Calculate annual emissions avoided by composting food scraps and yard trimmings instead of landfilling them. This free tool supports households and organics programs, accepts kg, lb, metric tonnes, and US short tons, and defaults to US EPA WARM version 16 methodology.
Calculation version2.0.0 · July 18, 2026
Default methodEPA WARM v16 · December 2023
Best forHousehold and program screening
PrivacyNo server upload or input tracking
Quick calculator
Choose a starting point
Used only when you load the EPA-derived household estimate.
Presets are starting points. They show their route and quantity assumptions here; replace estimates with weighed amounts whenever possible.
Correct the following before calculating:
Advanced assumptions and transport
EPA WARM v16 is appropriate for US household screening and program planning using a centralized windrow lifecycle. Facilities and formal planners should confirm local pathways in the full EPA model. Use the custom mode only when documented landfill and compost factors are available.
Composting route
WARM central routes already include collection/turning factors. Backyard and drop-off are transparent adaptations.
Distance for one trip to the drop-off site.
Converted to miles for vehicle factors.
Uses the weekly, monthly, or yearly period selected above.
Use less than 100% when the trip has other purposes.
EPA equivalency factors: 0.393 kg CO₂e/mile gasoline; 0.104 kg CO₂e/mile electric.
Enter a documented round-trip operating factor per vehicle-mile.
EPA WARM v16 published factors
Factors are metric tons CO₂e per wet US short ton. Positive values are emissions; negative values are storage or offsets. These remain fixed while WARM mode is selected.
EPA’s organic-material summary Exhibit 2-4 displays −0.05 for yard composting while its detailed Exhibit 2-5 and composting chapter display −0.11. This calculator uses the detailed −0.11 factor and flags the discrepancy for formal users.
Yard: (−0.20 landfill − [−0.11 compost]) × 0.13 = −0.0117 metric ton CO₂e, meaning 11.7 kg more under this comparison.
Net: 169 − 11.7 = 157.3 kg CO₂e avoided per year, or about 13.1 kg per month.
The food contribution dominates because WARM models readily degradable food methane and relatively little landfill carbon storage, while aggregated yard trimmings receive a substantial landfill carbon-storage credit. Published factors are rounded, so detailed component sums may differ slightly.
What the two methods calculate
EPA WARM v16: recommended screening mode
WARM is a streamlined lifecycle comparison beginning at the point of waste generation. This page compares the national landfill pathway with centralized aerated-windrow composting for food waste and aggregated yard trimmings. It includes landfill methane, gas recovery and energy effects embedded in the published factor, landfill carbon storage, compost collection and turning, fugitive methane and nitrous oxide, a food-compost fertilizer offset, and modeled soil carbon storage.
WARM’s food compost factor includes 0.03 MTCO₂e/short ton for transport and turning, 0.08 for fugitive emissions, −0.03 for fertilizer offset, and −0.24 for soil carbon. Yard compost includes 0.02, 0.12, zero, and −0.24 respectively. Finished-compost delivery is excluded. The factors do not include avoided production of food, and WARM’s embedded greenhouse-gas characterization differs from the editable custom pathway.
Custom IPCC inventory-style mode
This editable pathway estimates ultimate landfill methane from wet waste mass, DOC, DOCf, MCF, methane content, recovery, and oxidation. It subtracts compost methane, nitrous oxide, operations, and trip emissions, then adds an optional soil benefit. It is useful for facilities or planners with documented local parameters, but it is not a complete WARM lifecycle and should not be labeled a WARM result.
Buried organic material decomposes without oxygen. Food breaks down readily and can generate methane quickly; grass, leaves, and woody trimmings differ in degradability and decay rate. Gas collection, flaring or energy use, cover oxidation, moisture, and the timing of collection all affect emissions.
Why biogenic compost CO₂ is excluded
Carbon dioxide released as recently grown food and plant matter decomposes is normally treated as biogenic and excluded from these waste-management totals. Fossil CO₂ from vehicles and equipment, and non-CO₂ gases such as methane and nitrous oxide, remain included.
Why food and yard results differ
WARM models food waste as producing substantial landfill methane with relatively little stored carbon. Aggregated yard trimmings decompose more slowly, and undecomposed material receives a landfill carbon-storage credit. That can make the yard-only landfill-to-compost result small or negative even though compost has other soil, waste-diversion, and local benefits.
What is not included
The calculator does not value odor, nutrients beyond WARM’s food fertilizer offset, water retention, contamination, local air pollutants, compost-market displacement, home-pile construction, avoided food production, or finished-compost delivery. It assumes the entered material would otherwise be landfilled; incineration, animal feed, donation, sewer disposal, and anaerobic digestion require different baselines.
Use limitation: Results depend on the counterfactual destination and are screening estimates, not certified offsets. Formal inventories must use the required boundary, factor set, activity data, uncertainty rules, and independent review.
Factor register and source trust
Default factors are linked to the exact agency document location used. Retrieval date: July 18, 2026.
63.1M short tons food; 35.4M yard; population 327.2M
Editorial review: Starlight Tools transcribed the cited factors, documented the EPA yard-factor discrepancy, and checked the calculator against the test cases below. No external professional reviewer or certification is claimed.
1.0.0 · June 30, 2026: Initial editable IPCC-style landfill and compost calculator.
Composting carbon FAQs
How much CO₂ does composting save per year?
It depends on the amount and type of waste, the alternative disposal method, and transport. Under the EPA WARM v16 factors used here, one US short ton of food waste moved from landfill to centralized composting avoids about 0.65 metric tons CO₂e before any extra user trip. Yard trimmings can have a much smaller or negative landfill-to-compost difference under WARM.
Why does food waste save more than yard waste?
Food decomposes readily under anaerobic landfill conditions and can generate substantial methane. Aggregated yard trimmings decompose more slowly, and WARM credits carbon that remains stored in landfill, so their modeled landfill-to-compost benefit is much lower.
What does CO₂e mean?
Carbon dioxide equivalent, or CO₂e, combines gases such as methane and nitrous oxide into one amount based on their warming effect relative to carbon dioxide over a stated time horizon.
Does composting release greenhouse gases?
Yes. Composting can release methane and nitrous oxide from anaerobic pockets and nitrogen cycling, and centralized systems use fuel for collection and turning. Biogenic carbon dioxide from decomposition is normally excluded from this accounting.
Does landfill methane capture change the result?
Yes. Better landfill gas collection, oxidation, flaring, or energy recovery lowers net landfill emissions and therefore reduces the benefit attributed to diversion. Use the custom IPCC-style mode when verified local controls must be modeled directly.
Does driving to a compost site cancel the benefit?
It can. A dedicated trip may erase a small benefit, especially for yard trimmings. The calculator deducts the entered trip emissions and reports a break-even one-way distance when the pre-trip climate benefit is positive.
What if my waste would be incinerated or anaerobically digested?
Do not use the landfill comparison as-is. Incineration and anaerobic digestion have different emissions, energy offsets, and residue treatments. Use a model with the correct counterfactual, such as the full EPA WARM tool.
Can this result be used in a GHG inventory?
Treat it as a screening estimate, not a certified offset or inventory result. Formal reporting should follow the required organizational boundary, activity-data rules, approved factors, uncertainty treatment, and verification process.
FAQPage structured data mirrors the eight visible questions and answers above. Markup provides semantic context and does not promise a search-result feature.
