Carbon Removal Project

Carbon dioxide (CO2) removal extracts greenhouse gas out of the atmosphere and stores it in a secure form or place so it no longer contributes to climate change. Although it shares similarities with carbon capture – typically, a net-zero process – CO2 removal achieves net-negative emissions.

Large-scale removals will be necessary to achieve national and global climate goals. Initially, carbon removal could balance out hard-to-abate sectors such as aviation. With sufficient incentives, it may be deployed to address legacy emissions and bring down atmospheric concentrations of CO2.

Afforestation has provided the vast majority of CO2 removal to date, both in Aotearoa New Zealand and globally.  Releasing their carbon stores when damaged in storms and fires, forests are often a less durable form of removal compared to methods such as biochar application or geological mineralisation.

Our research project, led out of the University of Canterbury, is investigating more durable removal technologies well suited to New Zealand and capable of removing at least one million tonnes of CO2 every year.  

Our team of 16 academics, six postdoctoral researchers, 10 PhD students and a community-based researcher from institutes across New Zealand is supported by a grant from the Government’s Endeavour Fund until 2029.

Building on our team’s expertise, we’re focused on three technologies: 

At a hybrid bioenergy-geothermal power plant, waste wood is combusted to increase thermal output and remove carbon. Under one concept we’re evaluating, a concentrated source of biogenic CO2 is mixed with geothermal brine, which is reinjected underground away from the reservoir. Alternatively, pyrolysis transforms the wood waste into biochar, which locks away carbon in stable chemical rings – and when applied to farmland, boosts soil health.

Silicate-rich basalt or dunite rocks that naturally weather to form bicarbonate ions are mined and crushed to increase their surface area. This fine powder is applied to farmland, where it may also boost soil quality. The silicates react with dissolved CO2 in rainwater. The resulting bicarbonate ions wash down streams and rivers and out to sea to settle. Our research is developing a market-ready tool to track the rate of ion formation, accounting for both upstream production emissions and downstream carbon losses back to the atmosphere. 

While pivotal to construction, cement produces a significant share of global emissions, due to the calcining of limestone. Our materials team is working on a partial replacement for traditional Portland cement, using wood ash. This material – typically considered a waste product – is rich in elements that naturally react with CO2 directly from the air. Our initial experiments found cement incorporating the carbonated wood ash performs comparatively well. Balancing upstream production against the carbon sequestration, our aim is to produce a cheaper and lower-emitting, even carbon-negative, building material.

To assist the deployment of these technologies, we’ll explore how they could work – and outline the benefits and risks of their introduction – in a series of case studies.

Underpinning the technology R&D, the team will conduct broader energy planning, subsurface modelling and legal and cultural assessment. 

The team is modelling New Zealand’s likely energy demands to mid-century and a CO2 removal roadmap aligned with the country’s net-zero 2050 target. Combining geological, resource, economic and societal data, we will map the regions of New Zealand best placed to introduce removals tech. Our subsurface modelling will determine what is likely to happen to CO2 injected into hydrothermal systems, deep saline aquifers and disused oil and gas wells. Our geochemical experiments recreating the conditions of underground reservoirs will establish the rate at which dissolved CO2 mineralises into solid carbonates, to substantially reduce the risk of leakage.

Many carbon removal technologies will have environmental trade-offs, so we are monitoring co-benefits and harmful outcomes. Our legal and cultural scholars are reviewing relevant local, national and international legislation and policy as well as best practice measurement, verification and reporting practices. We’ll also explore how carbon removal fits with New Zealand's founding document, Te Tiriti o Waitangi and the tikanga, or Māori customary law and practices, of the Indigenous partners with whom we’re working.

Please follow our research as it is published here, but here are a few highlights:

• Science Perspectives: Can enhanced alkalinity store carbon durably?

• Geothermics: Techno-economic analysis of geothermal combined with direct and biomass-based carbon dioxide removal for high-temperature hydrothermal systems

• International Journal of Greenhouse Gas Control: Reducing uncertainty associated with CO2 injection and brine production in heterogeneous formations.

 If you’d like to learn more or collaborate, please get in touch.