(140a) Progress in Nutrient Recovery From Anaerobically Digested Wastes

Recovering energy from solid wastes such as organic fraction of municipal wastes and animal manures has been recognized as having great potential for generating renewable energy and reducing greenhouse gas emissions. A more desirable concept, however, is bio-refining with which the waste materials are converted to a series of co-products in addition to biogas. Anaerobic digestion is the most suitable technology for such an application because of its capability in handling mixed waste feedstocks at a relatively low cost. A major technical challenge is to identify targeted products and develop related processes to produce these products economically. Due to the fact that animal manure and many types of municipal wastes such as food wastes are high in nutrient contents, recovering these nutrients as co-products not only benefits resource recycling but also contributes to environmental protection in terms of air and water quality. The Bioprocessing and Bioproduct Engineering Laboratory at Washington State University has been actively investigating the chemistry of the effluents from dairy manure and food waste anaerobic digestion and from that chemical research, developing technologies for recovering nutrients from the effluents. This paper provides a summary of the most recent progress. The information will be useful to the engineering community in selecting and designing systems to recover nutrients from waste streams.