A form of biofuel found in hazelnut shells can be a new renewable energy source - using various thermochemical processes to extract oils from the waste material.

Researchers from the Heilongjiang Academy of Agricultural Machinery Sciences describe the new extracting biofuel from this renewable resource. This waste product remains after the hazelnut has been husked and used for a variety of applications. It uses different methods like gasification, liquefaction, and pyrolysis to generate a new renewable energy source that can also be used for a host of applications.

The new work, titled "Turning Hazelnut Shells into Potential Renewable Energy Source," details the Chinese researchers' work regarding the physicochemical and antioxidant properties of wood vinegar and tar fraction - materials in the biofuel extracted from hazelnut shells subjected to pyrolysis at 400 to 1000 degrees Celsius (752 to 1832 degrees Fahrenheit). The new study appears in the Journal for Renewable and Sustainable Energy, published August 24.

Hazelnut Shell
(Photo: Bob Embleton via Wikimedia Commons)

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Finding a New Use for Hazelnut Shells and Its Byproducts

Wood vinegar, a liquid substance extracted from the processing residual hazelnut shells, is traditionally used as a natural insect repellent, fertilizer plant growth inhibitor, or promoter and can also be used as a wood preservative deodorizer and additive to livestock feed.

Researchers found that the wood vinegar and the tar fraction leftover from the renewable resource processing contained the most phenolic substances, providing grounds for the team to examine its antioxidant properties. To do this, the team behind the new study used a tube furnace pyrolysis reactor. Researchers ground and sieved their samples to a powdered form about 75 to 380 micrometers wide using hazelnut shells from Liaoning Province, China. They then loaded a 20-gram sample of the renewable resource onto the reactor's quartz tube waiting area. The reactor was heated, and when it stabilized at the target temperature, the hazelnut shells were moved to the reaction region, heating it for 20 minutes. According to the US Department of Agriculture Research Service, this process is called pyrolysis, heating a biomass material without oxygen.

Biochar, the resulting charcoal-like material from the process, was measured as the ratio of the generated pyrolytic char to the original biomass weight. On the other hand, the yielded biofuel from hazelnut shells was computed from the additional weight on the condenser.

Extracting Biofuel from a Potentially Renewable Energy Source

Researchers then separated the two byproducts of the renewable resource using a centrifuge, which separated the wood vinegar from the tar fraction based on their respective densities. The aqueous material was the wood vinegar, while the stationary substance was the tar fraction after the process. Researchers then refrigerated both materials for the next set of processes and analysis. 

They uncovered the effect of the set pyrolysis temperature on the yield and the physicochemical properties of the wood vinegar and tar fraction in the extracted biofuel. With this information, future researchers now have a reference for examining further applications of hazelnut shell pyrolysis and further studies on wood vinegar and tar fraction extracted from the bio-oil.

"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 Liu Xifeng, one of the study authors, in a feature article from the Journal for Renewable and Sustainable Energy.


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