2. Introduction
Recognize and Define Problem
❖ Americans waste ⅓ food
➢ 133 billion pounds/yr (513 Tg)
➢ National food waste limit (50% by 2030)1
❖ Clemson University
➢ Same situation
➢ 30,000 people
➢ 700 tons/year (635,000 kg/year)
➢ Composting in place
1. Aubrey, 2015.
Image from Briggs, 2013.
3. Define Goals
❖ Biological
➢ Design process to consume significant amount of food
waste (130 kg/day)
➢ Viable products to offset time/costs
➢ Reduce food waste to usable compost (GI > 80%)1
❖ Structural
➢ Batch, continuous, or plug flow design
➢ Able to contain decaying food waste
❖ Mechanical
➢ Heater and/or fan to provide constant temperature
➢ Oxygen/Moisture control (varies)
➢ Able to remove products for utilization
1. Zucconi et al, 1981
4. Constraints/Considerations
❖ Constraints
➢ Required size can fit within campus infrastructure
(Cherry Crossing: ~3 Acres )
➢ Must be compatible with existing transport and loading equipment
➢ Staff time is limited
❖ Considerations
➢ Nutrient rich compost runoff can be a pollutant
➢ Harmful and pathogenic bacteria present in decaying material
➢ Large amounts of fresh food can attract local wildlife
➢ Anaerobic reactions can produce potent greenhouse gasses
5. User, Client & Designer Questions
❖ User
➢ What type of training will I need to operate this system?
➢ What type of maintenance will the system require?
➢ How frequently will the system parameters need to be
checked?
❖ Client
➢ What is the expected return on investment?
➢ How consistent do the system conditions need to be?
➢ How consistent are the properties of the products?
❖ Designer
➢ What state will the food waste come in as?
➢ How much waste will come in per day?
➢ What, if any, systems already exist to address the problem?
7. Past Data
Compiled from the municipal waste documents of Tom Jones, Director of Custodial & Recycling Services,
Clemson University Facilities
8. Past Data
❖ Compost Analysis Report
Compound Wet basis [%] Dry Basis [%]
Total Nitrogen 1.01 4.10
Carbon 12.37 50.04
C:N Ratio 12.21 12.21
Crude Protein 6.3 25.6
Fiber - NDF 5.9 23.7
Nonfiber Carbs -- 33.1
Fat 3.5 14.3
Ash 0.8 3.2
Bulk density 399 lb/yd3
Moisture 75.28 %
Performed October 2014 by the
Clemson University Agricultural
Service Laboratory
9. Possible Methods
Static Pile Composting
❖ Relatively easy to maintain
❖ Fertilizer
❖ Length of process
➢ 1-6 mos., + curing 1
❖ Low mass reduction (20%)2
Anaerobic Digestion
❖ Production of biogas
❖ Faster than static
composting (30+ days)3
❖ 40% mass reduction4
❖ More complex installation
❖ Higher costs - labor,
implementation
➢ Up to $11,000-51,000 per
year5
And...
1. Zucconi et al, 1981
2. Cornell Composting
3. American Biogas Council
4. Appels, et al., 2011.
5. Michigan Farm Bureau
10. Black Soldier Flies
❖ Self-harvest
❖ Valuable products
❖ Waste reduction
(40-60%)1
1. Diener, et al., 2009.
11. Potential Models
❖ Fed Batch
➢ BioPods
❖ Continuous
➢ Vermicomposting
(flow through)
Food waste in
Fertilizer
Food waste in
Fertilizer out
Habitable zone
Fertilizer
Habitable zone
Larvae
13. Black Soldier Flies
❖ Current system (BioPods)
➢ 4 pods that hold 38.5 kg (85 lbs) of food each1
➢ consumes 11.3 kg (25 lbs) of food per pod per day
➢ produces 0.454 kg (1 lb) of BSF per day (on average)
➢ Cleaned every 70 days (depending on larvae
density)
1. Approximate values from
David Thornton, organics
and Biofuels Project
Director
Image from Binh Dinh, 2012.
