Natural gas gas is often described as the cleanest fossil fuel. It produces 25–30% and 40–45% less carbon dioxide per joule delivered than oil and coal respectively, and potentially fewer pollutants than other hydrocarbon fuels. However, in absolute terms, it comprises a substantial percentage of human carbon emissions, and this contribution is projected to grow. According to the IPCC Fourth Assessment Report, in 2004, natural gas produced about 5.3 billion tons a year of emissions, while coal and oil produced 10.6 and 10.2 billion tons respectively. According to an updated version of the Special Report on Emissions Scenario by 2030, natural gas
Environmental impact of hydraulic fracturing life cycle of oil or coal. Until recently, Canadian provinces such as Alberta, Saskatchewan, and Nova Scotia produced over half of their electricity from coal combustion whereas Ontario has already completely phased out coal-powered electricity. Switching from coal- to natural gas-powered electricity can reduce carbon dioxide emissions by ~50% and also decrease the amount of NOx and SOx emitted to atmosphere. Lack of baseline data or before-and-after hydraulic fracturing sample collection and analysis makes it challenging to quantify environmental impacts (if any) resulting from hydraulic fracturing. Hydraulic fracturing fluids include proppants and other substances, which may include toxic chemicals. In