Further development of the mill sludge valorization process

加拿大纸浆和造纸行业每年产生约150万吨一级和二级污泥，这些污泥需要处置，并带来了重大的环境挑战。平均而言，纸浆和造纸米尔斯厂废水处理总成本的60%用于污泥处理。为此，Domtar Inc.，agglomerappulp and paper company有兴趣最大限度地减少其废弃污泥并将其转化为增值流，从而减少碳足迹，使其产品范围多样化，创造额外收入，并提高其在国际市场上的竞争力。例如，Domtar Windsormill的纸浆和纸张年生产能力分别为447，000吨和642，000吨，每天产生75吨污泥。工厂通过填埋的方式处理废弃污泥，这一过程既不经济也不环保。这是一个后续的Engage Plus提案，旨在进一步推进最初Engage项目的积极成果。Engage Plus提案将进一步研究通过一种新的回收工艺使Domtar的工厂污泥增值的机会，该工艺可以提高拟议的酶水解和发酵工艺的效率，并降低整体生产成本。Domtar米尔斯将直接受益于该项目的成果，通过升级废物污泥流增值产品，如糖和乳酸。Engage Plus项目将解决重要的里程碑，如优化酶和表面活性剂剂量，酶和底物回收，利用二次污泥等低氮源发酵初级污泥衍生的糖，工艺集成和优化。本项目主要包括以下几个方面：1）污泥组成分析; 2）酶活性/损失转化率分析; 3）可发酵糖最大释放量的酶用量优化; 4）二次污泥蛋白质溶解及蛋白质特性分析; 5）以二次污泥溶解蛋白质为氮源转化初沉污泥中的可发酵糖。

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.