Many governments, councils and companies have set themselves targets to be ‘net zero’ in terms of greenhouse gas emissions by a certain date, often 2050., writes Paul Scholes from ACT.

It sounds impressive, but it is not always clear what it means.

When you hear that even oil companies like BP and Royal Duch Shell have set such targets, or ‘ambitions’’, you could be excused for thinking there must be a catch somewhere. You would be right.

The net zero approach relies on a balancing of two separate measures. The first is to reduce emissions, while the second is to remove carbon dioxide (CO2) from the atmosphere and store it using both natural and engineered means.

A net zero target is met when any remaining difficult to reduce emissions, from aviation for example, are balanced by CO2 removals.

However, the engineered methods (known as Negative Emission Technologies or NETs) are at an early stage of development and it is not certain they can be deployed at the scale needed, or are even practical and deliverable. If they aren’t there will be a strong reliance on natural methods of carbon capture and storage, by planting trees, for example, and there is unlikely to be enough land available for this to be feasible.

Many scientists consider the net zero methodology to be false accounting in that, by anticipating being able to remove carbon, especially after 2050, we risk emitting more than we can afford to before 2050. We may also make less effort to reduce emissions now. A study by Lancaster University in 2019 concluded it would be better to separate the two routes of emissions reductions and carbon removal, rather than combining them in a single net zero goal.

You may wonder why we don’t just aim for zero emissions rather than ‘net zero’. Plenty of scientists believe we should be doing that, but it is too difficult politically.

There is a belief it would result in significant downturns in the economies of the richest countries. So in the negotiations over the Paris Agreement that nearly 200 countries signed up to in 2015, a compromise was reached.

The Agreement commits signatories (on a voluntary basis) to limit the global temperature increase this century to well below 2C above pre-industrial levels and to try to limit it to 1.5C.

Each signatory was allocated a carbon budget, based on the maximum amount of CO2 and equivalent gases, (collectively known as CO2e) that could still be emitted to have a chance of remaining within this temperature range.

Countries could decide how and when to restrict their own emissions within their budget, but in doing so, they were allowed to include methods to remove CO2 from the atmosphere.

In other words, with a carbon budget of one tonne, you can emit 1.2 tonne as long as you can find a way to remove 0.2 tonne.

So when our government legislated for ‘Net Zero by 2050’ the UK could still be emitting say 100 Mt (million tonnes) of CO2e per annum in 2050 (mainly from agriculture and aviation) and so must plan to remove at least the same amount to get to net zero.

The removal plan anticipates extensive tree planting and peatland restoration and the use of negative emission technologies known as BECCS (Bio-energy with Carbon Capture & Storage). BECCS involves planting trees or growing plants like miscanthus (elephant grass), which are then harvested and burnt in power plants to generate energy, with the resulting CO2 emissions captured and stored, usually by pumping them into exhausted gas and oil wells.

BECCS is the technology that underpins the carbon budgets agreed under the Paris Agreement, allowing countries to meet their net zero targets. The problem is, the technology is still unproven.

Net zero targets sound reassuring, but relying on negative emission technologies to hit those targets is a big risk.

For more information visit actionclimateteignbridge.org