Investigating Production Capabilities and Uses of Black Soldier Fly Larvae (BSFL) for Organic Waste Processing in the Urban Environment

Commodities

Practices

• Energy: food waste, biotechnology
• Soil Management: organic matter
• Sustainable Communities: urban agriculture

Among the popular insects used for composting organic waste, black soldier fly larvae (BSFL) are especially attractive because of their ability to thrive and quickly decompose many different types of organic waste, their classification as “not a nuisance species” and their use as protein for livestock feed (Romano, 2023). BSFL quickly converts waste material to insect biomass- at conversion efficiencies of 44%, 67%, 74% and 98% for manure, kitchen waste, fish and vegetable/fruit waste respectively (Nguyen et al., 2015). The complete cycle of food waste to mature BSFL is uniquely quick and requires only 1-3 weeks (Lopes et al., 2022).  Additionally, Black soldier fly larvae are considered easier to manage and harvest than other insects used for composting because they exhibit a “self harvesting” behavior where maturing larvae will exit their active food habitat for a dry pupating environment (Terrell, 2022). Technically advanced operations are run in European and North American companies, such as EnviroFlight, Oberland Agriscience, and Eawag, while simple but highly efficient systems are operated out of African and Indonesian countries like the Marula Protein Hub, ProteinMaster Nairobi, and
BSFL Colonies.

This natural technology has become very popular over the last decade, with plenty of available information and research being conducted on how to improve the bioconversion rates from the wasted nutrients to usable macronutrients, which feedstock mixes are best for BSFL decomposition, how best to incorporate BSFL into existing livestock and pet feeds, and how to grow the BSFL to maximum size most efficiently. To do this, BSFL must be maintained under ideal environmental conditions, including parameters such as humidity, nutrient composition, physical properties, temperature, and oxygen level in order to optimize bioconversion rates. 

In addition to their unique bioconversion abilities, BSFL makes for a nutritious, and sustainable, supplemental livestock feed once they are through their larval lifecycle. Crude protein and crude lipid contents of BSFL meal range between 40%-44% and 15%–49%, respectively, depending on the processing methods and substrates used (Tran et al., 2015). According to EnviroFlight, BSFL production offers a “protein per acre” measurement that is unmatched to any other
source of traditional protein feeds, with up to 1,000,000 pounds of protein per acre, compared to soybean with just under 1500 pounds of protein per acre as a double harvest. To extend the list of benefits that BSFL has to offer, there is research being done on the extraction efficiencies and techniques of chitosan, a derivative of chitin, and melanin. Both of these compounds, found abundantly in the shells of the BSF and the larvae, are being used in industries such as cosmetics, internal medicine, and micro-electronics (Abidin, 2020). 

Future Acres is currently planning and building a simple small-scale, vertically integrated BSFL composting system and aims to start processing urban food waste in early 2024. Our system will be environmentally controlled and vertically integrated to save space in the urban environment, which creates a novel system. Having the ability to control the temperature, humidity to optimal conditions, and having vertical integration, our system has the potential for extremely high efficiency. Utilizing common urban food waste as the input, we want to quantify the maximum capacity of our system
for food decomposition. This will create a benchmark for other urban farmers interested in incorporating insect farming to their operations.

Additionally, we want to record, and make available to other urban farmers, the production capabilities of livestock feed, and frass for additional revenue sources and summarize the issues that face urban farmers when running an urban BSFL composting system. Finally we want to begin to assess the use of frass in popular urban agriculture production systems like hydroponics and microgreens. 

While there are examples of using BSFL for food waste processing, there is very limited information specific to small-scale, urban, indoor environments of the Southern United States. For urban farmers that are interested to
start BSFL composting, basic questions need to be answered like - how much mixed urban waste can be processed with a BSFL system? How much revenue can be generated from an urban BSFL composting system? What are context specific concerns/management practices? How much compost and livestock feed can I produce?

Ultimately the question that needs to be answered is- Is it worth adding BSFL composting to an urban farm operation?. There's an absence of specific information and tailored methods for small-scale, highly urbanized environments; there’s confusion about the processing capacity for these systems when they’re optimized for food waste processing, and there are limited farmers with experience to share. With the help of the SARE producer grant, we aim to fill these gaps in knowledge about BSFL composting in urban contexts. 

We will run a study to:

1. Find management practices that maximize mixed urban food waste breakdown using BSFL and then 
2. assess the production capabilities and value of BSFL (lbs) and frass production (lbs) for livestock feed and soil amendments.

