Kraft pulping cleantech secures €1m for lignin separation technology

CHEMICAL pulping cleantech LignEasy has secured €1m (US$1.1m) to scale up its innovative separation technology which converts pulp waste into “high-value” bio-based materials, including plywood, construction materials, and plastic components.

Kraft pulp is traditionally produced by breaking down wood into small chips and dissolving them in a bath of sodium hydroxide and sodium sulfide at a temperature of around 160^oC to make pulp fibres.

Lignin that was part of the wood is depolymerised and removed from the fibres in a mix of cellulose and spent cooking chemicals. The resulting solution, called black liquor, is then burnt for energy in the kraft process.

Juho-Matti Karpale, CEO at LignEasy: “There are currently major issues with lignin wastage; a technology gap in achieving separation sustainably; and a pressing need to provide the chemical industry with eco-friendly alternatives to fossil-based raw materials.”

Sulfate-free

Current separation technologies use sodium sulfate for the final purification of the lignin, which can make its way into wastewater and lead to chronic respiratory disorders, skin irritation, and nausea. However, LignEasy’s filtration-based process removes the need for sulfur.

Eric Enqvist, a co-founder of LignEasy, said: “We can separate the lignin without introducing more sulfur into the closed loop of the pulp mill which, if you did that, you would have to purge the sulfur out somewhere, which becomes a chemical cost for the mill.”

Second most abundant biopolymer

Lignin makes up around 15–40% of the wood in trees, and around 30–50m t/y is produced, mostly as a non-commercial waste product.

Enqvist said: “Pulp mills produce more energy than they need, and you can take out part of this lignin to produce material of higher value than fuel.”

As an organic polymer, lignin is being studied for its applications in the biochemical, agrochemical, and food sectors. Another lignin-based startup, Lignovations, is currently trialling the material to replace chemical UV filters in sunscreen.

Enqvist added: “Lignin is the most abundant biopolymer after cellulose but it is underutilised, there is no real market for it.

“But if we can use it for making, for instance, phenolic resin, where we substitute phenol, which is a very far refined product of the petrochemical industry, if we can substitute phenol with lignin, we get the much higher value than its value as an energy source.”

LignEasy will put its investment, awarded by sustainability accelerator EIT InnoEnergy, towards the full development of its pilot plant, which is slated to become operational in October, producing 1 t/d of kraft lignin.