Net zero and carbon dioxide removal

Increasing greenhouse gases in the atmosphere are raising global temperatures, resulting in complex impacts known as climate change.  New goals and strategies are needed to mitigate and adapt to this changing climate.  In my conversation with Dr Steve Smith on the podcast, he provided insight into net zero and carbon dioxide removal, important features within climate change dialogue.  As policymakers and businesses now refer to these terms, it is helpful to understand them, so we can make informed decisions about who we vote for and from whom we buy.

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What is net zero?

The concept of net zero evolved from climate change research and is an internationally agreed-upon goal for mitigating global warming.  It refers to a state where there is a balance between the greenhouse gases entering the atmosphere and those removed.  Net zero is achieved either by the cessation of carbon dioxide (CO2)emissions or the removal of CO2 to match emissions.  The Intergovernmental Panel on Climate Change (IPCC) concluded net zero CO2 needs to occur by 2050 to prevent a maximum temperature increase of 1.5C (the preferable limit agreed upon by governments through the Paris Agreement 2015) from being exceeded.

Net zero in practice

In setting a net zero target, a country or company has to decide on the scope of its emissions.  Will it cover its direct emissions only (energy supply, for example) or include its wider carbon footprint (such as emissions relating to its customers or historical emissions)?

Net zero targets

In 2008, the UK became the first nation to set a legally binding climate change mitigation target through The Climate Change Act.  It’s always wonderful to be associated with a forward, leading nation; however, the UK is not on track to meet its targets.  As with anything, goals and targets are only as good as the means to achieving them.

About 120 national governments have a net zero target, and of the 2000 largely publicly listed companies worldwide, 700 have made pledges.  As you would expect, their levels of transparency and reporting vary.

Tracking net zero targets

Steve is involved in The Net Zero Tracker, aiming to increase transparency and accountability of net zero targets pledged by nations, states and regions, cities and companies.  They collect data on targets, published plans and reporting to determine how robust these targets are. 

Emissions vs removal

Currently, 40 billion tonnes of CO2 are emitted into the atmosphere from human activities every year.  CO2 removals are estimated to be 2 billion tonnes per year.  You don’t have to be a maths genius to know we are way off from reaching net zero.  Reducing emissions as quickly as possible must remain the priority.  However, emissions associated with some activities, such as agricultural land use, cement manufacture and aviation, will be hard to reduce by 2050.  It is therefore deemed necessary that methods of CO2 removal need to be scaled up.  In over 500 pathways scrutinised by the IPCC, all involve CO2 removal.


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Offsetting refers to outsourcing the reduction in greenhouse gas (GHG) emissions or the increase in GHG removals.  Typically they are organised through a marketplace for carbon credits or other similar mechanisms.  For example, an organisation undertaking flights may wish to offset these emissions by purchasing a carbon credit in an activity such as tree planting, solar panel installation or clean cook stove provision (it doesn’t have to be a carbon removal project).

Of the 700 companies pledging net zero targets, only about 2% discount the use of offsets, 40% plan to use offsets, and the remainder are ambiguous. 

Carbon dioxide removal

CO2 removal (CDR) is sometimes called GHG removal (GGR) or negative emissions.  Whereas reducing emissions prevents CO2 from entering the atmosphere, CDR covers techniques that capture CO2 from the atmosphere and store or chemically convert it in a place where it remains, such as trees, plant matter, soil, deep underground, in the oceans, or long-lived products.  CDR forms part of the ‘toolbox’ in the quest to stabilise our climate. 

Why might we need it?

  • To balance those difficult-to-prevent carbon emissions.
  • To help those countries who have contributed very little to historical emissions to reach net zero.  

CDR options

The Greenhouse Gas Removal Hub

Within the numerous options available, the CO2RE team (University of Oxford) are researching 5 CDR projects:

  1. Woodland creation and management – trees are fantastic at storing carbon and enhancing biodiversity, but they need to be planted in suitable locations to thrive and require managing.
  2. Peatland restoration – peatlands are carbon-rich wetlands, occupying 10% of the UK land area. Like all plants, they capture CO2 during photosynthesis but store more carbon than any other terrestrial ecosystem.  In the UK, this amounts to 3 billion tonnes of carbon; however, human activity has caused degradation, and restoration is required to keep carbon locked up.
  3. Biochar – wood, food waste or agricultural residues are heated in the absence of oxygen (pyrolysis), forming a carbon-rich, charcoal-like material that can be ploughed into soils, potentially improving soil structure and agricultural yields.    
  4. Enhanced rock weathering – silicate rocks, such as basalt, absorb COthrough natural chemical reactions when rocks erode.  Crushing these rocks extends the reactive surface area, increasing CO2 absorption.  Spreading over farmland may improve crop health and increase yields.  
  5. Bioenergy with Carbon Capture and Storage (BECCS) – perennial crops such as miscanthus grasses and coppice willow are grown and burnt to generate energy. Capturing the emitted CO2 during burning and durably storing it could make the process carbon negative. 

The State of Carbon Dioxide report

A collaboration of independent scientists has assessed global CDR.  They have discovered the majority of the 2 billion tonnes/year currently captured is through land-based (conventional) methods, such as tree planting, with only about 2 million tonnes/year relating to novel/technology options.  There is currently a gap between the proposed levels of CDR by nations and what is needed to meet the Paris temperature goal to limit warming to below 2°C and pursue efforts to achieve 1.5°C. Bridging the gap will require scaling up CDR or cutting the already ambitious emissions targets.


Targets are crucial, but a plan of action is required.  We’re off-track, and this needs addressing.  The emphasis has to be on reducing emissions, but it’s expedient to be exploring every (sensible) option that may benefit a warming climate.