Green Hydrogen
Green hydrogen uses electrolysis of water powered by renewable energy. This would reduce emissions but it remains very costly. Low-carbon hydrogen produced by electrolysis but using nuclear electricity is being done in China. (Green Hydrogen fuel, 2020)
The falling prices of solar and wind energy and the increasing use of hydrogen could see its production costs slashed by 2050, according to researchers BloombergNEF. They estimate it could be produced for between $0.80 (0.66 euros) and $1.6 a kilogram by then, comparable to natural gas. (Green Hydrogen fuel, 2020)
Grey Hydrogen
According to the International Energy Agency, global hydrogen production emitted 830 million tonnes of CO2 in 2017 — the equivalent of the combined emissions of Indonesia and the United Kingdom. (Green Hydrogen fuel, 2020)
At present, about 95% of the hydrogen that is produced is derived from fossil fuels using various thermochemical processes. Gasification consumes solids such as petcoke and coal. Other gas-phase reforming processes are fed with methane, naphtha, or refinery gas. Auto thermal reforming (ATR), steam methane reforming (SMR) and partial oxidation (POX) are the main thermochemical processes in play today. These processes produce syngas which is a mixture of hydrogen and carbon monoxide. Sometimes, two out of the three processes are combined in series to produce the desired ratio of carbon monoxide to hydrogen. If hydrogen is the target gas, carbon monoxide may be reacted with steam and converted to carbon dioxide and hydrogen in a subsequent water-gas shift reactor. These thermochemical processes produce about 10 kg of carbon dioxide (CO2) for each kg of hydrogen. If the CO2 is not captured, the resulting hydrogen is referred to as ‘grey’ or ‘black’ hydrogen. If this hydrogen is used in fuel cell powered cars, with a consumption of about 1kg of hydrogen per 100km, the net result would be emissions of 100 gCO2/km when upstream emissions are considered. This exceeds the current European fleet emissions target of 95 gCO2/km. The direct use of compressed natural gas in internal combustion engines would emit less CO2 from a total system perspective. (H2 methane pyrolysis, 2021)
Blue Hydrogen
The blue hydrogen comes from natural gas, capturing the CO2 during the process. Firms including ExxonMobil and ENI are pushing for this, but the CO2 sequestration process remains uncertain and costly. (Green Hydrogen fuel, 2020)
“Hydrogen derived from fossil fuels is not zero emissions, due to methane leakages along the value chain,” it says. “The International Energy Association (IEA) estimates that the oil and gas sector emitted around 70 million tonnes of methane in 2020 – over 5% of global energy-related greenhouse gas emissions. The Petra Nova project in the US captures just over a third of the flue gas from one of four coal-fired units, while the Boundary Dam project in Canada has an overall capture rate of 31%. There need to be controls over how CO2 will be used and where it will be stored, so that it will not be used to extract more oil.” (Restrict Blue Hydrogen, 2021)
The project, called H2Teesside, would account for 20% of the UK government’s ambition to have 5GW of low-carbon hydrogen production online by the end of this decade. The facility would use natural gas alongside carbon capture and storage to generate blue hydrogen. Carbon capture rates from the proposed H2Teesside plant are as high as 98%. The UK is well-positioned to develop blue hydrogen post its departure from the European Union, which leans toward green hydrogen following the European Commission’s hydrogen strategy. However, the UK is also home to ITM’s Gigafactory, a 1GW/year PEM electrolyser production facility. (BP 1 GW Blue, 2021)
