Geological Net Zero (GNZ)

Geological net zero is the concept that any carbon still being extracted from the ground (geological sources) must be balanced by an equal amount of carbon stored in permanent, safe geological formations.

Setting a goal to achieve geological net zero as part of a wider net zero target provides a back-stop to ensure that we reach our climate goals in time, which is essential to temperature stabilisations.

Unfortunately, the term ‘net zero’ has become ambiguous. There are loopholes, lack of accountability, lack of governance and dodge offsetting claims. Read our page on the challenges with net zero.

We need net zero to stabilise temperatures, limit global warming and halt climate change. But we also need to strengthen the standards, conditions and governance.

One strengthening in specification is ‘geological net zero’, which aims to specify the condition of net zero on fossil-origin CO2. We need to follow the like-for-like offsetting principle and ensure fossil fuels are only balanced by safe, permanent geological storage.

Net Zero requires a balance between human-induced emissions and human-induced removals. This is because it is widely recognised that it is difficult to reduce all emissions to zero, at least by second half of this century.

An important condition for the ‘net’ part of the equation, i.e., removals, is that the CO2 is permanently stored. Permanently is ambiguous, but should be understood as a removal has low risk of CO2 reversal. Furthermore, it is importance that the ‘balancing’ is done across fungible sources and sinks. This is the like-for-like principle.

Oxford Net Zero defines the like-for-like principle as ‘when a source of emissions and an emissions sink correspond in terms of their warming impact, and in terms of the timescale and durability of carbon storage’.

Yes, we really need nature-based solutions (NbS).

Firstly, NbS are important to compensate for land-use change emissions from deforestation, food production and other essential land activities. Secondly, NbS provides co-benefits for human health, air quality, habitat restoration and much more. But we cannot use NbS to compensate for fossil-origin CO2. Thus, we cannot use NbS to meet our geological net zero target.

It is important to separate these types of carbon sinks because

• (1) there is a limit to how much human-induced CO2 nature can take up,

• (2) it is difficult to ensure verify and report additionally, which is important when you compensate for fossil fuels, and

• (3) there is lack of fungibility in the permanence levels between fossil-origin CO2 and biological carbon storage. One is a short carbon cycle (biological timescales) and the other one is a long carbon cycle (geological timescales). We need to keep these systems separate!

NbS is very much needed, but cannot be used to compensate for continued fossil fuel production and use. Here we can only use safe, permanent geological storage to reach geological net zero!

This is a very complex question. Implementation is always dependent on individual country regulations, financial mechanisms, social licence to operate, and other country structures.

We think countries must set 2 targets. One target for emissions reduction, and one target for removals. The removals target should contain how much we are relying on technological storage and how much we are relying on biological storage. This should be reflected in countries’ national determined contributions (NDCs) in the UNFCCC process as well as key targets they track within national net zero strategies.

We also need the global community to monitor, verify and report the global geologically stored fraction. The Geologically Stored Fraction is the fraction of carbon dioxide still produced from fossil fuels and industrial processes that is captured, either at source or recovered from the atmosphere, and committed to permanent geological storage. The fraction needs to steadily increase to 100% by 2050. This needs to be tracked and verified globally, therein disaggregated to regional and national targets.

Finally, governments should intertwine GNZ with their definition of abated fossil fuels. We need the international community to recognise the like-for-like compensation as the importance of the geologically stored fraction on fossil fuels. If this happens, we can start doing annual stocktakes.

Remember that geological net zero is a target that ensures any carbon still extracted at the time of net zero is balanced by carbon stored in permanent geological formations.

To reach this, we need technologies such as geological carbon storage facilities and CO2 transport systems. We also need point-source carbon capture with storage (CCS) and carbon dioxide removals (CDR) such as direct air capture and bio-energy capture.

But remember that we also need rapid and drastic emissions reductions by shifting our energy supply away from fossil fuels towards renewable energy as well as demand-reduction and improvements in energy efficiency.

No, climate change is not just about CO2 emissions. Meeting geological net zero targets for CO2 emissions and rapidly reducing methane emissions will solve CO2-induced global warming, but it is important to remember we are also breaching other planetary boundaries.

We have already breached six of nine planetary boundaries. Read more about Earth’s Planetary Boundaries here.