A Study on the Technical and Economic Feasibility for Arable Agriculture and Biofuel Production on Landfill Covers in Southern Ontario

There are over 3,700 active and decommissioned municipal solid waste (MSW) landfill sites located in Ontario (MOE, 1991). Under current legislation, these landfill sites must be rehabilitated to a defined end use when decommissioned. In Ontario, the primary prescribed end use of closed landfills is typically agriculture, and that end use can lead to food-consumer concerns, due to the perceived risk of potential contamination from legacy materials found in landfills. Converting these sites to produce biomass-energy crops instead of food crops could mitigate that concern and also help to avoid the current controversy with bioenergy-crop production on high-capability agricultural land. In this study, a 3.5-year field program with subsequent verification and analysis investigated and developed rehabilitation prescriptions using locally obtained topsoil and soil-forming materials (subsoil) to develop anthropogenic soil profiles on top of a sealed landfill cover (clay cap). These prescriptions provided crop productivity at least as good as, and generally better than, local agricultural soils. Mixed forages and biomass-specific crops (warm season grasses) were grown on these soils in replicated plot trials to evaluate the efficacy of a range of soil treatments. Following establishment of technical feasibility for site rehabilitation, economic modeling was conducted to determine the feasibility of using these anthropogenic soils for the production of forage crops, biofuel feedstock, and simple energy products at a scale consistent with typical landfill sites in Ontario. An economic model was developed to aid proponents in selecting appropriate rehabilitation methods and to assess potential bioenergy-crop outputs for their site. This study demonstrated that while it is technically feasible to rehabilitate these waste sites to produce agricultural crops and/or biofuel feedstock, the scale of typical landfill sites makes it very difficult to compete, from an economic perspective, with conventional energy sources. However, the diverted incoming materials, such as leaf and yard waste, compostable biosolids, and paper mill waste, can be used in the development of manufactured soil profiles for rehabilitation, significantly reducing rehabilitation costs and facilitating more cost-competitive production of agricultural and biomass feedstock crops.