Natural gas is the only fossil fuel of which global proven reserves are increasing, both due to new discoveries of conventional reserves and due to new types of reserves, e.g. shale gas. Current proven and exploitable reserves amount to 60 and 20 years at current consumption level respectively.
Raw natural gas is pretreated and either liquefied into LNG and transported by tanker or transmitted by pipeline.
Because of a low carbon content and high efficiency in power production greenhouse gas emissions per kWhe natural gas based electricity are 40% - 60% lower compared with CO2 emissions for coal based electricity. The percentages include emissions for pretreatment and transportation of both fuels. Natural gas primarily consists of methane, the fossil fuel with the lowest carbon content, and produces 40% less CO2 per GJ of fuel compared to coal. Power generation based on natural gas is 30% more efficient than coal-based power generation.
The advantages mentioned above are partly offset for LNG production, because of the high energy demand for liquefaction. Long distance pipeline transmission also requires much energy and may be associated with small leakages of methane. The latter occurs in Russia especially. For both processes greenhouse gas emissions may amount to 25% compared with CO2-emissions for methane combustion.
The greenhouse gas emissions included in the ETM concern all processes mentioned above from extraction to combustion, except for emissions related to production of utilized hardware, e.g. the power plant. Interim storage of natural gas in e.g. reservoirs or salt caverns and production of shale gas have not been considered.
Natural gas contains negligible amounts of a polluting elements after conditioning. For combustion of natural gas normally only NOx emissions are relevant. NOx emissions can be reduced easily with simple technical measures, which is already standard policy requirement for power plants in the EU.
Raw gas conditioning may be associated with surface water pollution if separated heavy metals and condensable hydrocarbons are discharged on to surface water, e.g. at offshore conditioning installations. Venting or flaring of separated aromatics and other condensable hydrocarbons at conditioning plants may give air pollution and may significantly affect local air quality. This also applies to unabated SO2 emissions from conditioning plants.
All abovementioned types of pollution can be prevented with adequate abatement technologies and management.
The numbers and references used to quantify the fuel chain emissions for natural gas can be found on our 'Reference Manager'. The Fuel Chain Emissions documentation can be downloaded from here (will open in a new tab).