Most organic waste from households ends up in landfills, where it emits methane, a potent greenhouse gas. Composting food and garden waste instead of dumping it in landfills can considerably cut methane emissions and help combat global warming. A new study from the University of Illinois at Urbana-Champaign investigates the impact of curbside compost collection programs in New South Wales, Australia.
Collection bins for organic waste, recycling, and general waste in New South Wales, Australia. Image Credit: University of Illinois Urbana-Champaign
Governments around the world are interested in composting organic waste and reducing their methane emissions, and they are looking for ways to make waste collection more convenient for households. As municipal composting services were being rolled out in Australia, we wanted to measure how these policies affected household waste disposal behavior.
Becca Taylor, Assistant Professor, Department of Agricultural and Consumer Economics, College of Agricultural, Consumer and Environmental Sciences
Australia’s most populous state, New South Wales, implemented curbside programs between 2009 and 2015 to collect food and garden waste for recycling into compost. Each household was given three bins: one green for organic garbage, one yellow for recycling, and one red for general waste.
Public awareness campaigns explained to citizens what types of waste were permitted in the bins, and some councils supplied small kitchen caddies to facilitate the sorting process.
Taylor and co-author Lihini de Silva of Monash Business School in Australia evaluated household waste data from the New South Wales government’s annual waste and resource recovery reports between 2008 and 2015.
Taylor added, “We had access to data for all three curbside waste streams: landfill, recycling, and the newly added compost, so we could see spillover and linkages between them. We found the programs were very successful in getting organic waste out of the landfill. On average households redirected 4.2 kilograms of waste to composting, which represents 25% of the waste that previously went to landfills.”
In certain areas, people could deposit food scraps and garden waste in the green bins, but only garden waste was permitted in others. When the researchers analyzed the two categories, they found no significant variations in quantity, indicating that most of the compost came from garden waste.
“People were willing to compost garden waste if they were given the bins to do so. However, there is still room for improvement in getting food waste from landfill to compost, and additional interventions might be needed in addition to providing the bins,” Taylor stated.
Taylor and de Silva predicted that shifting one ton of organic waste from landfill to compost would result in a 6% to 26% reduction in methane emissions. They stated that these results might differ for other places because the estimates are based on the specific compost and landfill methods employed.
Taylor further stated, “We also wanted to see if composting affected other recycling or waste amounts. It could go either way – people could be reminded to recycle other waste as well, or the additional time and effort could result in less general recycling. Another concern was whether giving people an extra bin would increase the total amount of waste. However, we did not find significant effects on recycling rates, so it is not crowding out other recycling, but also not encouraging it. We also found no effects on the total amount of waste.”
Methane traps heat in the atmosphere approximately 30 times more efficiently than carbon dioxide. It stays in the atmosphere for significantly shorter periods, so lowering methane emissions has a more immediate influence on reducing global warming.
Landfills are the third largest source of human-caused methane emissions, behind fossil fuels and livestock. Composting organic waste instead of sending it to landfills is a significant and low-cost option to minimize methane emissions, the researchers stated.
“These compost collection programs facilitate methane emission reductions without reducing the amount of waste. This underscores that recycling is important, but generating less waste in the first place would result in even greater emission reductions. Both measures are important elements of sustainable practices,” Taylor concluded.
Journal Reference:
De Silva, L. and Taylor, R. L. C., et. al. (2024) If You Build It, Will They Compost? The Effects of Municipal Composting Services on Household Waste Disposal and Landfill Emissions. Environmental and Resource Economics. doi:10.1007/s10640-023-00834-x