Temperature & the compost process; an exploration of the failure mechanisms behind high temperature composting

Transcription

1 Temperature & the compost process; an exploration of the failure mechanisms behind high temperature composting Canada Compost Council, Calgary 2017 Geoff Hill PhD

2 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

3 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

4 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

5 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 Newsok.com JENNIFER CORBETT/The News Journal Greencoastrubbish.com

6 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,

7 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?

8 Oxygen in the film layer is what counts

9 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.

10 Temperature and Oxygen Aerobic Anaerobic N. Sauer

11 Odor vs Oxygen in Film Layer Strong Correlation

12 Facility #1 Not BMP FR

13 JP

14 Facility #3 BMP LE

15 Odor vs Oxygen in Film Layer Strong Inverse Correlation High peak aeration = low odor (via temp control) Temperature driven

16 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

17 BMP Design Compliance Drives Odour (actual side odor data) Odor from facility (OU/min/ton) BMP Operations Poorly Run Quality BMP Design Poor Design 500 5,000

18 BMP Aeration Design for temp. control An Aeration System Should Provide: Minimum mal-distribution Peak aeration rate of: Primary 3-8 cfm/cy Secondary cfm/cy Follow cooling demand Achieve PFRP (>55C) Then aerate hard to reduce temps to mesophilic range 18

19 Facility #3 BMP LE BMP Design

20 Temperature - C Airflow - cfm/cy Temperature control vs. Aeration Rate Very dynamic process needs automation Temperature Feedback Controlled Aeration Demand Curve Top Temp 8 Bottom Temp CFM/CY Hours Data from ECS CV Composter in Omak WA. Control Setpoints: #1= 62C, #2 = 52C

21 Temperature control vs. Aeration Rate CASP with Microporous Fabric Cover Peak Aeration Rate: 0.5 cfm/cy

22 Temperature control vs. Aeration Rate CASP with Microporous Fabric Cover 70⁰C & 10% O 2 is it aerobic? Does this show temperature control?

23 Temperature and Oxygen Anaerobic N. Sauer

24 BMP operations also critical Odor from facility (OU/min/ton) BMP Operations Poorly Run Quality BMP Design Poor Design 500 5,000

25 Odour Concentration (OU/m 3 ) Kelowna Composting Facility Odour Emissions: Before and After BMP Compliance Sept 17-18, 2008 May Primary zone, positive air Primary zone, negative air Primary zone, air off Biofilter surface Sample Location Secondary zone Top of a curing pile Final storage piles BMP Changes Include Double bulking agent Add black carbon ash (increase C/N) Mixing

26 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

27 Low ph process correlated to 100x Higher Odor Emissions Two Orders of Magnitude! C. Sundberg s PHD thesis

28 Summary Sustained higher temperatures, especially early, give rise to higher odours, NH 3, 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)

29 Geoff Hill, PhD Director Technical Services