Decarbonisation Technology May 2022 Issue






Onsite (100% dairy RNG)



Diesel equivalent

Onsite (27% dairy RNG)

Onsite electrolysis (renew power)

Central SMR (natural gas) (gas delivery)

Central SMR (natural gas) (liquid delivery)

Onsite electrolysis (grid power)

Onsite SMR (natural gas)

Renewable source

Fossil source


Figure 1 Energy pathway carbon intensities

sectors. Distributed production is also much more reliable than centralised models. Recent supply disruptions due to natural disasters caused by extreme climate change have highlighted the need for redundancy (Cole Smith, 2021). With a network of distributed hydrogen production plants, consumers can be assured that even if one site goes down, another source is close at hand. There are also emission reduction benefits. Locally produced hydrogen is distributed to nearby consumers via truck from the hydrogen hubs. Shortening the distance that hydrogen is transported and avoiding liquefaction reduces the carbon intensity of hydrogen. Of course, when considering the environmental impact of hydrogen, the production method is the most significant factor. Considering carbon intensity Green, blue, turquoise, yellow, pink, brown, grey, black, and white – not all hydrogen production technology is the same. With rapidly growing commercial interest in hydrogen, a colour wheel classification system has evolved to help simplify the different technologies (Ivanenko, 2020). Unfortunately, the nuance and complexity of the different technologies are critical to understanding their environmental attributes. To accurately account for the environmental value (i.e., carbon intensity) of a given molecule of hydrogen, rather than a categorical colour scheme, we need to utilise a quantitative carbon

intensity (CI) score. This score is based on the lifecycle emissions resulting from upstream, production, and downstream activities, measured in grams of CO₂ per megajoule of energy content. The GREET (Greenhouse gases, Regulated Emissions, and Energy Use in Technologies) Model was developed by the United States Argonne National Laboratory to understand a variety of different energy pathways, and is one approach that is recognised and respected by many industry experts and policymakers across North America, and is integrated with the California Air Resource Board CA-GREET 3.0 Model. With this context, let us explore the carbon intensity and colours of the most common forms of hydrogen production. Green hydrogen is typically defined by electrolysis, using electricity sourced from renewable energy sources such as wind, solar, or hydroelectricity to split water into hydrogen and oxygen using various membranes and catalyst materials. Currently, less than 1% of hydrogen is produced with electrolysis (IEA, 2019). To effectively scale up this technology, significant renewable energy capacity is needed. Individual projects must consider local grid interconnection constraints since many electrolysis plants are grid-connected with contractual power arrangements. Electrolysis is very energy-intensive and is dependent on electricity markets to ensure that production remains cost-competitive.


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