Synergetic valorization of organic and mining waste towards production of carbon-neutral organomineral fertilizer via catalytic wet air oxidation

Wet air oxidation (WAO) of grape pomace, an organic waste with low biodegradability generated worldwide, was performed to evaluate the production of a novel organomineral fertilizer. The synergistic effect of kimberlite rock powder, a mine tailing, was tested, as a potential waste-derived catalyst and potential carbon sink due to its alkaline earth-silicates content. The gaseous, liquid, and solid phases were characterized, and results were subjected to multivariate analyses to uncover data patterns. The products obtained from WAO were evaluated in bioassays for their soil amendment properties. The results revealed that temperature and kimberlite play an important role in the WAO oxidation performance and steadfast humic-like substances generation, while kimberlite serves as a nutrient source and partially as a sink for the CO2 produced during WAO via mineral carbonation. WAO products were found to possess beneficial properties as soil amendments, in terms of sustaining early plant development and alleviating salinity stress.