To maximize decomposition of organic waste, adequate oxygen and BSFL density need to be present within the organic matter mix. If these factors are not optimized, anaerobic conditions are created in the organic matter, and BSFL organic matter breakdown efficiency is reduced.  For this reason we will assess a few different ventilation rates and BSFL density rates for our specific vertically integrated system. Each treatment plot will be a tube filled with 25 lbs of homogenized organic waste receiving a treatment of ventilation rate and BSFL density. 

Variables:

• The independent variables of interest are: optimal ventilation rate and BSFL density
• The dependent variables of
  interest are:
  • Amounts (lbs) of organic
    matter decomposition
  • Weight (lbs) of BSFL
    production
  • % frass produced
• Control:
  •  the pounds of
    processed food scraps contained in each composting pipe (25
    pounds of food scrap)
  • the ambient temperature of
    the air in the facility (will be kept within the range
    75-85 degrees)
  • Food scrap input: the
    mixture of food scrap contained in each treatment (mix of
    most common “urban food scrap waste”)

The experimental design will be a split-plot, with ventilation as the main treatment, and BSFL
density as the
sub-plot
treatment. See experimental design in the image to the right;
each circle represents the composting tube that will hold 25 lb
food waste : 

Treatments: 

To determine the optimal ventilation
rate we will
measure the effects that different rates of airflow have on our
system bioconversion rate. 

We will introduce airflow to the
pipes for five minute intervals at 3 different treatments:

1. Treatment 1: every three
   hours,
2. Treatment 2: every six
   hours
3. Treatment 3: every eight
   hours. 

Temperature and humidity will be monitored throughout the experiment to compare how the different rates of airflow affect BSFL activity levels. At the end of a 2 week feeding period, the % of biomass converted will be assessed. 

To determine the optimal amount of young BSFL to add to each system to maximize speed of breakdown, we will be experimenting with three amounts of larvae added to the 25 pounds of food waste.

1. Treatment 1:  7,000,
   5-day-old BSFL (5-dol),
2. Treatment 2: 8,500, 5-dol
   BSFL
3. Treatment 3: 10,000, 5-dol
   BSFL

These treatment amounts are guided by previous guidelines and measurements taken by Christian Zurbrügg et. al. Their research in Eawag’s commercial composting system utilized around 300-360 BSFL per pound of food scraps (Note: 10,000 to 12,000 BSFL/15 kg food scraps = 303 to 363 BSFL per lb food scraps. Our control amount will be based on 11,000 BSFL/15 kg of food scrap, or 333 BSFL/lb of food scrap. Total BSFL for control will be 333 BSFL x 25 lb food scrap = 8,325 BSFL)..

Data Collection: 

At the beginning of each study iteration, 

1. the composition of the organic matter input will be recorded as: %meat/protein; %vegetables/fruit/mushroom; %breads/pastas. 

Throughout the study: 

1. Temperature and humidity of each plot will be recorded daily
2. Outdoor temperature and humidity will be recorded daily

End of study:

1. mature BSFL weight (lbs) after composting
   1. In order to measure BSFL
      growth rates, after 2 weeks of running the system, we will
      sample the weights of 100 BSFL from each of the
      experimental sub-plots. In order to measure the food scraps
      conversion, we will sift out and weigh remaining food
      scraps from each subplot. In order to measure the frass %
      we will estimate the usable frass from each sifted
      sub-plot.
2. the amount (lbs) of food scraps leftover after composting
   1. Food scraps will be sifted
      from frass and weighed.
   2. This will help us calculate
      the amount of food scraps converted
3. % frass produced
   1. Remaining frass after
      sifting will be weighed
4. observe/record the general activity level of the BSFL during feeding. 

We will repeat the study 3 times during winter and summer season, respectively, with a total of 6 replications of the study. This will help capture the variation of seasonality effects on our indoor climate, to ensure significance for statistical analysis (while we wish indoor climates were 100% controllable, this is simply not the case. In the heat of the summer our environment is slightly higher temperature and humidity). It is possible, that during the heat of the summer, or cool of the winter, that optimal ventilation and BSFL densities are different.

From the conclusion of the ventilation and BSFL density study, an optimal ventilation and BSFL density will be determined. Then the revenue of livestock feed and frass capability of this system will be assessed. The data to assess this will already have been collected through the study. 

The data will be analyzed using R software with ANCOVA, to assess the effects of ventilation hours and population densities, and their interaction effects on BSFL weight, and organic matter conversion % and end-product frass %.

By the end of our study, we will have the data to share the amount of general urban organic waste that can be processed by an urban BSFL operation and the potential production/revenue from livestock feed and soil amendment production.