Six (potentially) surprising side-effects from carbon dioxide removal tech

One leading carbon removal technology may also protect marine species from increasing sea acidity.

We’re working on carbon dioxide removal to ensure a safe future where we and future generations can thrive. But that’s not the only driver to do it: the various new technologies offer positive co-benefits, but these aren’t often well known.

For this post, we’ll be discussing four carbon dioxide removal technologies, so here’s a quick overview in case you’re not familiar:

• Biochar. Organic matter, typically wood, receives a heat treatment that effectively turns about half the carbon in the fuel into a very stable, long-lasting form of carbon. It’s added to soil, and boosts crop growth.

• Enhanced rock weathering. Rocks with a natural carbon-capturing ability are ground into a very fine powder. This is sprinkled over farmland. Within droplets of rainwater, the rock reacts with carbon dioxide from the air to form bicarbonate ions that are washed into rivers and out to sea, where they settle.

• Bio-boosted geothermal. Waste wood from forest harvesting, a carbon-rich material, is burned in boilers that energise steam to power turbines at geothermal power stations. The carbon from the wood is captured as a gas, mixed with geothermal fluid and reinjected underground – or transformed into biochar.

• Carbon-storing materials. Carbon dioxide from the air is captured, using various methods, and used to produce critical materials such as cement, chemicals and plastics.

Aside from fighting climate change, here are six good reasons to introduce carbon dioxide removal:

1. Less synthetic fertiliser Several carbon removal technologies offer soil fertilisation benefits – particularly relevant with recent conflict in the Middle East affecting the supply and cost of artificial fertilisers. Research suggests biochar and enhanced rock weathering may both lessen the amount of synthetic fertiliser required, while maintaining crop productivity. Biochar’s effect on crop growth is better studied, and research indicates that farmers using biochar can reduce synthetic fertiliser by at least one fifth, while seeing the same – perhaps even better – growth. That’s because biochar makes the soil better able to retain nutrients and water, and provides a home for beneficial bugs. Meanwhile, the powdered rock used in enhanced rock weathering can also be applied on farms to reduce the acidity of soils. It provides other nutrients important for plant growth. One research study suggests that biochar and enhanced rock weathering complement each other: meaning farmers get even higher soil fertility benefits by combining the two.

   
   

2. Extra renewable energy Trees do a wonderful job of absorbing carbon dioxide from the air and concentrating it into wood: no expensive machines required! Unlocking this carbon offers an additional benefit: energy. When wood is combusted, it releases both carbon dioxide and heat. Under the concepts we’re developing, the carbon gets captured and stored long-term: perhaps as carbon dioxide in an underground high-saline system or disused oil well, alternatively as biochar. Meanwhile, the heat turns a turbine and generates electricity. Since we intend to use waste and low-grade wood from New Zealand’s vast commercial forestry sector, this would produce a new form of homegrown, renewable electricity.

   
   

3. Healthier seafood Climate change is making the ocean more acidic, affecting the health of shellfish. As humans pump more carbon dioxide into the air, that’s affecting the natural balance of ions in the ocean. Extra carbon dioxide in the atmosphere produces additional H+ ions in the sea. These H+ ions react with, thus reducing, carbonate ions in the ocean. As shellfish use carbonate ions to make their shells, their reduced availability is bad news for the marine creatures and seafood lovers everywhere. However, enhanced rock weathering produces extra bicarbonate ions on the land, which wash into rivers and out to sea – neutralising H+ ions and boosting levels of oceanic carbonate ions. At least for the sea waters near these projects, the deployment of this technology can help lessen the problem of acidification.

   
   

4. Greener materials Carbon is the backbone of many of the world’s most useful materials: it’s central to the carbohydrates that make wood as well as polymers that make plastic. Sometimes when we pull it out of the air, it’s a good idea to do something with the resulting substances. When wood ash reacts with carbon dioxide from the air, we end up with a solid carbonate. We believe this is a good opportunity to partially replace some Portland cement – typically, a high-emitting product – to create roads and footpaths, while storing the greenhouse gas for well over 100 years. Other members of our team are investigating how captured carbon could be used to produce sustainable aviation fuel or key components, ammonia and methanol. Our counterparts elsewhere in the world are looking at how to make plastics out of captured carbon dioxide.

   
   

5. Less storm debris Some removal technologies will rely on wood to supply a concentrated source of carbon dioxide, which the tree breathed in from the atmosphere as it grew. To reduce costs and maximise the climate impact, it can be a good idea to use waste wood: the material left behind on the site after a commercial harvest, and often known as slash. As New Zealand experiences more intense storms in our hotter world, slash is becoming an increasing problem. Large pieces can be washed off hills, down rivers and out to sea during extreme weather events – often damaging ecosystems, bridges, roads and homes along the way. By removing this potential hazard and using it to remove carbon, downstream communities will be safer when the next storms arrive.

   
   

6. Less of a particularly potent greenhouse gas Tiny bugs in the soil produce a greenhouse gas that, molecule for molecule, warms the atmosphere around 270 times more powerfully than others: nitrous oxide. Humanity accelerates this natural gas-production process by adding nitrogen fertilisers to the soil to promote crop growth. But research suggests that both biochar and enhanced rock weathering can dampen this down. There are numerous ways biochar could affect the complex processes in the soil responsible for nitrous oxide production – the additive can alter the ground’s acidity levels, for example. A scientific analysis combining the results of hundreds of individual studies concluded that biochar reduces nitrous oxide production by about a third. Of note, some studies found little effect, while others saw reductions as high as 55%. This variety is likely down to the properties of soil in the study and the type of biochar used. While there is far less research on enhanced rock weathering, one study concluded that it too may reduce nitrous oxide production.

We're planning to use wood waste – known as slash – meaning it won't become debris in storms.

All these benefits on top of actively pulling planet-heating gases out of the atmosphere – there’s much to draw attention to carbon dioxide removal tech!

And lest we forget, Nature has been doing this for far longer and at a far greater scale than humanity.

Forests and wetlands naturally absorb and store carbon, and offer the most incredible array of additional benefits: from cleaner air and water, to the joy of hearing native birdsong.

While there’s work to be done to ensure any risks are carefully balanced by the benefits, we believe Aotearoa New Zealand will soon experience the positives of well-aligned carbon removal technologies.