– The pulp industry thinks that the results are very interesting. Instead of investing in a larger recovery boiler when increasing production in the mill, it may be more profitable to invest in the production of drop-in fuel that also has a positive effect on the climate, Elisabeth Wetterlund says, Associate Professor in Energy Engineering at Luleå University of Technology .
New recovery boiler costly investment
In pulp mills, about half of the tree becomes black liquor which is burned as a residual product in a recovery boiler, where energy and chemicals are recycled. For those pulp mills that today want to increase their pulp production, it is often the limited capacity of the recovery boiler that puts a stop to it. Investing in a new, larger recovery boiler is about billions of SEK in investment cost.
The researchers now show that pulp mills in such an expansion situation could broaden their core business by producing drop-in fuel from the residual products, instead of investing in a new recovery boiler. In this way, important biofuels can be produced, while the pulp mill simultaneously increases its capacity and profitability. In their calculations, the researchers have considered the conditions for the production of drop-in fuel in three different types of pulp mills with different energy situations. The greatest synergy effect is achieved in modern pulp mills with an excess of energy that is otherwise used to produce electricity.
– We believe that it can be of great economic importance for the pulp industry to be able to produce biofuels from the residual products in addition to the core business. Drop-in fuel is also strategically interesting for reducing carbon dioxide emissions from the transport sector, Elisabeth Wetterlund, says.
Increased duty to reduce next year
The fuel change in Sweden is carried out with a so-called reduction obligation based on the blend-in of drop-in fuels in fossil fuels, with the aim to reach the Swedish climate target of 70 percent reduction in greenhouse gas emissions from domestic transport by 2030. In The fuel change is enhanced with greater blend-in of renewable fuel (2020-09-11), the government describes how they also intend to decide on gradually increased quota levels in the reduction obligation until 2030, starting next year.
– With the reduction obligation in Sweden, the importance of manufacturing drop-in fuels can´t be overestimated, this is something we need to meet the requirements, Elisabeth Wetterlund, says.
Global key players important
The researchers have studied two main technological tracks for fuel production at pulp mills; lignin separation and black liquor gasification. Lignin separation means that the lignin - which binds the fibers in the wood - is separated from the black liquor, post-treated into liquid and then treated with hydrogen to diesel and petrol. Black liquor gasification is a process in which the black liquor is gasified, followed by synthesis first to methanol and then to petrol.
– In order to fully release the profits from fuel production in the pulp industry, global key players from the entire value chain need to work together, Elisabeth Wetterlund, says.
The research Drop-in-fuels from Black Liquor part streams-bridging the gap between short- and long-term technology tracks , about the pulp mills' production of drop-in fuel has taken place in collaboration between Luleå University of Technology / Bio4Energy, the above-mentioned pulp industries, Preem, SunCarbon and RISE. Elisabeth Wetterlund is also Deputy Director of Bio4Energy.