Land-Use Implications of Carbon Dioxide Removal: An Emerging Legal Issue?

Abstract

Science has expressed concerns that carbon dioxide removal (CDR) as a means to fight climate change could potentially increase competition for land and contribute to soil degradation. This paper aims to map out the potential land-use and soil implications of CDR to identify possible lines of political and legal conflicts. To this end, we will briefly introduce the most promising removal approaches, highlight existing preliminary estimates about their removal potential, give some basic assumptions about their effects on competition over land and the environment, and discuss the demand for political and legal action (Sect. 5).

1 Introduction

Parties to the Paris Agreement aim to hold the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the global temperature increase to 1.5 °C above pre-industrial levels. To achieve this, many scientists and governments agree that climate neutrality must be realized by 2050, i.e. there must be a balance between greenhouse gases emitted and the absorption of greenhouse gas emissions by sinks.¹ This objective reflects a broad consensus in the scientific community about what is necessary to avoid dangerous anthropogenic interference in the climate system.² Attaining climate neutrality, however, requires, drastic measures. Most importantly, the use of fossil fuels for energy production must be phased out and emissions from activities that are difficult to avoid have to be reduced as far as possible.

Several factors, however, not only make the goal of less than a 1.5 °C temperature increase very challenging, but in fact make an emission overshoot likely. First, the states’ current greenhouse gas reduction commitments under the Paris Agreement—the so-called Nationally Determined Contributions—are projected to only limit temperature increase to 2.4 °C.³ Second, even if states would undertake all necessary actions to achieve these (insufficient) goals, there is no guarantee that they will succeed in due time. Success in sufficiently reducing GHG-emissions depends on a myriad of social, political, and environmental factors and developments, some of which are difficult to generate or predict. Third, based on our current technical understanding, it is difficult to decarbonize some important sectors, such agriculture and transport.

Against this background, the IPCC in its 1.5 °C Report from 2018 has included so called “negative emissions” in most of its climate scenarios, implying that they will be necessary to some extent if less than a 1.5 °C or even 2.0 °C temperature increase is to be achieved.⁴ Negative emissions have broadly been defined as the “removal of greenhouse gases (GHGs) from the atmosphere by deliberate human activities (…).”⁵ The process of carbon dioxide removal (CDR), in turn, comprises different methods and techniques deployed to reduce the atmospheric CO₂ concentration (see below).⁶ In addition, the IPCC’s Sixth Assessment Report of 2022 also highlights the importance of CDR.⁷  It emphasizes that the quantity of removal activities required will depend on both the ambition and the success of mitigation efforts. Accordingly, projected extraction ranges from 100 GtCO₂ to 1000 GtCO₂ by 2100. The IPCC’s statement on negative emissions has sparked a lively debate in climate sciences and politics about appropriate actions to create negative emissions, and several industrialized countries such as Japan, Sweden, Germany, Canada, the USA, and the European Union have included CDR measures in their national climate policies.

Relying on the prospects of CDR, however, could bear several risks.⁸ Uncertainties regarding political, economic, and technical aspects may lead to the over-estimation of removal potentials, which could eventually end up leaving too much CO₂ in the atmosphere and creating so-called lock-in effects regarding the newly developed technologies.⁹ Second, there is a widely spread fear that the emerging option to retrieve CO₂ from the atmosphere may in fact reduce efforts to avoid CO₂ generation. This mitigation deterrence effect, as it is called, is fueled by a strong economic incentive to fully exploit the remaining fossil energy carriers and not loose former investments (stranded assets). Finally, different removal activities may potentially create various negative side effects, both on people and the environment.¹⁰

One reoccurring critique is that several of the removal options may require a lot of space, thus increasing local, regional and even global competition for non-degraded, agriculturally productive, or biodiverse land, which has globally become an increasingly scarce resource.¹¹ The chapter aims to map out the potential land-use and soil implications of CDR to identify possible lines of political and legal conflicts. To this end, we will briefly introduce the most promising removal approaches (Sect. 2), highlight existing preliminary estimates about their removal potential (Sect. 3), give some basic assumptions about their effects on competition over land and the environment (Sect. 4), and finally discuss the demand for political and legal action (Sect. 5).

