INSIGHT by Danielle Riedl and Katie Lebling.This article was originally published by the World Resources Institute.

In the past few years, carbon dioxide removal (CDR) has transformed from a little-known concept to a generally accepted component of climate action portfolios, with billions of dollars of public support and hundreds of millions of dollars in private spending supporting its growth.

This shift has been driven by the scientific consensus that removing carbon dioxide (CO2) from the air will need to play a critical role to limit global temperature rise to 1.5 degrees C (2.7 degrees F) — this conclusion was initially included in the Intergovernmental Panel on Climate Change’s landmark report on 1.5 degrees C in 2018 and notably underscored in the just-released 2023 Sixth Assessment Report.

CDR will play a critical role in helping meet climate targets, but it cannot be a substitute for drastically reducing greenhouse gas emissions, which must remain a top priority.

The growing interest and investment in CDR is spurring wide range of new CDR approaches and technologies. Each is at different stages of development, varies in where and how carbon is sequestered, and how easy it is to measure how much carbon is removed. While some approaches and technologies may provide unexpected and valuable co-benefits, many also present uncertain environmental and social impacts.

As carbon removal is a comparatively new field, developing a broad portfolio of technologies and approaches will be critical to reducing risks and costs and helping ensure there is capacity to remove carbon from the air at the levels needed in coming decades.

Here are four key things to know about the recent growth and diversification of the CDR field over the past several years.


1. Many new CDR approaches are emerging

Just a few years ago the CDR landscape was primarily made up of three companies — Carbon Engineering, Climeworks, and Global Thermostat — focused on direct air capture (DAC), arguably the most advanced and well-understood CDR technology. This portfolio has grown and diversified significantly over the past several years:

Direct Air Capture: Start-up companies, like Noya, are developing new DAC technologies that can reduce energy or resource use and can be integrated into existing infrastructure, which can avoid some of the challenges that come with siting new, standalone infrastructure. For example, DAC can be integrated into a building’s cooling towers, which remove a building’s heat by circulating water and air. The air moving through this cooling system can be redirected into pipes and stand-alone carbon dioxide capture equipment. The system uses small surface areas and could reduce energy needs. Other conceptions of DAC, such as a technology developed by Verdox, may be able to significantly reduce energy usage.

Biomass-based CDR: Instead of combusting biomass and capturing the emissions (as is done with bioenergy with carbon capture and storage, or BECCS), there is growing interest in using biomass — organic material from plants — for direct carbon removal. One iteration of this from Charm Industrial involves converting biomass left over from growing crops into a carbon rich “bio-oil” and injecting that into the ground where that carbon is sequestered. Another approach, developed by Kodama Systems, involves improving forest management practices, including forest thinning to reduce wildfires, combined with burial of residual wood for carbon removal.

MineralizationOcean alkalinity enhancement is a type of carbon mineralization that can be done with certain types of rocks that are reactive with carbon dioxide, such as olivine. Some companies, like Vesta, are looking into mixing this ground rock with sand and spreading it on beaches. In this way, the wave action helps speed chemical reactions that lock away carbon dioxide, while also helping replenish eroded coastlines, potentially reducing storm surges. On land, ground up basalt rock that can be applied to croplands to improve soil quality while it removes carbon.

Ocean CDR: Some companies plan to farm seaweed such as kelp or sargassum in the open ocean and are testing methods of sinking it to the deep ocean to sequester the carbon it contains. For example, Seafields cultivates and sinks sargassum by bursting its air sacs. Others, like Seaweed Generation, are collecting existing Sargassum and sinking it with automated vessels. In the past decade, sargassum has grown at explosive and invasive levels in the Central Atlantic, which could be linked to fertilizer runoff into the ocean. This approach could help alleviate that nuisance while removing carbon.

Crop Enhancement: Researchers and companies are exploring the use of enhanced photosynthesis for carbon sequestration. This is a process already used in agriculture to genetically modify, or breed, hybrid plant species to increase carbon dioxide uptake and sequestration in the soil. Some new CDR companies, like Living Carbon, are developing trees with enhanced photosynthesis capacity through gene editing so that they can grow faster and absorb more carbon dioxide. In one case, a metal accumulation trait can help these trees absorb metals through their roots, which can slow down the decay of wood, and allow these trees to be planted on land contaminated with heavy metals. Others, like Recapture, are using hybrid tree species, which are not genetically modified but are bred to absorb more carbon dioxide and grow faster. The tree’s wood is then used for building materials, storing embodied carbon.


>> click to zoom in  All opinions expressed are those of the author and/or quoted sources. is an independent and neutral platform dedicated to generating debate around ESG investing topics.

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