Structural Durability, Storage Stability and Microbiological Quality of Densified Paddy Straw Briquettes for Decentralized Biomass Utilization

Sustainable management of agricultural residues remains a major challenge, particularly in regions where surplus paddy straw is disposed of through open-field burning because of limited decentralized utilization pathways. This study evaluated the conversion of paddy straw into nutritionally formulated densified biomass briquettes using piston-press densification and assessed their storage stability under ambient subtropical conditions for 135 days. The briquettes were produced by incorporating paddy straw into balanced feed formulations for dairy calves and were periodically evaluated for structural durability, mechanical integrity, compositional stability, and microbiological quality. An integrated Storage Stability Index (SSI) was developed to quantify overall storage performance by combining physical, compositional, and microbiological indicators. The briquettes retained their structural integrity throughout storage with minimal disintegration, while their chemical composition remained largely stable, indicating limited nutrient degradation. Microbiological populations increased gradually but remained within acceptable limits up to approximately 120 days, with only coliform counts marginally exceeding the recommended threshold at the final evaluation. The SSI decreased from 1.00 to 0.88 over 120 days, indicating gradual but controlled deterioration under ambient storage conditions. These findings demonstrate that densified paddy straw briquettes provide a shelf-stable biomass-derived feed resource and represent a practical circular bioeconomy approach for decentralized agricultural residue management, improved biomass utilization, and enhanced fodder security.