2 CDR Methods

At present, a variety of different methods for the deliberate removal of greenhouse gases from the atmosphere are being discussed.¹² Discussion mainly focuses on the removal of CO₂ as the biggest contributor to the greenhouse effect.¹³ For removal activities to be effective in the long term, gases must be stored or sequestered in the ground, in the ocean or seabed, or in artificial reservoirs.¹⁴

CDR methods may be classified according to different characteristics.¹⁵ While some measures accelerate or expand the natural carbon sequestration processes, others are technology-based.¹⁶ Some methods store greenhouse gases terrestrially (e.g., in soil or in deeper ground-layers), others in the oceans or under the seafloor. Some techniques use biological processes for removal (esp. photosynthesis), while others use chemical or geochemical processes.

Of all terrestrial removal approaches, the “Bioenergy with Carbon Capture and Storage” (BECCS) is probably receiving the most attention.¹⁷ For BECCS, large-amounts of biomass are used to generate energy, then the resulting CO₂ is captured and stored underground.¹⁸ The biomass would stem either from energy crops, or from forestry or agricultural sources which may or may not be specifically planted for this purpose.¹⁹ Two other nature-based terrestrial CDR approaches include afforestation and reforestation, i.e. the planting of trees for creating new forests or re-planting trees in areas where there used to be forests.²⁰ Growing trees extracts CO₂ from the atmosphere, thus creating a carbon reservoir.²¹ Another discussed CDR option in this category would be the insertion of biochar into the ground. This involves “carbonizing” biomass (through thermochemical conversion or hydrothermal carbonization) and injecting the char into soils for storage.²² There is also the “enhanced weathering approach”—a process by which the natural decaying-process of certain rocks is artificially accelerated and CO₂ is chemically or physically bound. Enhanced weathering can be achieved, for example, by crushing silicate rocks that contain calcium and magnesium and then spreading particles over large areas of arable land. Finally, another nature-based terrestrial strategy to remove carbon from the atmosphere is to improve soil management practices to increase carbon sequestration.²³ On one side this involves strengthening utilization practices that expand the input of CO₂ into soils, e.g., through the rewetting and sustainable management and use of peatlands (i.e. paludiculture²⁴), generally improved agricultural practices, or systematic fire management in forests, and, on the other side, avoiding activities that promote the discharge of CO₂ from soils (e.g., the conversion of grasslands).²⁵

In addition to modifying or accelerating the terrestrial natural carbon cycle processes, technology-based approaches are being developed by which greenhouse gases are filtered out of the atmosphere (“Direct Air Capture” or DAC).²⁶ DAC approaches capture CO₂ from the ambient air, compress it, and then either store it underground (Direct Air Carbon Capture and Storage or DACCS), or put it to further use (Direct Air Carbon Capture and Utilization or DACCU), primarily using chemical binders.²⁷ Further use, however, results in negative emissions only if the removed carbon remains stored in the product. Accordingly, the duration of sequestration essentially depends on the lifetime of the products. DACCU approaches are climate-neutral at best, which is why they are also referred to as “circular carbon” approaches.²⁸

Here, carbon capture and storage (CCS), is of particular interest.²⁹ CCS does not aim at avoiding the formation of CO₂, but merely prevents its release into the atmosphere.³⁰ The CO₂ is captured during power generation or in the course of industrial production processes and then stored underground. CCS thus shares with DACCS and BECCS the storage element, since none of these approaches would be climate effective without storage.³¹ At the global level, CCS came into discussion as early as 2005 in international climate politics, including in a publication by the IPCC specifically dedicated to CCS.³² Discussions have recently been re-ignited and are expected to intensify due to the debate around CO₂ removal.³³

