Insecticidal and bactericidal characteristics of the bio-oil from the fast pyrolysis of coffee grounds

The aim of this study was to generate and characterize pyrolysis bio-oil from dried coffee grounds for the purpose of testing its pesticide characteristics towards selected microorganisms and the Colorado Potato Beetle. Dried coffee grounds were pyrolyzed to produce bio-oil. Pyrolysis was carried out at five different temperatures from 400 °C to 600 °C and at a vapor residence time of 5 s, to study the effect of temperature on the yield of the pyrolysis products. The trends clearly indicated a strong effect of temperature on the bio-oil yield. The highest bio-oil yield was found to be 43.8% at 500 °C. Gases were analyzed using gas chromatography–mass spectrometry (GC–MS). Gas yield increased from 17.6% at 400 °C to 32.1% at 600 °C. Char yield decreased from 35.2% at 400 °C to 19.6% at 600 °C. f the bio-oils produced between 400 and 600 °C were tested for bactericidal and insecticidal activities against pests found on plants in Canada that currently require improved control options. The dried coffee grounds bio-oil showed significant activity towards two bacteria (Streptomyces scabies and Clavibacter michiganensis subsp. michiganensis) and the Colorado Potato Beetle (Leptinotarsa decemlineata Say). The bio-oil was fractionated and tested for bactericidal and insecticidal activity. The most active fractions were analyzed using GC–MS. While some compounds in the bio-oil were active against both the insect and bacteria, the coffee grounds bio-oil also contained chemicals that provided additional insecticidal activity with no bactericidal activity.