The manufacture of cement, an essential component in concrete manufacture, is harmful to the environment and produces 5–10% of global man-made carbon dioxide emissions.

Every year, bio-product factories and pulp mills produce significant amounts of green liquor sludge and bio-ash, i.e. bio-residuals, which are classified as waste and still largely unutilised.

The KBB – Kestävä bioresiduaalibetoni (SBC – Sustainable Bio-Residual Concrete) project involved researching piloting the method of partially replacing the cement used in concrete with green liquor sludge and bio-ash. This process has not yet been tested in practice in Finland.

“The utilisation of effluents supports carbon reduction and decreases the use of non-renewable natural resources and environmental stress,” comments Project Manager Leena Turunen from JAMK.

The project involves creating a circular economy system in the northern Central Finland area, in which local SMEs’ low-carbon, Cleantech and resource intelligence know-how are developed. The network of businesses pilots the further processing of bio-economy effluents in accordance with a resource smart circular economy model.

The knowledge and know-how obtained will be used in their operations by concrete businesses in developing new low-carbon product families, for example.

The impetus for JAMK’s bio-residual fraction applicability research came from the Äänekoski bio-product factory’s need to sustainably dispose of effluent fractions, as well as the concrete industry’s interest in said fractions. It is estimated that approximately 50,000 tonnes of green liquor sludge ends up at Finnish landfill sites annually. This would be approximately 5% of the total amount of cement used in concrete. Quantitatively, all of the green liquor sludge could be used in concrete construction as an alloying element to replace cement, whereby it would decrease the carbon footprint of concrete construction.

The project involves all three major Finnish forest industry operators that produce bio-residual fractions, as well as several concrete industry businesses.