Terrestrial nature-based and terrestrial technology-based CDR methods are potentially complemented by ocean-based methods. While these methods will not directly impact land-use and soils, they will do so indirectly. They may possibly serve both as an alternative or a supplemental approach and may thus influence the scale of land-based methods. Different options are referred to as blue carbon, ocean alkalinization, ocean fertilization, and marine CCS. While marine CCS basically resembles land-based CCS in that it uses subsurface storage sites (under the seafloor), blue carbon includes techniques which store CO₂ in marine and coastal ecosystems, particularly through seagrass beds, salt marshes, and mangrove forests. The protection and expansion of these areas can contribute to carbon removal and storage.³⁴ Ocean alkalinization, in turn, aims to expand the sea’s capacities to absorb CO₂ by increasing its alkalinity, e.g. through the placement of Ca(OH)₂.³⁵ Finally, ocean fertilization aims to supply “fertilizers” (e.g. iron) to certain nutrient-poor ocean regions (usually far offshore) to stimulate algal growth, binding atmospheric CO₂. When the algae die, they sink to the bottom of the sea and store removed CO₂.³⁶

3 Removal Potential

Estimated removal quantities still vary widely for different CDR methods, for different countries, and for the global level.³⁷ The vast majority of scientists agree, however, that removal methods will not serve as an alternative to ambitious mitigation strategies.³⁸ Most importantly, if CDR methods were to effectively contribute to reducing CO₂ levels in the atmosphere, they would have to be applied at a large scale. Successfully scaling-up existing or currently tested approaches and rendering them effective, however, depends on multiple social (particularly economic, political, and legal), technical, and natural factors, many of which are difficult to predict or provide. For example, political commitment to ramp up removal techniques would strongly depend on emission reduction ambitions and gaps, consumer behaviour and interests (for example, with a view to consuming meat, flying, cars, etc.), and existing incentives for industries to make CDR a business case, etc. In addition, most removal methods will require huge commitments to research, development, and implementation regarding CDR methods.³⁹ Furthermore, large-scale afforestation, reforestation, soil management and BECCS would require successful long-term and sustainable management of forests or the cultivation of bioenergy crops. The duration of CO₂ storage by these means, however, can be -reversed by natural or human-caused factors, e.g., droughts, fires, and plant diseases). In the case of BECCS, again, CO₂ stored in geological reservoirs is less prone to this reversion.⁴⁰ Finally, the implementation of DACS-infrastructures may face acceptance problems. The subsurface storage of CO₂ in particular is unpopular in large parts of Europe (Table 1).⁴¹

Table 1 Estimated removal potential of different CDR-methods by 2050^a

Against this backdrop, two points become evident. First, CDR does not offer a quick fix to the climate problem. Second, at this point, assessing and estimating the structure, the size, and the removal potential, as well as the resource and spatial demands of future removal measures is extremely difficult, not only at national levels but particularly at a global level.⁴²

4 Land-Use Implications and Environmental and Economic Effects

Several authors have expressed concern that CDR measures could have major land-use implications. In particular, replacing ongoing uses for the purpose of CO₂ removal might increase competition over land. In our context, competition over land means that the use of land for CO₂ removal by one actor rules out, reduces, or makes more expensive the use of land by others. It is especially feared that food production and environmental conservation might be negatively affected.⁴³ Such effects are still difficult to predict as they will depend on the CDR activities to be deployed and other factors such as local context, management, previous land use and the scale to be applied.⁴⁴ Hypothetically, however, were CDR approaches to be developed at large scale, some specific basic effects seem likely.

