(568e) Mining Municipal Wastewater for Fertilizers and Catalysts After Crude Oil Extraction

Future Environmental Protection Agency (EPA) regulations on municipal wastewaters are expected to require the removal of nitrogen and phosphorus similar to other environmentally harmful components.  The current wastewater industry has identified that algal scrubbers are the most cost effective means of removing these trace macro-nutrients.  Cultivating algae at wastewater plants not only produces biomass which can be converted to a carbon rich biocrude but allows for efficient concentration of nutrients such as nitrogen, phosphorus and calcium.  Cultivation of algae in wastewater gives rise to significant differences in resultant biomass as compared to controlled fertilized algal growth.  Typically wide arrays of microorganism species are present, dominated by population preferences as dynamic wastewater nutrients vary.  Also, the relatively high inorganic content (alkali and alkali earth metals) of wastewater, compared to culture media, produces biomass with exceptionally large amounts of non-combustible ash material.  Extraction and conversion of organics from algal biomass is performed through hydrothermal means using subcritical water chemistry giving three main products; solid biochar, biocrude oil, and aqueous co-product.  Data collected from Lawrence, KS Wastewater Treatment Plant and laboratory bench-top studies have indicated that it’s treatment plant could produce >3300 lbs biochar per day and 6-9 barrels of crude per day.¹  The aqueous co-product has contained  >50% of elemental algal nitrogen.  The biochar can be as much as 20 wt% carbon and 10 wt% elemental phosphorus able to be used as soil amendments as is or be sold as a feedstock for fertilizer industry.  Studies have also indicated that the biochar can have interesting characteristics for catalytic supports as well.  This paper begins to determine the elemental fate of nitrogen and phosphorus for applications of solid and liquid fertilizers and characterizes solid biochar for catalytic purposes in terms of BET surface area and pore size, FTIR, NH₄-temperature programmed desorption with and without different calcination treatments and impregnation methods.

References:

1)      Griffin W. Roberts, Marie-Odile P. Fortier, Belinda S. M. Sturm, and Susan M. Stagg-Williams, Promising Pathway for Algal Biofuels Through Wastewater Cultivation and Hydrothermal Conversion, Energy and Fuels,  27 (2), 857–867 (2013).