Toxicity of lignin, cellulose and hemicellulose-pyrolyzed bio-oil combinations: Estimating pesticide resources

Biomass contains varying proportions of lignin, cellulose and hemicellulose, and when pyrolyzed, a liquid bio-oil is produced that can be converted to fuels and value-added products such as biopesticides for insect pest management. The objective of this study was to determine which biomass components are responsible for the insecticidal activity of biomass bio-oil by comparing the individual toxicity (LC50) of lignin, cellulose and hemicellulose bio-oils with the toxicities of mixtures of lignin, cellulose and hemicellulose bio-oils to the Colorado potato beetle (CPB) (Leptinotarsa decemlineata Say). Lignin, cellulose and hemicellulose individually as well as in mixture were pyrolyzed at 550 °C in a fluidized bed reactor with nitrogen as the fluidizing gas and silica sand as the bed material. Bio-oil collected from the reactor's condenser (aqueous and organic phases) and electrostatic precipitator (ESP) or demister pyrolyzed from the same biomass were combined proportionally on the basis of their respective yields. The different biomass components were mixed in equal proportions and then pyrolyzed to provide an artificial biomass bio-oil. Of the three individual component bio-oils, lignin was the most active and the ESP portion the most toxic compared to the other components and collections. Alone, it accounted for the majority of the insecticidal activity in the mixtures, but only the cellulose–hemicellulose bio-oil combination was determined to exhibit synergism. In contrast, the lignin–cellulose–hemicellulose bio-oil combination was determined to exhibit an antagonistic effect. Therefore, it is important to consider the type of biomass component or the proportion of lignin that makes up a particular biomass in order to produce a bio-oil for potential pesticide development.

► Lignin, cellulose and hemicellulose pyrolyzed at 550 °C in a fluidized bed reactor.
► Mixture of lignin, cellulose and hemicellulose also pyrolyzed.
► Toxicity or pesticide activity of various bio-oils compared.
► Lignin bio-oil is much more active than bio-oil from cellulose or hemicellulose.
► No synergy of lignin with other biomass components, but antagonistic effects.