Reclaiming phosphorus from liquid pig manure:

Precipitation of P as struvite (MgNH4PO4) from stored and anaerobically digested manure and implications for use as fertilizer


Team:

Project Lead: Nazim Cicek, Dept. Biosystems Engineering,  Email: nazim_cicek@umanitoba.ca
Graduate students: Joe Ackerman (PhD. candidate), Elsie Jordaan, M.Sc. Candidate (Struvite precipitation kinetics)

Funding: 

ARDI, MAFRI, Manitoba Hydro, and NSERC

Summary:

In cold climates, it is generally accepted that much of the methane produced by anaerobic digestion of animal wastes is used to keep the digester within the mesophillic range of operation (30-38° C) during winter months, sometimes yielding little or no net annual production for electricity or facility heating.

Optimizing digester tank insulation, enclosing the digester in a passive heating solar greenhouse, allowing influent to reach ambient greenhouse temperature and providing heat exchange between outflow and incoming digester wastes, the energy balance can be substantially improved.

Amending animal manure with high calorific value waste products such as glycerol (a byproduct of biodiesel production) can substantially boost biogas production rates, further improving the energy balance and enhancing the economic value of the process.

This research program evaluates glycerol amendment as a sample co-digestion strategy, and gathers data from a passive solar greenhouse and from lagoon-fed and direct barn -fed hog manure to model anaerobic digestion at 50° latitude in Western Canada.

Preliminary results indicate a greenhouse improved gas economy more than just insulation because a greenhouse allowed heat exchange and preheating of manure to ambient temperatures. Additionally, results show that careful amendment of manure with glycerol can boost biogas yields by up to 2.8 times while avoiding toxicity and operational problems.

Phosphorus recovery form the digested manure through struvite precipitation is being evaluated to add an additional layer of economic benefit to the process and to enhance overall sustainability.

Download pdf Thesis Article:  Development of an aerated struvite crystallization reactor for phosphorus removal and recovery from swine manure by Elsie Maria Jordaan

Download Final Report to ARDI