Text: Leena Koskenlaakso I Photo: Timo Porthan
VTT and Aalto University have joined the Academy of Finland's FinnCERES flagship programme to study the possibilities of using biochar made from brewery and pulp mill waste to fuel batteries, supercapacitors and solar panels.
Biochar made from organic waste is a renewable material that has properties similar to fossil coal. Biomass-based biochar can also be used as a raw material for electronic applications for recovering, converting and storing energy.
The Academy of Finland's four-year FinnCERES flagship programme, which was launched in 2018, explores the use of biochar produced by means of hydrothermal carbonisation in electronic applications.
– We need to find more affordable and more environmentally friendly yet energy-efficient ways to produce and store energy without having to rely on rare and expensive metals, says Research Scientist Virpi Siipola from VTT.
Siipola leads a team of VTT scientists who have been testing different kinds of biomass that show potential as a raw material for biochar. The most promising from the perspective of energy applications are spent grain and pine bark.
– Spent grain is a biomaterial consisting of lignin and pulp. It is a by-product of brewing that has traditionally been used as animal feed. What makes spent grain interesting is the fact that it contains high volumes of nitrogen, which is essential for electrochemical applications. Activated spent grain is especially well suited for solar panels. Pine bark also contains nitrogen, and activated carbon made from pine bark is best suited for supercapacitors, Siipola explains.
VTT's biochar production technique is based on hydrothermal carbonisation (HTC) and chemical activation. These two technologies increase the area and porosity of the char.
Aalto University's battery and supercapacitor research team is led by Professor Tanja Kallio.
– We are moving towards seasonal renewable energy production and a more mobile way of life that requires portable energy storage solutions. However, traditional materials are not enough to satisfy the demand for renewable energy storage. Biobased energy storage applications could be a solution to this problem, Kallio says.
Batteries and supercapacitors made from biochar could be used in mobile devices and, as long as the production process can be scaled up, in vehicles. Supercapacitors are already used in the brake systems of electric cars to recycle braking energy. They store the energy and release it to the battery as and when needed.
– Our initial findings show that biochar has a greater capacity than commercial materials, but we still need to improve and optimise the porosity of our biochar, Kallio explains.
Aalto University's second FinnCERES research team is working on dye-sensitised solar cells. The team is led by Academy Research Fellow Kati Miettunen.
– Solar cells consist of two electrodes: a transparent conducting electrode and a counter electrode. Our research focuses on the counter electrode, which is typically made of platinum, a rare and expensive metal. We are looking for cheaper, more environmentally friendly and more abundant materials that can be produced in new ways, such as by means of 3D printing. One option would be to use biochar instead of platinoima, Miettunen says.
– VTT's spent grain has performed well in our tests. It produces a large catalytic area and promises to deliver high efficiency. Biochar-based solar cells also appear to have a surprisingly healthy lifespan.