Managing Plastic and Food Waste Through Insect Farming

Insect farming using mealworms and black soldier fly larvae offers a two-step solution to manage plastic and food waste while reducing microplastics in soil.

Specific insect larval species have attracted attention for their ability to degrade synthetic polymers partially. Tangentially, entomocomposting is the process by which insects break down organic waste into valuable by-products. Insect-assisted plastic depolymerization combines both, with insects consuming a mixture of plastic and organic waste. A significant presence of microplastic residue in the final product is a limitation of current research for insect-assisted plastic depolymerization. A novel, two-step bioconversion system seeks to address this issue, with an end product that can improve soil health.

Farming Insects, Degrading Polymers

Uses of insect farming include producing protein-rich feeds and entomocomposting. One by-product of this process is frass, which typically has higher nutrient levels than organic fertilizers. This substance comprises larval feces, undigested food, larval fragments, and larval exuviae. Frass can positively impact plant growth as a fertilizer and exhibit protective effects against specific plant pathogens.

You can also read: Oxo-Biodegradable Packaging in Industrial Composting: Key Findings.

Certain coleopteran and lepidopteran larvae can consume and degrade polymers. These include polyethylene, polystyrene, polypropylene, polyurethane, and polyvinyl chloride. Thus, these insects offer an avenue for addressing plastic waste. Current processes for insect-assisted plastic biodegradation leaves frass with significant microplastic content. This poses a risk for using this by-product for soil enhancement. New research is expanding this process to add a second step, which significantly reduces microplastic content in the final product.

Step One: Mealworms

The first step of the proposed method involves the production of microplastic-rich frass by mealworms. Then, the frass undergoes pyrolysis, generating biochar. Because of its microplastic content, this biochar is not yet suitable for use as a fertilizer.

Step Two: Black Soldier Fly Larvae

Next, the biochar acts as a bulking agent during the entomocomposting of food waste. This step of the process uses black soldier fly larvae to produce “frasschar,” a carbon- and nitrogen-enriched substrate. Research suggests that these larvae can ingest solid particles, including microplastics, that are smaller than their mouth opening size.

Is it Scalable?

Both mealworms and black soldier fly larvae have an established role in organic waste bioconversion. Scientists have an extensive, preexisting knowledge of their biology. Additionally, these species have a low cost of rearing. In laboratory-scale studies, mealworms consumed an average of 0.2 to 0.7 g polystyrene per 100 larvae per day. In these studies, researchers mixed the plastic fragments with wheat bran in a 1:1 ratio.

This two-step approach offers an innovative method to overcoming a limitation of insect-assisted plastic degradation. The introduction of a second species reduces microplastic content and enhances biological properties in the final product. Though this method shows promise for scalability, additional research may prepare the process for industrial implementation.