Wednesday, 12 January 2011

False Viridor claims of zero or even negative carbon

Based on evidence submitted by CATI to the Assembly Petitions Committee, Dec. 2010

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.
Basic figure:
Burning 350kt/year municipal waste would emit 420kt CO2 [1 kt = 1 kilotonne = 1000 tonnes]
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.
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.

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