Project Description

Metsä Group’s next-generation bioproduct mill in Äänekoski, Finland uses several state-of-the-art technologies to contribute to the circular economy.

Metsä Group is the first forestry company in the world to introduce a large-scale sulphuric acid plant as an integrated part of the Äänekoski site’s pulp production. The plant captures and converts the mill’s odorous gases into sulphuric acid, a chemical needed to produce tall oil, another of the mill’s bioproducts. As a result, the bioproduct mill is self-sufficient with respect to this chemical, while its sulphate emissions to water and air are minimised. This investment is an important step towards a closed chemical cycle. The approximately €20 million investment is the first large-scale sulphuric acid plant in the world to be integrated into the pulp production process. With a value of €1.2 billion, the bioproduct mill is the largest investment in the history of the Finnish forest industry. Äänekoski is the most energy-efficient pulp mill in the world, and the centre of an industrial ecosystem in which other companies also participate.

This unique plant produces approximately 35 tonnes – one truckload – of sulphuric acid a day, equal to the amount required for the mill’s daily tall oil production. Due to internal circulation, the chemical does not need to be purchased externally, reducing transport needs by 360 truckloads a year.

Project Purpose

While sulphuric acid is a common and relatively inexpensive chemical, converting sulphuric gases into sulphuric acid in an integrated manner close to the mill has considerable environmental benefits. Based on this experience, sulphuric acid plants may become more common in conjunction with pulp mills.

Project Evaluation

Looking forward, sulphuric acid could also be used in the production of chlorine dioxide and in separating lignin from black liquor. There is thus the potential to develop an industrial ecosystem based on sulphuric acid production.