14. Black Soldier Flies
❖ Temperature ranges
➢ Survive- 0-45 ℃1
➢ Thrive- 23-43 ℃2
❖ Moisture Content
➢ Ideal- 50-60%3
❖ Available Oxygen
➢ Habitable- 15-20%4
❖ Microorganism reduction
➢ At 31℃, 99.99% reduction of E. coli5
❖ Composition varies with diet 1. Newby, 1997
2. Newby, 1997
3. Houg, 1993
4. Houg, 1993
5. Liu, et al., 2008
15. ❖ dm/dt equals zero in steady state (SS) conditions
❖ Multiple reactions can occur in a given system
❖ Sometimes easiest to analyze a process with multiple mass
balances
Mass Balance Equations
Steady State Non-Steady State
16. Ficks Law
❖ Where:
➢ Fx
is mass flux through the system
➢ D is diffusivity, a constant of the medium
➢ C is concentration of mass
➢ x is distance into system
17. Governing Equations
❖ Growth Rate
➢ Sigmoidal model used in insect
growth literature
❖ Most interested in knowing
development time
k = growth constant
a = k*inflection time
b = k
1. Banks, et al., 2014.
18. Governing Equations
❖ Thermodynamics and Heat Transfer
➢ Thermal Energy Equation
❖
➢ Heat generation term - modified Arrhenius
1. Gillooly, et al., 2001.
1
19. Governing Equations
❖ Aerobic Respiration
❖ Chemical Oxygen Demand
➢ For complete oxidation
❖ Moisture Mass Balance
1. Houg, 1997
1
1
1
20. Heuristics
❖ Past experience with BSF
➢ Joe and James
❖ Internships - composting
❖ Past data from waste stream composition analysis
❖ Experience in classes and labs
➢ Microorganisms and growth rates
➢ Bioreactors and design
➢ Mass and energy balances
21. Collected Field Data
❖ Density
Volume of food waste added: 2 gal = 0.00757082 m3
Mass of food waste added 7.803 kg
Density (m/V) = 7.803 kg/0.00757082 m3
= 1030 kg/m3
22. Optimum Moisture Analysis
❖ Confirmed optimum moisture of media as a
fraction of field capacity
Wightman et al
25. Analysis of Information
❖ Based on the information gathered through journal
articles, company websites, and heuristics, the
Black Soldier Fly design is believed to be the best
option.
❖ BSFs reduce food waste at a much faster rate and
produce multiple valuable products
❖ Compatible with current research at Clemson
26. Analysis of Information
❖ Identify knowns/given inputs:
➢ Mass flow rate (130 kg per day)
➢ Constant daily influent
➢ Needs to fit at Cherry Crossing
❖ Determine important design factors with black
soldier flies based on sources
➢ Temperature - winterization (year round operation)
➢ Air flow/oxygen - fans/pumps
➢ Moisture content
➢ Ramp slope/roughness
➢ Feeding rate
27. ❖ Mass Balances with respect to:
➢ Food:
➢ Fertilizer:
➢ Biomass:
❖ Total BSF Mass Balance:
Mass Balance Analysis
0
0
0
0
28. Growth Analysis
❖ Rgrowth
= Final weight/development time = average weight gain/time
❖ Development time
➢ affected nonlinearly for
feeding rate, temp, and
moisture
❖ Final weight
➢ affected linearly by feeding
rate
1. Data from Diener, et al., 2009.
29. Synthesis of Design
Fed Batch (BioPods) Continuous (Vermicomposting)
Image from Olivier, 2004.
Image from Vermivision, 2012.
Design Options
30. Sizing for Food Waste
❖ Based on TOC analysis, 40 days are needed for
complete food removal
❖ assuming:
➢ A habitable depth of 6” (0.152 m):
➢ Food waste density of 1029 kg/m3 1
❖ Retention area:
Aretention
= (Ṁfood
*τfood
/ρfood
)/(dhabitable
)
Aretention
= (130 kg/day*40 days/1029 kg/m3
)/(.152 m)=33.1 m2
❖ Daily thickness:
130 kg/day*40 days ÷ 28.4 m2
= 0.44 cm
1. epa.vic.gov.au
32. Optimizing Population
❖ For a given population:
➢ τBSF
= development time = 7.57*Rfeeding
-0.379
➢ Rfeeding
= Ṁfood
/Population = Ṁfood
/(Eggsin
*τBSF
)
❖ Can control feeding rate by adjusting daily egg and
food input
❖ Change inputs to yield the most products
34. Aeration of Media
❖ Approached as a method of increasing habitable
depth and decreasing surface area needed
❖ Flow of oxygen in reaches equilibrium with oxygen
uptake rate
❖ Needed to determine oxygen uptake rate
35. Carbon-Oxygen Demand
❖ O2
consumption directly related to growth/activity
with microbes
❖ COD = 1.44 g O2
/g FW
❖ At STP:
➢ [O2
]air
= 23.2% (by wgt)
➢ ρair
= 1.20 kg/m3
❖ Volume of air required for total oxidation of daily
food waste in flow is 168,350 L air/day
36. Aeration of Media
❖ Assuming:
