Purina had two jobs for one small bag. The soft plastic around its ONE Bifensis dry cat food had to keep the food fresh. The company also wanted to reduce its dependence on newly made plastic. Its answer was to buy chemically recycled plastic through a system called mass balance, then describe the dry-range packs as a mix of 30 per cent recycled plastic and 70 per cent virgin plastic.1
That sounds like a recipe for the bag. It is not quite one.
In mass balance, recycled and fossil feedstocks enter a shared plastics plant. A ledger follows the amount of recycled input through the system and assigns that amount to eligible products after process losses. The system can be audited without keeping every recycled molecule in a separate pipe. That is its practical value.
Purina's own UK explanation supplies the important turn. The company says it cannot tell exactly how much recycled plastic is in a specific bag. It can say that a defined amount was used to make a group of bags, with the recycled share varying between them.2 The 30 per cent is therefore an allocation across production, not a laboratory reading of the pack in your hand.
Then the bag reaches a second system. Purina says its new ONE packaging is technically recyclable in the UK, but tells households not to put it in home recycling. The empty bag must go to a larger supermarket instead.3 That extra instruction reveals a distinction the claim on the pack cannot answer: buying recycled input, making a pack compatible with recycling and actually returning its material to use are three different achievements.
Why plastics makers need the ledger
Chemical recycling breaks waste plastic into raw ingredients for new plastic. Those ingredients can enter the same large plant as oil- and gas-based ones. The plant may make several materials at once, so the streams mix.
The European Commission set out the method in rules for recycled content in plastic beverage bottles. When recycled material mixes with primary raw material, its share in each output is usually unknown. Mass balance keeps track another way. The weight from eligible used plastic must match the weight assigned to products and process losses.4
The rules also set limits. An input can be assigned only to a product it could really become. The balance cannot fall below zero. Under this beverage-bottle method, the period lasts no more than three months and stays within one site.4
ISCC PLUS is a voluntary system that certifies this type of supply chain. It says the certified input must arrive at the site. The plant must deduct losses and stay within its real output. The input must also have a possible chemical path to the product that gets the credit.5
These checks make mass balance useful without making it physical tracing. A small flow of recycled raw material can enter plants built for much larger fossil flows. The ledger can prove that contribution, even when no one can follow each molecule.
Britain will recognise the method for Plastic Packaging Tax from 1 April 2027. HM Revenue & Customs will require certified firms from the recycler to the pack maker. Each batch will carry papers that record the assigned amount. Firms must keep site records, count losses and avoid a negative balance.6 Those rules guard the ledger. They do not measure one finished bag, and they do not prove that Purina's bag will qualify.
The recycled input is real, but the number applies to the wider system. It is not a test result for the object in front of you.
That gives a buyer a simple first question: what does the percentage measure? Physical content is material shown to be in the product. Mass balance is input assigned within a controlled system. A certificate can make the second claim sound without turning it into the first.
Purina's change can help demand for recycled raw material grow. The number covers that supply-chain step. Buyers need other records for a bag's exact content, total production effect and route after use.
Collection is only the start of the second journey
The scale of the gap appears in a 2026 study of English household film. It estimated that 392,000 tonnes enters household waste each year. Councils collect about 15,000 tonnes for recycling, or four per cent. Store schemes collect less than 5,000 tonnes, around one per cent.7 These are figures for all household film, not Purina bags. They count collection, not finished recycling.
The same study found about 145,000 tonnes of UK film-sorting capacity. It found about 139,000 tonnes of reprocessing capacity. Much of that plant handles cleaner commercial film or rigid plastic instead. Home film can lose out because it is dirtier and less even. The study also found limited UK markets for the material made from it.7
England has delayed required home collection of plastic film until 1 April 2030.7 For now, a buyer must still use the special drop-off named by the pack maker.
If the bag enters normal rubbish, its route depends on the local waste contract. One possible route is an energy-from-waste plant.8 UK policy says those plants release fossil carbon because plastics are mixed into the waste.8 Heat and power from the plant can be better than landfill for waste that cannot be recycled. The plastic itself is still lost as a material.
One bag adds only a tiny amount, and its exact fossil share is unknown. The wider physical link is clear. Human activities, mainly through greenhouse-gas emissions, have caused global warming, according to the Intergovernmental Panel on Climate Change. It also reports broad harm and losses for nature and people from the changes already under way.9
Taking the empty bag to an accepted shop can keep it out of normal rubbish. The next steps still have to work. A sorter must recognise the film. Dirt and wrong materials must come out. A recycling plant must be able to use the pack, and someone must buy the new resin.
This investigation continues below.
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Better pack design still needs a working recycling system
A European research team modelled those steps for household flexible plastic. Its starting case sent the multi-material film to energy recovery or landfill. Two new cases added better sorting and recycling. They then used recovered polyethylene in packs built mainly from one type of plastic.
Across six environmental scores, the new cases cut the modelled pressure by 16 to 52 per cent against the starting case. These were model comparisons, not measurements of how much plastic was recycled. The study examined European household film. So its results cannot tell us what happens to this Purina bag after a British shop bin. Some recycling steps were still at pilot or partly industrial scale.10
Even so, the model did not make a closed loop. Material was lost during collection, sorting and recycling. Food safety and pack performance also limited how much used resin could return to sensitive packs.10
Guidance from the United Nations' work on plastic waste describes the same choice. Layers made from several materials can keep food fresh with little weight. Yet those layers can be hard to split and may make poor recycled plastic. A pack based on one plastic type can be easier to process. Coatings, inks and food-contact rules may still get in the way, while weaker protection can waste food.11
For a pack to cycle well, its full design must fit the real recycling plant. Its seals, print and barriers must work in that process or come apart cleanly. Every separated part needs its own route. The collection must reach the place where the pack is sold, and the recovered resin needs a buyer who can keep its value.
Tesco's current report supplies one route beyond a large-store bin. It says collected soft plastics are sorted to remove unsuitable items and then processed. Where possible, they become bags for life, garden furniture or planters.12 This is retailer-wide evidence, not a trace of this Purina bag or proof that it returns as equal-quality film.
Tesco's report still leaves a product-level gap. Evidence that closes it would link a collected batch to a named reprocessor, record how much usable resin came out and name the products that received it. The supermarket drop-off remains the lower-regret action, not proof that this bag was recycled.
Purina's use of recycled raw material is a step away from virgin plastic. It can help a young supply chain grow. The aim beyond it is a necessary pack with a clear design and a proven local path back to equal use. That path must also protect the food well enough to avoid waste.