COMPOST AND COMPOST TEA PRODUCTION: COMPOSITIONAL CHANGES DUE TO LEACHING AND AGING

The UT Compost facility composted over 2.7 million pounds of food waste, animal waste, and landscaping debris between July 2021 and June 2022 (https://sustainability.utk.edu/initiatives/campus-composting/). Identifying approaches that optimize the transition of these wastes into valuable compost is critical for improving management practices (e.g., blending ratios) and refining application strategies based on the quality of the compost and compost leachate. This study looks at temporal changes in the physical and geochemical characteristics during the aging of compost derived from combining woodchips with food waste from across campus. Each pile (windrow) is mechanically mixed (approximately every 2 weeks) to maintain the efficacy of the composting process. Currently, the facility splits the compost into 5 separate windrows with each representing differing levels of maturity, with the 1^st row being relatively fresh ( ~1-2 months) to the 5^th row being “mature” and ready for application to campus gardens and landscaping (~6 months). Samples from each of the 5 windrows were collected monthly, then dried, ground to a fine powder, and homogenized. Compost extracts (tea) were prepared by mixing prepared compost aliquots with distilled water for 24 hours and then filtered to separate the tea and residual solids. The data from the compost teas, residual solids, and dried compost will be used to better understand the geochemical fractionation that occurs during phase transfers - compost solids to compost tea – that would happen once applied to landscaping. Comparing data from multiple windrows over time will help identify pathways that are active during compost aging processes that may ultimately impact the quality of the compost produced. Results from this work will help the UT Compost facility optimize blending ratios (wood chips, food waste, other additions) and windrow management for generating compost products that are best suited for a range of applications.