Environmental impacts and co-benefits
CDR can require land, water, energy and other inputs, which may be associated with resource competition or depletion, raise pollution concerns and impact ecosystem quality. To appraise CDR options, we must go beyond assessing their potential role in climate change mitigation and investigate their wider environmental impacts and co-benefits. We consider impacts across the entire supply chain – from resource extraction and processing to transport and waste disposal – to identify environmental risks associated with a given CDR, as well as opportunities to improve its processes and enhance co-benefits.
As many CDR approaches involve large-scale land use, much of the environmental assessment comes down to the impact of different land cover and land management practices. For example, it is important to consider how the agricultural practices in growing ‘biomass’ crops for bioenergy with carbon capture and storage (BECCS) compare with current crop production, or how the impacts would change if there was a risk of natural vegetation being converted to biomass crops. In some cases, these impacts may be positive: some land-based CDRs deployed in appropriate locations have the potential to assist in biodiversity recovery, ecosystem restoration and climate adaptation, alongside their climate benefits.
To account for the environmental co-benefits and impacts potentially related to deploying and scaling up CDRs, we recommend the following environmental indicators.
See the Evaluation page for more detail on how we assess environmental impacts.
CO₂RE’s environmental indicators
Our framework assesses environmental sustainability through three key indicator sets: use of land and water, change of biodiversity, and quality of water, air and soil. These indicators can be largely assessed through Life Cycle Assessment (LCA) methods, as described on the Evaluation page.
Natural resource use: Land use and water use
Land use
Land is a key requirement for many CDR options, whether for growing biomass crops, planting trees, applying biochar or basalt, or building infrastructure. The land-use indicator captures how much land a CDR project requires, and how that requirement might change if the project is scaled up in the future. However, land use is not solely a question of the amount of land needed. The location and type of land used or converted, as well as how it is managed, all shape the environmental and social consequences of a project. For example, whether a CDR method is deployed on marginal ‘brownfield’ land or prime agricultural land can have very different implications for ecosystems, farmers and food systems.
Water use
Water is another contested resource that some CDR types need, particularly those reliant on growing biomass, afforestation and technical processes that require water inputs. The quantity of water required and the location that water is pulled from can have implications for local water scarcity and knock-on effects for the ecosystem and other users. The extent of water depletion and consideration of water scarcity are both accounted for in our framework.
This includes water used on-site, where the CDR method is directly applied, as well as water embedded in the upstream inputs, such as the water used in a nursery to grow tree saplings before planting.
Water availability varies enormously between locations, and the same volume of water can have very different impacts depending on where it is consumed. Using water in an already water-scarce region raises far greater concerns than the same usage in a water-abundant one. Capturing the local context is an important part of understanding a project’s true water footprint.
Biodiversity change
The biodiversity indicator captures how species diversity and abundance changes in response to CDR deployment. Depending on how and where they are deployed, CDR projects can pose risks to biodiversity, for example through habitat conversion or loss, but may also offer opportunities for biodiversity gains, such as through ecosystem restoration.
Measuring biodiversity is not straightforward. Biodiversity indicators could include a range of simpler metrics monitoring the diversity of life, from genetic diversity within individual species, to changes in population size and ecosystem species composition. There are also ongoing attempts to develop indicators that link biodiversity change and ecosystem health to ecosystem functioning, i.e. provision of ecosystem services such as pollination.
As such, it is challenging to detail all possible biodiversity indicators and where they may be important for this framework, but we suggest potential routes from the minimum recommended standard to more elaborate approaches on the Evaluation page.
Water, air and soil quality
Different land uses and types of managements have implications for water, air and soil quality. For example, fertilisers applied for growing biomass crops for CDR may be lost to water. Excessive nutrients in water could cause dense algal blooms, which can kill all life beneath them.
This indicator captures these kinds of impacts on ecosystem quality that go beyond greenhouse gas emissions alone, spanning nutrient runoff, air pollutants and soil contamination or degradation.
Importantly, CDR interventions can also deliver co-benefits in these same areas. Increasing soil carbon, for instance, can improve soil stability and reduce nutrient losses, while ecological restoration along waterways can help reduce downstream flood risk. Capturing both the risks and the potential co-benefits of a CDR method is central to understanding its full environmental profile.