Grantee Research Project Results
2018 Progress Report: Beetle larvae as biodegraders of styrofoam and organic waste
EPA Grant Number: SU839283Title: Beetle larvae as biodegraders of styrofoam and organic waste
Investigators: Nansen, Christian , Fowles, Trevor , Cheng, Brian , Favilla, Amanda
Institution: University of California - Davis
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 1, 2017 through September 30, 2018
Project Period Covered by this Report: September 1, 2017 through August 31,2018
Project Amount: $14,998
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2017) RFA Text | Recipients Lists
Research Category: P3 Awards , Sustainable and Healthy Communities , P3 Challenge Area - Chemical Safety
Objective:
This project sought to implement and optimize darkling beetle biodegradation to address challenges presented from disposing styrofoam, as well as quantifying aspects pertinent to the commercialization of the resulting byproducts. I started the project on September 1. The reason for starting then, was to be able to get successive generations of insect larvae to begin selectively breeding high performance biodegradation lines. The purchases include, containers for insect larvae and an order of 100k beetle larvae. If I did not start the project when I did, I would be unable to rear several generations under high selection pressures prior to the sustainability EXPO in the spring. The projects objectives accompanied with successes and failures are as follows:
- Increase beetle efficiency at biodegrading PS foam by supplementing diet. Test the effects that supplementary feed stocks, such as waste from regional tomato and wine producer, have on beetle efficiency at biodegrading PS foam. To do this we ran feeding trials comparing different ratios of feed stock additives to define the most efficient PS foam/additive feeding regime. We found that consumption rates for both styrofoam and the diets increased inside styrofoam amended diets (fig. 4).
- Styrofoam biodegradation performance. To do this, we ran trials modifying temperature, humidity, light conditions, and beetle age. Despite attempts to modify the environments of the larvae, we were struck with axillary problems associated with different changes that did not allow us to get a sufficient data set for modeling. Rather, we got a strong sense of a set of trade-offs on husbandry practice. For example, too much humidity for treatments with food wastes and there is significant mold. Also, batch rearing can become difficult to control mold even under dry conditions. Conversely, styrofoam is hydrophobic by nature so it does not take in any water. Dry temperatures then devoid water from the feeding substrate very quickly and lead to more cannibalism, hampering breeding trials.
- Breed a lineage of high-performance beetles. To do this we conducted individualized rearing trials to pinpoint individual beetles that are more adapted to biodegrade PS foam. These beetles then underwent selective breeding to create a linage of high-performance beetles. The duration of the project precluded success for this objective, in terms of developing a lineage. However, we consistently found high levels of placisity from all dietary treatments (fig 1-3). Meaning, there is considerable genetic merit to justify a breeding program given the sufficient funding.
- Compare beetle nutritive value compared to commercial insect meals. To do this we perform macro-nutrient analysis of beetles for comparisons to commercial insect meals used in animal feeds. This objective was satisfied, and the beetles have been sent to the UC Davis facilities for analysis. Results from this are still pending.
- Assess the efficacy of beetle frass as a soil amendment for growing seedlings. To do this we will took frass (excrement) collected from beetle larvae in objectives 2-4 and conduct a seedling growth trial, using the frass as a soil amendment. Here we found that additions of frass inhibited seed germination. Also, frass amendments above 25% show signs of root rot, and thus inhibited growth (fig 9). In addition, we note that the undegraded particles from the frass can easily become airborne, which may pose an irritant to workers.
- We will model and design a pilot system using the results of objectives 1-5 that maximizes the colony biodegradation performance and production of adult beetles. We did not complete this objective, as complications in the duration for breeding as well as issues scaling the process up did not allow us to move forward.
- We will establish a collaboration with the local high school to promote the principles of sustainability and showcase our model system as an innovative alternative to PS foam solid waste. We made strides both online and with the local newspapers to talk about styrofoam and environmental pollutions, as well as how the project may help alleviate them if properly worked out. However, due to the airborne styrofoam associated with the feces of the insects. We made the decision not to take them into the classroom.
