Byproduct of Biofuel Production Shows Potential for Insect Pest Management

The past 30 years have seen significant advances in the production of biofuels—liquid fuels such as ethanol and biodiesel that can be derived from renewable, nonfood, bio-based feedstocks such as lignocellulosic biomass or algae. Part of these advances is discovering uses for byproducts of the biofuel production process, and new research shows that some of these byproducts show promise as insecticides targeting stored product pests.

In a multimillion dollar project funded by the U.S. Department of Energy’s Bioenergy Technologies Office, my fellow researchers and I from the USDA-ARS Center for Grain and Animal Health Research (CGAHR), National Renewable Energy Laboratory (NREL), and Michigan State University set out to determine whether byproducts from cellulosic biofuel production could be used to manage an array of important agricultural and stored product insects. These byproducts—or “coproducts” as they’re deemed when found to also be of value—are poorly suited for fuel streams, but they could increase the cost effectiveness and sustainability of biofuel production by being applied for other purposes rather than going to waste.

One of the primary biofuel production processes is pyrolysis, in which biomass is deconstructed through high heat in the absence of oxygen. Our team of researchers examined coproducts heated to specific temperature ranges, also called “fractions,” from this pyrolysis process and found that they successfully mimic insect growth regulators when applied to a range of stored product insects, including the red flour beetle (Tribolium castaneum) and the confused flour beetle (Tribolium confusum). Our findings are published this month in the Journal of Economic Entomology.

Even at low concentrations, the oils were found to cause deformities in normal development such as incomplete metamorphosis or only partial hardening of the pupal case. In the end, many of the exposed larvae never matured to adults. At higher concentrations, there was 100 percent population suppression of both red flour beetle and confused flour beetle larvae. By contrast, adults were relatively unaffected.

Furthermore, the price point for the intermediate pyrolysis oil was very reasonable at less than $1 per kilogram (kg) to produce, while the final pyrolysis oil cost between $1.41 and $1.70 per kg. That’s just 0.9 percent of the cost of the commercially available insect growth regulators for stored product insects.

Finally, a greenhouse gas (GHG) emissions lifecycle assessment was also performed, and the team found the use of the pyrolysis oil could reduce GHG emissions associated with the insecticide production supply chain by 25–61 percent relative to that of a fossil-fuel based insecticide or pyrethroid.

Thus, the pyrolysis oil is incredibly inexpensive to produce, highly effective against insect larvae, and more sustainable than conventional alternatives. We are encouraged that adoption of such bio-oils as pest management tools in agriculture will help enhance the sustainability of using biofuels to source at least some of society’s energy, while contributing to global food security.

Source: Entomological Society of America