For decades, hydrogen production was dominated by steam methane reforming (SMR), mainly to supply refineries and chemical plants. In that classic configuration, the reforming furnace is fired with fuel, and the resulting CO2 is released to the atmosphere.

Today, industry is moving toward lower-carbon pathways. Existing SMR units can be upgraded through carbon capture, partial or full hydrogen firing in the furnace, or both, which reduces emissions without replacing the entire plant.

The Color Spectrum

In industry, hydrogen is commonly categorized by the carbon intensity of its production process:

• Gray Hydrogen: Produced via conventional SMR using natural gas, without any carbon capture. CO₂ is released directly to the atmosphere through the furnace stack.
• Blue Hydrogen: Produced via SMR or alternative reforming technologies, with Carbon Capture and Storage (CCS) applied to dramatically reduce atmospheric CO₂ emissions.
• Green Hydrogen: Produced via electrolysis powered by renewable energy, with no fossil fuels and no direct CO₂ emissions.

Between these poles lie several intermediate pathways, driven by technology choices that progressively reduce the carbon footprint of hydrogen production while maintaining industrial-scale output.

Core Hydrogen Technologies

The main hydrogen technology options are represented in four pathways, all of which Nextchem has in its technology portfolio: SMR, ATR, CPO, and electrified SMR.

Steam methane reforming (SMR):

SMR is the most widely deployed technology for hydrogen production. It works by passing a hydrocarbon feedstock (typically natural gas) over a catalyst bed in the presence of high temperature steam. The reaction requires an external heat source, typically a gas-fired furnace. However, this furnace-based heating is the primary source of CO₂ emissions in gray hydrogen. 

However, SMR plants can be adapted for lower carbon intensity by:

• Partially or fully replacing the furnace fuel with hydrogen (reducing combustion-related CO₂ emissions).
• Integrating post-combustion or process-stream carbon capture to produce blue hydrogen.

SMR is most economically suited to mid-range capacities, up to approximately 150,000 Nm³/h of hydrogen, and represents the basis of KT Tech's portfolio of over 60–70 reference plants worldwide.

Autothermal Reforming (ATR):

ATR eliminates the external furnace entirely by introducing oxygen directly into the reaction vessel, where partial combustion of the hydrocarbon feedstock generates the heat needed to drive the reforming reaction over a catalyst bed. This integrated thermal design significantly reduces direct emissions compared to conventional SMR.

ATR is the technology of choice for large-scale hydrogen and syngas production, with capacities scalable up to 600,000 Nm³/h of hydrogen equivalent, making it ideally suited as the front-end for:

• Large-scale ammonia synthesis plants.
• Methanol production facilities.
• Integrated hydrogen hubs requiring high-volume, low-carbon output.

ATR becomes economically competitive at around 200,000 Nm³/h and above, overlapping with the upper range of SMR applications.

Catalytic Partial Oxidation (CPO):

CPO takes the furnace-free approach one step further. In this configuration, the heat required for the reaction is generated entirely by the catalytic contact between oxygen and the hydrocarbon mixture over a highly active catalyst bed, with no separate pre-heater or burner required. The result is among the lowest CO₂ intensity of any fossil-fuel-based reforming technology. 

CPO is best suited for small to medium capacities, up to approximately 50,000 Nm³/h, and is the preferred solution when the project specification demands minimal process-side emissions.

Electrified SMR (eSMR):

The electrical steam methane reforming (eSMR) can be positioned as a bridge between blue and green hydrogen. This technology replaces the conventional gas-fired furnace with electric heating powered by an external electricity source. This eliminates the combustion-related stack emissions, making it a uniquely clean option when powered by renewable electricity.

The eSMR is particularly effective at smaller scales (up to approximately 10,000–15,000 Nm³/h per train) and is ideally suited to applications where:

• Renewable electricity is available at a competitive cost.
• Biogas (biomethane) is used as feedstock, potentially approaching carbon-neutral performance, depending on system boundaries and carbon accounting assumptions.
• Distributed hydrogen production is required, with minimal infrastructure for combustion management.

Comparing the Technologies: Capacity, Sustainability, and Application

Technology selection is about both carbon intensity and scale. Available feedstock and utilities, site constraints, and the regulatory environment of the specific project are other factors to be considered.

Below is a comparison of industrial hydrogen solutions, including their features, capacity and environmental impact.

Revamping Gray Hydrogen Plants

A major opportunity lies in revamping existing plants. Brownfield SMR units can be decarbonized through carbon capture, but implementation is often constrained by plot space and integration limits.

The primary engineering challenge is space: adding carbon capture units to an existing brownfield plant requires plot area that may not be readily available. Nextchem, through its subsidiary KT Tech, has successfully executed such revamps, but the practical constraints of site layout must be carefully assessed in each case.

For projects where a full greenfield redesign is possible, the step-change in carbon intensity offered by ATR or CPO, combined with CCS, typically delivers superior economics and a lower residual carbon footprint compared to retrofitting an existing SMR.

Integrated hydrogen value chain 

Hydrogen is not only an energy vector; it is also a key feedstock for ammonia, urea, methanol, and refinery processes. The integrated value chain can also reuse captured CO2 downstream in urea or methanol production.

This integrated approach is especially relevant for industrial clusters. It reduces emissions while improving asset efficiency across the hydrogen, ammonia, and carbon-management chain.

For industrial operators, the decision starts with a practical question: what is the right technology for the required capacity and carbon target? 

The answer may be a revamp of an existing SMR, a new ATR-based syngas plant, a compact CPO unit, or an electrified reforming solution. NextChem’s position in the market is built on exactly that flexibility: a portfolio designed to match industrial scale, emissions targets, and downstream integration needs.

Learn more about Nextchem’s Hydrogen technologies and our projects in the USA, Vietnam and West Africa.

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