Biomass can be converted into fuel and value-added products (e.g., biopesticides) by thermochemical processes (e.g., pyrolysis). Lignin, cellulose, and hemicelluloses are the principal components o f plant biomass. All three biomass components were individually, as well as in mixture, pyrolyzed at 550°C in a 0.078 m diameter, 0.52 m high fluidized bed reactor with nitrogen as the fluidizing gas and silica sand as the bed material. The first objective ofthis study was to determine which biomass fractions are responsible for the insecticide activity of biomass bio-oil, by testing the individual toxicity (LC50) of lignin, cellulose and hemicellulose bio-oils, toxicities o f mixtures o f lignin, cellulose and hemicellulose bio-oils as well as toxicities of lignin bio-oil fractions to the Colorado potato beetles (CPB) {Leptinotarsa decemlineata (Say)). The cellulose-hemicellulose bio oils combination showed synergism, whereas lignin-cellulose-hemicellulose bio-oils combination had an antagonistic effect. The combination of lignin bio-oil fractions of condenser aqueous phase, condenser organic phase and electrostatic precipitator (ESP) produced additive toxicity. The second objective was to investigate the pesticidal activity o f the bio-oil produced from lignin, cellulose, and hemicellulose individually pyrolyzed at two temperatures, 450 and 550°C, in a bubbling fluidized bed reactor. Three species of insects, the CPB, the cabbage looper (CL) (Trichoplusia ni (Hubner)), and the pea aphid (PA) (Acyrthosiphon pisum (Harris)) were used to assess the range of insecticidal effects of the different bio-oils. Bio-oil from lignin pyrolyzed at 550°C collected by an electrostatic precipitator, was the most active against the CPB at 30 mg/mL, while 3 mg/mL reduced aphid reproduction. The bio-oil did not produce any toxicity for the CL in the same concentration range. The lignin ESP bio-oil at 550°C was further separated
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into polar and non-polar .phases by liquid-liquid extraction using water and dichloromethane (DCM). The ESP-DCM phase retained the activity in the CPB bioassay, and was further ffactioned by semi-preparative high pressure liquid chromatography (HPLC). None o f the individual fractions was active, but a range o f fractions at the end o f HPLC collection when re-combined were found to be active. The recombined oil was analyzed by gas chromatography-mass spectrometry (GC-MS) to identify the active component(s). Six of the ten most abundant peaks from GC-MS chromatogram are polycyclic aromatic hydrocarbons (PAHs). Anthracene was confirmed by standard, while the other possible PAHs are pyrene, phenanthrene, fluoranthene, methyl substituted fluoranthene, and fluoranthene. Stearic and palmitic acid were also confirmed. The PAHs, stearic and palmitic acid are known to be toxic to insects, however none of these compounds is effective individually at the concentrations detected in the bio-oil fractions. Therefore, synergy between these compounds is likely providing the observed activity. From the perspective ofpesticidal action, this will make it harder for an insect such as the CPB to develop resistance to multiple compounds.
V Objective three was the optimization of pesticide production using a novel reactor
technology that can separate the bio-oil at specific temperature ranges. Lignin was pyrolyzed within a temperature range of ambient-600°C in a 0.13 m diameter, using a 0.15 m high mechanically fluidized reactor (MFR). The toxicity of the different temperature cuts was tested using the CPB bioassay. Bio-oil from the 250-300°C cut was the most active against the CPB, and when analyzed by GC-MS and compared to other temperature cuts, three of the ten most abundant peaks were confirmed as guaiacol, catechol, and stearic acid by standard. However, no CPB mortality was observed for the standard mixture which is the same as their concentration in the bio-oil indicating that other compounds are involved in the overall activity. Although tlie same amount of lignin biomass produces approximately four times more toxic bio-oil when it is pyrolyzed by bubbling bed reactor instead of MFR, the bio-oil production by MFR is more efficient because the expensive liquid-liquid extraction and HPLC separation can be eliminated to retain the pesticidal components o f the bio-oil
