Seasonal Effects on the Composting of Dairy Manure

Abstract

Abstract On-farm composting, an aerobic process used for the stabilization of manure and other organic materials, is usually carried out on outdoor surfaces in windrows. However maintaining optimal moisture contents, temperatures and oxygen concentrations year round under wet, dry, hot and cold conditions can be difficult. The objective of this study was to determine seasonal and weather effects on the composting of dairy manure-sawdust (3:1) (wet basis) in outdoor windrows. Two seasons (winter and summer), two turning frequencies and two turning methods were evaluated. One set of windrows (A) were turned using a self-propelled and tractor drawn windrow turner every three days for a total of 30 turns during 16 weeks. A second set (B) was turned once every 10 days. A third set (C) consisted of much larger piles turned every 10 days using a front bucket loader. Factors that were evaluated included volume, moisture content, volatile solids loss, mass loss, pH, oxygen and temperature gradients and bulk density. The functional relationships between variables (Pearson correlation) and season showed a direct effect for volume reduction (r2 > 0.95), surface area (r2 > 0.99), oxygen (r2 > 0.80) and bulk density (r2 >0.85) but pile size and turning frequency did not appear to have a significant effect (p > 0.05) on the physical and chemical characteristics of the cured composts. Results indicate that while wide variations in moisture content and temperature can occur during the composting process, final compost properties are very similar making it a feasible process in all seasons.