1. Quantifying the components of the mass and energy balance of a black soldier fly (BSF) food waste composting system Tiny but Hungry
Shwe Sin Win, Alicia Piscitelli, Steve Weinstein, and Sarah Brownell
Golisano Institute for Sustainability, Department of Chemical Engineering, and Design Development and Manufacturing
Rochester Institute of Technology, 111 Lomb Memorial Drive, Building 81, Rochester, New York, 14627
Introduction
Methodology
Results
Black Solider Fly Composting: The Black solider fly (BSF) (Hermetia illucens), a detritivorous insect, is native to moist temperate and tropical region of the world. BSLF can consume and convert many types of organic wastes such as municipal waste, meat, grease, animal manure and fecal sludge into valuable larval biomass: protein (50%), fats (39%)and carbohydrates (7%). BSLF can reduce the waste by about 39% (pig manure), 50% (chicken manure), and 68% municipal organic waste).
The results from the experiments were interpreted and the system was modeled for conduction using Fourier’s Law. Eq [1] – [5] allowed the team to model the heat transfer of the insulation.
Bench-scale experiments were conducted to analyze and determine the energy and mass balance parameters in order to determine requirements for scaling up.
1. Cultivation and measuring consumption rates: At 6 days old, 1,000 larvae (15mg (w)/larvae) were inoculated into 900 g (60 per larvae per day) of either post-consumer food waste or dog food and measured for biomass accumulation. The BSFL were kept at 25ºC and humidity (60-70%) in laboratory incubators for days.
2. Batch heat experiments: Samples of 25 larvae alone, 15g of dog food alone, 25 larvae with 15g dog food and a blank were placed in 58 mL test tubes, insulated with fiberglass and foam insulation, and kept in an incubator at 25 ºC and 60% RH during the test for a duration of 5 hours.
3. Batch respiration experiments: Using the same set up as above, the gas composition of air in a fixed volume reactor (58 mL test tube) was analyzed hourly using a Shimadzu 2014 GC TCD gas chromatograph.
LIFE CYCLE OF THE BLACK SOLIDER FLY
Graph 1 (left). The negative natural log of the temperature difference (y value) graphed as a function of time in seconds. The value for the slope of the linear trend line was used in determining the overall heat transfer coefficient for both the fiberglass and foam insulation combined.
Graph 2 (right). The negative natural log of the temperature difference (y value) graphed as a function of time in seconds. The value for the slope of the linear trend line was used in determining the overall heat transfer coefficient for the larvae and the dog food.
Modelling Heat Transfer Data
BSF COMPOSTNG: A PROCESS SUMMARY
Heat Energy generated by one larvae, = J/s (Watt)
= kJ/hr/larvae
Figure 1. Modeling the overall heat transfer coefficient by looking at the flow of mass and energy into and out of the system
Determination of Carbon Dioxide (CO2) emitted by BSFL during respiration
The average CO2 production rate are:
larvae alone: 0.2 mL/g larvae/hr (0.017mL/ larvae/hr) ;
food waste alone: mL/g/hr and
larvae and food waste: mL/g/hr.
Continuous Flow Reactor
Table 1.Economic and Environment benefits of BSFL food waste composting system.
Objectives
Little information is known about the economic and environmental viability of scaling up these systems for colder climates, nor optimal parameters (i.e. size, heat input, design, gasses released during larval processing of organic waste, etc.) for use in locations with high food waste generation
The objective of this project is to help us understand the parameters (heat, gases and ventilation) of maintaining BSF colonies in cold climates. These experiments will be designed to help us:
Understand the mass and energy balances of the BSFL food waste system
Determine quantities and types of solid products, by-products, and/or wastes generated by the system
Quantify the type and quantity of gases released from BSFL and the aerobic degradation of food waste in the system.
Implications and Future Work
Conduct a continuous feed BSFL food waste reactor prototype that can be easily scaled up based on food waste quantities.
Design and build a pilot-scale BSFL continuous reactor housed in a super-insulated “smart” shed based on the initial data from bench-scale experiments.
Collect and analyze the shed data to determine the cost and environmental viability of BSFL composting.
Perform life cycle assessment (LCA) to quantify the environmental impacts over the entire composting processes.
Comparison of Reference Case to BSF Composting Case:
GHG impacts and emission factors per ton of food waste processed for the reference case and the BSF composting case were compared.
Net GHG impacts were reduced by 9 kg CO2 e/t food waste treated.
If RIT converts 3 MT per week of food waste by the proposed BSFL composting, the five years of NPV is $54,387 and discounted payback period is less than 4 years.
References:
[1] Tomberlin, J. (2001). Biological, Behavioral, and Toxicological Studies on the Black Soldier Fly (Diptera: Stratiomyidae). Dissertation, University of Georgia: Athens, GA.
[2] Alvarez, L. (2012) The Role of Black Soldier Fly, Hermetia illucens (L.) (Diptera: Stratiomyidae) in Sustainable Waste Management in Northern Climates. Scholarship at UWindsor. Retrieved March 30, 2016 from:
[3] Čičková, H., Newton, G. L., Lacy, R. C., & Kozánek, M. (2015). The use of fly larvae for organic waste treatment. Waste Management, 35,