SAUNA: Sustainable pulping innovation achieving zero pollution through efficient wood residue feedstock utilisation

The kraft process currently dominates global virgin pulp production, representing 82% of the total, which amounted to 180 million tonnes in 2020. This process converts only half of the wood feedstock into fibrous pulp; the remainder is dissolved and primarily burned for energy and chemical recovery. Consequently, the kraft process generates significant pollution, including atmospheric emissions like CO2, SO2, NOx, total reduced sulphur (TRS), and particulates, in addition to wastewater, solid waste, and noise.

 

To address these environmental challenges, the SAUNA project develops a novel pulping concept. This initiative involves a consortium of 11 partners—five companies, four research and technology organizations (RTOs), and two universities—who are reconsidering all aspects of production, from feedstock and chemistry to unit operations and energy sources.

 

The new concept achieves a much higher product yield of 90% through a targeted fractionation of wood, which uses hot water extraction followed by alkaline oxidation. This method produces valuable hemicellulose and water-soluble lignin alongside the fibrous pulp. This approach reduces biogenic CO2 emissions by 80% compared to the kraft process. The resulting products are assessed for applications in packaging, adhesives, and polyurethane.

 

The use of a select, sulphur-free chemistry enables a significantly simpler chemical recovery process using wet air oxidation. This avoids the need for incineration in a conventional recovery boiler and lime kiln, which often rely on fossil fuels for process control. As a result, this new method eliminates emissions of CO2, SO2, NOx, and TRS, thereby mitigating climate change, acid rain, biodiversity loss, human health risks, and odours. The biorefinery’s design allows it to utilize energy from emerging renewable sources or power from small nuclear reactors.

 

The potential impact of this technology is substantial. If all European pulp production were to adopt the SAUNA technology, it would support 300 biorefineries. This shift would lead to annual savings in the EU of 49 million tonnes of CO2 (mainly biogenic), 13.5 kilotonnes of gaseous sulphur compounds (as S), and 36.5 kilotonnes of Nox emissions (as NO2).

Our main tasks

• Implementing sensors, monitoring, digital tools, and process control
• Development of a comprehensive assessment of the main sources and type of pollution
• Development of data management pipeline and integration of process models
• Process optimisation and control
• Definition and simulation of scenarios

Partners

VTT | KASTAMONU ENTEGRE | STORA ENSO OYJ | STORA ENSO AB | SINTEF | AALTO KORKEAKOULUSAATIO SR | ANDRITZ | UNIVERSIDAD DE VALLADOLID | IDENER.AI | RINA

Start date – finish date

05 / 2025 - 04 / 2028