h i g h l i g h t sLCA was used to evaluate an ethanol plant converting pulp and paper sludge. Enzymatic hydrolysis and neutralisation of the CaCO 3 are the environmental hotspots. Neutralisation and subsequent CO 2 emissions is specific to this raw material. Two optimisation scenarios were developed (reduced HCl usage and co-fermentation). a r t i c l e i n f o b s t r a c tThis work evaluates the environmental performance of using pulp and paper sludge as feedstock for the production of second generation ethanol. An ethanol plant for converting 5400 tons of dry sludge/year was modelled and evaluated using a cradle-to-gate life cycle assessment approach. The sludge is a burden for pulp and paper mills that is mainly disposed in landfilling. The studied system allows for the valorisation of the waste, which due to its high polysaccharide content is a valuable feedstock for bioethanol production. Eleven impact categories were analysed and the results showed that enzymatic hydrolysis and neutralisation of the CaCO 3 are the environmental hotspots of the system contributing up to 85% to the overall impacts. Two optimisation scenarios were evaluated: (1) using a reduced HCl amount in the neutralisation stage and (2) co-fermentation of xylose and glucose, for maximal ethanol yield. Both scenarios displayed significant environmental impact improvements.

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