Planning an Onsite Composting Facility: What We Learned

ByChris

On June 9, Betsy La Force, Sales and Business Development Manager at Green Mountain Technologies, walked our audience through the practical fundamentals of planning, launching, and operating a small-scale decentralized composting facility. We had 215 registrants and around 85 attendees joining from all over the world, including Kenya, Chile, Sweden, Mexico, Saudi Arabia, and Canada, alongside practitioners from across the United States. Many of those attendees are running these exact programs today, and the questions they brought turned the hour into a genuine working session rather than a one-way presentation.

Betsy presented remotely from the Mayo Clinic in Jacksonville, where her mother was in surgery that same morning. We’re grateful she chose to keep the commitment, and grateful for the depth she brought to it. What follows is less a transcript and more a distillation of the ideas worth carrying forward.

Why decentralized composting

The core problem Betsy kept returning to is access and proximity. Plenty of communities want to compost but don’t have a facility close enough to make hauling sensible. Her example was Beaufort County, South Carolina, where the nearest compost facility was nearly two hours away in Charleston County. For years the assumption there was simply that composting wasn’t feasible. Once the county explored processing organics onsite instead, the economics and logistics changed entirely.

Decentralized composting keeps the nutrients, the labor, and the benefits in the community where the material is generated. It avoids the fuel, the trucking, the wear and tear, and the rising cost of both land and landfill space. Betsy made the point that this is a fairly bipartisan issue: whether the motivating argument is environmental or purely fiscal, keeping organics out of landfills saves money and preserves a valuable resource. She framed the whole talk around what she called six core pillars of a successful operation, and the sections below roughly follow them.

The money usually decides things first

Funding is where most decentralized projects stall before they start, so Betsy spent real time here. Her central reassurance: you don’t need a new tax, a pay-as-you-throw overhaul, or a public bond election to make this work.

A useful framing for decision-makers is processing cost. On average, the full cost of handling organics, from pickup through hauling, fuel, and landfilling, runs around $200 per ton. Laying that number in front of a city or county council often reframes composting from an environmental nicety into a fiscal decision. Green Mountain has internal ROI spreadsheets they’re willing to share with anyone trying to build that case for their own location.

Three funding paths came up:

Grants remain available despite broader cuts to federal funding. Beaufort County secured a USDA Solid Waste Management grant of roughly $250,000, which covered their equipment and some of the softer startup costs without asking local taxpayers to foot the bill. Because the funding was already in hand, the county-level conversation to approve the program was minimal.

Policy roadmaps unlock local dollars. Getting composting explicitly written into a community’s comprehensive plan or climate action plan turns later budget requests into the simple funding of an already-approved directive that residents voted on.

Financing covers the gaps. A municipal lease-purchase agreement lets local governments buy capital equipment and pay it off over five to ten years, structured as an annual lease rather than long-term debt, which protects immediate cash flow.

Siting: the footprint is smaller than people expect

A common misconception is that a composting facility needs sprawling acreage. With an enclosed, containerized system the site strategy flips. Betsy’s emphasis was on co-location: putting the equipment on land the community already owns and operates. Convenience centers, transfer stations, public works yards, wastewater treatment plants, and existing landfills are all candidates. Traverse City, Michigan set aside less than a quarter of an acre for their system, with Carter’s Compost handling hauling and education through a public-private partnership.

Siting close to where the waste is generated is what dissolves the hauling barrier in the first place. Keep the technology in the community zone, and the long-distance costs largely disappear.

Permitting can be fast if you change the approach

Permitting is usually treated as the scariest checkpoint, and the default expectation is a long bureaucratic process. Beaufort County’s experience was the opposite. They got their project permitted in under 30 days, which drew genuine astonishment from the audience.

The lessons Betsy drew out: engage regulators on day one rather than after you’ve bought equipment or secured land, and approach them as a partner with a blank piece of paper, asking what you need to do to fit their rules. Then use existing rules to your advantage. Many states’ solid waste regulations contain conditionally exempt or low-risk tiers tied to volume thresholds, often under 5,000 tons per year. Decentralized volumes tend to fall comfortably inside those tiers.

