Physico-Biochemical Technology for Composting Low-Grade Coal and Cattle Manure

The sustainable management of livestock waste and low-grade coal (LGC) remains a critical environmental issue in Kazakhstan, particularly in agricultural and coal-rich regions. This study proposes an integrated composting approach using fresh and aged cattle manure in combination with low-grade coal obtained from the Ekibastuz and Kauchuken coal basins. The objective was to evaluate the physico-biochemical behavior of these compost mixtures and assess their suitability as organic fertilizers. Compost samples were prepared both under laboratory and field conditions using a mixture of manure, low-grade coal, and sawdust to regulate moisture content. The composting process was conducted over a 45-day period, during which pH, temperature, and moisture content were monitored. The average moisture was maintained at 55–60% using the Richards–Trautmann formula. Chemical composition analysis was performed using ATR-FTIR spectroscopy, which identified key functional groups such as O–H, C=O, and S=O, indicating the presence of alcohols, aldehydes, sulfoxides, and other organic compounds essential for microbial growth. Phytotoxicity of the compost was evaluated using a germination index (GI) assay with Lepidium sativum seeds. Results showed that composts containing Kauchuken coal demonstrated reduced phytotoxicity and supported higher seed germination compared to control samples made with manure alone. Microbial activity and morphology were further examined using Scanning Electron Microscopy (SEM), revealing dense colonization and enhanced microbial adhesion in LGC-based composts. The findings suggest that incorporating low-grade coal into cattle manure composting enhances compost stability, reduces toxic effects on plant growth, and improves microbial development. This physico-biochemical composting method offers an eco-efficient solution for transforming two waste materials into a valuable biofertilizer, with potential application in dryland farming systems across Kazakhstan and similar arid regions.