Analysis - CO2 accounting can mislead

Organisations and the government need to consider how to make measurements of carbon emissions from buildings more dynamic to factor in when electricity is used, according to consultants.

WSP|Parsons Brinckerhoff analysed the system used in UK building regulations and the Greenhouse Gas (GHG) Protocol to calculate carbon dioxide emissions from the energy consumed. These use an ‘emissions factor’, a single number, representing the average carbon of a country’s grid.

The consultancy compared this with the carbon emissions for every half-hourly period over the same year to demonstrate differences in intensity levels. It found that the amount of carbon emitted can differ widely depending on the time of day, season and year.

This has increasingly become an issue with more renewable energy feeding the grid causing greater fluctuate than in the past, according to Barny Evans, sustainability and energy expert at WSP|Parsons Brinckerhoff.

Companies trying to reduce carbon emissions by using energy storage would pay more in climate change levy and report higher emissions than those that are not under the current accounting methodology, he said.

Current accounting methods could also lead to bad decisions, such as prioritising solar energy over energy-efficient lighting, even though solar produces most electricity in the middle of the day in summer, when energy demand is lowest. It also disincentivises energy storage, he said.

Evans suggested that organisations and the government trial reporting their carbon emissions taking into account time of use. ‘We need to move to an agreed methodology that would reflect reality better,’ he said.

Cynthia Cummis, director of private sector climate mitigation work at the World Resources Institute, which developed the GHG Protocol, said the study provided a good area for further research. ‘The more accurate emissions factors are, the more useful they are for decision-making purposes,’ she said.

Bastian Buck, standards director at the Global Reporting Initiative, said more energy-intensive industries would have greater awareness of the fluctuations in emissions than those based in offices, because they tend to manage their energy more actively.


Catherine Early is a freelance journalist.

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