## 2 Structural Complexity and Composition of Native Lignin
### Agriculture: Lignin-Derived Fertilizers and Soil Amendments  
The agricultural sector is increasingly turning to lignin-derived fertilizers and soil amendments as sustainable and cost-effective solutions to improve soil health, enhance crop productivity, and address environmental challenges (Figure 5) [49]. Lignin, a byproduct of the paper and pulp industry, is a renewable and abundant resource that offers unique properties for agricultural applications. When processed into soil amendments, lignin  
Figure 4: Example of lignin-based carbon material used as an anode in lithium-ion batteries. improves soil structure, enhances water retention, and stimulates microbial activity, creating a more fertile and resilient growing environment [50]. Additionally, lignin-based products minimize nutrient losses through leaching and volatilization, ensuring that essential nutrients such as nitrogen, phosphorus, and potassium are more efficiently utilized by plants [51]. These benefits make lignin an attractive alternative to synthetic fertilizers, which are often associated with environmental issues such as soil degradation, water pollution, and greenhouse gas emissions. Leading the charge in the development and commercialization of lignin-based agricultural products are companies like Borregaard (Sarpsborg, Norway) ([[https://www.borregaard.com/](https://www.borregaard.com/)]([https://www.borregaard.com/](https://www.borregaard.com/)) accessed on 10 May 2025) and MetGen (Kaarina, Finland) ([[https://www.metgen.com](https://www.metgen.com)]([https://www.metgen.com](https://www.metgen.com)) accessed on 10 May 2025), which have pioneered innovative solutions to harness the potential of lignin for sustainable farming. Borregaard, a global leader in lignin valorization, offers products designed to improve plant nutrition, crop protection, biocontrol, seed coating, and other products to enhance soil health and reduce the environmental impact of agriculture. Similarly, MetGen's MET-NINTM technology platform focuses on converting lignin into high-value agricultural inputs that promote sustainable crop production while addressing key environmental challenges ([[https://www.metgen.com/lignin-products/](https://www.metgen.com/lignin-products/)]([https://www.metgen.com/lignin-products/](https://www.metgen.com/lignin-products/)) accessed on 10 May 2025). These companies have demonstrated that lignin-based products can achieve significant reductions in greenhouse gas emissions, making them a critical component of efforts to decarbonize agriculture and align with global sustainability goals. The application of lignin-derived fertilizers and soil amendments supports the principles of the circular economy by transforming an industrial byproduct into a valuable resource for agriculture. By reducing reliance on synthetic fertilizers, lignin-based products help lower the carbon footprint of farming operations, decrease dependency on fossil fuels, and promote the efficient use of resources. Furthermore, lignin's ability to improve soil structure and water retention is particularly beneficial in regions facing soil degradation and water scarcity, as it enhances the resilience of agricultural systems to climate change and extreme weather events [52]. The stimulation of microbial activity by lignin also contributes to the long-term health of soils, fostering a more biodiverse and productive ecosystem. Along with their environmental benefits, lignin-derived agricultural products offer economic advantages for farmers. By improving nutrient efficiency and reducing the need for frequent fertilizer applications, these products can lower input costs and increase crop yields, resulting in higher profitability. The scalability and cost-effectiveness of lignin-based solutions make them accessible to farmers of all sizes, from smallholder operations to large-scale commercial farms. Moreover, the integration of lignin into agricultural practices aligns with consumer demand for sustainably produced food, providing farmers with a competitive edge in the market.