The Possibilities of Black Liquor

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When making paper and pulp via the so called kraft process, residuals from the wood end up in a by-product called black liquor. Today the black liquor is usually burned for energy and heat at the paper mills, but what if part of it could be used to make transportation fuels instead? 

New report

Johanna Olofsson and Pål Börjesson from Lund University, and part of the SusValueWaste project team, have released a report with greenhouse gas calculations for methanol from different industrial byproducts/residues. The report particularly explores the possibilities of black liquor which is suitable for gasification. Because of its reactive properties, other materials could be mixed with it and piggyback on the advantages.

Mixing by-products for better utilisation

By mixing by-products with black liquor in the process of gasification, methanol fuels for ships or cars could be produced. The report presents a study looking at the resulting greenhouse gas emissions of such fuels and compared them to other potential pathways for using the by-products. For instance, crude glycerol, a by-product from biofuel production, could be used in gasification with black liquor, but it could also be digested to produce biogas. Comparisons and evaluations were made for the black liquor and for crude glycerol from biodiesel (RME) production, fermentation residues from wood-ethanol production, and forest logging residues converted to pyrolysis liquid.

New products from by-products

This oversight and related studies shows that it could be possible to blend different by-products with black-liquor and thereby produce methanol fuels. The greenhouse gases from such fuels most often compare well to those of fossil fuels according to current policy goals, but they also vary. It is not certain that the co-gasification route provides a better option for handling the by-products than other processes, especially if intermediary steps are necessary in order to blend them. There is however a potential opportunity to make use of the by-products by connecting different industries and processes, and thereby providing new products.

The report is a delivery from a project coordinated by the networking organisation f3 – The Swedish Knowledge Centre for Renewable transportation fuels, as well as the SusValueWaste-project.

Read the full report : Greenhouse gas emissions of methanol from co-gasification of black liquor with by-product biomass

Photo: Chemrec

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