Compostable Garbage Bags: Choosing the Right Mil for Your Bin

Compostable garbage bag thickness is measured in mil (thousandths of an inch), and the right choice depends on what’s going in the bag, how long it stays there, and where the bag lives during use. Buy the wrong thickness and you’ll either be paying for premium material you don’t need (overspec) or dealing with leaks and torn bags (underspec).

This article covers what each thickness is designed for, the practical decision tree for picking the right one, and the common compostable bag failure modes you can avoid with the right spec.

A quick refresher on mil

Mil = 1/1000 of an inch. So:
– 0.65 mil = 0.00065 inches
– 0.85 mil = 0.00085 inches
– 1.0 mil = 0.001 inches
– 1.5 mil = 0.0015 inches

The thicker the bag, the stronger and heavier it is. The thicker, the more it costs per unit. The thicker, the slower it composts at end-of-life (still composts, just slower).

For comparison, standard kitchen trash bags (LDPE) range from 0.7 mil (cheap) to 1.7 mil (heavy duty). Compostable bags typically run thinner than petroleum equivalents for cost reasons.

The standard thickness tiers

Compostable garbage bag manufacturers in 2024 typically offer these mil tiers:

0.5-0.65 mil — “thin”

The lightest compostable bag. Used for:
– Countertop compost collection (small countertop crocks, 1-3 gallon capacity)
– Light kitchen scraps that aren’t liquid-heavy
– Single-day or two-day storage

Strength: handles up to about 5 pounds without tearing risk. Cannot handle sharp objects (broken eggshells, bone fragments) or sustained moisture.

Cost: $0.08-0.15 per bag at case quantity (1,000+)

Typical use: small countertop compost crocks where the bag is changed every 2-3 days. Tied off and dropped into a larger outdoor bin.

0.65-0.85 mil — “kitchen”

The most common compostable bag tier. Used for:
– Standard indoor kitchen trash with mostly compostable contents
– 4-13 gallon kitchen bins
– 2-5 day use cycles

Strength: handles up to about 15 pounds. Some moisture tolerance. Can handle eggshells and modest sharp objects.

Cost: $0.12-0.20 per bag at case quantity

Typical use: indoor 13-gallon compost bin liners for households with curbside compost pickup. Replaced weekly.

0.85-1.0 mil — “heavy kitchen”

A step up for higher-moisture or longer-use scenarios:
– High-moisture food waste (heavy citrus, melon rinds, watermelon)
– Indoor bins that sit for 5-7+ days
– Bins shared by multiple households or larger families

Strength: handles up to about 25 pounds. Moisture-resistant for 3-7 days. Handles modest sharp objects.

Cost: $0.18-0.30 per bag at case quantity

Typical use: 13-30 gallon kitchen bins for larger households; first-tier B2B compostable bags for small restaurants.

1.0-1.2 mil — “outdoor”

For outdoor use and larger commercial-scale bins:
– 32-gallon outdoor compost bins
– B2B foodservice compostable trash bags
– Commercial composting operations (intake side)

Strength: handles up to about 50 pounds. Strong moisture resistance. Handles bones, sharp packaging waste, and heavy food residue.

Cost: $0.25-0.45 per bag at case quantity

Typical use: outdoor 32-gallon compost cans, foodservice operations with daily pickup, commercial composting facility intake.

1.5-2.0 mil — “industrial”

The heaviest compostable bag tier:
– Industrial composting operations
– Large-scale event waste collection (festivals, sports venues)
– High-traffic foodservice with delayed pickup

Strength: handles 70+ pounds. Strong puncture and moisture resistance.

Cost: $0.45-0.85 per bag at case quantity

Typical use: large outdoor compost bins (64-96 gallon), commercial composters processing C&D waste, event waste management.

A practical decision tree

To pick the right compostable bag thickness for your situation:

1. What’s the bin size? Smaller bins need thinner bags (less weight to support).
2. What’s the content type? Liquid-heavy = thicker. Mostly dry food = thinner.
3. How long between changes? Longer use cycle = thicker bag.
4. Indoor or outdoor? Outdoor = thicker (weather, UV, animal interest).
5. What’s your unit budget? Higher budget = thicker bag with margin to spare.

