Agricultural utilization of lignosulfonates

Lignosulfonates (LSs) are by-products of the pulp and paper industry from pulping of lignocellulosic biomass according to the sulfite process. This renewable material already plays a role in low-value applications, such as binding agents for fuel, pellets, as a feed additive, or as a dispersant. Another possible field of application of this technical lignin type is agriculture. It is known that this eco-friendly and cheap material can improve soil quality, fertilizer efficacy and replace or decrease the use of potentially (eco)toxic organic or inorganic substances. The use of LS in agriculture and five main strategies for the implementation of LS in soil are discussed in this review: LS as a complexing agent with micronutrients, co-pelleting of LS with (macro)nutrients, capsule formation with LS for coating of fertilizers or pesticides, LS as a biostimulant, and ammonoxidation of LS. All five ways can be beneficial in fertilizer-related applications, either to slow down the release of nutrients or pesticides, to substitute harmful chemicals, or to inhibit nitrification and modify fertilizer behaviour. Nevertheless, application and long-time studies are often missing, and more research is required for generating products that are economically competitive to commercial bulk products.