THE CONTEXT
The IPCC special report "Global warming of 1.5°C" (2018) states that all analysed pathways limiting warming to 1.5°C with no or limited overshoot use carbon direct removal (CDR) to some extent to neutralize emissions from sources for which no mitigation measures have been identified and, in most cases, also to achieve net negative emissions to return global warming to 1.5°C following a peak. The IPCC Sixth Assessment Report (2022) states that the deployment of CDR to counterbalance hard-to-abate residual emissions is unavoidable if net zero GHG emissions are to be achieved. Apart from reforestation and afforestation (covered in sections on NBS and bioenergy), the main CDR options are geoengineering or negative emission technologies (NETs) involving Carbon Capture and Storage (CCS): Bioenergy Carbon Capture and Storage (BECCS) and Direct Air Carbon Capture and Storage  (DACCS). BECCS involves capture and storage of CO₂ emitted by bio-energy use whilst DACCS involves capture of CO₂ from ambient air followed by its storage. Other options such as mineralisation and enhanced weathering of rocks and ocean fertilisation are also considered. NETs were originally proposed as stopgap measures over the interim period before sufficient emissions cuts could be achieved. However, in the absence of adequate progress on the latter, their long-term or indefinite deployment is being increasingly mainstreamed in IPCC mitigation pathways.

CCS involves capture of CO₂ emitted by fossil fuel and biomass fuel use, followed by compression, transport via pipeline and high-pressure injection into near-depleted oil and gas fields, saline aquifers, or ocean beds. It is currently not commercially viable except in combination with enhanced oil recovery (EOR) – making it questionable as a climate change response, though interesting for the fossil fuel industry. Another motivation for its deployment is to reduce stranded fossil fuel infrastructure. Carbon leakage remains a major concern: during transportation or along faults and fissures after injection, thus increasing emissions later. Environmental impacts such as water depletion, toxicity, acidification and freshwater eutrophication have also been indicated.

BECCS (Bioenergy CCS) has taken centre-stage in recent years as a key CDR option and integral part of IPCC mitigation pathways. Virtually all climate change models projecting a future consistent with the Paris Agreement assume a key role for BECCS, which involves large-scale biofuel crop cultivation. Important studies have indicated that large-scale BECCS deployment is likely to steer us closer to the planetary boundaries (PB) for freshwater use and lead to further transgression of the PBs for land-system change, biosphere integrity and biogeochemical flows, implying large risks for biodiversity, nutrient and water cycles. Other studies indicate BECCS could seriously compromise biodiversity and food security. While citing BECCS as integral to all widely accepted pathways limiting warming to 1.5°C, the IPCC 6th assessment report Climate Change 2022: Impacts, Adaptation and Vulnerability also cautions that its large-scale use could damage ecosystems directly or through increasing competition for land, with substantial risks for biodiversity as well as profound implications for water resources. Moreover, within safe boundaries BECCS is estimated to only compensate for less than 1% of current global GHG emissions. In addition BECCS shares the hazards of the transport, injection and storage phases of CCS. However, energy and fossil fuel companies and providers are heavily investing in CCS/BECCS; these include Eurelectric, ExxonMobil, Chevron, BP, Shell and other European energy companies.

Other CDR options or NETs considered in IPCC scenarios, such as ocean fertilisation and enhanced weathering, also have serious potential consequences for biodiversity. Ocean fertilisation could lead to nutrient redistribution, restructuring of ecosystems, enhanced oxygen consumption and acidification in deeper waters. It could cause toxic algal blooms and marine dead zones from plankton die-off. Enhanced weathering involves mining and large-scale surface dumping of olivine.

