Senior Design project

1. Site and Operations Redesign of
Composting Facility for City of Columbia
Rachel Cron, Shelby Green, Carrington Moore, Alena Senf, &
Mallory Ware
Clemson University, Clemson, SC
December 5th, 2019

2. Overview
● Introduction
○ Background
○ Rationale
○ Objectives
○ Approaches
● Literature Review
● Materials and Methods
● Results
● Takeaway Messages
● Acknowledgments

3. Introduction

4. Background: Project Description
● Our Senior Design group is partnering with Woolpert Inc. in Columbia, SC to
propose a well-established site and operations design to allow the incorporation
of municipal food waste into the City of Columbia’s current composting facility
waste stream.
Introduction

5. Background: Site Details
● Previously was a landfill
● 90-acre property divided into...
○ Compost facility → 32-acres
○ Humane Society → 8-acres
○ Jurisdictional Streams → 50 acres
○ FEMA Flood Zone → 42.4% 50-
acres
Figure 1: Project Site located at 110 Humane Society
Lane, Columbia, SC bound by I-77 in the South and
Shop Road in the North
Introduction

6. Background: Current Facility Operations
● Facility Type I
○ Composts Type I feedstock, permitted for
annual capacity of 15,000 yd3 of material
● Category 1 Feedstock
○ Grass clippings, leaves, sticks, bulk items (i.e.
furniture, & clothing) & building material
● Composting Technology
○ Hands-off composting technique, windrow
piles turned ~twice a year
○ Takes ~9 months for “coarse” finished
product & 1 to 2 years for a “fine” finished
product
Figure 2: Example of allowable
yard waste & bulk items
Figure 3: Example of allowable
yard waste
Introduction

7. Background: Current Facility Operations
● Facility Operations
○ Only 1 full time employee, but budgeted for two employees
○ Unground waste stored in large piles
○ Bidded contracts for processing → contractors come grind, sift, and place
material in windrows to begin composting process
○ Currently 4 to 5 piles ground a year
● Market Issues for Facility
○ No waste income from private companies due to tipping fees
○ Hours of operation are weekdays only
○ Minimum marketing of facility
○ Low, to no profit from sales
Introduction

8. Figure 4: Existing composting
facility in Columbia with various
pile size dimensions
Introduction

9. Background: Site Visit to Current Facility
Figure 5: Unloading of materials into piles
to store until ground, sifted, & composted
Figure 6: 15000 yd3 of unground
materials stored in rows to be processed
Figure 7: Site designed for 20 feet of
space between each pile
Figure 8: Loading finished compost
product into customers truck
Introduction

10. Rationale
● SC Solid Waste Management Annual Report - 2018
South Carolina
○ Population of 5.084 million
○ SC generated 4,289,591 tons of waste and recycled 28.5%
○ Goal: recycle at least 40% of its municipal solid waste by
2020 → needs to increase by 11.5%
The City of Columbia
○ Population of 411,592 people
○ Generated 331,803 tons of waste and recycled 15.5% of it
○ Only about 2% of the recycled waste was food waste
○ By increasing the percent of recycled food waste, the City
of Columbia could help SC reach its goal of 40% goal by
2020
Introduction
Figure 9: South Carolina’s Capital,
Columbia, and the associated counties

11. Rationale
● Composting is a recycling method that diverts food waste from landfills
● Current composting facility is a Type I facility
○ Not permitted to accept food waste
● Converting to a Type II facility
○ Columbia could reroute food waste from the municipal waste
stream to the composting facility
○ Composting food waste can reduce landfill waste by 30%
● Impacts
○ Lower the City’s carbon footprint
○ Hopefully reaching its goal of 40% recycled waste by 2020
Figure 10: Percentage of organic
waste that goes into landfills
Introduction

12. Objectives
The main objective of this project is to redesign a compost facility for the City of
Columbia. The specific objectives are to:
1) Evaluate alternative technology for incorporating food waste into the facility’s current
compost operations
2) Redesign the site layout and modify operational procedures based on chosen technology
3) Propose a plan to the city to show the redesigned facility could reduce fiscal impact and to
influence funding bodies to contribute
Introduction

13. Approaches
Figure 11: Schematic of tasks to complete project
Introduction

14. Task 1
To modify site operations by:
● Converting the facility to include food waste
● Evaluating the technologies of covered/open static aerated
windrows, covered/open turned windrows, or in-vessel
reactors
● Selecting the best technology
● Determining maintenance procedures for compost
technology
● Selecting necessary equipment for compost technology
● Securing a waste hauling service
● Quantifying compost capacity
● Specifying mixing procedures for feedstocks
Introduction

