(731c) Struvite Recovery from Manure By Way of Hydrothermal Carbonization

Dairies and other animal feed lots have grown in size in recent years. Traditional practices of manure disposal were focused on land application, but this is problematic for large operations. The manure is either applied heavily in nearby fields, leading to overapplication and deleterious effects on environment, or the cost of hauling to spread on wider spaced fields is prohibitive. At the same time, there is an opportunity to recover valuable nutrients in manure, primarily phosphorous but also nitrogen, into a valuable form and reduce the costs associated with manure management.

Hydrothermal carbonization has been established as a promising treatment technology for wet biomass. A recent study has shown its potential in solubilization of nutrient content of cow manure into the hydrothermal aqueous product specially when its combined with a strong organic acid such as citric acid. In the current study dairy manure was treated by HTC process at 170C for 10 minutes with different concentration of citric acid. The resulting liquid phase was then used as a supernatant for struvite crystallization at pH range of 9-10. We show experimentally effects of HTC reaction conditions on recovery of phosphorous in struvite. Different ratios of N:P and Mg:P were studied to obtain the optimum precipitation condition. The effect of different concentrations of the organic acid on the crystallization mechanism and the quality of the final struvite were investigated.