Composting can contribute to the zero waste initiative on the University of Arkansas (UA) campus. In-vessel systems like Earth Tubs™ are purported to provide better control of temperature and moisture during the composting process. Turning materials helps facilitate microbial activity and thermophilic composting. The goal of this research was to determine if turning frequency affects processing or final quality of compost made with pre- and post-consumer food waste feedstock and a wood chip bulking agent. Turning frequencies (treatment) of 3 days/week and 7 days/ week were evaluated simultaneously throughout three sequential runs. Temperature, pH, electrical conductivity (EC), and moisture content (MC) were measured weekly during vessel filling. When the vessels reached one-half to two-thirds volumetric capacity, the compost entered a 30- day composting period during which no food waste or wood chips were added to the vessels, but turning continued. Total C, N, C:N ratio, and hot water extractable C (HWEC) and N (HWEN) were also measured at the conclusion of composting. Recommended values for temperature, pH, MC, and total C:N ratio are all possible to reach when composting with Earth Tubs™, but there is little to no effect of 3 days/week versus 7days/week treatment on final quality of compost, and quality is not consistent over time between runs. Further research would need to be done to assess whether Earth Tubs™ are a viable option for large-scale food waste composting at UA, and whether the logistics of having the vessels off-site lend themselves to a sustainable campus-wide composting program.
Boyle, Paige E.; Savin, Mary C.; and Wood, Lisa S.
"The effect of turning frequency on in-vessel compost processing and quality,"
Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences. University of Arkansas System Division of Agriculture. 16:14-23.
Available at: http://scholarworks.uark.edu/discoverymag/vol16/iss1/6