First, terrestrial removal methods will have land-use impacts. They will introduce a new demand for land, i.e. surface or subsurface spaces are required for an additional purpose. The impact level would depend on the scale of the respective removal activity, which, in turn, would be determined by the amount of CO₂ that it is meant to remove from the atmosphere.⁴⁵ Where BECCS, afforestation, reforestation, and biochar would be carried out they would use terrestrial surface space and replace or reduce land-use opportunities for other uses (e.g. regular agriculture, forestry).⁴⁶ The rewetting of peatlands and increasing soil-carbon would also reduce opportunities to carry out conventional agriculture. In addition, scaling up technical approaches such as BECCS, DACS and CCS requires (a) the construction (or refurbishing) of large facilities for capturing and storing CO₂ and (b) reserving spaces suitable for removal and storage (i.e. using land which is geographically close to renewable energy sources and storage sites).⁴⁷ Finally, sub-surface storage of CO₂ may prevent the use of the respective areas for other sub-surface activities (e.g., storing different gases, or maintaining drinking water sources, and possibly geothermal energy exploitation⁴⁸).

Second, the land-use could have different economic effects that could be determined by many other factors, including, for example, the land’s past and future alternative uses.⁴⁹ At a basic level, nevertheless, adding another land-use practice would reduce the overall availability of land on the market and raise demand. Increasing demand for land could, in turn, make food production more expensive.⁵⁰ In addition, changed use practices could also reduce net gains from certain land-use practices (e.g. changing from regular agro-industrial production to paludiculture).⁵¹ It is important to point out, however, that although all CDR methods require a certain amount of surface or subsurface space, they may not necessarily create or increase competition over land. For example, spreading crushed silicate to enhance weathering over vast areas of arable land will not necessarily exclude, reduce or make more expensive agricultural practice and may even have a number of positive effects on soils (and possibly some negative).⁵² In addition, where negative side effects can be avoided, subsurface storage of CO₂ may have little effect on surface activities.

According to our understanding, competition over land would most likely increase where the overall availability of land for other purposes is reduced. This would also be the case where CDR methods would degrade land’s environmental status and reduce its potential for providing different ecosystem-services, such as providing clean drinking water or hosting ecosystems rich in biodiversity. The environmental impacts, particularly those on soils, water, and biodiversity, will vary depending on the removal activity, how it will be carried out, and most of all its scale.⁵³ To render CDR methods climate-effective, i.e. in order to remove significant quantities of CO₂ from the atmosphere, most approaches would have to be carried out at a large scale.⁵⁴ Large-scale removal, however, carries the risk of creating significant environmental harm.⁵⁵ For example, the introduction of biochar into soils over vast areas of land, though adding nutrients to soils, may also change the microbial composition of the soil if the addition of biochar is at high rates. This could lead to the reduction of genes related to plant immunity and defense.⁵⁶ Similarly sized enhanced weathering activities may have significant physical and chemical impacts on soils as well as on ground and surface water.⁵⁷ Building large-scale BECCS, DACS and CCS infrastructures will require substantial amounts of material (e.g. metals and chemicals) and the process of filtering carbon out of the air would demand large amounts of energy (in the form of heat and/or electrical energy).⁵⁸ Providing both materials and energy may also have significant environmental effects. With regard to the CCS technology, it is feared that the sequestered CO₂ could escape and that the storing process might set free chemicals or salty water from deeper ground layers and push them to the surface, where they could salinize and spoil soils as well as ground and surface water.⁵⁹

5 Preliminary Conclusions, Discussion, Outlook

Substantial uncertainties remain with regards to the potential impacts of the development of CDR. While it appears relatively easy to calculate the required scale and space for the different CDR approaches to remove certain quantities of atmospheric CO₂, it is much more difficult to predict (a) if, how, and when CDR can be scaled up in different countries or regions and (b) what effect that would have on competition over land, whether locally, at country-level, across borders, or at a global level.⁶⁰ Such effects may vary in different places and circumstances and will depend on many variables. Despite all these uncertainties it is clear that all large-scale CDR methods would require substantial amounts of surface or subsurface space, and that this can lead to changes in land-use practice, negatively affect the environment, increase competition over land, and possibly increase costs for food production.