15. Task 2
To redesign the site layout by determining:
● Windrow spacing and dimensions
● Grading for runoff management with minimal excavation
● Stormwater design including a retention pond
● Entrance and exit locations
● Product, contaminant, equipment, and waste storage areas
● Operations building and operating pathways
● Any additional site requirements necessary for permitting.
Introduction

16. Task 3
To reduce fiscal impact and receive funding
by:
● Compiled a list of entities for consistent
feedstock sources
● Created a survey to optimize marketability
of final compost product
● Estimate annual compost production
● Estimate operating and maintenance
expenses
Introduction

17. Multi-Faceted Design
Figure 12: Venn Diagram of
disciplines used in this project
Introduction

18. Literature Review

19. Compost Information
● Compost is organic matter that has been decomposed by
microorganisms, and contains significant benefits for soil quality
● Adding compost to soil…
○ Prevents nutrients from leaching away
○ Stabilizes soil pH
○ Stores excess carbon
○ Increases food production, water retention, and biodiversity
● Ideal C : N ratio is 30 : 1
○ This translates to a volumetric ratio of 2 parts Green : 1 part
Brown
■ Green: Fruit and vegetable scraps, coffee grounds, grass
clippings
■ Brown: Wood chips, tree clippings, hay, shredded
newspaper
○ Too much C = Slow microbial reactions
○ Too much N = Rotten smelling compost
Figure 13: Importance of healthy soil
Figure 14: Global challenges that composting
can help fix
Literature Review

20. Composting Processes
Phases of Microbial Growth:
● Mesophilic
○ Microorganisms initially breakdown feedstock
○ Moderate temperature between 68 -104°F
○ Breakdown causes temperature to rise into
thermophilic range
● Thermophilic
○ Breakdown of more complex compounds
○ Lasts from 30-over 100 days depending on
composting technology
○ Pile reaches / stays above 131° F to kill pathogens
● Cooling / Maturation
○ Mesophilic bacteria dominate
○ Develop the final compost product
○ Typically lasts around a week
Figure 15: Graph of microbial growth phases with temperature
Literature Review

21. Composting Process- Microbial Kinetics
● During the composting processes, the precise chemical changes and complex metabolic
processes of various microorganisms change with the composition of the feedstock
● Having multiple different types of microorganisms makes modeling the microbial kinetics
very complicated
○ Typically, Monod kinetic equations (1st order reaction rate) are used to model
microbial growth, but this is designed for modeling one type of microorganism
● Currently, deductive modeling is being explored as an effective way to model composting
kinetics
○ This is extremely detailed and is still being studied
Literature Review

22. Composting Facility Types
● Type 1
○ Yard trimmings and landscaping debris
○ Compostable bags
○ Current facility
● Type 2
○ Animal manure
○ Food waste (no raw meat)
○ Cooked meat from plate scrapings
● Type 3
○ Sludges
○ Fats, oils, and grease
○ Other organic residuals
Figure 16: Type I
feedstock example
Figure 17: Type II
feedstock example
Figure 18: Type III
feedstock example
Literature Review

23. Composting Technologies: Turned Windrows
● Waste material is collected into
long narrow piles called windrows
● The pile is regularly turned by
machinery
○ Promotes decay by
mechanically forcing
aeration
○ Regulates temperatures
● Height of piles needs to be
regulated in order to reduce the
risk of combustion
Figure 19: A windrow being mechanically turned
Literature Review

24. Composting Technologies: Aerated Static Pile
● Waste material placed in a pile on pad
with small holes
○ Air can be forced through by a
blower
○ Air can be pulled through by
suction based on negative
pressure created beneath the pad
● Both ways of aeration can be
combined for more effective
homogenization
Figure 20: Diagram of static aerated pile
Literature Review

25. Composting Technologies: In-vessel
● Waste material is placed in an
enclosed reactor
● Types:
○ Enclosed aerated static piles
○ Agitated vessels (often called
“drums”)
● Improve:
○ Moisture control
○ Temperature control
○ Odor control
Figure 21: Large, agitated vessel composting system
Literature Review

26. Advantages & Disadvantages of Compost Technologies
Table 1: Technology Comparison Chart
Literature Review

27. Retention Pond Design
● Purposes
○ Manage stormwater & erosion of sediment from
site
○ Avoid nutrient overload in nearby waterways
○ Preserve local infrastructure
● Primary components
○ Inlet/forebay → Diversion of water from site to
pond and sediment collection
○ Basin → Flow control, partial temporary storage,
partial treatment storage
■ Littoral shelf → Encourage plant life to
anchor bank of pond
○ Emergency spillway → Preparation for large storms
○ Outlet → Properly deliver water away from pond
● Remove nitrogen, metals, and suspended solids
twice as well as detention ponds Figure 22: Diagram of retention pond
Literature Review

