A pilot project at Stora Enso’s Heinola mill in Finland is converting sludge, a by-product of processes carried out in industry and agriculture, into biofuel.
Bio-sludge at the company’s Heinola fluting mill is produced as a by-product of wastewater treatment. The mill used to burn the bio-sludge at the power station for thermal power needed fossil-based fuel, however this was not in line with the mill’s long-term goal to achieve carbon neutrality in its operations.
In 2019, an industrial scale pilot plant was built in the mill area, using technology developed and patented by Swedish company C-Green Technology. Bio-sludge is dried in an energy-efficient way using pressure and heat, and is converted into biofuel.
"Our process, OxyPower HTC, uses an innovative application of hydrothermal carbonisation, which converts complex organic compounds into sterile odourless biofuel," said Erik Odén, CEO of C-Green.
The pilot plant processes 16,000 tonnes per year of bio-waste. The biofuel produced is used in the mill’s power boiler and to heat the nearby town of Heinola, which has around 20,000 inhabitants.
“The treatment of bio-sludge produced at our mill offers opportunities for a bio-based circular economy, which supports Stora Enso's environmental goals,” added Mikael Sillfors, development manager at Heinola Mill. “With this technology, we can save both the environment and costs.”
Stora Enso is investigating how much carbon dioxide (CO2) can be reduced with the treatment of bio-sludge. The company’s aim is to reduce the use of fossil fuels and get as close to net-zero CO2 emissions by technically and commercially feasible means.
A high proportion of biomass is already used in the internal energy production at the majority of Stora Enso’s mills. In 2018, the share of biomass in energy generation at its mill sites was 81%.
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