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Temperature & the compost process; an exploration of the failure mechanisms behind high temperature composting Canada Compost Council, Calgary 2017 Geoff Hill PhD
Temperature & the compost process; an exploration of the failure mechanisms
behind high temperature composting
Canada Compost Council, Calgary 2017
Geoff Hill PhD
Introduction to ECS
Founded in 1999
Located in Seattle
Engineers & Scientists
Equipment Manufacturer
Provider of Technical Services:
Facility Design
Compost Process Improvement
Air Emissions Testing & Modeling
Compost Process R&D
More Tools for Better Composting
Geoff Hill
Born in Calgary, AB
PHD compost science (UBC)
GM Fraser Richmond 200,000 tpy ASP
Consultant to Harvest Power
Digesters and food waste composters
Consultant (AgriService, HDR, ODK)
ECS Director of Technical Services
Outline
Odour failures in composting
Temperature for pathogen kill
Consequences of sustained high temperature composting
3 case studies: temperature, oxygen, odour production
How to control temperature & odour
BMP design & control system
BMP operations
Additional temperature challenges; food waste pH
Massive odor issues in composting facilities
Cedar Grove Composting, Everett and Marysville Gore cover (still operating)
4 lawsuits, cited for air violations by Puget Sound Clean Air
Peninsula Compost, Deleware Gore cover (closed)
$20M plant opened 2009
Harvest Power, Richmond Mal distributed negative ASP
Digester shut down and periodic closures
Orgaworld, London Ontario Charged 33 offences since opening in 2010
JENNIFER CORBETT/The News Journal
Newsok.com
Greencoastrubbish.com
Minimum temperature time relationship
Pathogen destruction
Need 1-2 hours at 55C
State, fed, provincial regs
3 days at 55C ASP (insulated)
15 days with 5 turns windrow
Vector attraction reduction
Ensure its stabilized
BC OMRR: >14 days, >40C and avg 45C,
Maximum temperature time relationships?
Why compost for 50 days at 75-80C? What are the consequences?
What is the real oxygen availability at this temperature?
Oxygen in the film layer is what counts
Henry’s Law
Henry's law states that at a constant
temperature, the amount of a gas that
dissolves in a liquid is directly proportional
to the partial pressure of that gas in
equilibrium with that liquid. It was
formulated by William Henry in 1803.
Temperature and Oxygen
https://www.biocycle.net/2013/12/17/measuring-oxygen-in-compostN. Sauer
Anaerobic
Aerobic
Odor vs Oxygen in Film Layer
• Strong Correlation
Facility #1 – Not BMP FR
JP
Facility #3 – BMP LE
Odor vs Oxygen in Film Layer
• Strong Inverse Correlation• High peak aeration = low odor (via temp control)
Temperature driven
ECS Mindset:Follow Industry Best Management Practices
(BMPs)
• Technology / Infrastructure• Aeration supply • Aeration distribution• Temperature control• Moisture control
• Operational BMPs• Mix• Pile heights• Maintenance• Monitoring
BMP Design Compliance Drives Odour(actual side odor data)
Odor from facility(OU/min/ton)
BMP Operations Poorly Run
Quality BMP Design 30-50 300-500
Poor Design 500 5,000
BMP Aeration Design for temp. control
• An Aeration System Should Provide:• Minimum mal-distribution
• Peak aeration rate of:• Primary 3 - 8 cfm/cy
• Secondary 1.5 - 3 cfm/cy
• Follow cooling demand• Achieve PFRP (>55C)
• Then aerate hard to reduce temps to mesophilic range
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Facility #3 – BMP LE
BMP Design
Temperature control vs. Aeration RateVery dynamic process – needs automation
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1 49 97 145 193 241 289 337
Air
flo
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Temperature Feedback Controlled Aeration Demand Curve
Top Temp
Bottom Temp
CFM/CY
Data from ECS CV Composter in Omak WA. Control Setpoints: #1= 62C, #2 = 52C
Temperature control vs. Aeration RateCASP with Microporous Fabric Cover
Peak Aeration Rate: 0.5 cfm/cy
Temperature control vs. Aeration RateCASP with Microporous Fabric Cover
• 70⁰C & 10% O2 … is it aerobic?
• Does this show temperature control?
http://www.princegeorgescountymd.gov/DocumentCenter/View/3452
Temperature and Oxygen
https://www.biocycle.net/2013/12/17/measuring-oxygen-in-compostN. Sauer
Anaerobic
BMP operations also critical
Odor from facility(OU/min/ton)
BMP Operations Poorly Run
Quality BMP Design 30-50 300-500
Poor Design 500 5,000
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Primaryzone,
positive air
Primaryzone,
negative air
Primaryzone, air off
Biofiltersurface
Secondaryzone
Top of acuring pile
Final storagepiles
Od
ou
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trat
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(O
U/m
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Sample Location
Kelowna Composting Facility Odour Emissions: Before and After BMP Compliance
Sept 17-18 ,2008
May 7 2009
BMP Changes Include• Double bulking agent• Add black carbon ash (increase C/N)• Mixing
Added challenges of food waste
• Starts low pH
• Mesophilic bacteria need to consume acids and raise pH
• Thermophiles inhibited at pH
• If pile heats rapidly to >60C and isn’t cooled, low pH will lock in place and process will stagnate for weeks
• Acrid burnt pickle smell
Low pH process correlated to 100x Higher Odor Emissions
Two Orders of Magnitude!
C. Sundberg’s PHD thesis
Summary
• Sustained higher temperatures, especially early, give rise to higher odours, NH3, and VOCs
• Inability to control temperature early results in low pH which inhibits decomposition and delays emissions until later in the process
• BMP aeration system is key to minimizing air emissions• Peak aeration rates of 4-8 cfm/cy during day 1-10• Even air distribution (principles developed in the 1960’s)• Maintain active composting temperatures <70⁰C >90% of
time and average temperatures < 60⁰C
• NOTE: Low aeration systems do not conserve more water than high aeration rate systems (2018)
Geoff Hill, PhD
Director Technical Services
www.compostsystems.com
206-713-7805
