Decomposition of land applied oily food waste and associated changes in soil aggregate stability

Since traditional methods of disposing of oily food wastes have recently lost favor, there is a current search for alternatives. Field- and laboratory-scale experiments examined the decomposition of oily food wastes applied to agricultural lands to examine this disposal option and potential agronomic benefits. Treatment rates of oily food waste equivalent to 3 to 11.3 g of C kg(-1) increased soil microbial biomass C in the field by up to five times control levels. Wet aggregate stability also increased with waste addition and was maintained over the course of the growing season. Laboratory incubation studies examining the biodegradation of canola oil and oily food waste showed that the oily fraction of the waste was not rate limiting, and that both substrates degraded rapidly with initial decomposition half-lives of 40 to 45 h and 70 to 94 h for canola oil and waste treatments, respectively. The extents of mineralization over 4 wk were up to 83 and 40% for canola oil and oily food waste, respectively, Similar to the field, increases in aggregate stability were measured in the canola oil incubation. Examination of the biodegradation data indicates two substrate pools are being sequentially decomposed, and that the added substrate is not directly responsible for improved structural properties. The longer lasting binding abilities of microbial products and bodies are the major contributing factors for the increased soil aggregation, It is concluded that the land application of oily food waste is agronomic ally beneficial by increasing soil microbial activity, and in turn improving soil structure through increased aggregate stability.