Quantification of Greenhouse Gas Emissions from Windrow Composting of Garden Waste

Microbial degradation of organic wastes entails the production of various gases such as carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and carbon monoxide (CO). Some of these gases are classified as greenhouse gases (GHGs), thus contributing to climate change. A study was performed to evaluate three methods for quantifying GHG emissions from central composting of garden waste. Two small‐scale methods were used at a windrow composting facility: a static flux chamber method and a funnel method. Mass balance calculations based on measurements of the C content in the in‐ and out‐going material showed that 91 to 94% of the C could not be accounted for using the small‐scale methods, thereby indicating that these methods significantly underestimate GHG emissions. A dynamic plume method (total emission method) employing Fourier Transform Infra Red (FTIR) absorption spectroscopy was found to give a more accurate estimate of the GHG emissions, with CO 2 emissions measured to be 127 ± 15% of the degraded C. Additionally, with this method, 2.7 ± 0.6% and 0.34 ± 0.16% of the degraded C was determined to be emitted as CH 4 and CO. In this study, the dynamic plume method was a more effective tool for accounting for C losses and, therefore, we believe that the method is suitable for measuring GHG emissions from composting facilities. The total emissions were found to be 2.4 ± 0.5 kg CH 4 –C Mg −1 wet waste (ww) and 0.06 ± 0.03 kg N 2 O‐N Mg −1 ww from a facility treating 15,540 Mg of garden waste yr −1 , or 111 ± 30 kg CO 2 –equivalents Mg −1 ww.