Engineering360: "Paper Mill Waste Repurposed as Lithium-sulfur Battery Cathodes"

But brown liquor is not a waste product.

It is concentrated and then burned in a recovery boiler and the sulfites are captured to be used again in the pulping process. This produces carbon-neutral energy for the mill and reduces the pulp plant's need for sulfur. In fact, many paper and pulp mills are a net-producer of sustainable electric power.