Which Intergovernmental Panel on Climate Change carbon default should I use for plastic scrap from my moulding line that is burnt: 75 percent, 80 percent or 50 percent?

In the Intergovernmental Panel on Climate Change (IPCC) 2006 waste guide, plastics carry 75 percent carbon in the municipal waste table and 80 percent in the industrial process waste table. Burnt in an incinerator, a tonne of plastic scrap gives 2.75 or 2.93 tonnes of carbon dioxide (CO2), about 7 percent apart.

The three defaults in the guide

• Table 2.4, municipal solid waste components: plastics have dry matter 100 percent, total carbon 75 percent of dry weight (range 67 to 85) and a fossil carbon fraction of 100 percent of that carbon (range 95 to 100).
• Table 2.5, industrial process waste, in percent of wet waste produced: the row "Petroleum products, Solvents, Plastics" gives total carbon 80, fossil carbon 80 and water content 0. The table says these apply only to process waste from the industries; office and similar waste is assumed to sit in municipal waste.
• Table 5.2, incineration and open burning: industrial waste has total carbon 50 percent of dry weight and 90 percent of that carbon fossil. Dry matter content is marked NA (not available). Table 5.2 gives one figure for industrial waste in general. The guide does not list what it contains, so it is not a plastics figure. Its Note 2 sends you to Table 2.5 for the industry type.

Which one fits a moulding line

Our reading: clean sprues, runners and rejects from a moulding or extrusion line are process waste from a plastics industry, so the Table 2.5 row matches by wording. Table 2.4 is titled municipal solid waste components. The waste pages already on this site use the 75 percent line. Our reading: both are IPCC defaults, so either is defensible if you say which and keep it the same every year.

The guide adds that where plant-specific data are available, the exact composition of the waste being incinerated should be collected and used. For a single-resin scrap stream, the carbon content on the resin supplier's data sheet beats any of the three.

Why 50 percent is not for pure plastic

The guide gives no composition for that figure. Treated as dry weight (our assumption, since the table gives no dry matter), a tonne of it gives 1.65 tonnes of CO2, 40 percent below the 2.75 from Table 2.4. Using it on clean plastic would understate the burn.

Oxidation is 100 percent for incineration in Table 5.2. The guide gives no open-burning oxidation for industrial waste; the burnt-waste page linked here uses the municipal 58 as the closest line, and covers methane and nitrous oxide.

80 tonnes of plastic scrap burnt in a year (example quantity)

• Equation: waste x dry matter x carbon x fossil fraction x oxidation x 44/12
• Table 2.4: 80,000 kg x 1.00 x 0.75 x 1.00 x 1.0 x 44/12 = 220,000 kg, 220 t of CO2
• Table 2.5: 80,000 kg x 0.80 x 44/12 = 234,667 kg, 234.7 t of CO2
• Gap between the two: 14.7 t, 6.7 percent of 220
• Table 2.4 carbon range of 67 to 85 percent: 196.5 t to 249.3 t
• Table 5.2 average treated as dry: 80,000 x 0.50 x 0.90 x 44/12 = 132,000 kg, 132 t

Quantity is an example. Methane and nitrous oxide from burning come on top; see the linked page.

What Senseible does here

Senseible reads fuel invoices and electricity bills into dated, fingerprinted records, so your kilowatt-hours and litres are on file by date. It does not calculate waste burning. Take tonnes burnt from your own scrap register and use the arithmetic here.

• Burnt waste: oxidation, methane, nitrous oxide
• CO2 from incinerating waste
• Plastic burnt in a cement kiln
• Burning waste on your own site
• Your MSME carbon number

Sources: IPCC 2006 Guidelines, Volume 5, Chapter 2: Waste generation, composition and management data (Tables 2.4 and 2.5), IPCC 2006 Guidelines, Volume 5, Chapter 5: Incineration and open burning of waste (Table 5.2, Equation 5.1)

Last reviewed 2026-11-06. Defaults are from the 2006 guidelines. If you change the method, say so and keep it for every year. Re-check against the guidelines edition your buyer or auditor names.