One of the surprising climate stories of 2022 was the rapid emergence of hydrogen as an immediate, not just potential, decarbonization technology. Major and unprecedented investments, both from government and the private sector, were initiated this year in Europe, the U.S., China and Japan. But while hydrogen technology is growing in popularity, questions remain: Can it be one of the biggest breakthroughs for climate mitigation, or is it largely a distraction?
It's likely a mixture: a viable, long-sought, low-carbon option for hard-to-electrify sectors like steel, chemicals and aviation, but also a clever oil industry ploy to extend the use of fossil fuels in sectors like power generation, road transport and home heating, which are more easily and affordably powered from the grid.
Only hydrogen that's produced by using renewable power to split water molecules into hydrogen and oxygen can truly be called carbon-free. But that electrolysis process wastes about 30% of the renewable energy used.
Hydrogen sourced from fossil fuels — whether linked to efforts to capture and sequester the CO2 or not — is not a reliably low-emission fuel.
To offer a genuine climate solution, hydrogen must be electrolyzed with either purpose-built renewable sources or drawn from renewable electricity flowing through grids that have already minimized their use of fossil fuel. Otherwise, making hydrogen as a fuel could well result in greater use of coal, oil or gas for generating electricity.
Even in the best case, hydrogen is a low-emission fuel, but not zero-emission. When combusted, it creates oxides of nitrogen. Even when used in fuel cells, climate risk remains. If leaked as a fugitive gas, hydrogen is itself a greenhouse gas, and it also interferes with the processes by which methane, a powerful greenhouse gas, is broken up and neutralized.
In the long term, the availability of green hydrogen is limited only by the amount of renewable generating capacity, access to water and the manufacturing capacity for ever greater amounts of electrolyzers, but that future state is still far away. No major current energy grid has sufficient surplus renewable power to warrant the diversion of wind and solar capacity on a large scale to hydrogen electrolysis.
Much of the focus on hydrogen, until recently, has been for transportation use. But electric batteries, which can use renewable power at much higher efficiency and continue to get lighter and cheaper with each year of innovation, are likely to be the dominant technology for powering road transport, from scooters and motorcycles to passenger cars to 40-ton long-haul trucks. But there are still transport uses where hydrogen's lighter weight may make it useful. For example, hydrogen may prove necessary to long-distance aviation and maritime shipping, since battery solutions for those energy-intensive uses may remain prohibitively heavy well into the future.
Hydrogen can also be used to produce synthetic hydrocarbons for fertilizer and chemical production, and can be substituted for fossil carbon in the production of steel. In these cases, we can't directly electrify — hydrogen would be replacing carbon-rich chemical feedstocks.
Indeed, sectors that are difficult to electrify, and therefore likely appropriate for hydrogen, amount to 25% of end-use energy demand in advanced economies. So the investment in scaling up electrolysis, and the renewable energy needed to power it, remains a major, robust and worthwhile challenge.
Still, in many or most energy end-uses, direct electrification from the renewable generation is much more efficient than the roundabout process of turning renewable electrons into hydrogen or, even less efficiently, into a hydrogen-derived synthetic fuel.
- Turning green hydrogen into methane and then regenerating power in a turbine wastes 80% of the energy originally captured from the sun or wind. Hydrogen fuel cells might be a niche long-term electricity storage technology, but not a power mainstay.
- Using a hydrogen-derived liquid fuel to power a truck takes five times as much renewable electricity as charging the batteries needed to transport an equivalent amount of freight. Almost all trucking will be better off powered with batteries than hydrogen fuel cells.
- Heating a building with e-methane originally sourced from renewable electrons takes 10 times as much energy as simply using a heat pump. We don't need to keep our gas pipelines in place for the hydrogen future.
In other words, all proposals to use hydrogen for road transport, heating and cooling buildings, or as a primary generating fuel ignore hydrogen's most effective role: It's the caviar of alternative fuels, not the meat and potatoes.
Some current proposals for hydrogen are, in all honesty, overhyped delay tactics, somewhat akin to the coal industry's decades-long campaign for the illusory promise of "clean coal." Gas utilities in 26 states have asked for ratepayer funds to test "blending" hydrogen into methane pipelines to power plants, factories and other large buildings. They argue this is somehow an "efficient" reuse of their infrastructure. It isn't.
The existing pipeline network can handle a mixture of only 6% hydrogen by energy, with the remaining 94% consisting of methane. Even if the pipeline blend can be increased through partial retrofitting, that 6% limit cannot be substantially exceeded until every single factory, power plant, furnace, water heater and stove on that segment of pipeline has been replaced with a hydrogen-compatible, high-temperature new model.
Of course the gas industry knows this. It hopes to keep on shipping methane to their customers for another 20 years while pretending to prepare for a replacement with "clean fuel." Eventually its leading companies will concede that their pipelines and customer furnaces and boilers can only handle methane — and the cheapest way, even 20 years from now, to obtain methane will be ... burning fossil fuels!
There is no identified low-carbon conversion strategy for retrofitting existing gas pipelines to to deliver hydrogen, or for households to burn it. We will, however, need to have hydrogen available in our industrial centers and at major ports and airline terminals. Those locations will also need superb grid connectivity for their electrical needs. Investing in an advanced grid to handle electrolysis would avoid the necessity of developing and building hydrogen pipelines. It's much easier to ship electrons than gas — and then to turn them into gas only in the infrequent cases where we can't more cheaply use electricity.
