How this calculator works
Plastic waste ends in four places: recycling, incineration, landfill and mismanagement. The OECD estimates that of the roughly 353 million tonnes generated in 2019, 9 percent was recycled, 19 percent incinerated, 50 percent landfilled and 22 percent mismanaged. A policy does not change every flow. It covers a share of the waste stream, such as single-use bags, and works on some of what it covers. Multiplying the waste by the coverage and by the effectiveness gives the plastic removed from the stream, adjusted for how completely each kind of policy removes it: a ban removes the item entirely, recycling removes less because some collected material is rejected, and producer responsibility improves collection without changing the product. The remaining waste keeps the baseline mix, so mismanaged waste and ocean leakage fall in proportion. Jambeck and colleagues estimated that a few percent of mismanaged coastal waste reaches the ocean each year, which is the leakage rate used here.
Formula
covered plastic = total waste x coverage. avoided plastic = covered x effectiveness x policy share, where the shares are 1.0 for a ban, 0.9 for reduction, 0.6 for recycling and 0.8 for producer responsibility. mismanaged before = waste x baseline mismanaged share. mismanaged after = (waste - avoided) x baseline mismanaged share. ocean leakage = mismanaged x leakage share. emissions avoided = avoided x 2.0 kg CO2e per kg, which in million tonnes is twice the avoided million tonnes.
Worked example
With 353 Mt of waste, a ban covering 30 percent of the stream at 40 percent effectiveness removes 353 x 0.30 x 0.40 x 1.0 = 42.4 Mt a year. Mismanaged waste falls from 353 x 0.22 = 77.7 Mt to (353 - 42.4) x 0.22 = 68.3 Mt. At a 3 percent leakage rate, ocean input falls from 2.33 to 2.05 Mt a year. The production emissions avoided are 42.4 x 2 = 84.7 Mt CO2e.
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Frequently asked questions
Are the policy effectiveness figures real?
No. They are transparent assumptions to show the arithmetic of coverage and effectiveness. A real policy evaluation measures the change in waste against a baseline with a control area, and even then the effect is hard to separate from economic growth and consumer behaviour.
Why does recycling remove less than a ban?
A ban stops the item being made. Recycling collects it, sorts it, and loses a share to contamination and rejects, and the recycled resin replaces only part of virgin production. Recycling is valuable, but per tonne covered it reduces less than not making the item.
Is the ocean leakage figure global?
It is a rough global average. Leakage is far higher in regions with poor waste collection and close to zero where collection and landfill are well managed. Enter a lower leakage rate for a high-income country and a higher one for a region where most waste is uncollected.
Does the carbon figure include incineration?
No. It counts the production emissions of plastic that is no longer made. If the avoided plastic would have been incinerated instead of landfilled, there would also be emissions from burning, which would change the comparison. The production saving is the conservative part of the picture.
Sources
- OECD (2022): Global Plastics Outlook, economic drivers, environmental impacts and policy options
- Jambeck et al. (2015), Plastic waste inputs from land into the ocean, Science
- Geyer, Jambeck and Law (2017), Production, use and fate of all plastics ever made, Science Advances
- Environment and Climate Change Canada: emission factors and reference values for greenhouse gas quantification (national inventory edition, updated annually)