in Kenya plays a crucial role in the economy by providing employment to small-scale and mid-sized fish farmers and contributing to food security. However, it also generates substantial waste, including fish offal and processing residues, which can pose risks to the environment and public health. While repurposing this waste for fishmeal production, fish oil, and organic manure presents potential waste reduction solutions, a significant portion of the waste remains unused.

Using circular economy principles, the Kenya Private Sector Alliance (KEPSA), in partnership with Rio Fish Limited, is piloting a potential waste reduction and wastewater treatment solution whereby fish waste is utilised as a feedstock for a biogas-to-energy plant. The biogas-to-energy process effectively captures methane emissions from decomposing food waste which is then converted to energy. The remaining decomposed material is nutrient rich and offers opportunities to be sold and used as fertilisers, livestock bedding, etc. Furthermore, appropriately treated wastewater can serve as a nutrient-rich water source for farming irrigation, fish growth, and production. This is crucial not only for safeguarding the environment but also for enhancing fish health and the overall efficiency and productivity of fish farms. Finally, by capturing the methane emissions, the project also contributes to reducing greenhouse gas emissions compared to if the fish waste was left to decompose in landfills.

SMEP is funding KEPSA to undertake a feasibility study on the pilot biogas-to-energy plant to determine its effectiveness and potential for scalability between August 2023 to September 2024. The feasibility study will draw insights from contextual analyses, which encompass technical assessment, economic analysis, and environmental and social impact assessment:

  • The technical analysis aims to evaluate the requirements for installing these piloting technologies at RioFish Limited.
  • The economic analysis will provide a preliminary assessment of the project’s financial viability, including the estimated costs, the potential revenues and profits, and the potential return on investment.
  • The environmental and social impact assessment will provide a preliminary assessment of the project’s potential environmental and social impacts, including the potential for water pollution, greenhouse gas emissions, and impacts on local communities and stakeholders.

Photo Credit: Victory Farms


KEPSA has successfully engaged with a biogas technology provider, Biogas International, for the design, fabrication and installation of the pilot biogas plant. During the design phase, various modifications were made to optimise digestion of the fish waste, particularly through the breakdown of fats and oils which can clog the biodigester, as well as to mitigate against the pungent odour often generated from the the decomposition of fish offal. Some of these modifications include the addition of a pre-digestion step, a biosanitation aerobic digestion step as well as co-digestion with water hyacinth. The harvesting of water hyacinth, a highly invasive species in Lake Victoria, for the co-digestion step will likely have the co-benefit of contributing towards managing the spread of this weed.

It was also determined that the capacity size of the plant should be increased from 50 cubic meters (T-REX 50) to 100 cubic meters (T-REX 100) to enhance the waste-treated capacity and the gas production required to run a modified generator. The changes provide an opportunity to test the potential of powering a freezer and, if successful, upscale to a cold chain at the fish farm. Following these design changes, the pilot biogas plant has been successfully fabricated and is ready for installation at the project site.

Due to several challenges, the project site has changed and a new partner, Rio Fish Limited, has been brought on board. New pre-feasibility assessments, including an environmental impact assessment and a gender and social inclusivity assessment will be undertaken at this new project site. These assessments are planned for mid-2024, following which the biogas plant will be installed and piloted. Biogas International will also provide technical assistance to monitor the amount of fish waste added to the plant and the amount of energy produced.

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August 2023 – September 2024



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