Wednesday, 12 January 2011
False Viridor claims of zero or even negative carbon
The Environment Agency approved the claim in their license determination, but failed to carry out a reality check. The first point is that the energy efficiency is not the 65% assumed by Viridor, but 20-22% for this type of incinerator, after deducting electricity used in the process. Second, Viridor fail to project the decreasing bio-component of municipal waste in future years and the decreasing carbon intensity of the UK el-supply.
Avoided landfill means less methane, counted in equivalent CO2 [called CO2e]
– take as 12% of Wales total (34kt/yr) on basis of Cardiff pop'n => 4 kt CO2e/yr
=> this is less than 1% of 420kt CO2 so negligible.
Wales Waste sector total CO2e is 1.3Mt CO2e/yr (2007 fig.**) so Viridor’s 420kt adds 33%.
# The fraction of bio-carbon is waste is 50% now, projected to decrease to ~35% by 2018:
=> Viridor's emissions of 'fossil' (non-bio) CO2 is 28kt pa – which adds 20% to the 1.3Mt
How much Offset for electricity (otherwise generated by large power stations) ?
# 20-22% efficiency => twice CO2 per kWh of the worst 35% efficient coal-power
[calculation per tonne waste 9.5GJ x 21%, 1.2tCO2
per tonne coal 27GJ x 35% per t coal, (80% x 3.75) 3.0t CO2
gives ratio of power per tonne of CO2 1.7 : 3.3GJe/tCO2]
The usual units kWh/kgCO2 – to convert divide by 3.6 => a ratio 0.47 : 0.9 kWh/kg CO2
Next discount 35% of CO2 as bio-carbon (from 2018 according to Defra) and
invert the units => ratio waste incinerator : coal becomes 1400:1100 g fossil-CO2/kWh
The Offset should be calculated not against the worst coal-plant but for average baseload electricity now and into the 2020s, as the UK supply becomes lower in carbon:
# by 2016-17 the UK carbon emissions (Fig. below) are 350 gCO2/kWh, ie. one quarter of Viridor’s
# by the mid 2020s, the UK carbon emissions drop below 140 gCO2/kWh, ie. one tenth of Viridor’s
# by the mid 2020s, all Welsh electricity is to be ‘renewable’ with carbon intensity near zero.
Conclude: from the start (2015) Viridor’s incinerator would be worse (1400 v. 1100) in fossil CO2 emissions than the worst coal-fired plant and nearly 4 times worse than the UK average generation (350 in the Figure)
Viridor’s claims of zero or negative carbon are false; their incinerator would add strongly to Wales greenhouse emissions.
By the mid 2020s, Viridor’s incinerator would be 10 times worse than UK average.
** figures from Greenhouse Gas Inventories for England, Scotland, Wales and Northern Ireland: 1990 - 2007 AEAT/ENV/R/2873 Issue 1 report Sept.2009to DECC, WAG etc. www.airquality.co.uk/reports/cat07/0909231418_DA_GHGI_report_2007_maintext_Issue_1.pdf
CO2e means CO2 equivalent, which includes methane with a greenhouse factor 26
Figure: UK average CO2 emissions per kWh of electricity generated, 2006-2050
Committee on Climate Change, Building a low-carbon economy – the UK’s contribution to tackling climate change - The First Report of the Committee on Climate Change. 2008.