Mineral Nitrogen recovery from manure slurry through multi-layer sorption of NH3 and CO2 onto pyrolyzed biochar
Nitrogen management is a major challenge in agricultural systems, its procurement and disposal costing farmers thousands of dollars annually. The shift toward sustainable farming highlights the need for tighter coupling between waste nutrients and nitrogen fertilizer.
In this project we look to a method by which nitrogen in dairy manure can be sustainably recovered through adsorption and precipitation reactions with biochar in the presence of carbon dioxide. Through column experiments, we will evaluate which nitrogen species in liquid manure, whether volatile ammonia, dissolved ammonia, or ionic ammonium, facilitates the greatest extent of ammonium bicarbonate precipitation. We will also evaluate the effect of biochar surface area and surface charge on nitrogen loading.
The final product, biochar intercalated with crystalline ammonium bicarbonate, is expected to contain between 10-20% plant-available nitrogen per unit weight biochar, a proportion commensurate to commercial fertilizers such as diammonium phosphate (18% N) and ammonium bicarbonate (17.7%). The effectiveness of our mineral-organic combination fertilizer will be tested in a greenhouse trial with wheat, with the expectation of improved plant nitrogen use efficiency compared to synthetic N and liquid manure. For, even as ammonium bicarbonate dissolves upon incubation in soil, extended retention in soil will be facilitated through repeated sorption and desorption on biochar surfaces over time.
Together with our collaborators from Cornell ProDairy, Innovation Center for US Dairy, and Green Tree Garden Supply, we look to develop a process by which liquid dairy manure can be re-purposed as dry, crystalline nitrogen fertilizer in a manner which neither compromises crop nutrient needs or environmental quality. The ultimate end goal would be to develop an alternative N fertilizer from the liquid fraction of separated dairy manure, C02, and biochar, which can be scaled to on~farm manure lagoons and industrial manure separation.