Ocean Plastics

No. The model makes no comparison between materials and no case for substituting one for another. It treats leakage as a property of the collection and waste-management system rather than of the polymer — a well-managed system leaks little and a poorly managed one leaks a lot, whatever the material is. Its conclusion, that closing the leakage pathway is the only intervention which changes the endpoint rather than the schedule, is an argument for investment in collection, recovery and closed-loop design.

The model cannot answer that, and it would be a misuse of it to say so. A full comparison would need to account for production energy, feedstock, mass, transport and end-of-life recovery, and for most of those the ranking depends on how many times the packaging is reused and how far it travels. What the model does show is narrower: whatever material is chosen, an open loop accumulates and a closed one does not.

Two assumptions, both adjustable. It can start from a higher estimate of what is already in the ocean, because published estimates differ by more than a factor of two. And it holds the leakage rate constant, where the OECD baseline assumes waste management keeps improving — the mismanaged share of waste falling from 22% to 15% by 2060 without new policy. Select the OECD starting stock and move leakage to the open marker to adopt their position; the stock still passes half a gigatonne and keeps climbing.

Three published estimates are offered, and they disagree substantially: 140 Mt at 2019 from the OECD, over 150 Mt at 2015 from the World Economic Forum and the Ellen MacArthur Foundation, and 263 Mt at 2015 from Kaandorp et al. in Science Advances. Worth noting that the second of these is widely requoted as 165 Mt, which is the same figure expressed in US short tons rather than tonnes.

It fragments long before it mineralises, and the degradation half-life is adjustable in the model so you can test optimistic assumptions. Even reducing it from 450 years to 20 leaves the stock rising, because the inflow outpaces the loss. One caution: the model tracks mass only. Fragmentation conserves mass while multiplying particle count, so exposure grows faster than this curve shows.

The arithmetic is stark. The largest such operation in the world recovered around 25 million kg in its best year, against roughly 11 million tonnes entering the ocean annually — a ratio of about 0.2%. Set removal to one hundred times current global capacity in the model and the 2100 figure barely moves. Removal addresses stock that has already escaped; it does not act on the flow.

No. The leakage rate is an effective, all-source rate fitted to estimates of total plastic in the ocean, so it already covers fishing gear, agricultural film, textile microfibres and tyre wear as well as packaging. Two of those behave differently from the rest: tyre wear releases an estimated 0.81 kg per person per year globally and accounts for 5–10% of all ocean plastic (Kole et al., 2017), and synthetic textiles shed an estimated 25–500 g per person per year in Europe (European Environment Agency, 2022). Both arrive as microplastic already, having never been a bottle or a bag, so neither is reachable by deposit schemes, beach cleans or surface collection. The bottle figures in the tool are a unit of mass, not a claim about what the plastic was.

Because tonnages are hard to picture and per-person figures are not. Nothing in the model assumes all plastic is bottles; a 1.5-litre PET bottle at about 35 grams is used purely as a unit of visualisation, applied to total plastic mass divided by world population.

Yes, with attribution to Hoskins Circular and a link to this page. The complete model specification — the equation, every parameter with its range and source, the 1950–2015 production series and results for six named scenarios — is published at ocean-plastic-model.json so the model can be replicated or criticised independently. Any particular set of assumptions can be linked directly by query string.

It doesn't. In the model, raising removal capacity lowers the absolute microplastic stock, because macro plastic that has been collected is no longer available to fragment. The second chart shows a difference rather than a level: microplastic in excess of what you would get by starting removal now. That curve rises with removal capacity because the more you could have collected, the more is forfeited by waiting.

No. It is an illustrative model whose outputs depend entirely on the assumptions selected, and it simplifies heavily: a single well-mixed pool, no sediment burial or beaching, no regional or polymer detail, mass basis only. Reference values are drawn from published sources whose authors have neither reviewed nor endorsed this tool.