Forecasting Organics Tonnage for a Municipal Compost Facility

A municipal organics forecast starts with how much food and yard material your service area generates, multiplies it by the share your collection programs will actually capture each year as they ramp up, then adjusts for seasonal peaks and contamination. The result is a curve, not a single number, and the facility should be designed to the peak it must handle in a phase you can afford now, with room to add capacity when the curve says so. This guide walks through each step with a worked example built on clearly labeled assumptions.

Key takeaways

Build the forecast in layers: generation, participation, capture, contamination, then season and growth.
Use your own data first (scale records, route weights, a local waste characterization study) and national or state figures only to fill gaps.
Food scrap programs ramp up over several years. Yard trimmings arrive with sharp spring and fall peaks. The two together set very different receiving and pad needs.
Design receiving and grinding for the peak week, and active composting for the peak month, unless you can store material safely in between.
Turn the curve into phases with clear expansion triggers, so capital follows tonnage instead of running ahead of it.
In California, SB 1383 requires jurisdictions to estimate organic waste disposal and the capacity they will need, so the forecast doubles as planning evidence.

Why the forecast decides the project

Tonnage sets pad area, aeration zones, equipment, staffing, permit limits and the per ton cost. Overestimate it and the capital is spread across too few tons. Underestimate it and the site runs over permitted capacity, piles grow past their design size and neighbors notice. The cost comparison guide shows how much utilization moves cost per ton, and the facility design guide turns the tonnage into cubic yards and acres.

In California, the forecast is also a regulatory product. CalRecycle’s capacity planning page says jurisdictions must estimate organic waste disposal, identify existing capacity in and outside the county that is verifiably available, and estimate the capacity that will be needed, while counties collect this information and report it to CalRecycle. Jurisdictions without enough capacity must submit an implementation schedule. The SB 1383 guide for cities and counties covers the wider duties.

Step 1: Estimate what the service area generates

Local data first

Scale records at your landfill, transfer station or existing compost pad, by material and month, for at least three years.
Route weights for current green waste and any food scrap pilots.
A waste characterization study of your own disposed waste. California jurisdictions can use the statewide waste characterization data and tools CalRecycle publishes for local planners, which include residential composition and business group rates. CalRecycle notes that those tools reflect a 2014 study and give estimates, not exact figures.
Large generators: grocery stores, schools, hospitals, food processors, institutions and event venues. Call them, because a few accounts can be a large share of commercial food tonnage.

National figures for context

EPA’s food material data estimates that about 63.1 million tons of food waste were generated in the United States in 2018, of which about 35.3 million tons were landfilled and about 2.6 million tons composted; EPA notes that 2018 was the first year of a new, broader methodology. EPA’s yard trimmings data puts 2018 yard trimmings generation at about 35.4 million tons, with about 22.3 million tons composted or mulched. These numbers show where the untapped tonnage sits nationally (food), but they are not a substitute for local data.

Step 2: Apply participation and capture

Generation is what exists. Capture is what arrives at the gate.

Participation (p): the share of households or businesses that set out organics. It rises as carts, education and enforcement roll out.
Capture among participants (c): the share of their organics that participants actually put in the organics cart instead of the trash.
Collected tons = generation x p x c, by sector and year.

Set p and c from your own pilot routes where you can, and state where every assumption came from. Model residential and commercial streams separately: commercial accounts often join faster where a state mandate covers them, while residential participation climbs with each cart roll-out phase.

Step 3: Adjust for contamination and residuals

Not every collected ton becomes compost. Plastic, glass, metal and packaging come in with curbside organics.

Contamination rate (k): share of incoming tons removed as residuals. Get it from load audits, a pilot, or a comparable program.
Processable tons = collected tons x (1 minus k).
Residual tons = collected tons x k. These go back to disposal and need their own haul and container plan.

Design receiving and pre-processing for collected tons (everything that crosses the scale) and the composting pad for processable tons plus amendment. For the processing side of contamination, see SG’s article on composting depackaged food waste and our list on handling depackaged food waste.

Step 4: Add bulking material

Food scraps are wet and dense. They need carbon and structure, usually from ground yard trimmings or wood chips, to compost well. If your own yard trimmings supply the bulking material, they are already in the forecast. If you must buy or import amendment, add those tons to the pad and receiving totals. The facility design guide shows how the recipe changes volume.

Step 5: Model seasons, ramp-up and growth

Seasons

Yard trimmings typically peak in spring and fall and drop in winter, while food scraps arrive more evenly each week. Build a monthly profile from your scale data and express it as a peaking factor: the peak month divided by the average month.

Ramp-up

A new food scrap program does not reach full capture in its first year. Model participation by year as carts roll out, with a slower case and a faster case.

Growth

Add population growth, new development and any expected change in commercial requirements. Keep growth separate from ramp-up so the board can see which assumption drives the result.

A worked example with assumed inputs

Every figure below is an assumption chosen to show the method. None is a typical or recommended value.

