Further development of the mill sludge valorization process

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The Canadian pulp and paper industry generates about 1.5 million tons of primary and secondary sludge everyyear, which requires disposal and presents a major environmental challenge. On average, 60% of the totalwastewater treatment costs of pulp and paper mills account for sludge disposal. For this reason, Domtar Inc., aglobal pulp and paper company, is interested in minimizing their waste sludge and converting it into avalue-added stream that can reduce the carbon footprint, diversify their product range, create additionalrevenues, and enhance their competitiveness on the international market. For example, the Domtar Windsormill, with annual pulp and paper production capacity of 447,000 and 642,000 tons, respectively, generates 75tons of sludge per day. The mill disposes of their waste sludge by landfilling, a process that is neithereconomically attractive nor environmentally friendly. This is a follow-up Engage Plus proposal that aims tofurther advance the positive outcomes from the original Engage project. The Engage Plus proposal will furtherinvestigate opportunities to valorize the mill sludge from Domtar through a novel recycling process that couldincrease the efficiency of the proposed enzymatic hydrolysis and fermentation process, and reduce the overallproduction costs. Domtar mills will directly benefit from the outcomes of this project by upgrading a wastesludge stream to value-added products such as sugars and lactic acid. The Engage Plus project will addressimportant milestones such as optimization of enzyme and surfactant dose, enzyme and substrate recycling,fermentation of primary sludge-derived sugars utilizing low nitrogen sources such as secondary sludge, processintegration and optimization. The following steps are essential to accomplish the project goals: 1)Compositional analysis of sludge; 2) Analysis of enzyme activity/loss conversion yields; 3) Optimization ofenzyme dose for maximal release of fermentable sugars; 4) Protein solubilization from secondary sludge andprotein characterization; 5) Bioconversion of primary sludge-derived fermentable sugars using solubilizedprotein from secondary sludge as nitrogen source.