The Effect of Denim Fabric as a Feedstock in Large Scale Composting of Manure/Bedding and Food Scraps

Abstract

This study provides scientific evidence for the process of denim biodegradation and the viability of including denim waste in large scale composting facility feedstock streams. Fourteen samples of denim using different dyes and dye processes provided by Cotton Incorporated as well as worn and unworn whole and scrap denim fabric were incorporated into a manure/bedding and food scrap windrow at the Cornell composting facility and in a bench scale laboratory trial. Grab samples of compost were analyzed for compost parameters, metals and PFAS. Visual observation of decomposition of denim showed polyester blended denim degraded at a slower rate than non-blended denim. However, after four months of hot composting, most of the denim had decomposed into organic matter, leaving only small pieces of the polyester thread, labels, and pockets. Bench scale degradation, tracked by carbon dioxide evolution and mass difference showed significant degradation at the macro and microscopic levels at day 75. Composting denim fabric has no detrimental effect on the composting process, nor on the quality of the resulting compost and thus can be used to grow cotton and other crops, reducing the carbon footprint, and contributing to the circular economy.