Quantifying vented by-product hydrogen: a case study in China

The International Energy Agency estimated that by-product hydrogen constituted 16 per cent of global hydrogen production in 2022, primarily through naphtha reforming during oil refining.

However, this definition of by-product hydrogen is quite narrow since it can also be generated through many other industrial and chemical processes like chlorine, coke, propylene or ethylene production. While some industries use a portion of this by-product hydrogen produced in the waste streams within their operations, a significant proportion has been vented into the atmosphere for decades, a practice that has been largely unnoticed by the public.

However, the venting of hydrogen can have adverse climate consequences. Recent studies analyzing hydrogen leakage have demonstrated that hydrogen’s global warming potential over 20 years could be as high as 40 times that of carbon dioxide. Consequently, estimating vented by-product hydrogen and investigating ways to mitigate this problem are important for the burgeoning hydrogen economy and to prevent any unintended climate repercussions.

By-product hydrogen is particularly significant in China, due to the strong presence of and high industrial and chemical output from the industries mentioned above. This report estimates China’s annual by-product hydrogen production from nine major industrial and chemical processes and uses a range of venting ratios to calculate the amount of hydrogen directly discharged into the atmosphere. Our analysis suggests that around 13-16 million tons (Mt) of by-product hydrogen are being produced annually in China through various industrial processes; meanwhile 1.6 to 8.1 Mt of that hydrogen is estimated to be vented into the atmosphere. The uncertain but potentially significant scale of venting hydrogen would make it a comparable or even larger source than hydrogen leakage from the whole hydrogen supply chain (estimated to amount to 2.4 Mt/y in 2020 in the world).

However, these estimates are subject to significant uncertainty due to data gaps and divergent estimates across different industrial processes. Assessing, addressing hydrogen’s fugitive emissions and promoting sustainable hydrogen consumption requires regulating by-product hydrogen’s production and prioritizing its capture and utilization. This includes assessing the feasibility and costs of by-product hydrogen usage.

By: Yushan Lou , Anne-Sophie Corbeau , Zhiyuan Fan