Co-Digestion with Biosolids - Critical Success Factors

Anaerobic digestion is a commonly used sludge stabilization process to produce stabilized grade B biosolids. It converts organic matter into biogas which can be used to generate electricity, and produce heat and digestate, a valuable fertilizer and soil conditioner.

Implementing co-digestion is gaining traction as a means to increase onsite energy recovery and move towards energy neutrality. There are number of co-digestion substrates available, some of these substrates include food waste, Fats Oil and Grease (FOG), Food Organics and Green Organics (FOGO), and high strength liquid waste.

This paper discusses two different co-digestion case studies for two different water utilities with different co-digestion substrates. The case studies assess the impacts of varying the quality of substrate on digester performance and the maximum substrate that can be added for co-digestion without deteriorating process performance. Critical success factors were also identified for successful implementation of co-digestion.