Compost Practices

Claudia Wagner-Riddle, K.A. Kumudinie, K.H. Park, R. Fleming, and M. MacAlpine. 2006. Aerobic Composting as a Strategy for Mitigation of Greenhouse Gas Emissions from Swine Manure. Workshop on Agricultural Air Quality, page 1203

Agriculture has been recognized as a major contributor of greenhouse gases, releasing both nitrous oxide and methane. The collection and storage of livestock manure has been identified as a significant source of greenhouse gases. New strategies are being investigated as to their potential for reducing emissions of nitrous oxide and methane. Aerobic composting of the manure before storage is believed to have potential for mitigating the release of greenhouse gases, but research has not fully quantified emissions during the active and curing phases of this process. In addition, nitrous oxide emissions from soils after the field application of composted versus untreated liquid swine manure has not been considered in past studies. Here we report on two studies measuring: 1) methane and nitrous oxide emissions during the active in-vessel and curing phase of composting liquid swine manure with straw, and 2) nitrous oxide emissions after field application of untreated liquid swine manure in comparison to composted liquid swine manure, carried out in Ontario, Canada. A mega-chamber approach and eight large non-steady chambers were used to quantify CH₄ and N₂O fluxes during composting. A flux-gradient method was used to measure N₂O fluxes from field plots after application of composted and untreated manure in fall 2004 until corn planting in spring 2005. A tunable diode laser trace gas analyzer was used in both studies to measure gas concentrations.

Methane and N2O emissions during storage and field application of treated and untreated liquid swine manure point to aerobic composting as a GHG mitigation practice. Comparison on a volume of manure basis for treated or untreated manure showed that most GHG emissions occur in the form of CH4, with N2O being negligible during liquid storage and <20% of GHG emissions during composting. Further comparison of manure treatments should consider other gaseous emissions such as ammonia.