What do we mean by 'decarbonise'?
When we talk about decarbonising something, like making electricity, we mean cutting down or stopping the carbon dioxide (CO2) that activity releases into the air. The word is also used for other gases that warm the planet, like methane.
To make things easier to compare, people often group all these 'greenhouse gases' together and talk about them as if they were CO2. That is why you might see eCO2 on some products. This means “carbon‑dioxide equivalent” - the total warming effect of all the gases, described as if they were an amount of CO₂.
Can we just decarbonise to get to Net Zero?
Net Zero requires Carbon Dioxide Removal to deal with industries:
-
that cannot practically be decarbonised (or prevent emissions of other greenhouse gases).
Characteristics of the things we can't yet decarbonise:
- Activities that require temperatures too high to be delivered by heat pumps or heating elements
- Activities that require high energy densities (e.g. a battery plane can't fly across the Atlantic, because it is too heavy to take off)
- Activities that require uninterrupted heat supply (backup heat/energy storage may be required at levels that cant be delivered by batteries - for example, steel solidifying and preventing future use if a smelter runs out of fuel)
- Emissions that result from biological processes (that we can't address as we can other things, by switching from fossil fuel, energy/heat to electrical energy/heat)
- AND, that are mobile and/or spread out, so can't be dealt with by capturing the CO2 from the (e.g.) chimney where it is emitted. For example, aviation, farming, military activities.
Can't we deal with these hard to decarbonise sectors by using hydrogen and synthetic (non fossil) fuels?
We can do for some of them, but even for those it may often make more sense to accept some emissions, balanced by carbon removal.
- Hydrogen is either made fossil fuels or from water in an approach that is likely to end up costing more than removing the carbon emissions that it is preventing.
- Done at large scales, synthetic fuels (for example, making something like jet fuel from CO2 and hydrogen) will need CO2 taken from the atmosphere as an input. In most situations it is unlikely to make sense to go through the three steps of taking CO2 from the air, generating hydrogen, and combining them into a fuel, rather than allowing the original CO2 to be emitted, then balancing it with removal from the atmosphere.