Enhancement of Microbial Activity during the Composting Process of Agricultural and Farm Waste Using Zeolite Solid and Suspended Nanoparticles

The use of nanomaterials in agricultural waste composting has emerged as a promising strategy to enhance the process and the agronomic quality of the product. Among the different materials, zeolite is characterised by its potential to reduce nutrient loss and favour microbial activity and organic matter degradation. This study compares the effect of the addition of solid and suspended zeolite nanoparticles on the composting process of agricultural waste and product quality. The study was conducted in reactors with 40 kg of substrate mixture under laboratory conditions. Zeolite in both application forms led to better process conditions, such as higher temperature peaks (65.3 °C and 63.8 °C for TZS and TZL, respectively; 60.5 °C for the control), higher abundance of bacteria in the thermophilic phase (9.97 × 1011 copies/g DM y 2.87 × 1011 copies/g DM for TZS and TZL; 2.42 × 1011 copies/g DM for the control), increased degradation of organic matter (a reduction in volatile solids of 28% and 23% for TZS and TZL, respectively; and 21% for the control) and a relatively higher nitrogen content in the product (2.4% and 2.1% for TZS and TZL, respectively; 2.2% for the control). In addition, zeolite treatments showed the highest abundance of the amoA gene during the process, suggesting that this amendment promotes nitrification in composting. This study demonstrates that the application of zeolite nanoparticles favours microbial activity. Its application in solid form shows the best results in the process conditions and the nitrogen content in the product.