Lignosulfonates, which are derived from lignin—a complex organic polymer found in plants—play a significant role in carbon sequestration, particularly in agricultural settings. Carbon sequestration is the process of capturing and storing carbon dioxide from the atmosphere to mitigate climate change, and lignosulfonates contribute to this by enhancing soil properties that promote carbon storage.

How Lignosulfonates Enhance Carbon Sequestration

When lignosulfonates are applied to soil, they influence the soil microbial community structure. This shift in microbial activity can:

• Reduce Greenhouse Gas (GHG) Emissions: By fostering a microbial community that minimizes the release of carbon dioxide and other GHGs, lignosulfonates help retain carbon in the soil rather than allowing it to escape into the atmosphere.
• Promote Soil Aggregate Formation: Lignosulfonates encourage the formation and stabilization of soil aggregates—small clumps of soil particles. These stable aggregates protect organic carbon from decomposition by shielding it from microbial breakdown, thereby enhancing long-term carbon storage in the soil.

Additionally, specific evidence shows that calcium lignosulfonate (CLS), a type of lignosulfonate, increases total organic carbon (TOC) in soil. For example, in studies conducted under salinity stress, CLS application improved soil chemical characteristics, leading to higher TOC levels. This increase in organic carbon content directly contributes to carbon sequestration by boosting the amount of carbon stored in the soil.

Environmental Benefits

Lignosulfonates are biodegradable and biobased, meaning they are derived from renewable plant sources rather than fossil fuels. This gives them an environmental edge over synthetic alternatives, likely resulting in a lower carbon footprint during production. Their eco-friendly nature makes them a sustainable option for enhancing carbon sequestration while supporting agricultural practices.

Limitations and Considerations

While lignosulfonates show promise, their water-soluble nature could pose challenges. Unlike lignin, which remains stable in soil, lignosulfonates may leach out under certain conditions, potentially reducing their long-term effectiveness for carbon storage. However, their ability to improve soil structure and increase organic carbon content outweighs this concern in many agricultural contexts.

Conclusion

Lignosulfonates contribute to carbon sequestration in soil by reducing GHG emissions, promoting stable soil aggregates, and increasing total organic carbon, particularly in conditions like saline soils. Their biodegradable and biobased properties further enhance their value as a sustainable tool for mitigating climate change through improved soil carbon storage. While more research could refine our understanding of their long-term impact, lignosulfonates are a valuable asset in agricultural carbon sequestration efforts