The new research focuses on how hazelnut shells respond to the process of pyrolysis – superheating them to between temperatures of 400 to 1,000C, and analysing what remains.
The word pyrolysis comes from the Greek terms pyro for “fire” and lysis meaning “separating”.
Exploring how different biomass sources respond to this kind of process could lead to new, highly efficient bio-oils which could be used in manufacturing processes such as the production of clean(er) fuels and/or chemicals.
In the study, researchers from Heilongjiang Academy of Agricultural Machinery Sciences in China used pyrolysis to obtain from the hazelnut shells products known as “wood vinegar” and “tar fraction”.
Wood vinegar is already often used in agriculture as insect repellent, fertiliser, plant growth promoter or inhibitor, or can be used as an odour remover, wood preservative and as an animal feed additive.
Tar fraction could be a substitute for heavy oil for industrial boilers, or it could be used as a liquid fuel for industrial feedstock, the researchers suggested.
“After these results, wood vinegar and tar obtained from residual hazelnut shells could be considered as potential source of renewable energy dependent on their own characteristics,” said study author Liu Xifeng.
The researchers found the pyrolysis temperature had a significant effect on the yield and properties of wood vinegar and tar fraction in bio-oil obtained from hazelnut shells.
Wood vinegar was the dominant liquid fraction with maximal yield of 31.2 per cent by weight obtained at 700C, which the researchers said was attributable to the high concentration of water.
Despite the authors’ assertion that “biomass is attracting growing interest from researchers as a source of renewable, sustainable, and clean energy”, there remain concerns about its overall impact on the environment, compared to using renewable sources of energy such as wind and solar power.
The burning of biomass-produced fuels in industrial quantities can release large quantities of CO2, which if not effectively captured and stored, will enter the atmosphere, worsening the climate crisis.
The research team said their work on hazelnut shells “sets the groundwork for further applications of bio-oil from waste hazelnut shell pyrolysis”.
The research is published in the Journal of Renewable and Sustainable Energy.