Municipal waste treatment, technological scale up and commercial exploitation: The case of bio-waste lignin to soluble lignin-like polymers

Abstract

The present chapter addresses municipal bio-waste, as worldwide easily available concentrated source of organic matter to convert to and recycle as valuable products for further use. Municipal bio-waste contains polysaccharides and lignin as major components. On the other hand, these are major components of biomass, generally. This implies that technology used for treating municipal bio-waste is likely applicable to other bio wastes, as well. Current biomass treatment technology addresses mainly the production of biofuel by fermentation of the polysaccharide fraction. Lignin is an insoluble recalcitrant material withstanding biochemical and chemical treatment. It inhibits fermentation microorganisms. Thus, the separation of lignin from the fermentable organic fractions is necessary. In addition, the separated lignin is regarded as secondary process waste, which needs disposal. A number of technologies are currently available for this purpose. These include lignin combustion, pyrolysis, hydrocracking, or aerobic fermentation. Yet, the bio-waste lignin fraction has further potential that can be exploited by low energy consumption chemical technology. The valorisation of lignin in this fashion would contribute important economic and environmental improvements to current waste treatment practices. Taking an Italian municipal bio-waste treatment plant as empirical case study, the present chapter reviews work performed in the last decade for the valorisation of lignin originating from the organic humid fraction and gardening residues obtained from the separate source collection of municipal bio-wastes. The work covers also agriculture residues, although in a relatively very limited extent. The chapter reports processes and applications related to new speciality chemicals stemming for research developed at EU technology readiness level 5. The results prospect sustainable processes and products, and the possibility to realize a business model with reduced entrepreneurial risk for the conversion of a municipal bio-waste treatment plant to biorefinery producing fuel and bio-based chemicals. However, the chapter does not provide the reader with a strong methodology for evaluating the potential sustainability. In addition, the proposed business model with reduced entrepreneurial risk is at a very early stage. It relies mostly on assumptions that need validation. The results related to agriculture residues demonstrate that, although mainly focused on municipal bio-waste, the developed technology is applicable as well to other bio-waste types.