Controlling nutrient loss in plant-soil systems using effluents from a zero-waste nitro-oxidation process for upcycling of agrowaste feedstocks

The use efficiency of fertilizer-nutrients in plants is usually low due to leaching and run-off losses. Lost nutrients pollute the environment, causing environmental health problems. Herein, cellulose nanofiber-containing effluents obtained from a zero-waste nitro-oxidation process for upcycling of organic feedstocks, namely, brewer's spent grain, horse manure, palm waste, and food waste, were applied as fertilizers (termed nitro-oxidation process-fertilizers) to a lettuce-cropped soil. A 5-week leaching event demonstrated significantly higher (P ≤ 0.05) nutrient loss from a commercial fertilizer than from the nitro-oxidation process-fertilizers. Depending on the feedstock, nitrogen, phosphorus, and potassium losses from the nitro-oxidation process-fertilizers were reduced by between 9.8 % and 39 %, 1.5 and 17.5 %, and 7.3 and 32.4 %, respectively, relative to commercial fertilizer. Compared to commercial-fertilizer, nitro-oxidation process-fertilizer from horse manure significantly improved lettuce yield, while no significant yield difference was observed with other nitro-oxidation process-fertilizers. Significantly higher nitrogen and phosphorus (12 and 346 %, on average) were retained in the post-harvest soil with all nitro-oxidation process-fertilizers than with commercial fertilizer, while residual post-harvest soil potassium was significant (8 % more) only with the spent grain nitro-oxidation process-fertilizer. The Langmuir Model used to describe the mechanism of potassium sorption on the surface of cellulose nanofiber showed R² values of 0.996 and 0.902 for adsorption and desorption, respectively. Collectively, these findings highlight the environmental benefits of cellulose nanofiber-containing nitro-oxidation process-fertilizer through mitigating nutrient losses and enhancing nutrient retention in soil, while serving as fertilizers for crop production.