➢ Rrespiration
= 0.5683 μl/mg/hr1
Fx
= -D*(dc/dx) = Biomass*Rrespiration
/Acomposter
Fx
= 1000 mgBSF
*0.5683 /0.621 m2
= 915.1 μl/hr/m2
1. Nespolo, et al., 2003.
38. Moisture
❖ Composting tends to be a dehydrating environment
➢ biological activity decreases at moisture levels < 50%
❖ Assume:
➢ Ss
= 25%, Sp
= 40%
❖ W = (1-0.25)/0.25 - (1-0.40)/0.40 = 1.50 g H2
O/g dry
FW
❖ Must lose 48.75 kg of water per day to maintain 60%
moisture content in reactor
39. Side effects of Aeration
❖ dm/dt = Wrespiration
-Wevaporation
≠ 0
❖ Evaporation increases with aeration
❖ Water source needed with aeration
40. Synthesis of Design
Winterization
❖ Determination of heat generation constants
`
1. Gillooly, et al., 2001.
Temperature-1
(1000/K)
ln(B0
/m3/4
)(W/g3/4
)
43. Synthesis of Design
Ambient Temp. (K) Method Final Temp. (K) Final Temp. (℃)
318
(45 ℃)
m= 0.9 kg/s 299 26
m= 0.9 kg/s
Wood insul., 1 in thick
299 26
m= 0.005 kg/s
Wood insul., 1 in thick
320 47
298
(25 ℃)
m= 0.9 kg/s 298 25
m= 0.9 kg/s
Wood insul., 1 in thick
298 25
m= 0.005 kg/s
Wood insul., 1 in thick
300 27
273
(0 ℃)
m= 0.9 kg/s 281 8
m= 0.9 kg/s
Wood insul., 1 in thick
293 20
m= 0.005 kg/s
Wood insul., 1 in thick
275 2
m= 0.9 kg/s, Full wood insul., 1 in 296 23
44. Extending Living Space
❖ Same amount of oxygen is needed, but aeration must
supply minimum concentrations (15%) throughout
❖ Available oxygen must be greater than or equal to
respiration rate or dead zone appears
49. Aeration Through Piping
❖ Based on minimal oxygen concentrations at 5.1”
➢ dead zones are possible at 5.1” from any air source
➢ must space aeration to eliminate dead zones
Far
zone
5.1”5.1”
5.1”
x x
45°45°
x = sin(45°)*5.1” = 3.62”
Spacing = 2*x = 7.24”
50. Pipe Sizing
❖ Using orifice equations:
➢ ⅛” (3.2 mm) orifice diameter
➢ 8 radial orifices per segment
➢ 7.24” spacing
➢ 2” pipe diameter
➢ alternating air flow between pipes (below)
➢ 7 psi stagnation pressure
air
air
Crowe et al 2009
53. How Constraints Handled
❖ Limited staff time
➢ 40 minutes per day for feeding
➢ 1 hour per day for BSF nursery
❖ Ramps on vermicomposter
➢ Dividers w/ramps
❖ Winterization - heated air flow with limit
59. Evaluation of Alternatives
Fed Batch System Continuous System
Aeration N/A Aerated Non-aerated
Mass Reduction 43% 43% 43%
Space ~ 50 m2
~ 13 m2
~ 34 m2
Winterization Possibly Yes
(air flow control +
insulation)
Yes
(air flow control +
insulation)
SS viability Nonexistent Theoretical Probable
Costs ~ $14,000 ~ $1530 ~ $2800
ROI 19 years 2.5 years 4.5 years
60. Evaluation of Alternatives
Fed Batch System Continuous System
Aeration N/A Aerated Non-aerated
Mass Reduction 43% 43% 43%
Space ~ 50 m2
~ 13 m2
~ 34 m2
Winterization Possibly Yes
(air flow control +
insulation)
Yes
(air flow control +
insulation)
SS viability Nonexistent Theoretical Probable
Costs ~ $14,000 ~ $1530 ~ $2800
ROI 19 years 2.5 years 4.5 years
61. Conclusions
❖ Goal achieved:
➢ Reduces mass by 43 %, converts rest to marketable
products
❖ Costs:
➢ $1530 overhead
➢ $25 per day on labor
➢ $1.40 per day on electricity
❖ Sustainability:
➢ Reduces amount of waste going to landfill
62. Conclusions
Questions Answered
❖ User
➢ What type of training will I need to operate this system?
