Composting System Buyer’s Guide for Private Composters and Haulers

For a private composter or a hauler, a composting system is a production asset: it earns on material coming in and on product going out, and it is limited by what the site and the permit allow. Buy the system that gives the most reliable throughput inside your permit on the land you control, and that you can expand in steps as contracts are signed. That is often an aerated, covered system where food waste and neighbors are involved, and often a plain windrow pad where they are not.

Key takeaways

  • Two revenue lines carry the business: gate fees for accepting material and sales of finished product. A system should protect both, not trade one for the other.
  • Feedstock contracts set the size of the first phase. Build for tonnage you hold in writing, and lay out the site for the tonnage you expect.
  • Contamination is a cost you accept at the gate and pay for at the screen. Put rejection rights in every contract.
  • Throughput per acre is driven by residence time and pile height. Shortening the active phase raises capacity without more land.
  • A permit that allows food waste, with room to grow, is hard to obtain and worth protecting. Odor complaints and air rule violations put it at risk.
  • Covered ASP is the wrong purchase for clean green waste on cheap rural land with no air rule to meet.

The commercial model in plain terms

Work the model without prices first. A private facility has two ways to earn and one long list of things it pays for.

Earned on the way in. The gate fee depends on what else generators and haulers can do with the material: the local landfill, a transfer station, a competing composter or a digester. Price each material against its own local alternatives, since the sites permitted to take food waste or biosolids are not the same ones that take yard trimmings.

Earned on the way out. Compost, mulch and blended soils sell on quality and consistency. A product with visible plastic or an unfinished smell sells at a discount or not at all.

Paid for in between. Land and pad, grinding, bulking material, labor, fuel, power, water, screening, residual disposal, testing and compliance. SG’s three-part series on infrastructure decisions, starting with Part 1, and the lifecycle cost guide walk through these drivers over the life of a site.

A hauler has a third consideration: an owned facility replaces a gate fee paid to someone else and secures an outlet for collection contracts. Mid Valley Disposal in Kerman, California is the example in SG’s material. SG’s profile says the company had no composting experience, ran a demonstration project to test feedstock mix ratios, emission control and the viability of entering the organics recycling market, and then built a full-scale SG BUNKER® System (profile).

Decision 1: Lock in feedstock before you size anything

Lenders and partners ask the same question: who is obliged to bring you material, and for how long. Diversion laws create the supply, but they do not send it to your gate.

In California, SB 1383 requires every jurisdiction to provide organic waste collection to all residents and businesses (CalRecycle). In New York State outside New York City, businesses and institutions that generate an annual average of two tons of wasted food per week or more must donate excess edible food, and must recycle the remaining food scraps if they are within 25 miles of an organics recycler; the state’s page says the threshold drops to one ton per week and the distance widens to 50 miles on January 1, 2027, and the threshold drops to half a ton per week on January 1, 2029 (New York State DEC). Distance-based rules like this mean that opening a facility can itself bring nearby generators under the law. The state laws guide covers other states.

What to settle in each feedstock agreement:

  • Minimum and maximum tonnage, and the delivery schedule by season
  • Material definition: food scraps, yard trimmings, depackaged slurry, biosolids, manure
  • Contamination limit, how loads are inspected, and what happens to a rejected load
  • Term and renewal, matched to the life of your financing
  • Who supplies bulking material if the stream is wet

Read the feedstock list for how each material behaves in a pile.

Decision 2: Decide how you will handle contamination

Plastic, glass and packaging cost money three times: in handling, in screening and in lost product value. California’s organics rules put some of the work upstream: jurisdictions must regularly track contamination and give feedback to residents and businesses (CalRecycle collection requirements). Your contracts and your receiving area do the rest.

  • Inspect and photograph loads at tipping, and charge back or reject by contract.
  • Place sorting or depackaging ahead of mixing, not after composting.
  • Size screening for the overs and residuals you will really get.
  • Budget for residual disposal as an operating line.

Mid Valley Disposal’s pilot, in SG’s account, reinforced how much upstream collection and source separation matter to composting results. SG’s article on composting depackaged food waste and the list of ways to handle depackaged food waste cover the equipment choices.

Decision 3: Work out throughput per acre

Land is fixed once you have a permit boundary, so capacity comes from how quickly material moves across the pad. A simple way to compare methods:

  1. Take annual tons and convert to volume using a measured bulk density for your mix.
  2. Multiply by the fraction of a year that material spends in the active phase.
  3. Divide by the volume one pile or bunker holds.
  4. Add curing, receiving, screening and storage areas.

Residence time is the variable a technology changes most. SG’s How It Works page describes a 4 to 8 week treatment time versus 8 to 12 months for open windrow, and SG says the SG MOBILE® System needs 60 to 80% less space than in-vessel or windrow. Treat those as the vendor’s figures and check them against a reference site with a feedstock like yours. Happy Trash Can in Bozeman, Montana is a small-scale case: SG’s profile says the company moved from bucket-turned static piles to an SG MOBILE System in 2018 to get more throughput on a similarly sized site, with its nearest neighbor less than 300 feet away (profile). The facility design guide shows the full sizing method.

Decision 4: Treat the permit as an asset

A private site usually needs approvals from three directions: solid waste, air and water. Each one caps something, whether tonnage, feedstock type, emissions or discharge. A permit that already allows food waste or biosolids at meaningful tonnage is difficult for a competitor to copy, and it is what a buyer of your business will pay attention to.

