Measurements of Greenhouse Gas Flux from Composting Green-Waste Using Micrometeorological Mass Balance and Flow-Through Chambers

Abstract

Greenhouse gases (GHGs) are produced during the composting process, but few studies have measured emissions from a full-scale windrow of composting green-waste. This is important for evaluating composting as a waste management option and for understanding how changes to current composting management practices could help reduce emissions. This study uses micrometeorological mass balance (MMB) and open flow-through chamber techniques to measure emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) from a windrow of composting green-waste in Northern California. The MMB technique yielded mean upwind–downwind concentration differences over the study period that showed sourcing of all three GHGs. CO₂ showed a stronger signal than CH₄ and N₂O. A strong diel pattern was found in the concentration differences at lower levels and fluxes of CO₂, with substantial noise likely obscuring any possible daily patterns for CH₄ and N₂O. Fluxes normalized by the time since the previous turn event revealed an initial rapid rise in CO₂ concentration differences (at lower levels) and fluxes, peaking close to 13 h after the turn event followed by a gradual decline. The same pattern was not as clear for the other two gases but overall declines in concentration differences and fluxes were apparent with increasing time since the previous turn event. Substantial differences between MMB and chamber calculated fluxes were found, due to both differences in the techniques as well as sampling frequency.

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgments

The authors thank everyone that assisted with this research and/or the production of this article including Xue Meng Chen, Tad Doane, Michael Mata, Thomas Shapland, and Richard Snyder. Also this work would not have been possible without the assistance of Grant Ingalls and the rest of the crew at Northern Recycling in coordinating access to the field site and turning of the compost pile.

Additional information

Funding

This research was funded under California Department of Resources Recycling and Recovery Agreement #IWM09027. Additional funding supplied by the J. G. Boswell Endowed Chair in Soil Science. Portions of KTPU’s participation in this project were funded by National Science Foundation prime award EF#1137306 to the Massachusetts Institute of Technology, secondarily awarded to UC Davis as sub-award no. 5710003122.