Ki Hydrogen, a UK cleantech startup founded in 2022, develops biomass electrolysis technology to produce green hydrogen and green chemicals from waste biomass. This innovative process requires much less energy input compared to traditional water electrolysis methods, making their solution more cost-competitive. Ki Hydrogen aims to achieve a production cost of $2/kg H₂ without relying on subsidies or low electricity prices.
Challenges: produce green hydrogen at a low cost
Hydrogen (H₂) is a crucial chemical feedstock for the production of fertilizer, plastics, and other essential products that directly address the basic needs of human society. The majority of the world’s hydrogen (over 60 million tons) is produced via the steam methane (CH₄) reforming (SMR) process. This process requires a significant amount of energy input and contributes about 2% of global carbon dioxide (CO₂) emissions. The SMR process emits between 5 and 9 tons of CO₂ per ton of hydrogen produced.
Green hydrogen is crucial for a carbon-neutral world. Green hydrogen is produced when electricity from renewable sources such as nuclear, solar, and wind is used to split water. Green hydrogen can decarbonize hard-to-abate industries, such as steel manufacture, long-distance transportation, shipping, and aviation. It can also be used to store renewable electricity seasonally.
However, green hydrogen is not yet cost-competitive with SMR-produced hydrogen. This is due to the high capital expenditure (CAPEX) and high operational expenditure (OPEX) of the present-day water electrolysis plants. The OPEX is by far the largest cost component, and it is dominated by the energy efficiency of the water electrolyzer and the cost of the input renewable electricity used to power it.
Modern commercial water electrolysers operating at a sub-megawatt scale require about 53 kWh of electricity to produce 1 kilogram of hydrogen. An electrolyzer with an energy efficiency of 83% consumes about 47.5 kWh of this total, while the engineering system consumes the remaining 5.5 kWh. The International Renewable Energy Agency (IRENA) has set a 2050 target of below 42 kWh/kgH₂ for electrolysis cell energy consumption. Thus, any improvement in net energy efficiency reduces the levelized cost of hydrogen.
Ki Hydrogen Technology
Ki Hydrogen is developing an innovative technology known as biomass electrolysis, which aims to produce green hydrogen from waste biomass feedstocks such as sawdust, agricultural residues, and forestry byproducts. The technology involves directly electrolyzing the biomass feedstock rather than using water as in conventional electrolysis. This allows them to extract hydrogen from the biomass while also producing valuable chemical byproducts. The technology can reduce the energy requirement for hydrogen production by up to 75% compared to conventional water electrolysis.
How Ki Hydrogen produces hydrogen via biomass electrolysis
Conventional water electrolysis splits water into hydrogen and oxygen. A water electrolysis cell consists of two half-reactions: the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER), as depicted in the diagram below.
The cathodic hydrogen evolution reaction is a straightforward two-electron process, whereas the anodic oxygen evolution reaction is theoretically a four-electron process. Even with the development of anodic electrocatalysts, the inherent sluggish kinetics of OER require a higher voltage, resulting in an increase in the electricity input of water electrolyzers.
The anode typically vents the low-market-value oxygen gas it produces, instead of capturing it for useful purposes. Furthermore, the simultaneous production of oxygen and hydrogen gasses would cause gas to cross the membrane, raising safety concerns.
Biomass electrolysis refers to the process of converting biomass—organic materials from plants and animals—into hydrogen gas through electrochemical reactions. It combines cathodic hydrogen evolution reactions with the thermodynamically more favorable and value-added electrooxidation reactions of biomass feedstock. The process operates at low temperatures (60-70 ºC) and does not produce any CO₂, with pure hydrogen as the only gaseous product.
The diagram below depicts Ki Hydrogen's biomass electrolysis technology to produce green hydrogen.