This article is part of illuminem's Carbon Academy, the ultimate free and comprehensive guide on key carbon concepts 

1. Introduction 

As already explored in previous articles, carbon projects can broadly be categorized into technology-driven and nature-oriented solutions. In this article, we dig deeper into the domain of carbon removal technologies, scrutinizing specific aspects of both natural and technological methodologies.

Below the aspects under consideration:

• Storage timescale: how long they will be storing the captured CO2
• Costs at scale ($/tCO2): financial cost per ton of carbon removal achieved when the technology is implemented at a large scale, often after initial research and development phases
• Price range
• 2023 average price per ton: amount of money required to remove one ton of CO2
• Mitigation potential (GtCO2/yr): how much CO2 they are likely to remove per year
• Risks: the dangers associated with a specific CDR technology
• Co-benefits: how it benefits communities
• Current state: current state of development
• Success subject to: what can determine the success of the CDR technology
• Funding needed for success: financial resources required to achieve desired objectives and goals effectively

The data presented herein is sourced from the following reports: The State of Carbon Dioxide Removal, RMI report, CDR.fyi.

2. A view at a glance

The graph below provides a concise overview of the key technologies:


image source: Advanced Biofuels USA

3. Nature-based solutions

3.1. Afforestation & Reforestation 

• Description
  Afforestation: establishing a forest or stand of trees in an area where there was no forest, contributing to environmental conservation and ecosystem restoration
  Reforestation: methodically planting trees in areas affected by deforestation or degradation to restore and replenish forest ecosystems
• Cost at scale ($/tCO2): 0-240
• Mitigation potential (GtCO2/yr): 0.5-10
• Risks: Reversal of CDR through wildfire, disease, pests. Reduced catchment water yield and lower groundwater level if species and biome are inappropriate. Finite carbon carrying capacity of land; capacity may be reduced under climate change.
• Co-benefits: Water produced and increased biodiversity

3.2. Blue Carbon

• Description: Enhancing and safeguarding coastal and marine ecosystems like mangroves, seagrasses, and salt marshes, recognized for their significant ability to capture carbon
• Cost at scale ($/tCO2): Insufficient data
• Mitigation potential (GtCO2/yr): <1
• Risks: Vulnerable to reversal through sea level rise. Difficult to quantify CDR accurately.
• Co-benefits: Can contribute to ecosystem-based adaptation, coastal protection, increased biodiversity. Could benefit human nutrition or be used to produce fertilizer for agriculture, to produce a methane-reducing feed additive, or as an industrial feedstock.

4. Tech-based Solutions

4.1. Enhanced Weathering

• Description: A geoengineering technique that speeds up natural mineral weathering to capture and store atmospheric carbon dioxide
• Storage timescale: 10,000+ years
• Cost at scale ($/tCO2): 50 - 200
• Price range: $ 132-1577
• 2023 average price per ton: $ 371
• Mitigation potential (GtCO2/yr): 2-4 
• Risks: Mining impacts; air quality impacts of rock dust when spreading on land; heavy metal contamination from some rock types.
• Co-benefits: Reduced soil acidity and increased nutrient supply, which can enhance plant growth and soil carbon sequestration

Enhanced Rock Weathering (Terrestrial)

• Success subject to: Approach proving safe for humans and the environment at scale 
• Funding needed for success: $250-700M over 7-20 years

Enhanced Rock Weathering (Coastal)

• Success subject to: Methodology cost effectiveness, environmental safety, and wide deployment across multiple continents
• Funding needed for success: $250-630M over 7-20 years

4.2. BECCS

• Description: A technology harnessing energy (biofuels, electricity, heat) from burning biomass like feedstock or waste, capturing emitted carbon dioxide, and storing it underground indefinitely
• Storage timescale: 10,000+ years
• Cost at scale ($/tCO2): 15 - 400
• Price Range: $ 300
• 2023 average price per ton: $ 300
• Mitigation potential (GtCO2/yr): 0.5-11
• Risks
  - Loss of biodiversity
  - carbon stock and soil fertility if from unsustainable biomass harvest
  - Energy requirements across the full life cycle, land use, and water requirements from scale up
  - limited waste biomass supply
  - cost
• co-benefits: Bioenergy (bio-electricity, biofuel, biogas) displaces fossil fuels and enhances fuel security. Reduction in air pollution when engineered BECCS facilities displace in-field biomass burning. Utilization of residues provides additional income and can improve crop growth and health. Purpose-grown biomass crops can enhance biodiversity, soil health, water quality and land carbon.

BECCS to fuel

• Success subject to: Breakthroughs in CCS technologies and sufficient supply of sustainable feedstocks
• Funding needed for success: $225M-$950M over 5-20 years

BECCS to electricity

• Success subject to: Breakthroughs in CCS technologies and sustainable biomass feedstock supply
• Funding needed for success: $300M-$1.5B over 5-15 years

4.3. DACCS (Direct Air Carbon Capture and Storage)

• Description: a process that utilizes specialized technologies to draw carbon dioxide directly from the air, often employing chemical sorbents or absorbents, and store it underground
• Storage timescale: 10,000+ years
• Cost at scale ($/tCO2): 100 - 300
• Price range: $ 440-2054
• 2023 average price per ton: $ 715
• Mitigation potential (GtCO2/yr): 5-40
• Risks: High water and energy usage, high energy requirements could lead to growing competition for low-carbon energy or increase GHG emissions, environmental impacts, and cost.
• Co-benefits: water produced
• Success subject to: Breakthroughs in materials, process design, and equipment, and increased cost effectiveness.
• Funding needed for success: $400M to $3B over 13-20 years

4.4. Biochar 

• Description: a type of charcoal produced from organic materials through a process called pyrolysis, used primarily as a soil amendment to enhance soil fertility and carbon sequestration
• Storage timescale: Centuries to millennia
• Cost at scale ($/tCO2): 10 - 345
• Price range: $ 42-250
• 2023 average price per ton: $ 131
• Mitigation potential (GtCO2/yr): 0.3-6.6
• Risks: Increased demand for biomass from unsustainable biomass harvest; uncertain degree of soil permanence; and land use, and water requirements from scale up. 
• Co-benefits: Increased crop yields; reduced non-CO2 emissions from soil; resilience to drought.
• Success subject to:
  - Improvements in carbon efficiency of biochar formation
  - supply of sustainable biomass feedstock.
• Funding needed for success: $450-650M over 10-12 years

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