These figures are necessarily approximations but not without justification. We use the following figures for the calculations:
Power consumption per node = 36 Watts
Cost per kWh = $0.19
CO2 generated per MWh = 346 kg
We assume the worst possible case where all the power is generated in coal-fired powerstations. The figure of 346 kg per MWh comes from Intergovernmental Panel on Climate Change (IPCC). Guidelines for National Greenhouse Gas Inventories (2006).
Comparison with Bitcoin
In May 2020 the Bitcoin network consumed approximately 4.72TWh of electricity. Source: Digiconomist
Using the same worst-case all-coal production scenario it would have produced 1,633,120,000 kg of CO2 in just one month. The Bitcoin network consumes more electricity processing 1 transaction than the Crown network consumes in a whole day.