Results

Afforestation and reforestation

Potentials and key side-effects of afforestation and reforestation. See bottom of page for symbol explanation (Source).

Potentials and costs

  • The availability of sustainable land drives variation in potentials
  • Costs depend on the region considered – higher in the global North, lower in the tropics
  • Cost estimates in the scientific literature have increased over time
  • Our 2050 costs and potentials:
    <3.5 GtCO2/yr
    5-50 $/tCO2 (500 Mha; marginal land; tropics)

Side-effects, readiness, permanence

  • Many positive and negative side-effects are highly implementation dependent: fast growing mono-culture plantations can impact on local biodiversity; native agroforestry systems could have local economic and environmental benefits.
  • Land-use is a major challenge with regard to competing priorities, such as food production and conservation
  • Forest carbon saturates within period of decades to centuries
  • Sequestered carbon is vulnerable to natural and human-induced disturbances, such as renewed deforestation or degradation
  • Forests require on-going management to maintain permanent carbon sinks

Biochar


Potentials and key side-effects of biochar. See bottom of page for symbol explanation (Source).

Potentials and costs

  • Biochar potentials depend on the availability of biomass and land
  • Costs depends on the scale of application, specific processes and technology upscaling assumptions
  • There are efficiency limits in the process (only 25% of plant biomass gets stored)
  • Our 2050 costs and potentials:
    <2 GtCO2/yr
    30-120 $/tCO2

Side-effects, readiness, permanence

  • Biochar has a series of co-benefits: increased yields and reduced drought losses; reduced CH4 and N20 emissions from soils; and soil quality improvements
  • Negative side-effects are implementation and scale dependent; e.g. indirect land-use change, albedo effects etc.
  • Biochar is very stable and cannot be easily reversed

Bioenergy with carbon capture and storage

Potentials and key side-effects of afforestation and reforestation. See bottom of page for symbol explanation (Source).

Potentials and costs

  • Potentials are limited by the availability of “sustainable“ biomass rather than sufficient storage
  • The variability in estimates are explained by assumptions regarding agricultural yields and sustainability constraints
  • Cost variations are determined by the feedstock, process and technology pathways considered
  • 2050 potentials and costs:
    < 5Gt CO2/yr
    100-200 $/tCO2

Side-effects, readiness, permanence

  • There are a variety of negative side-effects raised in the literature
  • Land competition and indirect land-use change are particular concerns
  • Costs beyond 2050 are expected to rise due to increased competition for land and biomass
  • Innovation and deployment are lagging far behind what we see in scenarios

Direct air capture

Potentials and key side-effects of direct air capture. See bottom of page for symbol explanation (Source).

Potentials and costs

  • High costs are major barrier to market entry right now. These are largely comprised of up-front capital costs.
  • There is a large disagreement about costs and little transparency behind estimates
  • Potentials seen by many as limited solely by economic costs and the barriers to upscaling
  • Our 2050 costs and potentials:
    < 5 GtCO2/yr
    100-300 $/tCO2

Side-effects, readiness, permanence

  • Little is known about side-effects (apart from storage issues)
  • Costs are expected to decrease over time
  • There is a high energy penalty for DAC use
  • Little is known about the integration of DAC within energy systems

Enhanced weathering

Potentials and key side-effects of enhanced weathering. See bottom of page for symbol explanation (Source).

Potentials and costs

  • There is an abundance of suitable rock material; potentials are limited by transportation and infrastructure requirements
  • Costs depend on the scale of extraction and application, the process type and the region of application
  • Our 2050 costs and potentials:
    <4 GtCO2/yr
    50-200 $/tCO2

Side-effects, readiness, permanence

  • While materials are abundant, the upscaling of mineral production and related infrastructure is a major bottleneck
  • Co-benefits include improved soil quality, crop yield increases and enhanced crop nutrition
  • Ecological impacts arise from large scale mineral production and transportation, but also due to potential heavy metal release, or risks to human and animal health from fine grained particulate pollution

Ocean fertilisation

Potentials and key side-effects of ocean fertilisation. See bottom of page for symbol explanation (Source).

Potentials and costs

A series of experiments have demonstrated that potentials are limited and high uncertainties are involved with regard to efficiency of method.

Side-effects, readiness, permanence

  • Negative side-effects include ocean acidification, the alteration of local food webs and ecosystems, and anoxia from extensive plankton bloom
  • Permanence is heavily debated and depends on in which ocean system the carbon is sequestered; there has been little experimental or modelling data to reduce uncertainty on the long-term viability of carbon storage

Soil carbon sequestration

Potentials and key side-effects of soil carbon sequestration. See bottom of page for symbol explanation (Source).

Potentials and costs

  • Variation in potentials are driven by assumptions of available land for application
  • Cost ranges are mainly related to the size of potential (and thus extent of interventions) to be applied in a given area
  • Negative costs found for 20% of the potential
  • Our 2050 costs and potentials:
    <5 GtCO2/yr
    0-100 $/tCO2

Side-effects, readiness, permanence

  • Many co-benefits have been documented (soil carbon, soil quality, agricultural production)
  • Potentials are limited by saturation, which is reached within decades
  • The stored carbon is fragile to human and natural disturbances
  • Interventions are complexity as many actors are involved

Symbol explanation