The cleanest solution, green hydrogen, uses electricity from carbon neutral energy sources to split water into hydrogen and oxygen. But this is highly inefficient. By the time the hydrogen is ultimately consumed for heat or electricity, more than half of the energy content of the original electricity is lost (see also this blog post).
New concerns over hydrogen
Most recently, a third challenge has come to light: hydrogen leakage. Until recently, leakage had simply been viewed as an economic loss. But there is far more at stake. Leaked hydrogen reacts with scarce OH radicals in the atmosphere. That leaves fewer OH radicals to react with methane. Leaked hydrogen thus extends methane’s atmospheric lifetime, worsening its effects on the climate.
Researchers examined these factors together to evaluate the climate benefits of various hydrogen usage scenarios.4 Scenarios involving only green hydrogen deliver strong climate benefits relative to the fossil fuels that are replaced, assuming hydrogen leakage rates to be low. But as soon as blue hydrogen is introduced to the mix, and hydrogen leakage rates are assumed to be higher, the benefits decline, and in some cases disappear altogether. For example, a scenario with 30% blue hydrogen and leakage rates exceeding 3% would lead to more warming over a 20-year period than would the fossil fuels hydrogen replaces.5
How much hydrogen would actually leak?
The answer is that we don’t know, because very little research has been done. There is reason to believe that hydrogen would leak more than natural gas, and some estimates of natural gas leakage put it over 3%.6 The most comprehensive study to date estimates the likely leakage rate for hydrogen to be 2.9 – 5.6% but acknowledges that it might be higher.7
There are powerful lobbying groups urging policy makers to expand the use of hydrogen as extensively as possible. The fact that these lobbyists are funded by oil and gas producers is no surprise. Not only does blue hydrogen make use of natural gas, but the business of distributing and selling hydrogen also matches the fossil fuel companies’ competitive advantage in the energy industry.8 Many people, me included, are extremely concerned about what ambitious plans for hydrogen usage could lead to, both for energy consumers and for the climate.