Biological Carbon Sequestration and Obstacles to its Use in CO₂ Emissions Mitigation: A Review

Introduction

An unpleasant product of modern global industrialization and economic development has been the use of fossil fuels. The combustion of such fuels, while powering nearly every facet of the human existence, also produce large emissions of greenhouse gases (GHGs).  These gases, the principal of which is CO₂, trap heat in the atmosphere; this drives climate change and its associated challenges, including global warming, drought, and flooding. In order to mitigate these outcomes, and the global economic and health crises they would cause, these elevated CO₂ levels must be controlled. One means by which this can be achieved is through the practice of biologic carbon sequestration.

This study reviews research concerning biologic carbon sequestration, its various implementations, and the obstacles hindering its use in mitigating CO₂ emissions.

What is biologic carbon sequestration? 

Biologic carbon sequestration, along with geologic and aquatic, comprise the three principal forms of carbon sequestration. Baurov (2021) describes carbon sequestration as the process of removing carbon dioxide from the atmosphere and storing it in environmental reservoirs, such as the ocean and terrestrial ecosystems. It is driven by natural processes that are artificially stimulated to “accumulate CO2 at a greater rate than would otherwise have occurred” (Farrelly et al., 2013). 

Biologic carbon sequestration specifically refers to the storage of carbon in terrestrial ecosystems, such as forests, peat marshes, and coastal wetlands. This sequestration is driven by the “transfer of atmospheric CO2 into plant biomass through photosynthesis and conversion of biomass into stable SOC [soil organic carbon] through formation of organo-mineral complexes” (Lal et al., 2018). These natural activities are enhanced by proper land-use, such as forestry, wetland restoration, and sustainable farming practices.

What are the various implementations of BCS?

Forestry

Forests are significant contributors to the terrestrial carbon reservoirs, with global forests storing more than double the amount of carbon in the atmosphere (Peñuelas & Raupach, 2008). Practices such as afforestation (planting trees on land with no previous tree cover), proforestation (protecting existing forests and growing them to full potential), and reforestation (restoring forests on deforested or harvested areas) work to increase the carbon sequestration by increasing forested land area, increasing carbon density in existing forests, and reducing emissions that result from deforestation and degradation (Peñuelas & Raupach, 2008; Moomaw et al., 2019). 

Wetland restoration

Wetlands are an important carbon reservoir, as they contain 15% of soil carbon while only comprising 6% of the global land area (Baurov, 2021). Wetlands sequester carbon through “high rates of organic matter inputs and reduced rates of decompositions” (Pant et al., 2003). Wetlands are often drained for development purposes, such as damming to form bodies of water and adding pavement, releasing the carbon stored in the ecosystems for long periods of time (Baurov, 2021). Restoration of the wetlands bolsters the presence of one of the most efficient carbon sinks. 

Sustainable agricultural practices

Typically, croplands are soil carbon depletors, containing 25–75% less SOC than their

counterparts in other natural terrestrial ecosystems (Lal et al., 2015). This is a result of  a number of factors, such as a lower return of carbon from biomass, higher losses of SOC by erosion, mineralization and leaching, and variations in soil temperature and moisture (Lal et al., 2015). This is combated by sustainable management practices, such as conservation agriculture, precision farming, and no-till agriculture (Lal et al., 2015). 

What are obstacles to the use of BCS in CO₂ mitigation?

Terrestrial carbon storage systems are vulnerable to disruptions such as “fire, disease, and changes in climate and land use” (Eric Sundquist et al., 2018). The warming of soil as a result of increasing global climate change is perhaps the most significant of these. This warming causes soil carbon to be converted to carbon dioxide by temperature-sensitive soil microbes (Amundson & Biardeau, 2018). This decreases the magnitude of the maximum sequestration potential, and over the next 20 years will release between 100 and 600 Gt of carbon from soil (Amundson & Biardeau, 2018). In boreal forests and northern peatlands, warming causes large-scale thawing of permafrost, leaving soil carbon vulnerable to fire and decomposition (Eric Sundquist et al., 2018). 

Economically, the labor and materials required to establish and maintain biologic carbon sequestration systems, including “farmer-based research and planning, … new equipment, infrastructure, labor, and management”, are capital-intensive (Amundson & Biardeau, 2018). Although these investments are necessary, the billions needed for this work can be off-putting to both government and private investors. Conservation programs may seem to be the right path to go down, however, there are a number of distinct barriers to their success. These include a lack of “technical assistance to farmers … to engage and assist farmers in adopting the present conservation programs that are offered” and “farmer resistance to the intrusion of privacy and government regulations” (Amundson & Biardeau, 2018).

Conclusion

Biologic carbon sequestration is a proven effective method of carbon emissions mitigation. However, it faces a number of obstacles to its expansion. Steps must be taken to overcome these hindrances to avert an imminent climate crisis.

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