Assessing the Agronomic Quality of Compost from a Novel Rapid Composting System for Agri-Food Waste Valorization

Purpose This study aims to evaluate the quality and limitations of compost produced in a novel automated closed system within 7–10 days compared to the compost produced under a traditional windrow system and a commercial organic fertilizer. Methods The compost maturity was evaluated using Solvita® stability test and phytotoxicity test. Mineral nitrogen (N) dynamics and enzyme activities were determined in unamended control soil and soil samples amended with the composts and organic fertilizer during a 91-days long incubation experiment. Results The compost from the closed system had a higher C:N and NH 4 + :NO 3 − ratio than the threshold for matured composts; however, its application at a rate of 5% (volume-based) did not affect cress germination. A significantly higher mineral N concentration was recorded in treatments with organic fertilizer (+ 17 to + 397%) and traditional compost (+ 11 to + 100%). In contrast, lower mineral N and higher dehydrogenase enzyme activities were recorded in the closed system compost than in the unamended control. Conclusion Applying the closed system compost in soils increased microbial activity while decreasing N availability, indicating the need for further research that synchronizes nitrogen availability with crop demand. The novel rapid-composting closed system shows the potential for valorizing farm waste, nutrient cycling, and improving soil health.