Corrugated, moulded fibre or RPC: which for fresh produce?

Why corrugated fails in the cold chain, and what the fix costs

Standard corrugated board loses strength as it absorbs moisture, and this is the single most common packaging failure in produce cold chains. A carton rated for a stacking load at 50 percent relative humidity can lose 30 to 50 percent of its edge crush strength inside a few hours in a chiller running near 90 percent humidity, which is exactly where most fresh produce needs to sit. The failure shows up as pallet-bottom cartons bulging and buckling under the weight of the layers above, not as visible wetting, so it is easy to miss during loading and only becomes obvious after several hours in transit.

The fix is a wet-strength or wax-coated board, or a corrugated grade with a moisture-resistant coating on the liner, and it is not optional for anything moving through a cold chain longer than a same-day local delivery. Wet-strength resins raise the per-unit cost of the carton, typically a meaningful premium over standard single-wall board, and coated boards add further cost again. Buyers who standardise on plain single-wall corrugated for cold-chain export lanes to save on unit cost are usually paying for it later in collapsed pallets and rejected loads, not in the packaging invoice.

Double-wall corrugated recovers some of the lost strength margin and is worth the extra cost for bottom-tier cartons on any pallet stacked more than five or six layers high, even where the top layers can use single-wall. Mixed-wall pallets are a legitimate way to control cost without accepting the failure risk on the layers carrying the most load.

Stacking strength: how each material actually degrades

Corrugated degrades on two axes at once: humidity, covered above, and duration under load, known as creep. A carton can hold a static load comfortably for the first hours and then slowly compress over a multi-day sea voyage as the fibres yield under sustained compression, which is why a carton that looks fine leaving the packhouse can be visibly crushed on arrival with no single dramatic event in between. Ventilation holes cut into the panel faces for produce airflow reduce the compression strength further, sometimes by 15 to 30 percent depending on hole size and placement, so ventilated produce cartons need a stronger base board than a solid equivalent to hit the same net stacking load.

Moulded fibre trays are not generally stacked to the same heights as cartons in the first place: they are typically used as a tray-in-carton or tray-in-crate format, where an outer corrugated or plastic shell carries the stacking load and the moulded fibre does the cushioning and separation job inside it. Treating moulded fibre as a standalone stacking solution is a common design mistake and it fails the same way corrugated does, only faster, because the material is thinner and more open-structured.

RPC stacking strength does not meaningfully degrade with humidity or with repeated use within its rated life, which is the main reason it holds up better on long, humid ocean lanes and in high-turnover retail backrooms where cartons get re-stacked multiple times. The tradeoff is that RPC strength is fixed by mould design: you cannot upgrade a crate's rating the way you can step up to double-wall corrugated, so if a produce line's weight or fill height changes, the whole crate specification has to change with it.

Ventilation, cooling performance and protection for delicate produce

Forced-air and room cooling both depend on airflow reaching the produce, and this is where corrugated and RPC diverge most in practical terms. RPC crates are almost always designed with a fixed, generous open area on the sides and base, commonly in the 5 to 8 percent range of total surface area, which is engineered once into the mould and stays consistent crate after crate. Corrugated ventilation holes are cut per carton design and are easy to under-specify because every hole is a strength tradeoff, so corrugated cartons for produce that needs fast pre-cooling, such as berries or leafy greens, need a deliberate ventilation design rather than a generic template borrowed from a different product.

For delicate, high-value produce such as stone fruit, table grapes and soft berries, moulded fibre earns its place through individual-cell cushioning rather than stacking strength. A moulded fibre tray with separate cavities per fruit prevents the bruising that comes from fruit-on-fruit contact inside a bulk-packed carton, and this reduces shrink and rejection rates on the receiving end in a way neither plain corrugated nor a bulk-filled RPC does on its own. The realistic setup for high-value delicate produce is moulded fibre trays inside a corrugated or RPC outer, using each material for the job it is actually good at rather than asking one material to do both jobs.

RPC ventilation, once fixed by the mould, cannot be adjusted per commodity the way a corrugated ventilation pattern can, so a single RPC crate design used across multiple produce categories is a compromise on cooling performance for at least some of them.

