2.Choosing a method

You can calculate (standard method or mass balance), measure in the stack, or combine both. Most aluminium plants calculate CO2 and use the PFC methods below.

Always use the best available data: EN/ISO standards, the most accurate instruments without unreasonable cost. A cost is only "unreasonable" if it exceeds the benefit, valued at €80 per tonne CO2e; improvements up to €4 000 a year are never unreasonable. Check for better data sources once a year.

Sources: MA Annex II A.3 points 1, 6, 8 p.29-31, B.2 p.33.