Home / Blog / Sustainability & Compliance

Carbon Footprint of a Dry Bag

What a bag footprint actually measures

Two boundaries matter and they are routinely confused. Cradle-to-gate covers everything up to the moment the finished bag leaves the production facility: raw material, film extrusion, fabric weaving, hardware, printing, assembly energy and packaging. Cradle-to-grave adds distribution, the use phase and end of life. A brand quoting a number without naming the boundary is quoting something you cannot compare.

The second thing that must be stated is the functional unit. For a dry bag the honest unit is not one bag but one bag delivering a defined service: for example, keeping 20 litres of kit dry for five years of weekend use. Without that, a heavier bag with a longer life looks worse than a light bag that is replaced every season, which is backwards.

The accounting convention matters too. A screening assessment attributes the total to the bag and reports a single number. A fuller life-cycle assessment allocates co-products, models the electricity grid by region, and separates fossil from biogenic carbon. The ISO 14040 and 14067 series sets out how those studies are structured, and that series is the reference a credible report cites.

A working inventory for a 20 litre welded bag

The table below is a screening-level inventory for a 445 g bag built from 0.5 mm TPU film laminated to a 420D polyester face, with polyester webbing, acetal hardware and a single printed logo. Emission factors are typical published ranges for virgin materials, and the grid factor used for assembly energy is 0.58 kg CO2e per kilowatt-hour, which is representative of a Chinese manufacturing grid rather than a European one.

Read the share column rather than the absolute numbers, because factors move by region and by year. What does not move is the shape of the distribution: materials dominate, assembly is small, and freight can be either invisible or dominant depending on the mode. Any footprint conversation that starts with production energy is starting in the wrong place.

Two lines are easy to miss and worth flagging. Print paste and labels look trivial at 8 g but carry a disproportionate impact because ink chemistry is energy intensive per kilogram. Packaging is the other: a single polybag plus a share of the export carton is about 45 g of material per bag, more than the webbing and thread combined.

Material choice: the biggest single line

Film dominates because it is the heaviest component and because polyurethane sits at the energy-intensive end of the polymer range. Polyester and polypropylene are cheaper in carbon terms per kilogram; nylon and TPU are more expensive. That does not automatically make a nylon bag the wrong choice, because a fabric that lasts three times as long wins on an annualised basis, but it does mean polymer selection should be a deliberate decision with numbers attached.

Recycled content is the most direct lever on this line and it works differently for each polymer. Recycled polyester face fabric and recycled webbing are mature, widely available and cut roughly a third of the fabric impact. Recycled TPU is harder: post-industrial regrind is available at meaningful percentages, post-consumer material is limited, and both come with a weldability question that has to be tested rather than assumed.

The PVC comparison is worth stating plainly because it surprises people. PVC resin carries a lower footprint per kilogram than TPU, so a pure cradle-to-gate comparison can favour it; the difference shows up in service life, in end-of-life handling and in the additive package. Our TPU versus PVC guide sets out the trade-off, and our recycled TPU guide covers what recycled content does to weld strength.

Energy in cutting, welding and assembly

Assembly is a surprisingly small line and that is worth internalising before anyone spends money optimising it. A 20 litre bag needs roughly four weld passes, and a radio-frequency cycle of four seconds at 8 kW is about 0.009 kWh per weld, so all the welding comes to under 0.04 kWh. Cutting, printing, inspection and packing roughly double the total to about 0.14 kWh per bag.

At 0.58 kg CO2e per kilowatt-hour that is about 0.08 kg per bag, under four percent of the total. Halving assembly energy would save 0.04 kg, which is less than a tenth of what swapping the face fabric to rPET saves. The reason to measure it anyway is that the same meter data drives cost, and a line that wastes energy usually wastes film too.

Grid factor is where the number moves. The same physical bag assembled on a grid at 0.25 kg CO2e per kilowatt-hour shows 0.035 kg for assembly instead of 0.08 kg, and a facility with on-site solar reduces it further. That is why a footprint report should state the grid factor used, and why our welding energy guide reports energy per hundred bags rather than a single headline figure.

Freight: the line that can double the footprint

Freight per tonne-kilometre differs by a factor of fifty between modes. Sea freight sits around 8 to 15 grams CO2e per tonne-kilometre, road around 60 to 120, and air freight between 500 and 1,100. A 0.45 kg packed bag moved 10,000 km therefore costs about 0.05 kg by sea, 0.4 kg by road and roughly 2.7 kg by air, which is more than the entire manufacturing footprint of the bag.

The operational lesson is blunt: air freight is a carbon decision, not just a cost and lead-time decision. One air-freighted shipment to hit a launch date can outweigh every material improvement made in the preceding two years of development. The mitigation is planning rather than technology, because 35 to 50 days of bulk production plus sea transit is predictable if the calendar is built around it.

Consolidation helps at the margin. A half-full container carries the same ship as a full one, so the per-bag figure rises as utilisation falls, and a programme shipping 5,000 bags in a 40-foot container does better per unit than one shipping 800. Carton cube matters for the same reason: a bag that packs flat rather than boxed improves utilisation and can cut the freight line by a quarter.

Packaging and the end-of-life line

Packaging is about four percent of the bag footprint and it is the easiest line to cut without touching the product. A single polybag at 18 g plus a share of the export carton comes to about 45 g per bag and roughly 0.09 kg CO2e. Switching to a recycled and recyclable mailer, or eliminating the individual bag where the product ships in a carton anyway, removes most of that at negligible cost.

