Food waste is the single largest category of material sent to landfills in the United States, accounting for approximately 24 percent of municipal solid waste by weight. When food waste decomposes anaerobically in landfills, it generates methane, a greenhouse gas with 80 times the warming potential of CO2 over a 20-year period. The EPA estimates that landfilled food waste accounts for approximately 14 percent of total US methane emissions from human activities.
TerraFuture's community composting program was launched in 2022 with a straightforward goal: divert food waste from landfills, reduce methane emissions, and produce high-quality compost for community gardens and urban farms. After three years of operation, the program has reached a meaningful scale, and the data tells a compelling story.
2024 by the Numbers
In calendar year 2024, our network of 6 community composting sites processed 50.3 tons of food scraps and yard waste collected from 1,840 participating households and 34 food service businesses. That represents a 67 percent increase over our 2023 total of 30.1 tons.
The 50.3 tons of diverted organic waste translates to approximately 126 metric tons of avoided CO2 equivalent emissions, calculated using the EPA's WARM model for food waste diversion from landfill to composting. This accounts for both avoided methane generation and the carbon sequestration benefit of applying finished compost to soil.
Our six sites produced 18.2 tons of finished compost in 2024, distributed to 28 community gardens, 3 urban farms, and 14 school garden programs at no cost. The nutrient value of this compost, based on laboratory analysis showing average nitrogen content of 1.8 percent, phosphorus of 0.9 percent, and potassium of 1.2 percent, is equivalent to approximately 4,200 dollars in commercial fertilizer.
How the Program Works
Each composting site operates on a three-bin thermophilic system, with active compost, curing compost, and finished compost managed in a continuous rotation. Sites are located on donated land at churches, community centers, and public housing complexes, chosen for accessibility to participating households.
Participants receive a 5-gallon countertop collection bucket and compostable liners. Collection occurs weekly at neighborhood drop-off points staffed by trained volunteers. Each drop-off takes approximately 2 minutes per participant, and our data shows that convenience is the single strongest predictor of sustained participation. Households within a quarter mile of a drop-off point have a 12-month retention rate of 84 percent, compared to 52 percent for households more than a half mile away.
Composting is not complicated. The challenge is logistics, not biology. When you make it convenient for people to do the right thing, the data shows that most of them will.
Contamination and Quality
A persistent challenge in composting programs is contamination, the presence of non-compostable materials such as plastic bags, stickers, and packaging in food waste streams. Our contamination rate in 2024 averaged 3.2 percent by weight, well below the 8 to 15 percent range typical of municipal curbside organics programs.
We attribute this low contamination rate to three factors: in-person collection at staffed drop-off points, where volunteers can provide immediate feedback; clear visual guides provided with each collection bucket; and a deliberate decision to accept only food scraps and yard waste rather than the broader range of organics accepted by curbside programs.
The resulting compost consistently meets the US Composting Council's Seal of Testing Assurance standards for pathogen reduction, maturity, and heavy metal content. Independent lab tests show that our compost meets Class A standards for fecal coliform and Salmonella, with heavy metal concentrations well below EPA Part 503 limits.
Economics and Scaling
The program's total operating cost in 2024 was 142,000 dollars, or approximately 2,825 dollars per ton of waste diverted. While this exceeds the per-ton cost of landfill disposal, which averages approximately 85 dollars per ton in the Portland area, the comparison is incomplete. When methane emission costs are valued at the social cost of carbon of 51 dollars per metric ton of CO2 equivalent, and compost value and community health benefits are included, the net social benefit of the program is approximately 87 dollars per ton of waste processed.
TerraFuture plans to expand to 10 composting sites in 2025, with a target of processing 100 tons of organic waste annually. We are also exploring partnerships with Portland's Bureau of Planning and Sustainability to integrate community composting into the city's forthcoming food waste reduction strategy.
