Chemical pretreatments for odorant emission control of poultry byproducts and dynamic reactions during soil application

Presently, many meat byproducts are land-applied as fertilizer. Expansion of this practice has led to significant public outcry over odors associated with meat byproduct fertilizers. Unlike biosolids or manure application, which have been well studied, land application odor control for mostly undigested meat byproducts has received little attention. In the case of the poultry industry, the most land-applied meat byproduct is dissolved air flotation (DAF) solids. In this work, chemical pretreatments, including addition of agricultural lime, quick lime, acid, or oxidizers were considered for DAF solids odor control. The application method for quick lime was also considered – including pre-mixing versus surface application of quick lime after DAF solids. These experiments were conducted in controlled mesocosm environments with real soil, environmental perturbation to understand moisture effects, and were performed until odor extinction (~200 hours) to capture longer-term behavior. The results revealed that pre-mixed quick lime (pH of 12) entirely removed volatile fatty acid (VFAs) odors without worsening sulfur-organic emissions (a common issue with liming). Meanwhile, agricultural lime delayed odor emissions and other chemical treatments either produced more emissions or levels similar to the control. A follow-up mechanistic study determined that VFA volatilization in mesocosm systems was due to percolation of liquid from DAF solids and acidification in the soil. Complete mixing with the acidic soil amplifies odor emissions. This study provides important insights into overarching mechanisms that lead to malodors in meat byproduct land application.