CHALLENGE URBAN


Heat pumps are seen as crucial to cutting carbon emissions from the built environment. But, writes Roger Courtney, this approach may not be practicable when it comes to heating urban environments


W


ith the UK having set itself a target of an 80% cut in greenhouse gas (GHG) emissions by 2050, compared


with 1990 levels, it is widely accepted that ‘decarbonising’ both the built environment and energy supplies is vital to achieving this reduction. The built environment is, of course, a signifi cant contributor to carbon dioxide emissions. But while CO2 is the main component


of GHG emissions, other gases (notably methane from agricultural processes) contribute to the total. In its Fourth Carbon Budget report (December 2010), the Committee on Climate Change (CCC), an independent advisory body established under the Climate Change Act 2008, noted that emissions from international shipping and aviation were not included in the 1990 baseline. The CCC expressed the view that these should be included when considering the 2050 target. Taking this into account, and assessing that


a reduction in emissions of gases other than CO2 will be more difficult to reduce than the CO2 contribution, the CCC concluded


34 CIBSE Journal August 2011


that achieving the 2050 target for GHGs will require a 90% reduction in CO2 emissions compared with the 1990 baseline of around 600m tonnes (MT). This means that CO2 emissions will need to be reduced to around 60MT by 2050. UK CO2 emissions in 2008 were some


490MT; Table 1 shows the approximate distribution across different forms of fossil fuel use. The scale of reduction required between now and 2050 is clearly very challenging. The CCC has projected a rapid decline in


the carbon intensity of electricity generation through the construction of nuclear and carbon-capture-and-storage plants, and from the growth of renewable sources. The potential for reductions in transport and industry will depend on developments in battery technology and biofuels (including the availability of the latter) but achievement of the 60MT target is likely to require reductions of around 80% from 2008 levels in emissions from transport and industry. A possible distribution of 2050 emissions


across the various sectors is shown in Table 2. While these figures represent only one


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