Biochar vs Other Carbon Sequestration Methods: A Comprehensive Review

As global warming intensifies, reducing atmospheric carbon dioxide (CO₂) has become a central challenge. In addition to mitigating emissions at their source, society must actively remove existing CO₂ from the atmosphere and store it in stable reservoirs — an approach known as carbon sequestration. In recent years, emerging strategies such as biochar-based carbon sequestration have gained increasing attention due to their long-term stability and environmental co-benefits. This review examines the mechanisms of biochar-based sequestration and compares it with other major carbon removal pathways.

Introduction to Biochar: How It Captures and Stores Carbon

Biochar is a carbon-rich solid formed by pyrolyzing biomass at ~350–700°C under low-oxygen conditions. Its aromatic carbon structure resists microbial degradation, enabling long-term carbon storage in soils. Typically, 30%–60% of original biomass carbon is retained in biochar after pyrolysis—much higher than natural decomposition.

Biochar Carbon Storage Process

1. Carbon capture: Plants absorb CO₂ through photosynthesis and store it in biomass.
2. Carbon stabilization: Pyrolysis converts a portion of this biomass carbon into stable biochar that can persist in soils for hundreds to thousands of years.

Biochar vs Natural Carbon Cycle

Biochar vs Natural Carbon Cycle
Feature	Plant Residues	Soil Organic Matter	Biochar
Source	Plant residues after harvest or litter	Decomposed residues and microbial products	Biomass converted through pyrolysis
Decomposition	Rapid microbial breakdown	Slow microbial breakdown	Highly resistant to decomposition
Carbon Retention	1–20 years	10–100 years	~100–1000 years
Cycle Type	Short-term natural cycle	Medium-term natural cycle	Human-designed long-term storage
Return to Atmosphere	Fast	Moderate	Very slow

Biochar vs Forest-Based Carbon Sequestration

Forest-based carbon sequestration means forests absorb CO₂ from the atmosphere through photosynthesis and store carbon in woody biomass, roots, leaf litter, and soils. This approach is well-established and provides multiple ecosystem benefits. However, the stored carbon is vulnerable to disturbances such as wildfires, pests, disease, and harvesting, which reduce long-term permanence. Large-scale forest expansion may compete with other land uses.

Dimension	Biochar	Afforestation
Source	Waste biomass	New plant growth
Carbon Stability	High	Medium–High (released when trees die)
Land Dependence	Medium (requires soil application)	High (requires large-scale land)
Co-benefits	Soil improvement, yield increase	Biodiversity, habitat restoration
Risks	Cost, feedstock supply	Fire, pests, logging

Biochar vs Soil Carbon Sequestration

Soil carbon sequestration includes various ways of managing land, especially farmland, so that soils absorb and hold more carbon. Increasing soil carbon is accomplished in various ways, including: (1) reducing soil disturbance by switching to low-till or no-till practices or planting perennial crops; (2) changing planting schedules or rotations, such as by planting cover crops or double crops instead of leaving fields fallow; (3) managed grazing of livestock; and (4) applying compost or crop residues to fields.

This approach is cost-effective, compatible with existing farming systems. However, soil carbon is relatively dynamic and can be released back into the atmosphere under changes in management or climate. Additionally, soil carbon stocks may eventually reach a saturation point.

Feature	Biochar	Soil Carbon Sequestration
Carbon Source	Waste biomass	Crop residues, organic amendments, and soil management practices
Carbon Stability	High	Medium, easily re-emitted
Cost	Medium	Low
Risks	Feedstock availability, production cost	Poor management can lead to carbon loss

Biochar vs Ocean Carbon Sequestration

Ocean Carbon Sequestration occurs as oceans store carbon through physical processes like physical solubility (CO₂ dissolution), biological pumps (phytoplankton uptake and sinking), and carbonate chemistry. Human interventions, such as iron fertilization or alkalinity enhancement, are being explored to enhance this natural carbon storage.

Feature	Biochar	Ocean Carbon Sinks
Carbon Source	Plant residues or organic waste converted through pyrolysis	Atmospheric CO₂ absorbed by seawater or captured by marine life
Carbon Stability	High; long-term fixed in soil	High; but human interventions carry ecological risks
Controllability	Production and soil application are controllable	Difficult to control; monitoring and verification are challenging
Additional Benefits	Improves soil and agricultural productivity	Large-scale natural carbon reservoir, ecosystem services
Risks	Feedstock, production cost	Ecological impact, uncertainty of enhanced sequestration

Biochar vs Direct Air Capture and Carbon Storage (DACCS)

Direct Air Carbon Capture and Storage (DACCS) systems are technologies designed to remove carbon dioxide (CO2) directly from the atmosphere and then store it in geological formations underground or in other long-term storage facilities. DACCS typically involves several steps:

• Air Capture: DACCS systems use chemical processes or sorbents to capture CO2 directly from the air. This captured CO2 is then concentrated for storage.
• Carbon Dioxide Separation: The captured CO2 is separated from the air and concentrated into a pure stream of CO2.
• Storage: The concentrated CO2 is then transported to storage sites, typically deep underground, where it is injected into geological formations such as depleted oil and gas reservoirs, saline aquifers, or other suitable geological formations. The CO2 is stored securely to prevent its release into the atmosphere.

Feature	Biochar	DACCS
Carbon Source	Plant residues or organic waste converted through pyrolysis	Directly captured from ambient air
Carbon Stability	High; long-term fixed	High; can be stored permanently
Land Requirement	Moderate; applied to soil	Low; flexible deployment
Cost and Energy	Medium; dependent on feedstock and process	Very high; requires large amounts of low-carbon energy
Additional Benefits	Improves soil and crop yield	Achieves negative emissions; limited ecological co-benefits
Scalability	Limited by biomass availability	Theoretically unlimited, but constrained by cost and energy

Comparative Analysis: Biochar vs. Other Carbon Sinks

Carbon Sink Method	Stability	Cost	Co-benefits	Controllability	Scalability
Biochar Carbon Sink	★★★★★ (long-term stable)	Medium	Improves soil, utilizes waste biomass	High	Medium
Forestry Carbon Sink	★★★	Low	Significant ecological benefits	Medium	Medium–High
Soil Carbon Sink	★★ ~ ★★★	Low	Enhances soil fertility	Medium	Medium
Ocean Carbon Sink	★★★★ (naturally large capacity)	Low–High	Technology-dependent	Low	Very High
DACCS	★★★★★	High	Strong controllability	Very High	Medium

Overall, biochar sits in a favorable niche: it provides durable carbon storage while delivering tangible agricultural and environmental co-benefits. When feedstock is a waste stream and pyrolysis energy is utilized, the net climate and economic case strengthens.

Conclusion

Biochar represents a multifunctional carbon sequestration pathway that combines durable carbon storage with meaningful co-benefits for soil health, agricultural productivity, and pollution mitigation. Compared with traditional sinks such as forests and soils, biochar offers higher carbon permanence and distinct agricultural advantages, while remaining more affordable than technologically intensive options like direct air capture.

Challenges remain—cost, standardization, and consistent agronomic performance across contexts—but biochar’s potential to integrate waste valorization, climate mitigation, and sustainable agriculture makes it a compelling component of diversified net-zero strategies. In practice, biochar will likely be most effective when deployed alongside forests, soil-management practices, ocean-based strategies, and engineered removal technologies as part of a portfolio approach to climate mitigation.