Based on these:

• Apartment kitchen, countertop crock, change every 2-3 days: 0.5-0.65 mil
• House kitchen bin, 13 gallon, change weekly, average moisture: 0.65-0.85 mil
• House outdoor compost bin, 32 gallon, weekly pickup: 1.0-1.2 mil
• Restaurant kitchen bin, daily change, mixed waste: 0.85-1.0 mil
• Commercial composting facility intake: 1.5-2.0 mil
• Event waste collection: 1.2-1.5 mil

What “compostable” actually means in this context

The compostable claim has two valid certification standards:

BPI-certified (US ASTM D6400):
– 90% biodegradation within 180 days
– Industrial composting conditions (140°F+)
– No eco-toxicity
– No fragments larger than 2mm
– The dominant US certification

TÜV Austria OK Compost Home:
– 90% biodegradation within 365 days
– Ambient temperature (68-86°F)
– Suitable for backyard composting
– A subset of “compostable” bags can meet this

OK Compost Industrial (TÜV Austria):
– Similar to BPI but EU-equivalent
– Industrial composting conditions

For most commercial buyers, BPI certification is the minimum. For backyard composting, OK Compost Home is the more stringent and meaningful certification.

The compostable claim is meaningful only when paired with appropriate disposal. A “compostable” bag in landfill behaves much like a plastic bag — it doesn’t biodegrade meaningfully in landfill conditions. The bag has to go to a commercial composter (or backyard pile, for home-compostable bags) for the compostable claim to be operational.

Material composition by tier

Different mil thicknesses often correspond to different material blends:

0.5-0.65 mil: typically pure PLA + PBAT blend, very flexible
0.65-1.0 mil: PLA + PBAT + PCL blend, increased durability
1.0-1.5 mil: PLA + PHA blends, or starch-based blends with PLA reinforcement
1.5-2.0 mil: typically reinforced PHA-PLA blends or starch+PLA composite layers

The thickness selection often determines the polymer blend. Heavier bags use more expensive but more durable polymers.

Common failure modes

Compostable bags can fail in specific, predictable ways:

Bottom split during lifting: bag is too thin for the contents. Switch to a thicker mil.

Slow tear at the top closure: bag is degrading faster than expected. Possible causes: too much moisture absorbing into the bag, very acidic content (citrus), or expired bag stock. Use fresh bags from a sealed package.

Bag becomes papery and crumbles: ambient humidity is too high during storage or use. PLA-based bags degrade faster in humid conditions. Store in cool, dry conditions.

Bag holds well but won’t seal at the tie: the tying-on-the-bag-itself technique works less well with compostable bags than petroleum. Use a separate twist tie (paper-based, also compostable) or a paper closure strip.

Bag falls apart in the compost facility: this is actually the desired outcome. Don’t be alarmed by the compost facility reporting that bags “fell apart” — that’s biodegradation working as intended.

Storage and shelf life

Compostable bags degrade over time even unopened. Shelf life is:

• 12-18 months for thinner bags (0.5-0.85 mil)
• 18-24 months for thicker bags (1.0-1.5 mil)
• 24+ months for industrial-grade bags

Store in cool, dry conditions. Heat and humidity dramatically reduce shelf life. Use first-in-first-out inventory rotation for high-volume operations.

Sizing — match the bag to the bin

A bag that’s too small doesn’t line the bin properly. A bag that’s too big wastes material at the top. Bag sizing:

• 3-gallon countertop: 11″x16″ to 13″x18″ capacity
• 13-gallon kitchen tall: 24″x32″
• 20-gallon kitchen: 30″x37″
• 30-32 gallon outdoor: 33″x40″ to 36″x45″
• 64-gallon outdoor: 45″x57″
• 96-gallon outdoor: 55″x72″

Match the bag dimensions to the bin perimeter and height. Most bin manufacturers print recommended bag dimensions on the bin label.

Cost calculations

For a 200-bag/week operation (about right for a 200-seat restaurant):

• 0.65 mil bag at $0.12: $24/week, $1,250/year
• 0.85 mil bag at $0.18: $36/week, $1,870/year
• 1.0 mil bag at $0.25: $50/week, $2,600/year

The annual cost difference between mil tiers is meaningful — $625-$1,350 per year for a single operation. Spend on the thicker bag when the use case demands it; spend on the thinner bag when it’s enough.

For comparison, equivalent petroleum bags would run:
– 0.7 mil LDPE: $0.05 each, $520/year
– 1.0 mil LDPE: $0.08 each, $830/year
– 1.5 mil LDPE: $0.12 each, $1,250/year

The compostable premium ranges from 1.5-3x petroleum. As compostable bag volume scales globally, the premium is slowly narrowing.

