Exploring the energy potential of fast-growing broadleaves

Wood from poplar of different diameters. Photo.
Poplar wood of different diameters. Photo: Sruthy Vattaparambil Sudharsan


Stina Johannesson

The global demand for bioenergy has increased the focus on how to produce and use biomass for energy and other purposes in a sustainable way. In a Trees For Me research project, PhD student Sruthy Vattaparambil Sudharsan and professor Kentaro Umeki look into the biomass properties of fast-growing broadleaf trees and its potential for different, sustainable energy, and other related biomass-based, uses.

The knowledge on how the properties of biomass from fast-growing broadleaf trees differ from more conventional biomass has created a need for further research, according to Kentaro Umeki, professor of energy engineering at Luleå University of Technology and supervisor of PhD student Sruthy Vattaparambil Sudharsan.

“For example, does growing trees faster mean that the biomass will be less dense, which makes it more suitable for bio-oil production than for biochar? And will fast-growing broadleaves contain a lot more extractives, such as resins, wax, and proteins, compared to ordinary biomass, which could increase the profitability to extract those chemicals before using the rest of the biomass for energy?” Those are some of the questions raised in the research project, says Kentaro Umeki.

Many practical uses

The overall aim of the research project is to propose efficient and sustainable thermochemical conversion processes for fast-growing broadleaved species, which includes focus on combustion (heat and power production), gasification (biofuel, ammonia, methanol and hydrogen production) and pyrolysis (biocarbon and bio-oil production). The potential practical implementation ranges from production of chemicals, sustainable aviation fuels, biochar for steel production, battery raw materials and other high-end applications rather than just using biochar for soil improvement, and more.

And these new implementations require new knowledge on how the biomass will behave in different conversion settings, according to Kentaro Umeki.

“When we start looking at these applications, it becomes more important to gain detailed knowledge on biomass properties with respect to what is called organic fraction, which shows the detailed composition, particle density, and so on, unlike when you only look at combustion, where the major technical issues are ash-related problems.”

Initial focus on poplar

“Fast-growing broadleaf trees are very suitable for energy production as these tree species are economically viable, have higher growth rate, and can be harvested at much shorter intervals”, says Sruthy Vattaparambil Sudharsan, PhD student in Trees For Me and Luleå University of Technology, who is the one working the most with the research project. She explains that the tree species, forest management, and consequent growth rates have a significant effect on the feedstock properties and fuel conversion characteristics.

The differences between fast-growing broadleaf tree species will be investigated, but the initial focus is on poplar. 

“We will look into how different thinning treatments and stem diameters of second rotation poplar trees affect the feedstock composition”, says Sruthy Vattaparambil Sudharsan. How such properties could affect the potential biochar and bio-oil production, and the suitability of biomass properties for various future biorefinery value chains will then be investigated.

The industry awaits the results

There’s a big interest from the industry and the research results will be validated in some large-scale trials with industrial partners, with the ambition to contribute to an increased knowledge on which applications have the highest techno-economic potential. Kentaro Umeki points out that there are plenty of energy and materials applications that are waiting for predictable and large volumes of biomass supply.

“To use biomass residues left from biomass harvest for timber and paper productions, which is what we do, is needed to decrease the use of fossil fuels”, Kentaro Umeki concludes.

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