Composting residuals from a strawboard manufacturing facility

The purpose of this research was to investigate the compostability of waste residuals from a strawboard manufacturing facility. Phase 1 used bench-scale reactors to compost various recipes using three feedstock materials (straw, process unders, and livestock lagoon sludge) at different moisture levels for a nine-week period. Water addition and the addition of unders to the compost mixture increased degradability. The livestock lagoon waste did not significantly improve degradability. Phase 2 focused on the straw feedstock, investigating the effects of straw particle size using four unshredded: shredded straw ratios (by volume): 100:0; 67:33; 33:67; and 0:100. The recipes were composted in 140 L rigid plastic containers for a period of 180 days at a moisture content of 70% (wet basis). Volatile solids (VS) and lignocellulose degradation was greatest for recipes containing both shredded and unshredded straw, with the recipe containing 67% shredded straw performing the best (35% VS removal). Pure unshredded and shredded straw had VS reductions of 29% and 26%, respectively. Total volume reductions ranged from 80 to 90%. Hemicellulose was completely degraded for all recipes by day 95. By day 180 cellulose content had decreased from 3.75 to 0.75 g/g ash for all four recipes. By day 180, lignin degradation was greatest for recipes containing both shredded and unshredded straw (reduction from 1.0 to 0.4 g / g ash) while lignin content decreased from 1.0 to 0.6 g / g ash for the other recipes. It was concluded that recipes containing a mixture of shredded and unshredded straw provided better composting conditions.