A note on bag-to-content compatibility

Compostable bags handle most kitchen waste well. A few compatibility considerations:

• Liquid-heavy waste (soup, broth, watermelon rind): use 0.85+ mil
• Sharp objects (eggshells, bone, broken hard plastic packaging): use 1.0+ mil
• Acidic waste (lots of citrus): use 0.85+ mil; rotate bags more frequently
• Hot food waste (just-prepared, still warm): let cool before adding to bag; heat can degrade thinner bags

For B2B operations, the standard procurement guideline: spec the thickness needed for the most demanding typical use case. If you have one customer that generates heavy liquid waste, spec for that customer.

A note on color

Most compostable bags are green (signaling compost destination) or off-white/clear (more natural look). Some considerations:

• Green opacity: hides contents from view, signals “compost bin”
• Clear/translucent: lets staff verify contents at a glance
• Brown kraft printed on PLA film: more “natural” aesthetic for premium operations
• Custom-printed with logo or messaging: B2B branding option

For most operations, green opaque is the default and works fine. Custom branding only at sufficient MOQ (5,000-10,000+ units).

Related compostable products

Compostable garbage bags work alongside the rest of a compostable program:

• Compostable food containers for to-go
• Compostable bowls for soup and entrées
• Compostable utensils for cutlery
• Compostable cups and straws

The bags handle everything that comes out of these other products. A coherent program uses certified compostable bags throughout — front-of-house bin liners, back-of-house collection, outdoor staging, hauler pickup.

Two real case studies

Case 1: A 65-seat Italian restaurant in Brooklyn

This operation handles standard restaurant waste: pasta scraps, vegetable trimmings, bread, some bones, citrus. They previously used 0.6 mil compostable bags ($0.12 each) and reported about 8% bag failure rate (bag tears during disposal, weeping at the bottom, smaller bags compressed into larger bags causing leaks).

They switched to 0.9 mil compostable bags ($0.20 each). Failure rate dropped to under 1%. Annual cost increase: about $800 for the 200-bags-per-week operation. The labor savings (no more dealing with leaks and bag failures) more than offset the cost.

Lesson: a cheap bag that fails 8% of the time costs more than a moderately priced bag that fails rarely.

Case 2: A 24-classroom elementary school cafeteria, Bay Area

This operation serves about 600 students daily. They use compostable bags for student-side waste collection (8 bins total at lunch service) plus kitchen-side collection (4 bins). Initial bag choice: 0.85 mil at $0.20 each.

Problems encountered:
– Student-side bins received heavy liquid waste (juice spills, condensation from cold lunches)
– Bottom split rate: about 4% over the first semester
– Switched student-side bins to 1.0 mil at $0.28 each
– Kitchen-side bins stayed at 0.85 mil

Lesson: different use cases within the same operation may need different bag tiers. Don’t standardize on the cheapest option across all bins; match the bag to the bin.

What the EPA says

The EPA hasn’t issued specific guidance on compostable bag thickness, but their solid waste management framework supports the differentiation between commercial composting (which accepts certified compostable bags) and household composting (which generally doesn’t process compostable bags efficiently).

For commercial operators, the relevant federal context:
– EPA’s CPG (Comprehensive Procurement Guidelines) includes compostable foodservice items in its preference lists
– BPI’s testing protocols align with ASTM D6400 standards
– State-level mandates (California SB 1383, Vermont Act 148, Massachusetts food waste ban) all reference certified compostable bags as acceptable

For operations under state organics mandates, certified compostable bags are essentially required for food waste source-separation. The thickness choice within that certified category is the operational decision.

The short version

For most operations choosing compostable garbage bags:

• 0.65-0.85 mil for indoor kitchen bins with weekly pickup
• 0.85-1.0 mil for restaurant kitchens with daily pickup or moisture-heavy waste
• 1.0-1.2 mil for outdoor bins and harder use cases
• 1.5-2.0 mil for industrial or extreme conditions

The right thickness saves you money without sacrificing performance. The wrong thickness costs you in either premium spend or operational hassle. Test with samples; commit to volume.

A small note: don’t store compostable bag inventory in damp basements or unheated warehouses. Heat and humidity dramatically reduce shelf life. Cool, dry storage is essential.

For most B2B operations, the right compostable bag is the lightest mil that handles the typical use case reliably. Heavier is better-safe-than-sorry, but the cost premium adds up across thousands of bags per year. Match the bag to the bin to the contents, and the operation will work smoothly.

For B2B sourcing, see our compostable supplies catalog or compostable bags catalog.

For procurement teams verifying compostable claims, the controlling references are BPI certification (North America), EN 13432 (EU), and the FTC Green Guides on environmental marketing claims — these are the only sources U.S. enforcement actions cite.