In the pursuit of achieving a net-zero carbon future, the International Energy Agency (IEA) has laid out ambitious targets, with a particular focus on Direct Air Capture with Carbon Storage (DACCS) aiming to capture almost 60 Mt CO2/yr by 2030. This article delves into the landscape of Engineered Carbon Dioxide Removal (CDR) technologies, their potential, and the challenges they face.
The Engineered CDR Landscape
Engineered CDR technologies, although promising, are still in their early stages of development. The IEA's net-zero scenario emphasizes the urgency of investing in these technologies to ensure their scalability and timely deployment.
Carbon Removal Technologies
Carbon removal methods can be broadly classified into Natural Climate Solutions (NCS) and Engineered CDR. Engineered CDR solutions, crucial for achieving the desired targets, encompass Biochar Carbon Removal (BCR), Bioenergy with Carbon Capture and Storage (BECCS), Enhanced Rock Weathering (ERW), and DACCS.
- 1. Biochar Carbon Removal (BCR)
BCR involves creating charcoal through the pyrolysis of biomass, such as crop residues, grass, or trees, at high temperatures without oxygen. Biochar, when mixed with soil, enhances fertility and exhibits potential durability for centuries. The cost of biochar removal is estimated to be $10–$345 per tonne of CO2, with a mitigation potential of 0.3–6.6 Gt CO2/year by 2050. Its affordability positions biochar as a rapidly scalable option, although its potential is limited by the availability of sustainable biomass.
- 2. Bioenergy with Carbon Capture and Storage (BECCS)
BECCS involves burning biomass for energy or biofuel production, with subsequent carbon capture from flue gas. The cost of BECCS is estimated at $15–$400 per tonne of CO2 removed, with a mitigation potential of 0.5–11 Gt CO2/year by 2050. While momentum is growing, the limited availability of sustainable biomass poses challenges to BECCS scalability.
- 3. Enhanced Rock Weathering (ERW)
ERW mimics the natural CO2 cycle by spreading ground-up minerals like dunite or basalt across various surfaces to absorb atmospheric CO2. The IPCC estimates the cost of ERW at $50–$200 per tonne of CO2 removed, with a mitigation potential of 2–4 Gt CO2/year by 2050. Despite uncertainties, ERW stands out for not requiring new infrastructure or technology.
- 4. Direct Air Capture with Carbon Storage (DACCS)
DACCS employs fans and filters to selectively trap CO2 molecules from ambient air, with the captured CO2 stored underground. The cost of DACCS is projected to decrease to $100–$300 per tonne of CO2 removed by 2050, with a mitigation potential of 5–40 Gt CO2/year. However, the current high costs and limited scalability due to energy-intensive processes pose challenges.
Challenges and Opportunities
The scalability of Engineered CDR technologies, particularly DACCS and BECCS, is hindered by factors such as high costs, infrastructure requirements, and limited availability of sustainable resources. Collaboration, innovation, supportive policies, and investments are crucial to overcoming these challenges and driving down costs, making these technologies more accessible and effective in the journey towards a net-zero future.
As the IEA's net-zero scenario necessitates significant carbon removal by 2030, Engineered CDR technologies play a vital role in achieving these targets. Continued investment, research, and collaboration are essential to realizing the potential of these technologies and addressing the challenges that currently impede their widespread adoption. Only through concerted efforts can society transition to a sustainable and low-carbon future.
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