# How do I count CO2 from burning coal washery rejects in a power plant?

Canonical: https://senseible.earth/answers/coal-washery-rejects-power-co2

The same way as coal: tonnes burnt times carbon content times 44/12. Rejects carry much more ash and much less energy than run of mine coal, so the CO2 per tonne is lower but the CO2 per kWh is usually higher. Use a lab analysis of the rejects you burn, not a coal default.

## Calculation

- Tonnes burnt from weighbridge records.
- Carbon content or gross calorific value from lab tests on each lot.
- CO2 = tonnes x carbon fraction x 44/12, or energy x a coal factor matched to the rejects.

## Why per kWh can rise

High ash lowers boiler efficiency and raises auxiliary power, so more fuel carbon is burnt for each kWh sent out. Calculate per kWh from your own heat rate.

## Who reports it

The plant burning the rejects reports the CO2 as Scope 1. The washery that sells them does not count it again.

## What Senseible does here

Senseible reads fuel, electricity and freight invoices into a dated, fingerprinted record per site, so each figure you send a buyer can be traced back to the documents behind it.

- [Indian coal emissions by GCV](https://senseible.earth/answers/indian-coal-emissions-by-gcv)
- [Coal power CO2 per kWh](https://senseible.earth/answers/coal-power-plant-co2-per-kwh-heat-rate)
- [Opencast mine methane](https://senseible.earth/answers/opencast-coal-mine-methane-and-diesel)

Sources: [IPCC 2006 Guidelines, Volume 2 Energy (fuel defaults)](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-10-21.