Mr Oliver Levers1, Professor Jason Hallett1, Professor Rob Law1, Professor Jon Lloyd1
1Imperial College London, South Kensington, United Kingdom
Lignin, produced as a waste product of biomass processing, has the potential to be used as a soil amendment. Utilising wastes in this way increases the carbon sequestration potential of the bio-refinery via increasing carbon stocks stored in the soil. Additionally, lignin may also improve soil structure and health. Second-generation biomass processing technologies produce less chemically modified lignin as a biproduct which better mimics natural residues found in soils, compared to more chemically modified Kraft lignin. These more natural lignins take the form of insoluble powders, and are clearly shown to bind and interact with clay to form stable aggregates. Here, interactions with clays (kaolinite/montmorillonite) are demonstrated, and the formation of particulate-clay interactions are investigated following wet/dry cycles. This research utilises a new method of characterising particulate interactions with clay minerals, without the need for advanced spectroscopic instrumentation such as atomic force microscopy. Additionally, the disruption of particulate interactions by water are investigated via slaking analysis, using a modified flow cell. Video image analysis is used to determine slaking kinetics, which illustrates different breakdown processes occurring on different timescales – related to aggregate composition and porosity. These results clearly demonstrate the potential of technical lignin to increase soil aggregation and increase resistance to slaking via purely abiotic means. Additionally, these results demonstrate new methods to determine particulate-clay interactions and slaking breakdown kinetics, which can be used to engineer better soil amendments.