Decarbonisation Technology November 2026 issue

When CO 2 is fed to a plasma under the right conditions, it is split into CO and oxygen atoms. When an additional carbon carrier is introduced along with the CO 2 (such as methane from biogas), oxygen is consumed to make even more CO, and hydrogen is also produced. In other words, dry reforming of methane (DRM) is performed (see Figure 2 ). DRM can be used in combination with methane pyrolysis for e-syngas production. The German start-up Graforce GmbH has pioneered a process it calls ‘Plasmalysis’. This can convert a typical biogas feed of 50% methane and 50% CO 2 to syngas with a 1:1 ratio of hydrogen to CO. To enrich the syngas to a 2:1 ratio of hydrogen to CO, which is required for methanol production and FTS for liquid fuels, Graforce proposes to use methane pyrolysis to generate additional hydrogen and blend this with the 1:1 syngas from the plasma-induced DRM. Methane pyrolysis can be executed in several ways, many of which can be electrically heated using renewable sources of power. In each case, solid carbon is generated by the process as the methane molecules are split into hydrogen and carbon. This avoids the formation of CO 2 and enables the production of a high-value carbon co-product (see Figure 3 ). The nature of the solid carbon drives the economics of this pathway to e-syngas. Some methane pyrolysis processes produce low-value soot. Others can yield carbon black, graphite, or graphene, which may have a value between €1,000 and €5,000 per tonne. Some are able to produce ultra-high-value carbon nanotubes, which can be worth up to €20,000 per tonne. Bi-reforming using plasma decomposition The Belgian start-up D-CRBN uses a non- thermal plasma reactor for sustainable syngas production. Several years ago, its system was demonstrated with a biogas feedstock containing about 40% methane and 60% CO 2 . The resultant syngas had approximately a 1:1 ratio of CO and hydrogen. For hydrogen production, methanol synthesis or FTS fuels, the ideal ratio of hydrogen to CO in the syngas is 2:1. The addition of steam to the biogas introduces new reaction pathways into the plasma system. Methane reforms not only with the CO 2 but also with the water in the bi-reforming

Electrical catalytic steam methane reforming (e-SMR), Bi-reforming

Plasma CO 2 , steam and methane splitting, Bi-reforming

CO, steam & methane

Plasma arc

Syngas

POx RWGS

Catalytic POx RWGS

Oxygen & CO

Hydrogen

Catalyst bed

Syngas

Figure 2 Green sygas production technologies

reaction. In this case, the atoms recombine to produce syngas at the 2:1 ratio. Turquoise hydrogen is produced from methane pyrolysis using plasma to intentionally yield solid carbon. However, D-CRBN focuses on circular syngas production, and the steam injection assists in achieving this goal with the avoidance of soot, coke, or solid carbon production. The long-term operability of plasma systems is a key factor for industrial users. During operation, the electrodes producing the plasma tend to be eroded by the intense heat and flow of electrical current. D-CRBN has an advantage over conventional plasma torches because its torch uses a high-frequency pulsed plasma system. This enables its electrodes to have an extended life, meaning lower maintenance costs and reduced downtime. Electrochemical reduction of CO 2 The US-based start-up Twelve has developed an electrolyser that converts water and CO 2 to syngas. When the electrolyser is fed with