The Biogas Production Plant at Umeå Dairy — Evaluation of Design and Start-up

Abstract: As a part of a large project at Norrmejerier, a biogas production plant has been constructed at Umeå Dairy. In this plant wastewater, residual milk and whey are decomposed and biogas is produced. The biogas is burned in a steam boiler. The biogas plant is designed as an anaerobic contact process, with sludge separation and recirculation by a clarifier. The fat in the substrate is treated in a separate reactor. The purpose of this study is to evaluate the design and start-up of this biogas production plant. Further, the interaction with the contractor responsible for construction and start-up is evaluated. The plant is generally well designed, the process conditions are suitable and the objectives are realistic. However, the seed sludge is unsuitable and the time plan is too optimistic. At the end of the period of this study, the plant was running and all central components are performing as intended. Still, the objectives have not been reached. This is mainly attributed to the poor quality of the seed sludge. The management of the plant and the interaction with the contractor has generally been good. Most problems that arose were of typical start-up nature. Others were due to insufficient planning or lack of communication. Further, several design flaws were identified during start-up. Washout of sludge has been one of the most significant drawbacks during start-up. This inconvenience seems to be the result of improper seed sludge and a too hasty increase of the organic loading rate.