M.P. Hayes

Many manufacturers and aquaculture producers strive to create environmentally sustainable practices for their businesses, but for waste, there is an inadequate framework for disposal methods that reduce the environmental impact. There are 350 permitted aquaculture or seafood businesses in Louisiana that have an economic impact of $2.4 billion annually and employ one out of every 70 jobs in the state, according to the Louisiana Department of Health. Most processors spend a minimum of $50,000 per year on waste removal services for solid waste. Through partnerships with the LSU AgCenter, research is being conducted to transform a common waste stream into a source of organic fertilizer.

The byproducts of many seafood processing operations are the wastewater effluent that contacts the products during the processes and nutrient-enriched solid shells. For many facilities, there is an expense associated with the collection, storage, treatment and transportation of these waste streams. The cost of disposal over time can minimize the company’s revenue and create a bottleneck for the manufacturing processes. Though many studies have been conducted on the use of seafood waste, the limiting factor is high chitin content. Chitin is a nitrogen-containing polysaccharide with a comparable structure to cellulose. To access or “unlock” the valuable nutrients in shells, the chitin must be broken down. This is normally done through chemical digestion, which adds a processing cost to create a beneficial use product from waste, such as fertilizer. There are numerous companies that provide this service for densely populated groups of processes. In Louisiana, the geographical isolation of processors makes it difficult to dedicate a single facility for the chemical processing of waste shells. To create more practical solutions for waste management, research has turned to organic solutions using insect larvae to break down shells.

Industrial insect rearing is a commercialized business that offers high-protein-source feedstocks for poultry, swine and aquaculture production. There are many different species of insects that have relatively fast generation cycles used in these industrial operations. The black soldier fly (BSF) was chosen for these research trials because of many benefits, including the flies’ high protein content, relatively short lifecycles, no known vector for transmitting disease and no known effects on human or environmental ecosystems. Like other species used in insect farming, BSF larvae are capable of decomposing various organic solid wastes into a nutrient-dense material called frass. The organic frass yields a suitable soil amendment that can be chemically characterized to determine its nitrogen, phosphorus and potassium (NPK) ratio, a measurement of the three of the most important macronutrients for plant growth. This form of compositing offers an avenue for waste valorization, which involves converting waste products for a beneficial community use.

To develop a waste valorization pathway to convert seafood processing waste to agricultural fertilizer, the research team has characterized shrimp and crab shells using the LSU AgCenter Agricultural Chemistry lab. The analysis provided data for nitrogen, phosphorus, potassium, protein, fat, fiber, metals and minerals to trace compounds throughout the insect-farming processes. For the initial trials, it was noticed that the shrimp and crab shells had fluctuating nutrient concentrations with an average NPK percentage of 3.0 N, 2.5 P and 0 K for shrimp shells and 3.7 N, 2.3 P and 0.3 K for crab shells. The slight fluctuations in nutrient content are associated with the season change and species variability from the partnering seafood processors. By analyzing each unique batch of shells, the data can be traced through the insect-rearing process to ensure the nutrient percentages in the frass are valid. A preliminary trial was conducted using small-batch diets of 100 grams of various homogenous blends of ground seafood shells and a proprietary industrial insect feed. Each seafood trial, the volumes of shells were increased from 25% to 100% to determine the viability of the diet for larvae. These trials were replicated for both shrimp and crab shells to determine independent diet formulations for both seafood industries. Each diet trial was tested in triplicate to compare with a control sample of 100% insect feed. After eight days, the larvae were harvested and allowed to evacuate for growth and survival rate measurements. Additionally, frass and larvae samples were sent to the Ag Chemistry lab for analysis to trace chemical parameters from the original waste stream through the larvae digestion processes.

Key findings from the preliminary diet trials showed similar larvae survival rates for shell blends up to 60%. The growth rate of larvae slightly declined with the increase of shells in the diets. This can be mitigated by extending the feeding time longer than eight days or increasing the number of larvae per trial. The decline in growth rate was not associated with chitin content because of the increased calcium in the larvae when analyzed. The seafood waste shells contained significantly more calcium than the proprietary insect feed, and as the blends of shells increased, the larvae calcium percentage also increased. Thus, it is believed the larvae were able to consume the homogenized shells.

The 25% blends of shrimp and crab had the highest NPK percentages at 2.3 N, 0.7 P and 0.9 K and 2.6 N, 0.7 P and 0.9 K, respectively. With the nitrogen and phosphorus results being lower than the original input, it can be concluded that more larvae or longer feed times are needed for the trials. The increased potassium content was seen due to the high percentage of insect feed in the diet blend.

The LSU AgCenter team has started the next round of testing, increasing the volume of diet blends from 100 grams to 8.35 pounds (3,788 grams). These trials will be conducted for both shrimp and crab shells at five blends between 25% and 60% waste. The data produced from this macro-experiment will show scalability and identify the optimized nutrient concentration for the frass. This will pivot the project into collaborations with AgCenter assistant professor of landscape horticulture Damon Abdi for amendment viability using plant trials and a food web analysis with Jeff Plumlee from the team’s recently funded 2025 AgCenter Center of Excellence Crop Development and Biotechnology proposal. With an immediate need for innovative solutions for waste valorization for seafood byproducts, the use of insect farming may offer feasible onsite composting opportunities for waste stream reduction and generation of beneficial-use products.

M.P. Hayes is a dual-appointed assistant professor in the LSU AgCenter School of Plant, Environmental, and Soil Sciences and Louisiana Sea Grant.

This article appears in the summer 2025 edition of Louisiana Agriculture.

Black soldier fly larvae are pictured blended with a seafood waste diet to help break down the seafood waste and transform it into a frass that can be used as fertilizer. Photo by Shristi Upadhyaya

Graduate researcher Shristi Upadhyaya conducts her master’s degree research on mixing seafood shell diet blends. Photo by M.P. Hayes