The enclosed nature of an in-vessel system does a lot of the regulatory work. Because the container is sealed, there’s no exposed food waste and no runoff. The Earthflow has a leachate collection system built into the floor, so excess moisture is contained and recirculated rather than risking groundwater. That containment is what gives a regulator the confidence to issue a conditional exemption in weeks rather than months. (Beaufort still needed a certified compost operator under South Carolina law; team members earned that certification both online and in person.)

The engineering, and one warning worth repeating

Betsy described the Earthflow as plug-and-play: fabricated inside a retrofitted shipping container, shipped to the site, then connected and commissioned by engineers with a couple of days of onsite operator training. A few points stuck:

It’s a continuous-flow system with roughly a 21-day retention time for food scraps. The smallest 20-foot unit handles about 500 pounds of food scraps per day, balanced with about 500 pounds of carbon bulking agent. A visible traveling auger moves and homogenizes the material from front to back, which she likes because the whole process stays observable, useful when education or volunteers are part of the program.

The warning: carbon is what actually composts, not the food scraps. If a machine claims to make compost in 24 hours with no carbon added, it’s almost certainly a dehydrator, not a composter. The output is dried food scraps that turn slimy when rehydrated, not a usable soil amendment. If your goal includes producing real compost, make sure the technology actually produces it.

Odor control comes from forced aeration through the floor combined with negative pressure drawing air through a biofilter, which keeps the process from going anaerobic. The system also logs core temperatures automatically; state rules often require the pile to hold 131°F for several days to kill weed seeds and pathogens. Electricity for the small unit runs about 20 kWh per day, roughly $150 a month. Total equipment cost for Beaufort was about $160,000.

One more thing people forget: the material that comes out of the vessel looks and smells finished but is still hot and biologically active. It needs roughly 30 days of curing in a static pile before use. That step is labor-free but not optional.

The human element and contamination

Technology handles a lot, but Betsy was clear that success still depends on people. Every program needs a dedicated champion who owns the results, and it needs operational redundancy through cross-training so the program doesn’t halt when one person is out. Day-to-day, operating the machine is closer to a bolt-on task than a full-time job: get material from point A to B, follow the carbon-to-nitrogen recipe (roughly 2:1 by volume, 1:1 by weight), and keep the bulk density around 800 pounds per yard for airflow. Carbon often doesn’t need to be purchased; diverted leaf and yard waste or free wood chips through services like ChipDrop can supply it.

On contamination, her honest answer was that there’s no silver bullet at this scale. The approach is multi-layered. On the front end, education works remarkably well: in Charleston, requiring participants to pass a short composting quiz to receive an access code for locked drop-site bins resulted in almost zero contamination, far better than the team expected. Pair that with clear signage, give operators a grabber to pull out obvious trash, and screen the finished material on the back end to catch produce stickers and stray plastics.

Scaling: the hub-and-spoke model

The real payoff of decentralization isn’t one successful project, it’s a repeatable blueprint. Betsy described a hub-and-spoke model where modular containerized systems are deployed across existing convenience centers as the network grows. Each new vessel means fewer trucks on the road and fewer tons paying tipping fees, with returns that compound as the network expands. The framing she landed on: this turns waste management from an out-of-sight taxpayer liability into a circular-economy engine that produces high-grade soil amendment for parks, roadsides, and local agriculture.

Questions from the field

The Q&A surfaced a lot of practical detail. A few highlights:

Capacity and throughput. The smallest unit handles about 500 pounds per day, roughly two curbside carts of food scraps, enough to start most residential drop-off programs. Beaufort estimated that capacity would serve them for their first five years. You don’t have to fill the vessel to capacity; with less mass it simply takes longer to reach thermophilic temperatures.

Climate. The containers are highly insulated sea cans built for all-weather outdoor use. Ambient temperature doesn’t meaningfully interfere with the process, though extreme environments may warrant a simple lean-to.

International funding. For the Global South, Betsy pointed toward UN and international development funds and, more practically, public-private partnerships, for instance partnering with a resort or hotel that has land and capital but no appetite to run a program. Chris added that a financial spreadsheet proving the economics is often the most persuasive opening move.

