Abstract
The progressive decline of using fossil sources in the industry means that alternative resources must be found to produce chemicals. Waste biomass (sewage sludge) and waste lignocellulosic resources (food, forestry, or paper industries) are ideal candidates to take over from fossil sources. Municipal sewage sludge, and especially primary sludge, has a significant proportion of cellulose in its composition. Proper treatment of this cellulose allows the production of interesting chemicals like levulinic acid that are precursors (bio-blocks or building blocks) for other organic chemical processes. Cellulose was extracted from municipal wet primary sludge and paper industry dried sludge with a commercial ionic liquid. More than 99% of the cellulose has been recovered in both cases. Extraction was followed by the bleaching of the cellulose for its purification. In the bleaching, a large part of the ash was removed (up to 70% with municipal sludge). Finally, the purified cellulose was converted in levulinic acid by catalyzed hydrothermal liquefaction. The reaction, done at 170 °C and 7 bar, catalyzed by a tailored Brønsted acidic ionic liquid produced levulinic acid and other by-products in smaller quantities. The process had a conversion of cellulose to levulinic acid of 0.25 with municipal sludge and of 0.31 with industrial sludge. These results fully justify the process but, require further study to increase the conversion of cellulose to levulinic acid.
Highlights
The fossil sources are non-renewable and, will be depleted in near future
The cellulose is recovered from wastewater treatment plant (WWTP) primary wet sludge and paper industry dried mixed sludge, from primary treatment and membrane bioreactor purge
Purified cellulose was treated by catalyzed hydrothermal liquefaction to produce levulinic acid
Summary
The fossil sources are non-renewable and, will be depleted in near future. Scientists are exploring how to produce chemicals from biomass sources in order to meet the human needs. There are 12 building blocks, or chemical platforms, essential molecules which can be converted to a wide range of chemicals or materials. These building blocks can be obtained from waste biomass without exposing supplies like food, feed, and forests and in general, biodiversity of the world. The valorization of the waste biomass is beneficial from a point of view of sustainable waste management. The valorization is economically attractive by eliminating waste disposal fees and giving value to wastes [1]
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