Horizons Environment — part of Scottish Water — is considering investing in the equipment necessary for its existing anaerobic digesters to be able to accept organic waste. This will require the upgrade of the digesters, which form part of the sludge treatment centre at Cumnock Waste Water Treatment Works, East Aryshire. Ramboll prepared a feasibility study, which forms the business case for investment.
The scope of the study included the identification of potential efficiency improvements in the existing system and an examination of how the co-digestion of waste and sewage sludge could improve the biogas yield, and thus the heat and power potential. We undertook a detailed review of existing plant operations and productivity, and we reviewed the proposed upgrade in relation to the potential user-demand for the biogas.
A series of phases was developed for Horizons Environment that would allow them to stage the investment in such a way that each upgrade phase could be proved before the next proceeded. An investment financial model was developed, and the optimum use of the biogas considered based on end-user location.
This technology is still in its infancy in the UK, and Ramboll consultants were able to use their expertise gained working on similar facilities in Sweden to advise the client. The study outlined clearly the relevant regulatory requirements and incentives relating to biogas generation.