Air rules shape technology choice in parts of California. South Coast AQMD Rule 1133.3, as amended September 5, 2025, requires operations that process more than 5,000 tons of food waste a year to run the active phase of any pile with more than 10 percent food waste on an aeration system vented to an emission control system, and requires such systems to reach a control efficiency of at least 80 percent for VOC and for ammonia, or to stay under emission rate limits per ton that the rule sets (SCAQMD Rule 1133.3). In the San Joaquin Valley, Rule 4566 governs organic material composting with requirements that step up by throughput, at 100,000, 200,000 and 750,000 wet tons per year (SJVAPCD Rule 4566). The 80 percent level is a top tier, not what every site must meet, so read the rule for your district and your tonnage.

Ask vendors for emission test reports with the test conditions, and ask whether the system has been tested against your district’s rule. SG reports greater than 95% VOC control in third-party testing, and its article on air quality rules and facility design gives its view of the trend. Mid Valley Disposal’s vice president, quoted in SG’s profile, said it made a difference in selection that the technology was already a proven solution for meeting VOC emission reductions in the San Joaquin Valley district. The California air rules list compares covered systems on this point, and the permitting guide covers the sequence.

Odor is the other threat to a permit. Natural Soil Products in Tremont, Pennsylvania composted biosolids in open windrows until, according to SG’s profile, complaints from the surrounding community brought heightened scrutiny from regulators in 2022. The company ran a pilot with one SG MOBILE unit that year and then installed 18 covered bunkers, which SG says were fully operational by late 2023 (profile). Covered ASP with a GORE® Cover is designed to contain odors at the pile; it does not manage a receiving area that is left untidy.

Decision 5: Phase growth to match contracts

Overbuilding ties up capital in idle pads. Underbuilding turns away tonnage. Phase the site so that each step is paid for by signed material.

Stage Trigger Typical system step What to design in from day one
Prove it No operating history, or a new feedstock Pilot with a mobile covered ASP unit, leased or purchased Data collection for permit and lenders
First commercial phase First multi-year feedstock contract Several mobile units or heaps on a prepared pad Pad grades, power and water sized for the next phase
Scale Contracted tonnage exceeds pad capacity Permanent bunkers with in-floor aeration Space for added bunkers, curing and storage
Expand New contracts or a permit modification Added bunkers in blocks Stormwater and leachate capacity

SG’s product range follows these steps. SG describes the SG MOBILE System as installed in days to weeks, depending on the site, and offers it through a leasing program that it says allows moving to a permanent SG BUNKER System later. 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. All use positive aeration controlled by oxygen and temperature feedback through the SG COMPOST CONTROL™ System, with no building and no biofilter. The system comparison guide sets the three side by side.

Small operators are part of the picture. West Maui GreenCycle in Lahaina, Hawaii started an SG MOBILE System in August 2022 that SG’s profile lists at 700 tons per year, to take source-separated organics from local schools while staying a good neighbor (profile).

Decision 6: Sell the product before you make it

Product revenue is the line most often overestimated. Before you buy:

  • [ ] Name the buyers: landscapers, soil blenders, growers, public agencies
  • [ ] Find out what specification each buyer uses and what test results they want
  • [ ] Decide which products you will make: screened compost, mulch, blends
  • [ ] Plan storage for the off season
  • [ ] Check public demand. In California, SB 1383 requires cities and counties to procure recovered organic waste products, including compost and mulch, against an annual target (CalRecycle procurement)

Consistent process control is what makes consistent product. The compost quality metrics list explains what buyers test for.

Where covered ASP or SG is not the right fit

  • Clean yard trimmings, rural land, no air rule. A turned windrow pad costs less to build and uses equipment you may already own.
  • Short or uncertain feedstock contracts. Do not put in permanent bunkers on a one-year supply. Lease, or wait.
  • Packaged food waste with no preprocessing. No composting system fixes a contaminated input. Solve receiving first.
  • Energy sales as the business case. Anaerobic digestion earns on gas; composting earns on gate fees and soil products. Many sites pair them.
  • A site with no power and no budget for it. Aerated systems need electricity. Solar is an option at some sites; see the solar composting guide.

FAQ

How do I size the first phase of a private composting facility?

Size it to the tonnage you hold under contract, plus a modest margin, and lay out the pad, power and drainage for the next phase. Starting with modular units lets you add capacity when a new contract is signed. A first phase that runs full teaches your crew the process and gives you operating records to show the next customer.

What contamination limit should I put in feedstock contracts?

Set a limit your screening can handle while still meeting your product specification, and tie it to load inspection at the gate. Include the right to reject or surcharge loads, and require the supplier to correct repeated problems at the source. Start strict. It is easier to relax a limit for a good supplier than to tighten one after product quality has slipped.

Can a hauler with no composting experience run a facility?

Yes, with a pilot and training. SG’s profile of Mid Valley Disposal quotes the company saying it had no composting experience and that the demonstration project improved its understanding of food waste composting and helped with expansion design. Plan for a trained site lead, a vendor training period at startup, and ongoing technical support.

Should I lease or buy the first system?

Lease when tonnage is unproven, when you are testing a new feedstock or site, or when capital is committed elsewhere. Buy when contracts are long and the site is permanent. SG’s leasing program covers the SG MOBILE System and, according to SG, includes delivery, setup, training and technical assistance. The lease versus buy guide compares the two paths.

Next step

Bring your contracted tonnage, feedstock mix and site plan to SG through the contact page and ask for a phased layout with capacity at each stage. If you want operating data on your own material first, start with pilots and demos.

Related guides

← All commercial composting guides

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