It’s not glamorous. It’s not trendy. In fact, it’s downright grubby. But the work that a Georgia Tech researcher and his students are doing is improving campus sustainability, one pound of food waste at a time. 

David Hu, a professor in the George W. Woodruff School of Mechanical Engineering and the School of Biological Sciences, gave his senior-level biology class this semester a unique assignment: Feed food waste to black soldier fly larvae, collect the organic byproduct (called “frass”), and analyze the results. What they’ve found so far is a composting method with the potential to dramatically reduce harmful greenhouse gas emissions while producing a nutrient-dense fertilizer. 

“There’s something special about these grubs,” said Hu, who is also a faculty member within the Parker H. Petit Institute for Bioengineering and Bioscience. “They smell, and they’re kind of ugly, but they process food extremely efficiently. When we feed them, they eat twice their body weight, finish that in five hours, and you can do it again the next day. Traditional composting could never be that fast.” 

Using a unique closed-loop system pioneered by private-industry partner and early-stage startup Biotechnica, the larvae eat their way through more than 300 pounds of food in one semester, creating valuable frass that students harvest. When the larvae mature into adults, they fly into a shared chamber to reproduce, make more grubs, and start the process over again.  

“You can get a turnaround from food waste to frass in a day or two, and then from the raw frass to our ground-up frass that we use for our plants,” said Mikkelle Peters, a fourth-year biology major in Hu’s class. “It’s just a much quicker process to get rid of the food waste.” 

Feeding and studying an army of larvae that can eat more than 10 gallons of food a day keeps Hu’s students busy. The solution? Divide and conquer. 

The first group in the process gathers and grinds food scraps to feed the grubs, then collects the frass they produce. The next group mixes the frass with soil and analyzes its chemical makeup, comparing its nutrient density to commercial fertilizers. A third group uses the fertilized soil to grow vegetables like arugula and radishes that are measured against plants grown using synthetic fertilizer. The final two groups observe the environmental conditions that affect productivity and analyze the grubs’ digestion to uncover the secrets to their success. 

More testing will need to be done on outdoor farms to provide rigorous results. Data over the past few semesters were, at times, inconsistent. But the students’ projects reveal a lot of promise for future experiments. Despite limitations to the study, including a small sample size and minor instrument malfunction, the students have been able to find helpful nutrients in their product and grow certain crops more successfully with frass than with commercial fertilizer. Unlike chemically based products or some traditional composts that need to be specially treated, black soldier fly frass is organic and easily processed. 

“A lot of fertilizers can cause harmful runoff, and they can change soil balances over time,” Peters said. “Frass is a natural product, has more fibrous material, and has a lot more organic compounds.” 

In addition to the science that the students are exposed to, Hu said it is also eye-opening for them to see the work of sustainability. The project is an excellent case study for how a small group can make a big impact. 

“The students have learned a lot,” Hu said. “For one of the activities, we had them bring in their own food waste from home to feed the composter. They realized that a person makes pounds of waste per day.” 

According to the Office of Sustainability, the campus produces about 400 tons of food waste per year. Although Georgia Tech boasts one of the largest commercial composters on an urban campus in the Southeast, the machine can only process 175 tons per year. That leaves a gap that Hu said his research might one day be able to fill. 

“Right now, it’s working,” he said. “We want to expand and see if it can work some more. The big issue is visibility, getting people to know that what we’re doing is good. Because in some ways, saving the planet takes energy.” 

One of the main energy sources for the experimental composter is something Hu hopes to reduce: manpower. With a campus the size of Georgia Tech’s, it’s a very labor-intensive process for students to collect food waste from campus partners. Hu hopes that more community members will volunteer, not only to collect food, but also to improve the system. 

“We need people power — people willing to volunteer to move, because right now, campus produces a lot of waste in different places,” he said. “And we also need biologists and engineers and computer scientists. We need people to make this system more well-engineered.” 

Although the current black soldier fly composter still has some flaws, Hu said his goal is to create an affordable, climate-friendly food waste recycling system that can scale up to support U.S. agriculture. By solving problems at the local level, his research is potentially removing economic and operational barriers to sustainability. But, according to Hu, the final step to long-term success is community involvement. 

“In the end, we need people who care,” Hu said. “It doesn’t take that much effort to do a little bit, and a little bit can go a long way.”