The potential scale of CDR projects justifies worrying about these possible effects. Two aspects regarding land use and food security are of particular concern.

First, it becomes clear though that the potential for severe conflicts are globally unevenly distributed. Increasing land or food prices, for example, would predominantly affect food insecure regions.⁶¹ According to the FAO, “moderate to high rates of hunger and/or child undernourishment still affect 53 countries.”⁶² The number of people who are insufficiently nourished was recently estimated to lie between 690 million and 820 million people.⁶³

Second, land for food production is not necessarily scarce at a global level; it is scarce in some regions and often inefficiently, unsustainably, and—arguably—unethically used. The production of animal-based food, for example, is one of the most important factors in this regard. While the consumption of meat products are estimated to have tripled since the 1960s (due to population growth, increasing affluence, urbanization, and globalization),⁶⁴ its negative effects on human health and the environment are well understood.⁶⁵ Industrial meat production is particularly demanding of space. For example, according to the FAO, approximately 26% of the ice-free terrestrial surface is used for animal grazing and 33% of arable land is used for growing crops for animal feed.⁶⁶ In some countries, the share of land used for growing fodder for animals is much higher and often fodder is also imported from third countries. In Germany, for example, 60 to 70% of agricultural land is used for growing plants for animal feed. It has also been estimated recently that if humans would choose a vegan diet, agriculture would eventually need only a quarter of the land it uses today. If meat from cattle and sheep were avoided, agricultural land use could be cut in half.⁶⁷ Still, CDR leading to changes in land use practices, degrading land, increasing competition over land, and possibly raising costs for food production and consumption could create social, ethical, environmental or legal conflicts, some of which are local, some of which are global.⁶⁸ It may particularly affect poor consumers in both rich and low-income countries. For those who live under food insecure conditions, rising costs for food can be life-threatening.

Against this background, developing and deploying CDR measures at large scale will require political and legal action. At present, a large-scale development and deployment of CDR would basically be unregulated (maybe with the exception of ocean fertilization⁶⁹), including those approaches which may lead to competition over land (and have negative effects on the environment or food production). Considering their potential transboundary or possibly even global effects thus calls for an internationally coordinated governance approach. This will be particularly important with a view to integrating CDR-measures into the international climate regime (e.g. clarifying how the removed carbon can be counted with regards to achieving nations’ Nationally Determined Contributions under the Paris Agreement), to guarantee their effective and non-collusive implementation (e.g. adopting transparent accounting systems to prevent green-washing practices), and ultimately avoiding negative side effects, including those investigated here as well as mitigation deterrence.⁷⁰

At present, there is, however, a range of international policy and legal instruments that aim to protect land and soil from degradation. Since human induced factors contributing to land and soil degradation are so manifold these days (e.g. urbanization, deforestation, unsustainable agricultural practices, unsustainable use of water etc.), so are policies and laws aiming to keep land in good condition.⁷¹ Some of them are binding, some of them are not. In the event that removal activities would steeply increase, these different political and legal requirements would have to be taken into consideration, and land degradation would have to be avoided in order to comply with them. At a fundamental level, future regulations need to be guided by some basic objectives and principles. First, the UN’s “Sustainable Development Goal 15 (Target 3)” lays down the following political goal: “By 2030, combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradation-neutral world.”⁷² Particularly with a view to avoiding transboundary effects, protecting the climate through CDR must neither lead to transforming one environmental problem into another nor transferring hazards from one region to another. In this light, would be called upon to remove CO₂ by mainly using their own territory. Where removal or storage activities would be carried out abroad, operators are to be required to ensure that their activities, including their investments in land, would not negatively affect food security and the environment in the destination area. Activities and investments would have to comply with safeguards and standards, for example, similar to those developed for transboundary investments in farmland.⁷³