Evaluation of Bioactivators for Composting Yard Waste

Abstract

The evaluation of the efficiency of yard waste composting (grass clippings/wood chip mixture) was studied for seven commercially available bioactivators, two naturally occurring bioactivators, and one control (absence of bioactivator). The overall decomposition response for each bioactivator was evaluated by comparing four indexes of composting efficiency. These were weight loss, change in volume, loss of volatile solids, and oxygen uptake rate. Four experimental blocks were set up in the field, and two experimental blocks were set up in the laboratory. The physical/chemical characteristics were monitored for all samples as a function of time, and individual bioactivators were evaluated so that interrelationships between indices could be studied. One of the seven commercially available bioactivators evaluated in this study ranked better than the Control, but did not rank as well as the Finished Compost or the Surf ace Soil bioactivator. Since Surface Soil and Finished Compost are both available at no additional expense, substitution of more expensive bioactivators is not recommended. Surface Soil and Finished Compost bioactivators were felt to be unnecessary if the composting process was not restricted to a four to six week turnover time. The data suggest that the efficiency of the composting process is directly related to what type of microorganism is present, and the amount/form of both available carbon and nitrogen. Finished Compost and Surface Soil both had significant levels of naturally occurring microorganisms and a available source of nitrogen.