SG BUNKER®, SG HEAP® and SG MOBILE® are three layouts of the same process: a covered aerated static pile under a GORE® Cover, with positive aeration run by the SG COMPOST CONTROL™ System. Choose SG BUNKER for a permanent, high-throughput facility, SG HEAP for a low-infrastructure site that may grow, and SG MOBILE for a pilot, a temporary need or a site with no infrastructure yet. The choice is about tonnage, site and permanence, not about a different biology.

Key takeaways

• All three systems use the same core technology. Sustainable Generation (SG) says its pilot units are the “same core technology as all full-scale” systems, so data from one layout carries to the others.
• SG states a range of 5,000 to 500,000 tons per year for SG BUNKER and 1,000 to 100,000+ tons per year for SG HEAP. The SG MOBILE page states no tonnage range.
• SG describes SG MOBILE as installed in days to weeks, depending on the site. SG’s FAQ page says complete SG BUNKER installations are typically online within 6 to 12 months, depending on site and permitting.
• SG SOLAR® is a power option and SG COMPOST CONTROL is the monitoring layer. Neither is a fourth composting system.
• Many sites move through the layouts in order: SG’s own example is Prince George’s County, Maryland, which piloted with SG MOBILE units and later installed SG BUNKER systems.
• None of the three fits if you need energy recovery, have a liquid feedstock, or run a clean yard trimmings windrow site with ample land and no regulatory or neighbor pressure.

What the three systems have in common

SG’s How It Works page describes one process under the name SG Advanced Composting™ Technology: a static pile on an aeration floor, covered with a GORE Cover, with computer-controlled positive aeration. That page lists the aeration floor as “in-ground trenching or on-grade pipe” and offers the three layouts as choices to fit “your feedstock, capacity, and footprint.”

The shared points, all from SG’s pages:

• Cover. SG is the exclusive GORE Cover partner for North America and Oceania, as stated on the GORE partnership page. Covered ASP with a GORE Cover is designed to contain odors at the pile.
• Aeration. Positive aeration controlled by oxygen and temperature feedback. SG states that the technology needs no enclosed building and no biofilter.
• Pathogens. SG says the process is designed to meet the EPA Part 503 PFRP time and temperature requirements. EPA does not certify composting systems, so your own temperature records are what a regulator reviews.
• Emissions. SG reports greater than 95% VOC control in third-party testing.
• Treatment time. SG’s How It Works page describes a 4 to 8 week treatment time versus 8 to 12 months for open windrow.

Because the process is shared, the decision comes down to four practical questions: how many tons, on what site, for how long, and how soon.

SG BUNKER: permanent, high-throughput facilities

The SG BUNKER page calls it a “high-capacity” covered ASP system “tailored for municipal, industrial, and commercial operators managing large volumes of organic waste”, and the How It Works page labels it “high-throughput permanent installations”.

• Capacity range SG states: 5,000 to 500,000 tons per year.
• Who SG designs it for: “space-limited, compliance-driven, high-throughput facilities”.
• Feedstocks: SG’s products page lists food waste, green waste, yard trimmings, biosolids, agricultural manures, source-separated organics and anaerobic digestion digestate.
• Controls: full integration with SG COMPOST CONTROL.
• Timeline: per SG’s FAQ page, typically online within 6 to 12 months, depending on site and permitting.

SG BUNKER fits when the tonnage is known, the site is yours for the long term and the permits will be written around a fixed facility. SG’s bunker page gives the DSNY Staten Island Compost Facility as a 16-unit example; see the Staten Island project profile.

It does not fit when tonnage is still a guess, when the site is leased short term, or when a board wants proof before it funds permanent works. In those cases start with one of the other two.

SG HEAP: low infrastructure, room to grow

The SG HEAP page describes “a low-infrastructure, high-throughput solution designed for farms, municipal yards, and commercial sites that seek proven results with minimal complexity”.