Progress Summary:
We take the opinion that using beetles in sutu, that is within the beetle, is not an economic feasibility. Rather, further research into their capabilities to degrade styrofoam should come from exploration of the microbes within the organism. This line of research may develop a way to contain styrofoam and break it down as a process of fermentation. This would alleviate several of the challenges we faced that relate to upscaling this process. First, safety is of the upmost importance. Therefore, the air particulate of styrofoam that comes from the feces of the insects is a potential hazard. Styrofoam by itself is rather inert and immobile. The small portion of the feces that made from undigested styrofoam is mobile and under the microscope seems to have a high surface area, allowing it to float. A second concern was that it is difficult to maintain a colony with sufficient humidity requirements, we find the hydrophobic nature of the styrofoam diet either makes the remaining diet too susceptible to mold or to drying out. With pockets of both then scaled to large sizes. Doing this work in a large bioreactor with a microbe would eliminate both problems. However, there are two findings which are very promising. First, in all the trial we conducted we found significant plasticity in the response to diet (fig 3). That is, even an the ancestral (commercial) diet the mealworms showed individuals that were low performers and others that were very good performers. While this was also observed in the styrofoam only diets, the fact that it was found in every other diet suggests that there is significant genetic variability within the populations to warrant breeding. While we originally proposed using breeding as a means to develop styrofoam specialist lineages, the innate plasticity (variability) means nearly all diets can produce specialist strains, principally the food waste streams produced industrially like wine, tomatoes and almonds. Finally, another interesting discovery was that addition of styrofoam to any diet increased the weight gain and bioconversion of both parts of the diets (fig 4, 6, 8). We do not know exactly what this suggests, but this phenomena was witnessed with high significance.
Figure 1. Change in weight for oat and styrofoam mixed diets. Note how there is plasticity in the response to both styrofoam and oats. This indicates room for more breeding.
Figure 2. Weight change for styrofoam only diet. Note that the percentage of styrofoam eaten is less than in the diets where there was added mixtures of food , see fig. 1.
Figure 3. Weight change for oat only diet. Note that the percentage of oats eaten is less than in the diets where there was added mixtures of styrofoam , see fig. 1.
Figure 4. Reduction rate (g) of Styrofoam and Oats in the the Styrofoam + Oats diet, and comparing them to the diet reduction rate in the Styrofoam and Oats treatments.
Figure 5. The average production of frass (g) from the three dietary regimes.
Figure 6. Ranked comparison of weights between polystyrene and oats. The ranking is based on the weight of individuals and diets. This was done to determine the difference between Styrofoam and Mixture.
Figure 7. Change in larval weight over time, for each dietary regime. The graph shows that there is more growth in the Mixture compared to the other two dietary regimes.
Figure 8. Mealworm larva weight change over the course of the individual feeding trials (120 days).
Figure 9: Day 14 f fertilizer trials with the frass (excriments) from the experiments. Note the dramatic drop off in growth after 25%.
It is our opinion that the bioconversion of styrofoam into insect protein, fat, and feces happens a) too slow to allow sufficient upscaling to make the project more economical; b) produces more particulate than expected, which can have harmful effects to workers without the proper and necessary safety precautions; c) increases the generation time of the insects, thereby slowing down the potential of breeding; and d) produces an end product (ground insect meal) that is met with much suspicion by the public. For example, throughout the duration of the project, despite demonstrating the interesting phenomena that there is higher rates of consumption and weigh gain when styrofoam is added to the insects’ diet, people were skeptical of the biomass produced by the larvae. They often asked what the insect meal may be used for, and whether it was safe to use as an animal feed. While these are apt questions, they are outside of the purview of this particular experiment. While we have reason to believe that the hydrocarbons of the styrofoam may just be making their way into fat and exoskeletal generation, we are unsure about the overall toxicity of the larvae. We would suggest that if this technology was to be adapted and used at a larger scale that a serious investigation into the toxicity of the products are undertaken.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
Cradle to cradle, life cycle analysis, recycling technologies, closed loop recycling, renewable feedstocks, model for sustainability, feed stocks, recycling, waste to value, agricultural byproducts, animal feedRelevant Websites:
UC Davis Graduate Student Scores EPA Grant Involving Mealworms and Styrofoam Exit
Why These Mealworms Don't Miss a Meal Exit
EPA awards grant to UCD for innovative technology project Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.