Published in mid-August in Energy Science & Engineering, the report “How green is blue hydrogen”, the result of research by scientists from Stanford and Cornell Universities, caused quite a controversy and reverberated far beyond the industry. The results, obtained by Robert Howarth and Mark Jacobson, suggest that blue hydrogen pointed so far as an environmentally and economically beneficial alternative to grey hydrogen, is in fact far from low carbon.
In the past two weeks, many new questions have arisen around hydrogen, which, not without reason, has long been pointed by experts as a remedy for the pollution generated by the burning of fossil fuels. Methods of its production and possibilities of application in industry, power engineering, and transport have been known and implemented for years. But they are particularly important now, as the growing effects of climate change increasingly affect our daily lives and threaten the future of the planet. The increased mobilization of representatives of governments, international organizations, and companies in the area of production and exploitation of hydrogen in the economy is not accidental. It is going to play an important role in the decarbonization process, especially in those sectors where electrification is difficult, expensive, or simply impossible, such as long-distance freight transport and air transport.
Blue hydrogen
Most of the hydrogen currently produced in the world is exploited in the refining and food industries. Unfortunately, it is still about 95% gray hydrogen from fossil fuel processing. This is an extremely carbon-intensive process that generates more than 800 million tons of annual carbon dioxide emissions into the atmosphere and accounts for 6% of total global natural gas consumption. In direct opposition to it stays green hydrogen, which is the only one characterized by total zero-emission, achieved thanks to using electric energy from renewable sources in the production process.
The focus of Howarth and Jacobson’s study, blue hydrogen, has so far been described by the hydrogen strategies of some countries around the world, including Poland, as a transition stage between fossil fuel hydrogen and green hydrogen. Due to the still-high costs of hydrogen production from RES, it was supposed to guarantee a gradual and affordable transformation, which would eventually move towards zero-emission solutions.
Blue hydrogen is a relatively new term and refers to hydrogen which, like grey hydrogen, is produced by steam reforming of natural gas, but thanks to the application of carbon capture and storage (CCS) methods in the process enables reduction of emissions – according to assumptions, even by 50-90%. It is hardly surprising that the giants of the gas industry have long been emphasizing its potential and pointing out that it is the best and the most beneficial alternative to fuels in the energy and transport sectors.
„How green is blue hydrogen?”
A study by Robert Howarth and Mark Jacobson has decisively changed the way people think about blue hydrogen and has called into question the environmental benefits and thus the validity of its use in the economy. The researchers’ analysis suggests that blue hydrogen, described as a fuel with zero or low greenhouse gas emissions, can in fact generate much higher levels of greenhouse gas emissions than traditional fossil fuels. Why do the obtained results contradict the commonly known assumptions about this method of hydrogen production?
The answer is simple. Most research has focused primarily on the production process itself and measuring the carbon capture potential. Howarth and Jacobson took their analysis a step further and considered the full life cycle of blue hydrogen produced from natural gas – from gas extraction, through the production process and CO₂ capture methods.
According to them, total carbon dioxide emissions for blue hydrogen must be considered as the sum of emissions from the SMR, emissions from the energy used for heat and pressure to drive the process, emissions from the energy used to drive the carbon capture equipment, and indirect emissions associated with the production and transportation of natural gas.
Based on numerous studies, Howarth and Jacobson assumed that about 3.5% of the natural gas already enters the atmosphere during mining. They also took into account the emissions produced during electricity generation. The results are clear. The total greenhouse gas footprint of blue hydrogen is more than 20% higher than burning conventional fuels. Even with the more optimistic scenario, where the gas leakage rate was at about 1.54%, emissions were only slightly reduced and still remained high relative to burning natural gas alone.
What is the actual level of blue hydrogen emissions?
Determining carbon capture capacity is extremely difficult. According to the researchers, there are currently only two plants in the world that commercially produce blue hydrogen – a Shell-owned company in Canada and a plant operated by Air Products in the state of Texas. Hence, it is difficult to obtain data to estimate the actual process parameters. For carbon dioxide generated in the SMR the reported capture efficiency ranges from 53 to 90%. Data released by Shell shows an average efficiency of 78.8%, with daily statistics that can fluctuate to as low as 15%.
In the baseline analysis, Howarth and Jacobson propose a CO₂ capture rate of 85% – midway between the average indicated by Shell and the generally accepted best case of 90%. This results in 5.8 g CO₂ per MJ emitted from the reforming process using capture methods. Importantly, carbon capture focuses solely on the process itself. This means that the carbon dioxide produced by burning natural gas (which provides the heat and pressure necessary for the combustion) can volatilize increasing emissions and lowering the final average capture efficiency rate.
It is worth noting that the study did not take into account emissions of other greenhouse gases (e.g., nitrous oxide) and, in addition to carbon dioxide, focused only on emissions of methane, which is an extremely potent greenhouse gas. Its impact on climate warming could be up to 100 times greater than CO₂ – up to 25% of the net global warming that has occurred in recent decades could be caused by methane, according to scientists.
The results of the study show that greenhouse gas emissions resulting from the production of blue hydrogen are high, precisely because of the release of carbon dioxide and methane over the full life cycle of hydrogen. Total carbon dioxide equivalent emissions for blue hydrogen are only 9-12% lower than for gray hydrogen, and methane emissions are much higher due to the increased use of natural gas for CO₂ capture. This results in a greenhouse footprint that is 20% higher than burning natural gas and coal and up to 60% higher than burning diesel for heating.
What next with blue hydrogen?
Blue hydrogen was named the future of Poland and many other countries still strongly dependent on the exploitation of fossil fuels. In light of new research and, more importantly, stricter emissions regulations, it is difficult to say that it is still any kind of alternative to fossil fuels. The potential of green hydrogen as the only guarantee for achieving the 2050 zero-emission targets is highlighted all the more strongly today.
