Mitigation of peak oil is another alternative, and combined cycle power generation using natural gas is the cleanest source of power available using fossil fuels, producing about 30% less carbon dioxide than burning petroleum and about 45% less than burning coal. The major difficulty in the use of natural gas is transportation and storage because of its low density. Natural gas pipelines are economical, but are impractical across oceans. Due to its high energy density and ease of handling, oil has a unique role as a transportation fuel. There are, however, a number of possible alternatives. Among the biofuels the use of bioethanol and
Coal in Australia of production was exported (389 Mt out of 503 Mt total). Coal mining in Australia has been criticized by members of the environmental movement, due to carbon dioxide emissions during combustion. This criticism is primarily directed at thermal coal, for its connection to coal-fired power stations as a major source of carbon dioxide emissions, and the link to climate change and the effects of global warming on Australia. The burning of coal for electricity produces 29% of Australia's total greenhouse gas emissions, based on 2013-2014 Clean Energy Regulator data. The Carbon Pollution Reduction Scheme, which followed the draft report in