Residential food scraps generated: 35,000 tons per year (assumed)
Residential participation: 25% in year 1, 55% in year 3, 65% in year 5 (assumed)
Capture among participants: 50% (assumed)
Yard trimmings already collected: 25,000 tons per year, growing about 1% a year (assumed)
Commercial food scraps: 1,000 tons in year 1, 3,000 in year 3, 6,000 in year 5 (assumed)
Contamination: 8% of incoming tons (assumed)
Yard trimmings peaking factor: 1.6 (assumed)

Year	Residential food	Yard trimmings	Commercial food	Collected total	Processable (after 8%)
1	4,375	25,000	1,000	30,375	about 27,900
3	9,625	25,500	3,000	38,125	about 35,100
5	11,375	26,000	6,000	43,375	about 39,900

Residential food in year 5 is 35,000 x 0.65 x 0.50 = 11,375 tons.

From annual tons to design tons

For year 5:

Average month, yard trimmings: 26,000 / 12 = about 2,170 tons. Peak month: 2,170 x 1.6 = about 3,470 tons.
Average month, food scraps: (11,375 + 6,000) / 12 = about 1,450 tons, assumed steady.
Peak month collected: 3,470 + 1,450 = about 4,920 tons, against an average month of about 3,610 tons. Receiving and pre-processing size to this figure.
Peak month processable, after 8% contamination: 4,920 x 0.92 = about 4,530 tons.
Annualized peak rate for the pad: 4,530 x 12 = about 54,300 tons per year, before any purchased amendment.

So a site that receives about 43,000 tons (about 39,900 processable) in year 5 needs active composting capacity closer to a 54,000 ton annual rate in its peak month, unless ground yard trimmings can be stored and fed in over the following weeks. Storage is often the cheaper answer, but it needs pad space, fire protection and a permit that allows it.

Step 6: Turn the curve into phases

A phase plan lets the board approve capacity when the tonnage is real.

Phase	Sized to	Trigger to start the next phase	Typical decisions
Pilot	A few routes or one sector	Recipe, temperatures and contamination proven	Lease or buy pilot equipment, test feedstock mixes
Phase 1	Year 3 peak month, processable tons	Monthly receipts reach an agreed share of Phase 1 capacity for a set number of months	Pad, aeration zones and permit sized for Phase 2 if possible
Phase 2	Year 5 to 10 peak month	Same trigger, measured against Phase 2 capacity	Add zones or systems on the prepared pad
Build-out	Final forecast year	Growth or new mandates	Permit modification, curing and storage expansion

Write the trigger as a measured number, not a date. Three practical rules help:

Permit for the build-out tonnage if the regulator allows it, so expansion is a construction project, not a new permit.
Grade and drain the pad for the next phase during the first one, where the budget permits.
Pick a technology that adds capacity in modules.

Prince George’s County shows a modular path in Sustainable Generation’s (SG) material. According to SG’s profile, the county piloted an SG MOBILE® System with GORE® Covers in 2013 to test food and green waste, added SG MOBILE units in the following years to reach 12,000 tons per year, and installed 12 SG BUNKER® Systems for a facility SG lists at 57,000 tons per year. SG rates the SG HEAP® System at 1,000 to 100,000+ tons per year and the SG BUNKER System at 5,000 to 500,000 tons per year, and it describes SG MOBILE as installed in days to weeks, depending on the site. SG’s leasing program names meeting near-term diversion mandates and bridging gaps between grant phases as municipal uses, which can fit the pilot and early ramp-up years.

Forecast checklist

[ ] Three or more years of scale data by material and month
[ ] Local or state waste characterization data, with its year
[ ] Large generator list with contacts and estimated tons
[ ] Participation and capture assumptions by sector and year, with sources
[ ] Contamination rate from load audits or a pilot
[ ] Amendment tons if bulking material is imported
[ ] Monthly peaking factors for yard and food streams
[ ] Low, expected and high cases
[ ] Phase plan with measured expansion triggers
[ ] In California, consistency with the jurisdiction’s SB 1383 capacity planning estimates

FAQ

How far ahead should a municipal organics forecast go?

Far enough to cover the facility’s design life and the permit term, typically with annual detail for the first five years and coarser steps after that. In California, align it with your jurisdiction’s SB 1383 capacity planning so the two do not contradict each other. Revisit the forecast every year once collection starts, using actual scale data.

Should we design for average tonnage or peak tonnage?

Both, for different parts of the site. Receiving, tipping floor and grinding must handle the peak week. Active composting should handle the peak month unless you can safely store ground yard trimmings and feed them in later. Curing and product storage follow annual averages more closely, adjusted for when compost sells.

What participation rate should we assume for a new food scrap program?

Use your own pilot routes if you have them, then programs similar to yours in housing type, cart design and enforcement. State each assumption and its source, and show a slow and a fast case. Avoid a single national figure, because participation varies widely with program design and local requirements.

How does contamination change the facility size?

Contaminated tons still cross the scale, so receiving and pre-processing must handle them. They leave as residuals, so the compost pad sizes to what remains. High contamination also adds labor, disposal and haul cost. A pilot or load audit gives the rate to use.

Next step

Build the curve with your own data, then test the recipe and contamination rate on a small scale before sizing Phase 1. SG’s pilots and demos page describes running batches of your own feedstock to produce data for permits, grants or board approval, and the consulting page describes its pre-design support for capacity targets and layout.

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