The document summarizes a senior design project utilizing food waste at Clemson University. It introduces the problem of food waste and goals to significantly reduce the 700 tons of food waste produced annually on campus. Two potential methods are analyzed: static pile composting and anaerobic digestion. A literature review covers past campus waste data, models like fed-batch and continuous systems, and use of black soldier flies. Mass balances, growth models, and heat/mass transfer equations are developed. A continuous vermicomposting system is selected, with aeration piping design to maximize habitable space. The system is estimated to cost $1530 and achieve a 2.5 year return on investment while reducing waste by 43%.

1. Senior Design
Utilization of Food Waste
Joe Hummer, Cassidy Laird, James Rogers
23 November, 2015

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?

6. Literature Review

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

12. Food Waste Composition Over Time
1. Ritika, 2015.

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

23. Confirming Development Time and
Weights
• Pupation time has potential to be as small as 10
days

24. Design Methodology &
Materials

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

31. Batch Process Reactions
Time (days)

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

33. Developementtime(days)Growthrate(g/day)ComposterBiomass(g)
Time (days)

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.

37. Flow of Oxygen

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 H2O/g dry
FW
• Must lose 48.75 kg of water per day to maintain 60%
moisture content in reactor
• or 1.50 g H2O for every gram of dry FW added

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)

41. BO ≍ Eg in energy balance

42. Synthesis of Design
• Flow of Thermal Energy

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

46. Aeration Placement: Too Deep

47. Aeration Placement: Too Shallow

48. Goldilocks!
• Placed 0.26 meters (10.2”) deep
• Habitable zone greater than 0.4 meters (15.7”)

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

52. Physical Design
• Side view
❖ Top View

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

54. Evaluations

55. Sustainability
• Ecological - Reduce waste going into environment
• Economic - Potential marketable products
• Biodiesel
• Protein
• Fertilizer
• Social/Ethics
• Aesthetics (smell), Bug cruelty (3 Rs)
• Changing household ideologies to reduce the
amount of wasted food

56. Budget/Economics

58. Bill of Materials

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?

63. Timeline

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.

65. Questions?