Reverse logistics and where RPC pooling breaks down

RPC economics depend entirely on the crate coming back. A pooling provider's model works by amortising the crate's higher upfront cost across many trips, commonly 15 to 40 uses over the crate's service life depending on the pool operator and produce type, with the provider handling collection, washing and redistribution between users. Where that loop exists, meaning both the exporter and the destination retailer or wholesaler are in the same pool network and there is a reliable return leg, RPC's per-trip cost usually undercuts a single-use carton bought fresh every time.

Export lanes break this model more often than domestic distribution does. A crate shipped from a packhouse to an overseas port, through a wholesaler, into a retailer's backroom and onto a shelf has left the pool's collection network entirely unless the destination market has an equivalent pooling operator with a reciprocal or interconnected scheme. Where no return leg exists, the exporter is paying for a crate rated for dozens of trips and getting one, which is close to the worst case for RPC economics rather than the best one. This is why RPC is common on regional and domestic lanes with a strong retail-side pooling infrastructure, and far less common on long-haul export lanes to markets without an established pool operator.

Loss rate is the other reverse-logistics number that determines whether RPC pencils out. Pool operators typically budget for a single-digit percentage of crates lost or damaged per cycle on well-controlled domestic lanes; that rate climbs sharply on lanes with multiple handoffs between unrelated parties, informal wholesale markets, or any leg where the crate changes custody without a scan-based tracking step. A buyer evaluating RPC for a new lane should ask the pool provider for the actual loss rate on that specific corridor, not the headline domestic average, since the two numbers are often very different.

Retailer mandates and end-of-life claims

Large grocery retailers in several markets now specify RPC for particular produce categories, most commonly leafy greens and soft fruit, as a condition of supply into their distribution centres, driven by their own handling efficiency and sustainability reporting rather than by produce protection alone. Where a retailer mandate exists, it overrides the cost comparison: the supplier either uses the retailer's approved crate system or loses the listing, and checking the specific retailer's current packaging specification before committing to a packaging format for a new account is worth doing before, not after, the first shipment is rejected at the dock.

On end-of-life claims, corrugated and moulded fibre are both widely recyclable through standard paper and board recycling streams in most developed markets, provided they are not heavily wax-coated, and moulded fibre is additionally compostable in many municipal or industrial composting systems depending on the base fibre used. RPC's environmental claim rests on reuse rather than recyclability: a well-run pool with a high trip count has a lower material footprint per use than single-use packaging, but that claim only holds if the pooling loop is actually closed. An RPC crate that gets lost, damaged and landfilled after two or three trips because the reverse logistics broke down on an export lane has a worse footprint than the single-use corrugated carton it replaced, since it consumed more material and more transport energy per successful trip. Any reusable packaging claim in a sustainability report or retailer submission should be tied to the measured trip count on the specific lane, not to the pool's theoretical rated life.

A worked cost comparison over a season

Take a worked example, with illustrative numbers rather than a real supplier's pricing, for a mid-size packhouse shipping leafy greens on a regional lane with a genuine return leg available. A wet-strength corrugated carton suited to that cold chain costs a low single-digit dollar amount per unit, delivered, and is used once. An RPC crate suited to the same produce might cost several times that per crate to purchase outright, or carry a per-trip pooling fee in the range of a bit more than the corrugated carton's unit cost, when a pooling provider is used instead of an owned fleet.

Over a five-month season shipping several thousand units a week, the corrugated cost is simple: unit price times total units shipped, with no return leg to account for. The RPC pooling cost adds the per-trip fee across every shipment, plus the pool provider's collection and wash charges baked into that fee, minus whatever saving comes from not having to source, store and dispose of single-use cartons at the packhouse end. Modelled out, the crossover point in this kind of comparison typically lands around 12 to 15 trips per crate before RPC's higher unit cost is offset by the lower per-trip pooling fee: below that trip count, corrugated wins on total season cost even before counting the RPC-specific risks of loss and no-return-leg exposure covered above.

The practical takeaway is to run this calculation per lane, not per company. A packhouse can rationally run corrugated on its export lanes and RPC on its domestic distribution in the same season, because the trip count and return-leg reliability, not a blanket packaging policy, are what determine which material actually costs less once losses and reverse logistics are counted rather than assumed away.