➢ What type of maintenance will the system require?
➢ How frequently will the system parameters need to be
checked?
❖ Client
➢ What is the expected return on investment?
➢ How consistent do the system conditions need to be?
➢ How consistent are the properties of the products?
❖ Designer
➢ What state will the food waste come in as?
➢ How much waste will come in per day?
➢ What, if any, systems already exist to address the problem?
64. References
❖ American Biogas Council. 2015. Frequent Questions. American Biogas Council. https://www.americanbiogascouncil.
org/biogas_questions.asp. Accessed November 2015.
❖ Appels, L., J. Lauwers, J. Degreve, L. Helsen, B. Lievens, K. Willems, J.V. Impe and R. Dewil. 2011. Anaerobic digestion in
global bio-energy production: Potential and research challenges. Renewable and Sustainable Energy Reviews. 15(9): 4295-
4301.
❖ Aubrey, Allison. 2015. It’s Time To Get Serious About Food Waste, Feds Say. NPR. Available at: http://www.npr.
org/sections/thesalt/2015/09/16/440825159/its-time-to-get-serious-about-reducing-food-waste-feds-say. Web accessed 16
September 2015.
❖ Binh Dinh, 2012. https://binhdinhwssp.wordpress.com/tag/binh-dinh/.
❖ Briggs, Justin. 2013. US Food Waste. Food Waste. Stanford University. http://large.stanford.edu/courses/2012/ph240/briggs1/.
Accessed Nov 2015.
❖ Cornell Composting. 1996. The Science and Engineering of Composting. Cornell Composting Science and Engineering.
Cornell Waste Management Institute. http://compost.css.cornell.edu/science.html. Accessed November 2015.
❖ Gillooly, J.F., J.H. Brown, G.B. West, V.M. Savage and E.L. Charnov. 2001. Effects of Size and Temperature on Metabolic
Rate. Science. 293(5538): 2248-2251.
❖ Houg, R. T. 1993. The Practical Handbook of Compost Engineering. Boca Raton, FL: Lewis Publishers.
❖ Larson, Judd, Sendhil Kumar, S. A. Gale, Pradeep Jain, and Timothy Townsend. "A Field Study to Estimate the Vertical Gas
Diffusivity and Permeability of Compacted MSW Using a Barometric Pumping Analytical Model." A Field Study to Estimate the
Vertical Gas Diffusivity and Permeability of Compacted MSW Using a Barometric Pumping Analytical Model. N.p., 2012. Web.
22 Nov. 2015.
❖ Liu, Q., J.K. Tomberlin, J.A. Brady, M.R. Sanford and Z. Yu. 2008. Black Soldier Fly (Diptera: Stratiomyidae) Larvae Reduce
Escherichia coli in Dairy Manure. Environ. Entomol. 37(6): 1525-1530.
❖ Michigan Farm Bureau. Frequently asked questions about Anaerobic Digesters (ADs). https://www.michigan.
gov/documents/mda/MDA_AnaerobicDigesterFAQ_189519_7.pdf.
❖ Nespolo, R. F. "Intrapopulational Variation in the Standard Metabolic Rate of Insects: Repeatability, Thermal Dependence and
Sensitivity (Q10) of Oxygen Consumption in a Cricket." Journal of Experimental Biology. 206.23 (2003): 4309-315. Web.
❖ Olivier, Paul A. 2004. Disposal apparatus and method for efficiently bio-converting putrescent wastes. US 6780637 B2.
❖ Ritika, Pathak, and Sharma Rajendra. "Study on Occurrence of Black Soldier Fly Larvae in Composting of Kitchen Waste."
International Journal of Research in Biosciences 4.4 (2015): 38-45. Web.
❖ Vermivision, 2012. http://vermivision.net/?page_id=2
❖ Zucconi, Franco, Antonia Pera, Maria Forte, and Marco De Bertoldi. "Evaluating Toxicity of Immature Compost." BioCycle 22.2
(1981): 54. Web.
❖ Wightman, J. A., and M. Fowler. "Rearing Costelytra Zealandica (Coleoptera: Scarabaeidae)." New Zealand Journal of
Zoology 1.2 (1974): 225-30. Web.