Apart from CDR or NETs, another category of geoengineering technologies involves solar geoengineering or solar radiation management (SRM) that lowers atmospheric heat by bouncing sunlight back into space before it reaches the earth's surface. This can be achieved by injecting aerosol particles into the stratosphere or by modifying clouds and/or surface albedo to reflect sunlight. All SRM techniques modify the planet's radiative balance and are likely to alter the hydrological cycle and mess with weather patterns, disturbing ecosystems and biodiversity in unpredictable ways. It has been estimated that – even if SRM were used only temporarily – the long atmospheric life of CO₂ could lead to a quick and massive warming effect on abrupt termination and have a catastrophic effect on biodiversity. While SRM is not yet specifically included in official mitigation pathways, lack of action on actual emission reduction could force its future deployment.

The potential threats posed by large-scale geoengineeering deployment for biodiversity could be unpredictably greater than those from renewable energy expansion, further emphasising the urgent need for careful coordination between conservation efforts and RE implementation. Moreover, reliance on geoengineering could hinder a green transition by leading to technology lock-in, or by locking society into a high-temperature pathway if they are unsuccessful at reducing global warming to the extent assumed, or by normalising a carbon budget deficit via offsetting. Many scientists have expressed strong reservations and made multiple calls for a more holistic assessment of NETs.

EU POLICIES ON NEGATIVE-EMISSION TECHNOLOGIES
The adoption of the EU Green Deal, the Climate Law and the subsequent proposals to enhance energy and climate targets for 2030 have made carbon capture and storage technologies an important part of the EU decarbonisation effort. The Climate Law states that solutions based on carbon capture and storage (CCS) can play a role in decarbonisation, especially for the mitigation of process emissions in industry. CCS is considered key to tackling inherent CO₂emissions from energy-intensive processes in industries such as cement, iron and steel, aluminium, pulp and paper, and refineries. Its contribution via bio-energy carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS) is also included, as is its potential as a platform for low-carbon hydrogen production.

The Commission Communication (2021) on Sustainable Carbon Cycles lists key actions to support industrial capture, use and storage of CO₂. The communication also proposes the way forward to certify carbon removals towards establishing sustainable and climate-resilient carbon cycles. The key actions include developing methodologies to quantify climate benefits of sustainably produced building materials with carbon storage potential, an integrated EU bioeconomy land-use assessment, better support for industrial removals with the Innovation Fund, Horizon Europe support in the next work program (2023/24), a study on the development of the CO₂ transport network, update guidance for the CCS Directive, and organising an annual CCUS forum. forum. The Circular Economy Action Plan (2020) had also mentioned a forthcoming framework for the certification of carbon removals to incentivise uptake and increase circularity of carbon, in full respect of the biodiversity and zero-pollution objectives. In November 2022 the Commission followed this up with a Proposal for a Regulation establishing a Union certification framework for carbon removals, which seeks to (i) ensure the high quality of carbon removals in the EU, and (ii) establish an EU governance certification system to avoid greenwashing by correctly applying and enforcing the EU quality framework criteria in a reliable and harmonised way across the Union. The quality criteria for carbon removal certification involve following quantification rules with specific baselines, demonstrating additionality, ensuring long-term storage, and supporting sustainability objectives on climate change, biodiversity, pollution and a circular economy.

A report (July 2022) from an EU-supported project CCS in a biodiversity and land use perspective notes that the impact of CCS on land use and biodiversity requires thorough investigation. Its assessment of the biodiversity and land use impacts of CCS led to detailed recommendations on EU deployment of CCS/BECCS/DACCS. Its recommendations include making biodiversity and other ecosystem sustainability considerations a pre-requisite for the production and use of biomass for industrial or energy purposes. On CO₂ capture its recommendations include systematically conducting a comprehensive life cycle assessment of CCS/BECCS/DACCS projects, including a full set of environmental impact indicators, beyond GHG emissions, to assess impacts on land use and biodiversity. Regarding CO₂ transport and storage its recommendations include minimising corridors, actively monitoring and restoring disturbed land with native species, and ensuring strict measures by operators to prevent CO₂ leakage during transport and storage. While indicating that Northern Europe has optimal conditions for the deployment of BECCS plants, the report concludes that – for the same energy yield – renewable hydrogen and electricity from wind turbines have lower land requirements than biomass, indicating a lower impact on biodiversity.