RSS Feeds

Email a Friend Printer Friendly

Verification of national methane estimates now possible

April 25, 2001

New methods for verifying estimated greenhouse gas emissions, developed by scientists at Royal Holloway, University of London, will play a significant role in assessing reductions in methane emissions, important in national compliance with Kyoto protocol targets.

David Lowry, Craig Holmes, Nigel Rata and Euan Nisbet of Royal Holloway’s Department of Geology, in collaboration with Phillip O’Brien of the Martin Ryan Marine Science Institute of the National University of Ireland, have developed a package of tests for validating national statistical methane emissions estimates. Such measurements are independent of national administrations and can be made outside national borders, so therefore have a potential use in creating a basis of trust in multination agreements.

The main goal of the team’s 5-year study, just published in JGR Atmospheres [16 April 2001], was to use direct atmospheric measurements to verify official estimates of methane emissions in a major urban area, in this case London. To date, assessments of methane emission are made by very precise but often highly inaccurate ‘bottom up’ statistical calculations. For example, bovine emissions are estimated by deriving an estimate of emissions per cow and multiplying by the number of cows in the region, while landfill emissions are estimated by measuring emissions per ton of waste and multiplying by the total waste disposal in the region.

The researchers found that a combination of atmospheric concentration, isotopic and meteorological data enabled verification of statistical estimates of methane emissions from London. They were able to identify and characterise the different major sources of methane and compare the findings with existing statistical data on methane sources for the London region. The research also gives a useful insight into the seasonality of emissions and it will ultimately contribute to the understanding of global emissions distribution and reduction.

Methane is the second most important greenhouse gas in terms of its global warming potential after carbon dioxide, but its reduction is much easier and cheaper to achieve and less socially disruptive. The Kyoto protocol allows countries to meet greenhouse gas reduction targets by cutting back on gases other than CO2, so methane reduction would seem a logical priority in any bid to comply. The study demonstrates that it is possible to use isotopic monitoring to identify targets for methane reduction.

The Royal Holloway study showed that London’s methane emissions are mostly from two major sources: 80% comes from waste processing, mostly from landfill sites, and 20% comes from fossil fuels, mostly due to leakage in the gas distribution network. Furthermore, the study suggests that methane emissions for London were significantly greater, by 40-80%, than the statistical estimate for 1996/97. In the UK, most identified methods for the reduction of methane emissions from landfill are in the process of being implemented. While gas leak emissions are of a far lower order than landfill emissions, there is clearly wide scope for reducing gas leaks in UK, given a less inhibitive regulatory framework. The researchers state that gas leak reduction should become a priority in UK and European greenhouse policy, given the relative ease and potential profit of such action.

ENDS


Royal Holloway, University of London