28. Stormwater Maintenance
State requirements for retention ponds:
● Side slopes: max of 3 horizontal: 1 vertical
● Basin: length to width ratio no less than 3
● Depth: permanent pool must be between 3 and 8 feet deep
● Outflow: must remove ½ inch of runoff over 24 hours following a
storm
● Liner: clay for porous ground to encourage retention
Ground cover considerations:
● Ground cover type can decrease the site’s peak flow/required retention pond capacity
○ Plant dense grass/vegetation on flow path
○ Lay compost on flow path
Literature Review

29. Charleston County Case Study
● 70 turned windrows on site
● Municipal or commercial trucks
deliver waste
● Designed to allow space between rows
for loader and water trucks
○ Moisture and temperature closely
monitored
● 45-day process for final compost
○ Waste processed through grinders
○ Deposited to windrows
○ Modified Static Aerobic Pile (MSAP)
Method
○ Trommel removes large pieces
● Generates 60,000 tons of compost per year (primarily composed of yard waste)
Figure 23: Provided by the City of Columbia
Literature Review

30. Greenville County Case Study
● Designed to have annual capacity of
12,000 tons of compost
● Partnered with Atlas Organics
○ Food waste collection service
○ Compost production service
○ Compost quality testing through third party
● Residential waste material accepted
● Organic farming approved
● Primarily food waste/woody biomass
feedstock
○ No biosolids or manure
● 45-day process for final product
○ Forced aeration, windrow,& screening
technologies
Figure 24: Provided by the City of Columbia
Literature Review

31. Materials and Methods

32. Materials and Methods Overview
● Selecting Compost Technology
● Capacity Calculations and Windrow Sizing
● Material Mass Balance of Compost Process
● Stormwater Calculations and Design
● Site Design
Materials & Methods

33. Selected Compost Technology
The composting technology selected for the City of Columbia’s composting facility
redesign was turned windrow because...
● Facility already operates with turned windrows, allowing an easier transition
● Ability to accept a larger variety of feedstock, including meat and grease
● Ability to produce large volumes of product
● Ability to transition to static aerated pile technology in the future
● Generalized in literature to have lower installation costs
● Mimics the most natural decomposition process
Materials & Methods

34. Capacity Calculations and Windrow Sizing
● Windrow pile footprint chosen:
○ 16’ wide x 200’ long
● Height to base width relationship:
○ H = 0.38 * width
● DHEC requirement of 20’ between each pile
● Using material capacity of 15,000 yd3
○ Volume of each pile calculated = 193. 20
yd3
○ 77 total piles needed for 15,000 yd3
capacity
● Total acreage required for pile footprint and
required spacing between each row is 12 acres
● Concrete pad or other ‘approved’ base
underneath windrows required by DHEC
Figure 25: Diagram of calculated windrow
dimensions
Materials & Methods

35. Material Mass Balance
Figure 26: Unit operation of
material mass balance
Materials & Methods

36. Stormwater Calculations
Rational Method for determining runoff
where:
Materials & Methods

37. Stormwater Calculations
Trial design of detention pond using relationships from literature where:
Materials & Methods
where:

38. Results

39. Pre-Development Conditions
Impervious Surface: ~0 acres
Pervious Surface: 32.24 acres
Referring back to Figure 4.
Results

40. Pre-Development Conditions - 3D
Figure 27: 3-D visual of
existing contours
Results

41. Proposed Site Layout
Figure 28: AutoCAD schematic of the
proposed site plan
Impervious Surface: 14 acres = 54 %
Pervious Surface: 12 acres = 46%
Results

42. Post-Development Conditions - 3D
Figure 29: 3-D visual of
proposed contours
Results

43. Post-Development Conditions - Drainage Map
Figure 30: Drainage map of proposed
site plan
Cut: 81,078.9 CY
Fill: 215,583.7 CY
Results

44. IDEAL Modeling Overview
3 Models will be discussed...
1. Pre-development
2. Post-development, no pond
3. Post-development, pond
Results

45. IDEAL Modeling: Pre-Development
Figure 31: Pre-development
hydrograph for 24-hr 100-yr
storm
Results

46. IDEAL Modeling: Post-Development without Pond
Figure 32: Post-development
hydrograph for 24-hr 100-yr
storm
Results

47. IDEAL Modeling: Post-Development with Pond
Figure 33: IDEAL model for
flow in and out of retention
pond
Results

48. IDEAL Modeling: Post-Development Including Pond
Figure 34: Post-development
hydrograph for 24-hr 100-yr
storm
Results

