Decarbonisation Technology - August 2024 Issue

An example workflow for the exploration process is shown in Figure 1 . Natural hydrogen as a renewable resource The USGS considers that some of the gas in natural hydrogen fields may be renewable, given the rapid rate of hydrogen generation via water reduction. Some researchers have proposed that reservoirs, traps, and seals may not even be necessary to produce hydrogen. It may be possible to tap into rocks that are generating hydrogen or have hydrogen migrating through them to produce the hydrogen gas as it is being generated. Other scientists propose that hot water could be injected into iron-rich rocks that are not currently generating hydrogen to stimulate generation (Ellis & Gelman, 2023) . In the context of the move away from carbon emissions as part of the energy transition, such opportunities are exciting and merit significant research and development. At the same time, it should be noted that serpentisation is not a catalytic process (Zgonnik, 2020) . Carbon intensity and colours of hydrogen For those who like the use of hydrogen hues, the terms gold hydrogen or white hydrogen have been applied to natural hydrogen. The colours of hydrogen include grey for reforming of natural gas when the co-produced carbon dioxide is emitted into the atmosphere, or blue when these emissions are captured and stored. Green hydrogen is manufactured from the electrolytic splitting of water using renewable electricity (Himmat, 2024) . The International Energy Agency (IEA) and World Energy Council (WEC) promulgate that, ultimately, the carbon intensity of the process is more important than the colour (World Energy Council, 2021; IEA, 2023) . The average carbon intensity of global hydrogen production in 2021 was 12-13 kgCO2eq/kgH2. The US introduced a technology-independent, clean hydrogen standard of 2 kgCO2eq/kg H2 (US DoE, 2021). The carbon intensity for electrolytic hydrogen ranges from 1 kgCO2eq/Kg H2, using a national average share of renewable electricity, to zero when the electricity source is fully renewable. The EU’s Renewable Energy Directive requires that electrolytic hydrogen production be

powered by additional renewable electricity capacity for the hydrogen to be classified as renewable (European Commission, 2023) . From the outset, the carbon intensity for natural hydrogen will be close to zero. A small proportion of the hydrogen is likely to be used to provide clean energy for the drilling and extraction processes. Regardless of the source of hydrogen, it will be important to minimise hydrogen losses to the atmosphere during handling, storage, and transport. The current lack of Infrastructure for the production and transport of clean hydrogen is considered a significant factor impacting the developing hydrogen economy (IRENA, 2022) . Globally, there are currently just 4,500 km of hydrogen pipelines (IRENA, 2022). In the EU, in 2024, just 4,000 km of planned hydrogen pipelines are in advanced stages of planning or construction, against a target of 30,000 km of pipelines by 2030 ( Holm, 2024) . Pipelines may be the best solution for short- distance transport, whereas liquefaction and liquid organic hydrogen carriers (LOHCs) are being developed for longer-distance transport. Economic assessment Hydrogen demand is currently 94 Mt/a, 98% of which is manufactured and reforming of natural gas or a by-product of oil refining. Demand is predicted to grow to between 150 Mt/a and 500 Mt/a by 2050 (PWC, 2024; World Energy Council, 2021) . One of the factors limiting the growth is the anticipated cost for hydrogen meeting the clean hydrogen standard of <2 kgCO2eq/kg H2 . In 2021, the US Department of Energy (DoE) launched the Energy Earthshots Initiative with the Hydrogen Shot, which set a cost target of $1/kg for clean hydrogen over the decade to 2031 – an 80% reduction (US DoE, 2021). Current costs for electrolytic hydrogen based on projects where electrolysis is powered by a dedicated renewable electricity source are in the range $3-8/kg (PWC, 2024) . PWC points out that the most attractive production regions for electrolytic hydrogen are those with abundant, low-cost renewable resources (Middle East, Africa, Russia, China, USA, and Australia). By 2050, electrolytic hydrogen production costs in these regions could be $1-$1.5/kg, while in other