§ Ms. RuddockTo ask the Secretary of State for the Environment what is the carbon coefficient assumed for motor spirit and derv in producing carbon dioxide emissions; and what are the latest estimates of carbon dioxide emissions in the transport sector, broken down into road, rail and air transport.
§ Mrs. Virginia Bottomley[holding answer 29 June 1989]: Estimates of carbon dioxide emissions from fuels are made by multiplying the fuel consumption figures by a factor which is the assumed carbon content of the fuel in question. These factors are subject to constant revision as more information becomes available from suppliers about the carbon content of their fuels. The factors used in calculating carbon dioxide emissions from petrol and derv are 855g/kg and 857g/kg of fuel used respectively.
The most recent estimates of carbon dioxide emissions from road, rail and air transport for 1987 are based on 61W information supplied by Warren Spring laboratory. Both the carbon content of fuel and fuel consumption figures are subject to revision. These are the current best estimates available. In 1987, 96.2 million tonnes of carbon dioxide were emitted by road transport. The figures for rail and air transport are 2.2 million tonnes and 18.4 million tonnes of carbon dioxide respectively. Emissions from aircraft using fuel supplied in the United Kingdom will not all occur in United Kingdom air space. The figure of 18.4 million tonnes is an estimate of emissions occurring world wide from aircraft fuel supplied originally in the United Kingdom. The figures given here differ slightly from those published in the Department's "Digest of Environmental Protection and Water Statistics 1988", because of updating.