• Capacity range SG states: 1,000 to 100,000+ tons per year.
• Where SG says it is used: agricultural operations (manure, bedding, mixed feedstocks), municipal green waste yards, transfer stations and rural organics collection points, and pilot projects moving to full scale.
• Feedstocks named on the page: yard trimmings, manure, food waste and mixed feedstocks.
• Operation: SG states no turning is required in the primary phase, and that the layout is “easy to expand or adapt”.
• Timeline: SG’s FAQ page says SG HEAP systems “can launch in weeks”. The page gives no firmer figure, so ask for one in writing for your site.

SG HEAP fits when you want covered ASP performance with the least fixed construction, when capital is the constraint, or when the facility will be expanded in steps. SG positions it for “operators seeking minimal capital investment”.

It does not fit as well when the site is tight and every square foot must carry maximum tonnage. SG positions SG BUNKER, not SG HEAP, for space-limited sites.

SG MOBILE: pilots, temporary capacity and sites without infrastructure

The SG MOBILE page describes “an easily deployable” covered ASP system “designed for fast and flexible organics recycling, without the need for costly infrastructure”. SG’s products page calls it a “composting system in a box”: the aeration blower, piping and GORE Cover come with a mobile unit that can move from site to site.

• Capacity range: the SG MOBILE page states no annual tonnage range. Capacity grows by adding modules (“add piles, not buildings”).
• Best for, per How It Works: “pilots, small-medium sites, or off-grid use”.
• Site needs: SG’s article on mobile processing says it can be installed on a compacted pad with limited infrastructure.
• Space: SG states it requires 60 to 80% less space than in-vessel or windrow.
• Setup: SG describes SG MOBILE as installed in days to weeks, depending on the site.
• Controls: each unit comes with SG COMPOST CONTROL integrated.
• Leasing: SG’s leasing program is built around SG MOBILE, and that page says a lessee can add units, move systems or transition to a permanent SG BUNKER system.

SG MOBILE fits a pilot, a seasonal surge, a remote site, or the first phase of a program whose tonnage will be known only after collection starts. SG’s pilots and demos page says on-site commissioning and training are included with a pilot.

It does not fit as the end state for a large regional facility. SG’s own example shows the path: Prince George’s County piloted SG MOBILE units in 2013 and, according to SG, installed 12 SG BUNKER systems in 2018. See the Prince George’s County profile.

Where SG SOLAR and SG COMPOST CONTROL fit

These two are add-ons to any layout, not alternatives to one.

SG SOLAR. The SG SOLAR page describes solar panels, an inverter and battery storage, with direct integration into SG COMPOST CONTROL, to power SG systems “without the need for diesel, utility connections, or costly infrastructure”. SG lists the top of a landfill, rural, restricted and undeveloped areas with limited grid access as the target sites. Consider it when the electrical service, not the pad, is what delays the project.

SG COMPOST CONTROL. The SG COMPOST CONTROL page describes a cloud-based platform that tracks temperature, oxygen and blower metrics, sends alerts, stores recipe settings for different feedstocks, and exports reports. SG says it works with all SG systems, “whether you’re managing one pile or 100”.

Decision table by tonnage, site and timeline

Use the table to shortlist, then confirm with a site-specific design. Capacity figures are SG’s stated ranges for each system.

Your situation	SG BUNKER	SG HEAP	SG MOBILE
SG’s stated capacity range	5,000 to 500,000 tons per year	1,000 to 100,000+ tons per year	No range stated; modular
Under 1,000 tons per year	Below stated range	Below stated range	Candidate (pilot or small site)
1,000 to 5,000 tons per year	Below stated range	Candidate	Candidate
5,000 to 100,000 tons per year	Candidate	Candidate	First phase or pilot
Above 100,000 tons per year	Candidate	Ask SG (page says 100,000+)	Pilot only
Tight site, strict air or water permit	SG’s stated design case	Possible	Possible for small tonnage
Farm, green waste yard, rural transfer point	Usually more than needed	SG’s stated design case	Possible
Leased or temporary site	Poor fit	Possible	Best fit
No grid power	With SG SOLAR	With SG SOLAR	With SG SOLAR
Timeline SG states	Typically 6 to 12 months, site and permit dependent	“Can launch in weeks”	Days to weeks, depending on the site
Tonnage unknown, need data first	Not yet	Not yet	Pilot first

