Explainer Series | Removing carbon dioxide from the atmosphere

Key points

• Carbon Dioxide Removal (CDR) refers to drawing down CO₂ from the atmosphere and storing it elsewhere. CDR takes place in natural and man-made forms.
• Carbon removal projects may be eligible for carbon credits to help mitigate hard to avoid emissions.
• There are risks associated with CDR as we don’t yet understand all impacts or its full potential as a solution and have some unanswered questions regarding storage timeframes.
• The CDR sector is in its infancy and is not yet developed at the scale required to meet our climate goals. It has potential for significant results if the technology and economics can mature.
• CDR should not be viewed as a replacement for widespread emissions reductions and decarbonisation, but as a complementary tool.

Introduction

The call for carbon emissions reductions on a planetary scale is well accepted, as carbon emissions and subsequent impacts continue to grow. However, simply reducing emissions will not suffice. To ensure we meet climate targets, we will also need Carbon Dioxide Removal (CDR) on some level to draw down emissions from the atmosphere and ensure safe and long-term storage of existing and newly created carbon. How much CDR we need will depend on our capacity to first reduce. With such an urgent need for carbon mitigation, can CDR help us meet our climate goals?

What is Carbon Dioxide Removal?

CDR refers to the process of drawing down (removing) and storing carbon emissions (sequestering) from the atmosphere.

Removals might occur within an organisation’s boundary (within boundaries removals) or be purchased from outside an organisations boundary (offsetting).

Carbon can be stored in:

• Plants and trees
• Soils
• Underground reservoirs
• Rocks and minerals
• The ocean
• Products (like concrete or bio-based plastics)

Carbon is released into the atmosphere from a range of activities but not all of it is removed through natural sinks (places that sequester carbon). Currently, more carbon is in the atmosphere than can be sequestered, figure 1 below demonstrates this.

Figure 1: Emission sources and natural sinks (Sourced from: Project Drawdown)

How might Carbon Dioxide Removals help fight climate change?

CDR works by reducing the atmospheric concentration of carbon dioxide, earth’s key warming agent. The less carbon in the atmosphere, the better chance we have of reducing potential warming. Mass carbon drawdown has a role to play to help us meet Paris climate goals (see Figure 2).

Figure 2: GHG emissions abatement pathways from 2010 to 2100 (Sourced from: UN Emissions Gap Report 2017)

CDR methods may be broadly categorised as either nature-based solutions or technology-based solutions. Nature-based solutions such as blue carbon (the drawdown of carbon dioxide by coastal and marine ecosystems), soil carbon, and peat soil carbon removals are examples of potentially large-scale methods. Benefits include increased biodiversity, and even positive social and community impact.

Technology-based solutions such as Carbon Capture and Storage (CCS) refer to point source capture of carbon dioxide from industrial processes, before safely storing or utilising the carbon. It’s sibling, Direct Air Capture, (DAC) sucks ambient air straight from the atmosphere, drawing out CO₂ through a chemical reaction. DAC solutions needs to suck massive amounts of air to achieve significant drawdown, and is being worked on globally as an option to scale up production to achieve a meaningful global impact.

We broadly understand the processes that drawing down carbon but the challenge is implementing CDR in a permanent, safe and scientifically robust way.

Figure 3: Technology based examples of carbon dioxide removal (Sourced from: About CCUS – Analysis - IEA)

Challenges and risks associated with Carbon Dioxide Removal

The elephant in the room is what’s known as ‘permanence’ or ‘durability’.

Essentially how long can we store removed carbon? Decades? Hundreds of years?

Many argue, this is not long enough. CO₂ stays in the atmosphere for up to 1000 years! How do we account for pests, fire, and other re-release risks? We need longer storage solutions than a few decades, and to achieve gold-standard carbon storage we’ll need to rival the geological, million years storage timescale of the Earth. Such as the storage offered by rock weathering and mineralisation, blue carbon and peat soils storage. Technologies that inject carbon into the lithosphere provide a technological long-term storage solution. In conjunction, we need emissions reductions to occur widely and deeply across all sectors and countries. This reduces the need for carbon removal in the first place.

It’s also important to ensure we don’t create one problem by trying to solve another. CDR is still emerging, and nature-based solutions especially hold potentially massive implications for land use, water, nutrients, and energy across the globe. Like anything operating at this magnitude, there needs to be science based insights that are proven before being rolled out at scale.

Notable Carbon Dioxide Removal projects

Chevron currently operates the largest CCS system in the world at the Gorgon LNG plant off the West Australian coast, although has been accused of failing to meet expectations regarding sequestration targets. CCS efforts by Equinor, a Norwegian multinational energy company, have captured and stored over 23 million tonnes of CO₂ under the Norse sea. The scale of these projects are impressive, but there is a counter argument that these schemes prolong our reliance on fossil fuels. Here in Aotearoa, the Energy Efficiency and Conservation Authority (EECA) has co-funded a $5 million project to install a biomass boiler and CO₂ capture unit at Southern Paprika, one of New Zealand's largest capsicum providers.

Iceland is home to the world’s largest DAC plant, Orca, which was switched on in 2021 and claims to be capable of removing 4,000 tonnes of CO₂ per year. Other projects of note include CarbonCure who inject captured CO₂ into concrete during mixing. This converts it into a calcium carbonate mineral that enables long term (thousands of years) storage.

