Traditionally, hydrogen has been produced predominantly via steam methane reforming (SMR), a process in which methane in natural gas reacts with steam at high temperature, producing hydrogen, and carbon dioxide (CO2) as byproduct. Hydrogen produced via this method is commonly referred to as grey hydrogen. Although this method is cost-effective, it contributes significantly to greenhouse gas emissions if CO₂ is not captured and instead released into the atmosphere.
In contrast, turquoise hydrogen presents a cleaner alternative, as it is produced via methane pyrolysis. Unlike SMR, methane pyrolysis does not produce CO₂. In this process, methane from natural gas is exposed to high temperatures, typically between 800 °C and 1200 °C, in the absence of oxygen. The stable methane (CH4) molecules are thermally split into hydrogen gas (H2) and solid carbon (C).
However, there are several challenges associated with turquoise hydrogen production that limit its commercial scalability. These include high CO₂ emissions from natural gas use and energy input, limited cost competitiveness, and challenges with the handling of the solid carbon byproduct.
1. High CO2 emissions from natural gas use and energy input
Turquoise hydrogen has an overall emission intensity of 0.5-4.0 kg CO₂-equivalent per kg of hydrogen (kg CO2e/kg H2) compared to ~10 kg CO2e/kg H2for grey hydrogen. Although turquoise hydrogen production does not emit CO₂ like grey hydrogen, it still depends on natural gas as a feedstock and requires high energy input. As shown in Exhibit 1, emissions from the use of natural gas can contribute up to 80% of the overall emission intensity of turquoise hydrogen. Additionally, the energy required for the pyrolysis reaction also accounts for a substantial portion of the total carbon emission intensity of turquoise hydrogen.
Exhibit 1: Emission intensities of turquoise hydrogen associated with feedstock use and energy input
2. Limited cost competitiveness
Turquoise hydrogen can cost $4-5 per kilogram (excluding potential revenue from the sale of solid carbon byproduct) compared to $1-2 per kilogram for grey hydrogen. For example, the energy costs for turquoise hydrogen production can be roughly three times higher than those for SMR, as shown in Exhibit 2. This cost disparity between grey and turquoise hydrogen poses a major barrier to the commercial viability of turquoise hydrogen.
Exhibit 2: Energy costs of grey vs. turquoise hydrogen production
3. Challenges with the handling of the solid carbon byproduct
Methane pyrolysis produces roughly three tons of solid carbon for every ton of hydrogen. While global hydrogen demand is currently around 100 million tons annually, demand for carbon-based products such as graphite represents only 10–20% of that volume. Without a scalable market or effective handling solution for the solid carbon, this byproduct may become a bottleneck to the wider adoption of turquoise hydrogen.
In summary, while turquoise hydrogen presents a promising pathway to low-carbon hydrogen, it faces several key hurdles that must be addressed for it to scale commercially. These include CO₂ emissions from natural gas use and energy input, high production costs, and challenges in handling the large volumes of solid carbon byproduct. In a future blog, we will explore the opportunities to overcome these barriers, along with recent innovations that aim to address them.
– Edmund Lam
Please contact us if you would like to learn more about turquoise hydrogen or gain broader insights into hydrogen market dynamics, outlook, policies and regulations, cost and economics, and technology developments.
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