Gasoline, diesel, and heating oil are all hydrocarbon fuels. Almost every drop of them available on the planet today comes from petroleum. But that isn’t written in stone. Each of these fuels is, at bottom, a different combination of hydrogen and carbon. You can make all of these fuels without using any petroleum. You just need hydrogen and carbon (together with some additives and blending agents), and a way of polymerizing them. And if you made both the hydrogen and carbon using low- or zero-carbon methods, the lifecycle environmental impacts of using fuels made from them would be much lower than those of petroleum.
None of this is impossible, or even all that difficult. In the case of hydrogen, we’ve known for over a century how to make hydrogen by splitting water with an electric current; this is electrolysis. If the electricity comes from low- or zero-carbon sources, you have a sustainable way to produce hydrogen.
Unfortunately, electrolysis is not currently suited to industrial-scale hydrogen production. So nearly all manufactured hydrogen today comes by splitting natural gas in an emission-intensive process called steam methane reformation (SMR). But concerns over the greenhouse gas (GHG) emissions of SMR, and recent advances in water-splitting, mean water-splitting is poised to come into its own.
In addition to conventional electrolysis, this could happen in any or all of the following three ways.
- Photochemical. Mimicking photosynthesis, photochemical processes use light energy reacting on artificial molecules immersed in water to initiate the electron transfer necessary to split water. The most promising of these was patented in 2006, and is now the focus of a significant Canada-U.S. research and development effort.
- Thermal electrolysis. The efficiency of electrolysis increases in the presence of significant heat. If this heat were generated using low- or zero-carbon methods, and the electricity came from similarly low- or zero-carbon sources, then thermal electrolysis would be a sustainable way to split water.
- Thermal chemical. When water is reacted with certain chemical combinations in the presence of heat, it splits into its component atoms. Again, if the heat were generated with low- or zero-carbon sources, this method of splitting water would also be sustainable.
The latter two of these will enter widespread use when nuclear reactors are developed specifically to produce hydrogen. Nuclear heat is GHG-free.
What about the carbon component of synthetic hydrocarbon fuels? Again, it is not impossible, or even all that difficult, to get carbon. The element is produced in gargantuan quantities, in the form of carbon dioxide (CO2), by coal-fired power generating plants. Coal-fired power plants in North America currently put over two billion tonnes of CO2 into the atmosphere every year.
And with the growing high-level policy interest in capturing coal-plant CO2, large amounts of high-purity gas will soon be available. In fact, the difficulties associated with storing it underground will make turning into synthetic hydrocarbon fuel all the more attractive. Utilities, used to viewing CO2 as a problematic waste, will see it as another profit center.
Imagine the environmental benefits of recycling carbon on such a grand scale. Combined with the next big development in transportation equipment—the plug-in hybrid vehicle—this will dramatically reduce transportation GHGs (which typically account for around a quarter of the GHGs in developed countries). This would be the biggest and most meaningful application of the three Rs since the concept entered into mainstream usage.
As for bonding, or polymerizing, hydrogen and carbon, we’ve known for over half a century how to do that. The Fischer-Tropsch synthesis was developed between the world wars, and has been perfected steadily since then. As early as this June, there could be an international standard for jet fuel consisting of a 50-50 blend of petroleum and FT fuel.
Make no mistake, this will happen. The question is, how rude will be the wake-up call? I think it was Schumpeter who said that technology is impatient and impolite. The age of low-carbon hydrocarbons is nearly upon us and almost nobody knows it. A lot of noses are about to go out of joint.
[…] This all hangs on our ability to manufacture low-carbon hydrogen on a massive scale. And that means developing better ways than conventional water electrolysis using wind or solar power. The two most promising approaches are splitting water with (1) solar light, and (2) nuclear energy to provide heat and electricity. For more detail, see this article. […]