26 February 2013
Posted in Center Information
Assessment of Yard Trash Disposal in Florida Class I Landfills: Impact on Energy, Climate Change, Recycling and Business
Yard trash is currently banned from disposal in lined landfills in the State of Florida. This research study was conducted to examine the potential impacts of removing this ban. Removal of the ban would allow combined collection of yard trash with household garbage, which would have the potential to increase efficiency of waste collection (lessening thetotal number of trucks and miles traveled), and provide the associated economic and environmental benefits of this heightened efficiciency. Additionally, a model was developed to simulate energy production and greenhouse gas generation from a landfill where co-disposal of yard trash is practiced. If yard trash were disposed in lined landfills equipped with a system to collect and utilize the methane produced by the decomposing waste, combined disposal of yard trash with garbage could result in additional methane production. Based on estimated methane potentials, 0.9 m3 (28 ft3) of extra methane can be produced from co-disposal of MSW and yard trash compared to the methane production of a MSW only landfill. For example, when comparing the methane generation using a 10 acre of hypothetical standard landfill, approximately 54 million cubic feet of additional methane would be generated from a MSW landfill practicing yard trash cp-disposal over the entire landfill life. The landfill capacity, however, was reduced to 5.7 years compared to the capacity of MSW only landfill (6.2 years). This additional methane was equivalent to 5,800 MWh.
While a reduction in the number of collection trucks potentially results in reduced greenhouse gas emissions, the net greenhouse gas production would also depend on the production of greenhouse gases at the landfill. The potential contribution of greenhouse gas emissions associated with the biological decomposition of the waste is considerably larger than those emissions associated with the collection and transport of the waste. The resulting balance is very sensitive to the methane capture efficiency at the landfill. If the methane capture efficiency is not close to 100%, the net greenhouse gas emission is greater for the scenario where yard trash is landfilled, because the added methane to the atmosphere offsets the greenhouse gas savings realized from the collection of combined wastes. However, the model results show that co-disposal of yard trash and MSW increased methane generation and it subsequently increased the energy potential: approximately 15-35% of more energy can be gained by co-disposal of MSW and yard trash when methane is efficiently captured and converted into energy.
Conversations with several county solid waste managers suggest that many municipalities would likely not recommend combined collection. Residentially-collected yard trash is typically managed in programs either operated by the municipality or contracted by the municipality specifically for managing this segregated waste stream. The fate of these systems would clearly be a factor in a municipality's decision whether or not to institute collection of combined wastes. For commercial yard trash processing facilities that manage commercially-collected yard trash, the impact of removing the ban would depend on their ability to compete with landfill tipping fees andon their location.