Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Crop, Soil and Environmental Sciences

Advisor

Savin, Mary C

Reader

Wood, Lisa S

Second Reader

Scott, J Thad

Abstract

Composting is one way to 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, and have screw augers for turning materials, which 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 over time throughout three vessel filling and composting processes. 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. Turning of the food waste continued. Additionally, total C, N, C:N ratio, and hot water extractable C (HWEC) and N (HWEN) were measured at the conclusion of composting. Recommended ranges and 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. The Earth Tub™ systems were not equipped to complete composting within a 3 week period, as composting took between 10-32 weeks in each of the three runs. For large-scale composting of food waste feedstock with wood chip bulking agents on the UA campus, more research would need to be done to assess whether Earth Tubs™ are a viable option, and whether the logistics of having the vessels off-site lend themselves to a sustainable campus-wide composting program.

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