Nature-based solutions are also underway in the form of constructed wetlands and blue carbon solutions, along with the obvious solution of reforestation. Other projects take a more creative approach to CDR. Project Vesta is in the research phase and spreads carbon-removing sand made of the mineral olivine onto beaches, where wave action takes it out to sea. There, the sand dissolves, countering ocean acidification and permanently removing carbon dioxide from the atmosphere. Others such as Aspiring Materials in Aotearoa are investigating olivine too.

Charm Industrial uses plants to capture CO₂ from the atmosphere, before converting biomass into a stable, carbon-rich liquid that is stored deep underground. Perhaps the most unconventional idea yet is that by High Hopes Labs, who are sending carbon grabbing balloons up into the atmosphere. These are just a few examples from an array of organisations working in CDR.

Future of Carbon Dioxide Removal

Strong signals exist that CDR is rapidly gaining momentum. It is already included in target setting by the IPCC, and GHG Protocol guidance on accounting for removals, which is due early 2023. This guidance is in high demand and will outline how to account for removals and sequestration across both land and technology-based CDR. For a more Kiwi-centric view, check out Ara Ake’s summary of CCUS applicability for Aotearoa.

All the while, regulatory and market forces continue to increase awareness and scrutiny into carbon across businesses, governments, and countries globally. The response to this has been significant, especially from technology sectors.

Notably, the newly launched Frontier, an advance market commitment backed by the likes of Stripe, Meta, McKinsey, Alphabet, and Shopify aims to accelerate the development of carbon removal technologies and is looking to guarantee future demand by buying an initial US$925M of permanent carbon removal between 2022 and 2030. Fundraising by Climeworks has been announced to the tune of $650 million, not to mention a $100 million X-prize for carbon removal technologies launched by Elon Musk.

Technology-based CDR is advancing at a rapid pace, but Nature-based CDR is also experiencing growth, particularly for soil carbon and blue carbon. In May 2021, VERRA, one of the organisations that certifies projects for carbon credit generation (along with Gold Standard), released a methodology to account for blue carbon removals by mangroves in the Gulf of Morrosquillo, Colombia. This approach is expected to remove 1.2 million tonnes of CO₂ over 30 years.

At the intersection of nature and technology, bio-energy with carbon capture and storage (BECCS) has been highlighted by the IPCC as a significant opportunity for low or zero carbon energy. A space to watch both here and abroad.

What’s the difference between carbon removals and offsets?

Importantly, carbon dioxide removals is often viewed by organisations in managing their carbon inventories. There are three principles that are considered as part of Toitū Envirocare’s Carbon certification programmes. This might occur in the form of purchased carbon credits that exist outside an organisation’s boundary (offsetting), removals directly occur within an organisation, or removals occurring within an organisation’s value chain within boundary removals.

Certain levels of rigor determine whether a carbon offset can be utilised within a Toitū carbon certification programme inventory. For example, a carbon removal project must be ‘additional’ to business as usual and must be protected contractually from being sold multiple times, or ‘double counted’. If a business chooses to offset through our programme then it must meet our criteria and standards. Toitū is a member of ICROA (International Carbon Reduction & Offset Alliance) to ensure that only the highest quality credits are purchased and used for claims under the Toitū carbon certification programme.

Figure 4: Toitū Envirocare’s explainer of removals and offsets

How carbon credits are quantified and categorised is evolving, like everything else ‘carbon’. Standards such as the Oxford Offsetting principles define leading practice around different carbon credit projects. This is where terms such as permanence and durability come into play (i.e. the length of time that carbon is guaranteed to be stored). These timescales can vary from as short as 10 years (if re-release is likely), decades, or hundreds of years (secure woody biomass) and thousands of years (DAC/CCS, mineralisation, peat soils, and blue carbon). Advocacy for ‘ton-year’ carbon accounting offers a pathway for ‘long-term’ credits to be held and priced at a higher value than ‘short term’ credits.

One strategy to focus offsetting efforts on is to enforce ‘like-for-like’ carbon offsets. By this method, for example, an oil company responsible for fossil fuel emissions wouldn’t be able to neutralise them by planting trees. To do so would not result in a net balance, as carbon has been removed from the lithosphere (underground where it was safely stored for millennia) and then transferred to the atmosphere. To then offset those emissions by storing carbon in woody biomass is less secure than in its original form as oil underground, arguably supercharging the biosphere with readily available, burnable carbon deposits. Like-for-like offsetting requires fossil carbon emissions to be offset by storing carbon back underground, instead of planting trees - incentivising decarbonisation, alternative fuels development, and safeguarding the use of forestry CDR for those who need it.

Summary

CDR is evolving, but already destined to play a key role in climate change solutions. While we have an existing toolkit of both nature-based and technology-based solutions at our disposal, implementation and carbon accounting still pose challenges, not to mention the need to avoid unintended consequences. Nature-based solutions provide the attractive prospect of mother nature having done all the engineering for us – in concept, who could argue against the ‘re-wilding’ of our planet as an answer to the climate crisis?

Alternatively, technology is capable of rapid growth and holds the potential to create entirely new industries when market forces align - think how automobiles, smartphones, or the internet has changed our world. In our quest to achieve CDR on a global level we may find ourselves with a carbon removal sector that rivals the size of the current oil and gas industry. What’s clear is there is no one solution that is the answer. A suite of CDR practices is likely to be employed. There’s no silver bullet, as they say, but there may be silver buckshot.