49. Comparison of IDEAL Models
Peak Discharge (cfs) Runoff Volume (ac-ft)
Pre-Development 59.39 16.12
Post- Development, No
Pond 75.45 15.26
Post-Development with
Pond 43.22 12.32
Results
Table 2: Result Summary of IDEAL Stormwater Models

50. Retention Pond Pre-Sizing Result
Figure 35: AutoCAD schematic of the proposed site layout
Results

51. Final Proposed Retention Pond
Referring to Figure 35
Results
● Base area: 0.459 acres
● Top area: 0.96 acres
● Total height: 9 feet
○ Total = EMS height + freeboard
● Outlet barrel diameter: 2 feet
● Riser
○ Diameter: 30 inches
○ Height: 8 feet
○ 4 orifices (8 inch diameters)
● Emergency spillway weir
○ Height: 8 feet
○ Width: 10 feet
● Littoral shelf
○ Hawthorn and royal fern
Figure 36: Top view of retention pond

52. Material Mass Balance
Figure 37: Material mass
balance results
Results

53. Proposed Operations Plan
● Processing time: 12-16 weeks = 84-112 days
● Yearly production: 4,327 tons
● Equipment: Komptech Topturn X55
○ Width of 16.4 ft that fits our pile size
● Turning frequency
○ First Month: Turn weekly
○ Remaining Months (2-3): Turn once or twice
■ Turning less frequently during this time period
reduces moisture loss
● Temperature measurements
○ Measure temperature each time windrows are turned
○ Measure temperature every 25 ft along the windrow
○ Make sure measurement is taken at least 3-4 ft into the windrow for accurate readings
Figure 38: Komptech Topturn X55
Results

54. Proposed Operations Plan
● Moisture content measurements
○ Ideal moisture content is 40-60%
○ Can do a “squeeze test” to physically check moisture
content
■ Take a handful of compost and squeeze
■ If the handful of compost cracks and falls apart →
moisture is less than 40%
● Add water to piles
■ If water leaks out of the handful of compost →
Moisture is greater than 60%
● Add wood chips to piles
○ Can also check with a Compost Moisture Meter
Figure 39: REOTEMP Garden and
Compost Moisture Meter
Results

55. Proposed Operations Plan
Figure 40: Compost
mixture design flowchart/
block diagram used post
testing of feedstock sample
Results

56. Required Permits
Table 3: Permits required from City of Columbia and SCDHEC
Results

57. Marketing
● Consistent influent food waste need to
be secured
● List of entities including restaurants,
hospitals, grocery stores, universities,
etc.
● Survey for potential influent food waste
clients
○ Tipping fees
○ Hauling services
○ Quantity of food waste
Results
Figure 41: One of various entities to
consider for food waste influent

58. Cost Analysis
Results
Table 4: Investment cost, operational costs and annual income

59. Takeaway Messages

60. Takeaway Messages
● We learned that…
○ The composting process has to be monitored and
kept at certain temperature and moisture levels,
each being very critical
○ Specific C and N levels are necessary for efficiency
of bacterial degradation
● Our site redesign could...
○ Reduce food waste in landfills
○ Encourage community participation and
involvement
● Compost helps fight against food insecurity by physically
and chemically improving existing soil conditions
● Healthy soil is imperative for long-term agricultural
production, especially since the global population
continues to grow
Figure 42: Composting is a
sustainable agricultural practice

61. Multi-Faceted Design
Figure 43: Venn Diagram of
disciplines used in this project

62. Acknowledgements

63. We would like to thank...
Deb Sahoo, Senior Engineer/Subject Matter Expert/Task
Leader at Woolpert
Wesley Harrison, Senior Engineer for City of Columbia
Samantha Yager, Solid Waste Assistant Superintendent at
City of Columbia
Holly Elmore, Founder & CEO, Elemental Impact
Chantal Fryer, Senior Manager, Recycling Market
Development at Department of Commerce
Britt Faucette, Director of Research and Technical Services
Kim Charrick, Sustainable Management of Food including
Food Recovery Challenge for Hospitality Sector at US EPA
Mary Pat Baldauf, Sustainability Facilitator; City of Columbia
Douglas O’Flaherty, VP of SC Restaurant and Lodging
Association
Jim Lanier, VP of operations at Earth Farms Organics
Dr. Prasada Rangaraju, Clemson Civil Engineering
Professor Earl Hayter, Adjunct Associate Civil Engineering
Professor
Leo Cassule, Clemson Civil Engineering Transportation
Department
Dr. Christophe Darnault & Ms. Jazmine Taylor

64. Thank you!