Extended producer responsibility rules make packaging a compliance question as well as a carbon one. Several markets now levy fees by material and weight, so a packaging specification that ignores them creates a cost line downstream. Our plastic-free packaging guide and EPR rules guide cover what to specify.

End of life is where a mono-material design pays off. A bag built entirely from one polymer family can be mechanically recycled into panels and accessories, which avoids roughly 0.8 kg CO2e compared with virgin input. A mixed laminate of polyester fabric bonded to TPU film, with acetal hardware and polyester webbing, has no clean mechanical route and typically ends up in landfill or incineration.

The use phase is smaller than people assume

A dry bag has no heating element, no motor and no detergent-heavy wash cycle, so its use phase is genuinely small. Rinsing with cold fresh water twenty times a year uses a few litres each time and emits almost nothing; air drying in shade uses none. Even a hot machine wash at 60 °C, which we do not recommend, adds only about 0.5 kg CO2e per cycle and would have to happen every week to matter.

Repair is the use-phase action that does count, and it counts indirectly. A 30 g patch that extends a bag from three years to eight years removes the need to produce two replacement bags, each carrying 2.2 kg CO2e. Repairing is therefore worth roughly 4 kg CO2e per bag repaired, which makes a patch kit one of the highest-leverage items in the whole system.

The comparison that matters for a buyer is annualised. A bag used weekly for eight years emits about 0.28 kg CO2e per year; the same bag used for one season and discarded emits 2.2 kg in that single year. Nothing else on this list comes close to that spread, which is why our product life guide leads with durability rather than material swaps.

Ranking the reduction levers

Put the levers in order of saving per bag and the priority list becomes obvious. Avoiding air freight saves about 2.65 kg; doubling service life saves about 1.1 kg over ten years; recycled TPU and rPET together save about 0.6 kg; mono-material design for recyclability saves about 0.8 kg at end of life; packaging changes save 0.07 kg; and halving assembly energy saves 0.04 kg.

Cost and difficulty do not follow the same order, which is the useful part. Packaging and fabric switches are cheap and fast. Recycled film needs requalification and costs more per kilogram. Service life is a design and specification question that costs little per unit but takes discipline. Freight requires calendar planning, which costs nothing in money and a lot in project management.

How to read a footprint claim

Four questions expose almost everything. What is the boundary, cradle-to-gate or cradle-to-grave? What is the functional unit, one bag or one bag-year? Which emission factors and grid region were used? And was the study reviewed, internally or by a third party? A claim that survives those four questions is comparable; one that does not is decoration.

Watch for the three common distortions. The first is a boundary that stops at the facility gate while the language implies a full life cycle. The second is an annualised figure with an assumed service life that no test supports. The third is a headline percentage reduction measured against the worst possible baseline, usually air freight or virgin everything, which inflates the achievement without changing the product.

Offsetting deserves a separate note. An offset is not a reduction, and a footprint report that leans on offsets rather than on material and logistics changes has not reduced anything. Rank reductions first, offset the residual, and keep the two lines separate in any published figure; that separation is the single clearest signal of an honest claim.

What to ask a production partner

• Ask for the boundary and the functional unit in writing before you look at any number.
• Request the emission factors used, including the grid factor for assembly energy.
• Ask which recycled content percentages have been weld-tested, not just quoted.
• Request a bill of materials with masses so you can rebuild the inventory yourself.
• Ask what the carton cube is per size so you can model freight per unit.
• Ask whether the construction is mono-material or mixed, and what end-of-life route follows.
• Check the packaging specification against the sustainable buying checklist before sign-off.

The strongest position is a massed bill of materials rather than a single number, because it lets you rebuild the inventory with your own factors and compare two programmes on the same basis. Any partner who can produce a component mass list can support a footprint study; one who cannot is quoting a number rather than calculating one.

Two external references close the loop on method and context. Greenhouse gas accounting conventions and conversion factors are published by the US EPA, and climate context and observation data are published by NOAA; both are the kind of primary source a reviewer expects to see cited in a report.

Setting a target you can actually measure

Pick a unit and a baseline year, then commit to a number per bag rather than a percentage. A target of 1.8 kg CO2e per 20 litre bag by 2030 from a 2.26 kg baseline is measurable, auditable and comparable across sizes. A target of a 20 percent reduction is neither, because it can be met by changing the mix rather than by changing the product.

Report the levers separately as you go, so progress is attributable. Freight, recycled content, packaging and service life each have a distinct owner inside a programme, and a single blended number hides which one is working. Most brands find that the first year delivers the cheap wins in packaging and fabric, and that everything after that depends on design decisions made two seasons earlier.

Putting the numbers into a specification

A sustainability specification reads like any other: polymer family, recycled content with a test method, mono-material or mixed construction, packaging material and weight, carton cube, and the freight mode assumed in the target. Add a durability requirement, because service life is the largest lever and it has to be specified in cycles or years rather than implied.

Verify at the same cadence as any other claim. A recycled content declaration without a supporting test report is a statement, and a service life claim without an abrasion or flex test behind it is a guess. Ask for the report, check the date, and keep it with the lot number so the two can be matched if the claim is ever challenged.

Programmes that want the numbers to hold up usually standardise on one film platform and one freight plan so that a single inventory covers several sizes. Waterproof bags have been produced on our line since 2014 in an SGS-verified 4,950 m2 facility with seven production lines, 149 machines and a 200,000 piece monthly capacity; sampling runs 6 to 10 working days, bulk runs 35 to 50 days, inspection is to AQL 2.5, terms are T/T 30/70 FOB Xiamen and the minimum is 500 pieces. Material options sit in the eco-friendly range and the wider product line, and the production-side detail is in our low-carbon production guide.