PFAS. A recurring question from Utah and elsewhere concerned PFAS contamination in compost end markets. The short answer is that in-vessel composting doesn’t destroy PFAS. Biochar can bind PFAS for a time through its porous structure and hydrophobic surface interactions, but binding isn’t destruction, and the durability of that binding needs further study. This is a topic worth a dedicated future session.

Thank you

A sincere thank-you to Betsy La Force and Green Mountain Technologies for an exceptional, generous presentation, delivered under personal circumstances that would have given anyone reason to reschedule. Thanks as well to everyone who attended and asked such thoughtful questions; the engagement is what made the hour as valuable as it was. Betsy noted that helping people work through this process is a big part of her job, so anyone with follow-up questions is welcome to reach out to her directly or connect with Green Mountain on LinkedIn or Instagram.

Resources surfaced during the webinar

These links were shared by Betsy, Chris, and attendees throughout the session.

Green Mountain Technologies / Earthflow

  • Green Mountain Technologies and the Earthflow in-vessel system (presenter’s company)

Funding and grants

Financing and policy models

Other models and operators

Compostable packaging

PFAS research

  • The potential for binding PFAS using biochar and phytoremediation — Josefin Svensson, master’s thesis, Lund University (2021): https://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=9059536&fileOId=9059537
    A few cautions on the thesis above. This is a student master’s thesis and has not been peer-reviewed, so treat it as supplementary reading rather than authoritative research. The title names two separate techniques, not one: biochar immobilizes PFAS in place by adsorption, while phytoremediation uses plants to take PFAS up so the biomass can be harvested and hauled off. Biochar does not phytoremediate anything, and neither method destroys PFAS. The thesis is useful on one narrow point: it supports the idea that adsorbing PFAS onto biochar is not the same as destroying it. It also makes clear that no studies have established how long PFAS stay bound to biochar, or to what extent that binding holds. This remains an open knowledge gap. Finally, the paper should not be cited as evidence that biochar remediates PFAS. Trapping a contaminant in place is not remediation, and even phytoremediation only relocates PFAS into plant matter that still has to be destroyed by high-heat processing. Applying that kind of heat to compost would kill the living cultures that make compost valuable in the first place. The thesis itself does not claim otherwise.
  • Stabilization of PFAS-contaminated soil with activated biochar — Sørmo et al., Science of the Total Environment (2021), peer-reviewed and open access: https://doi.org/10.1016/j.scitotenv.2020.144034 Ruta Jordans (a webinar attendee), who raised the PFAS question during the session, supplied this peer-reviewed study, and it reinforces what the student thesis above only suggested. The researchers found that biochar can sharply reduce PFAS leaching from contaminated soil, by up to 98–100% in low-organic soil at high doses, and that binding gets stronger with longer PFAS chain length, confirming the role of hydrophobic interactions. Two caveats keep it consistent with everything above. First, this is immobilization, not destruction: the PFAS stays put, bound in place, rather than being eliminated. Second, the strongest results come from activated biochar (a high-energy product made at 800–900°C with steam or CO₂, closer to commercial activated carbon than to compost biochar) and the effect weakened considerably in organic-rich soil, where competing organic matter clogged the biochar’s pores. A compost pile is full of organic matter, which is exactly the condition where the study found biochar performs worst, so these high numbers almost certainly would not hold up in compost.

Training and certification

Zero Waste USA events

Video Slide Deck Chat

* Correction: During the webinar, the PFAS binding was attributed to biochar’s high cation exchange capacity (CEC). That mechanism is what lets biochar hold onto nutrients and water in soil, but it isn’t what binds PFAS. Because most PFAS are negatively charged, they’re captured mainly through hydrophobic interactions with the fluorinated tail and physical entrapment in biochar’s pores rather than through cation exchange. That temporary sequestration also works far better on long-chain PFAS than on short-chain ones, which are much less attracted to biochar. As industry has shifted toward short-chain PFAS, biochar has become correspondingly less effective against the compounds now most common in the environment.

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