Swedish wood products manufacturer Setra Group has revealed that it plans to build a biomass pyrolysis plant adjacent to its Kastet sawmill in Gävle, Sweden. The company has announced a public consultation in accordance Chapters 9 and 11 of the Environmental Code as part of its permitting application process. A statement of the consultation will, together with an environmental impact assessment, be included as part of the application for permission that Setra plans to submit.
According to the consultation documentation, the pyrolysis oil is to be produced from sawmill residues, sawdust and shavings, from Setra Kastet sawmill. The sawmill produces around 231 000 m3 sawn wood per annum using pine (Pinus sylvestris) only and pyrolysis plant will utilise the entire production of sawdust and shavings from the sawmill.
On an annual basis, the pyrolysis plant is expected to need close to 85 000 tonnes of sawdust calculated at 55 percent moisture content thus additional sawdust may need to be sourced from other (Setra) production units. The pyrolysis oil yield depends on several parameters but the plant is expected to have a maximum annual capacity of 32 000 tonnes pyrolysis oil.
Energy cascading and integration
The process begins with the drying of feedstock down to about 5 percent moisture content before entry into the pyrolysis reactor. The pyrolysis gases formed are condensed and stored as pyrolysis oil. From 1.5 MWh biomass, approximately 1 MWh of pyrolysis oil is obtained 0.5 MWh by-products in the form of char, non-condensable gases and residual heat.
The total thermal energy demand for the plant, for drying the feedstock and running the reactor, is pegged at around 22 MW of which the combustion of char and non-condensable gases in a fluidised bed (FB) steam boiler will provide up to 10 MW.
The balance needed to dry the sawdust down to 5 percent moisture content, is planned to be supplied as residual heat from the nearby BillerudKornäs pulp mill and from Bomhus Energi AB’s biomass-fired combined heat and power (CHP) plant both of which Setra Kastet has already energy cooperation with. The residual steam from the pyrolysis plant will be used by Setra Kastet for its dry kilns.
Available feedstock for additional plants
The pyrolysis oil can be further processed into vehicle fuels at a third-party facility or used replace fossil oil in district heating and combined heat and power (CHP) plants. The Swedish Environmental Protection Agency (Naturvårdsverket) has granted Setra’s pyrolysis project SEK 117 million (≈ EUR 11.34 million) from the Climate Step (Klimatklivet) initiative programme to reduce carbon emissions.
As far as we know, this will be the first pyrolysis oil plant on an industrial-scale in Sweden, said Pontus Friberg, Enterprise Risk Manager at Setra.
Looking at the other wood industries in Sweden, more pyrolysis oil plants would be feasible. Setra estimates that on a national basis, around 4 million tonnes of sawdust is available annually that could be transformed into pyrolysis oil.
We must also remember that bio-oil is only one of all the new products we can develop in the forest industry. There are many more as yet undiscovered areas in the value chain where we can find benefits, concluded Pontus Friberg.
Setra Group operates ten wood processing facilities in Sweden including nine sawmills that have a combined sawn wood output of over 1.5 million m3 (2016).