How to choose in five steps

1. Fix the tonnage and its growth. Write down tons per year now, in three years and at build-out, by feedstock. Compare each figure to the stated ranges above.
2. Describe the site. Usable area, surface, drainage, power, distance to neighbors, and whether you own it. A site with no power and no paving points to SG MOBILE with SG SOLAR, at least to start.
3. List the permits. Solid waste, air and water. A permit written for a fixed facility favors a permanent layout. If the regulator wants a demonstration first, SG’s consulting page says SG runs pilot demonstrations, “often using our SG MOBILE System”.
4. Set the date. If material must be processed this season, only a layout that SG says launches in days to weeks is realistic.
5. Decide the path, not only the first purchase. Ask whether the first system is the final one or a step. SG’s leasing page describes moving from SG MOBILE to a permanent SG BUNKER system as a planned route.

Bring these five answers to the first design conversation.

Where none of the three fits

A covered ASP layout is the wrong tool in some cases, whichever of the three you pick.

• You want energy. Composting produces no biogas. If renewable gas or power is the goal, anaerobic digestion is the technology to evaluate. Covered ASP can then treat the solid digestate, as SG’s digestate page describes.
• The feedstock is liquid or pumpable. A static pile needs structure and porosity. Slurries need dewatering or a bulking agent first, or a different process.
• Very small volumes. SG’s How It Works page puts the lower end of the technology at 100 tons per year. Below that, a school, garden or community bin system is more proportionate.
• Clean yard trimmings, ample land, no pressure. A turned windrow site with distant neighbors and no air district rule driving covers may not gain enough to justify aeration and covers. The methods comparison sets out that trade.
• A permit that requires full enclosure. If the local authority has written an enclosed building into the approval, an outdoor covered system needs a permit change before it is an option.
• PFAS concerns in biosolids. Composting does not destroy PFAS. No layout changes that.

FAQ

Is SG BUNKER a different technology from SG HEAP and SG MOBILE?

No. SG presents all three as layouts of one covered aerated static pile process using the GORE Cover, positive aeration and SG COMPOST CONTROL. They differ in how permanent the installation is, how much site construction is involved, and the tonnage SG states for each. Process data such as temperature and oxygen records are gathered the same way in all three.

Can I start with SG MOBILE and move to SG BUNKER later?

Yes, and SG describes that route on its leasing and pilot pages. Its example is Prince George’s County, Maryland, which SG says piloted SG MOBILE units in 2013, added units as food scrap volumes grew, and installed 12 SG BUNKER systems in 2018. Ask SG which components carry over to the permanent facility, because the pages do not list them.

What capacity can one SG MOBILE unit handle?

The SG MOBILE product page does not state a tonnage range, and it describes capacity as modular: you add piles as volume grows. Because batch size depends on feedstock bulk density and residence time, ask SG for a throughput estimate based on your own recipe. A pilot is the most reliable way to confirm it.

Do I need a building or a biofilter with any of the three?

SG states that its covered ASP technology uses positive aeration with a GORE Cover and needs no enclosed building and no biofilter. Whether your permit accepts that is a local decision. Confirm it with your solid waste and air regulators before you fix the layout, and ask SG for test reports relevant to your district.

Next step

Send SG your tonnage by feedstock, a site plan and your target date, and ask for a layout recommendation with the reasoning shown. Start at the contact page, or review all three systems on the products page first.

Related guides

• From Contract to Commissioning: How an SG Composting Project Is Delivered
• How to Run a Composting Pilot
• Lease vs Buy Composting Equipment
• Solar-Powered and Off-Grid Composting: When It Makes Sense
• Aerated Static Pile Composting: The Complete Guide

← All commercial composting guides

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