Reality → Energy → World energy → Transportation
For geological, environmental, and political reasons it is crucial to reduce the consumption of non-renewable oil. Electric and hydrogen-powered cars can bring down oil consumption, but presently have little impact on overall CO2 emissions [1] . Synthetically produced fuels (ranging from hydrogenated tar-like bitumen [2] through coal and gas-based liquid fuels [3] to biofuels [4] ) presently replace about 4% of world petroleum production with dim prospects for significant growth [5] . Increase of oil consumtion could be controlled by cars with lower fuel consumption and improved traffic management [6] . In the long run, there might also be breakthroughs in new biofuel technologies and 'clean' electricity generation [7] .
As long as electricity is produced mainly from coal and gas, electric cars contribute little to overall CO2 emission reduction. A hydrogen fuel cell-electric drive produces no harmful emissions and has a higher efficiency than a combustion engine (about 40% vs. 30%), but these advantages are offset by energy losses and increased emissions in the production of hydrogen from natural gas (to test the feasibility of 'green' hydrogen production, a pilot project in Germany generates hydrogen through electrolysis of water with excess wind power).
Canadian oil sands (see also Oil Sands 101 and Statistics) presently contribute about 4% to world oil production. They became the prime source of Canada's oil production and US oil imports. In comparison, indigenous US oil shale projects, envisaged at the time of the 1973 and 1979 oil shocks, never took off for economic and environmental reasons.
Coal and gas-based liquid fuels contribute about 0.5% to world oil production. The Fischer-Tropsch process provided liquid fuels from coal for the German Wehrmacht during World War II. In the 1950s, the process became the cornerstone of the world's first and only commercial coal liquefaction plant in politically isolated South Africa. Today, Sasol produces liquids from gas piped from Mozambique and has commercialized its gas-to-liquids (GTL) technology (see Oryx and Shell). On a global scale, GTL is unlikely to replace much oil due to competing gas uses and uncertain reserves.
Biofuels, consisting of ethanol and biodiesel, contribute about 4% to world fuel supply for the transport sector. Ethanol is produced through fermentation of sugar (carbon dioxide is a byproduct). The United States, with about half of world ethanol production, are the largest producer of corn-based ethanol, which accounts for about 10% of the country's gasoline consumption. Brazil, with about a third of world ethanol production, is the largest producer of sugarcane-based ethanol, which accounts for about a quarter of the country's gasoline consumption. Biodiesel is produced by chemically treating vegetable oils (mainly soybean, rape, palm oil) with methanol. The US is the largest producer, with about 15% of world biodiesel production, accounting for 3% of the country's diesel consumption.
Oil sand and oil shale operations are highly controversial, mainly due to high CO2 emissions and significant air and water pollution. Even the apparently cleaner biofuels have negative environmental and social impact. Ethanol from corn reduces carbon emissions only marginally, consumes almost as much energy as it produces, impacts the environment negatively through increased fertilizer/pesticide application, and affects commodity and food prices with global repercussions. In developing countries, similar negative economic and social effects are attributed to palm oil used as feedstock for biodiesel.
Smaller and lighter cars would reduce fuel consumption. Expansion of public transport, increased use of 'intelligent' transportation, and more active traffic management can dampen private car use and ease traffic flow.
Conceivable advances in synthetic biology might eventually lead to biofuel from algae or cellulose. Artificial photosynthesis might eventually be helpful for 'clean' production of hydrogen. Ultimately, 'clean' electricity for electric vehicles might also become available from nuclear fusion.