Compost Maturity Testing in Ontario Cecily Flemming Standards Development Branch Ontario Ministry of the Environment and Climate Change (MOECC)

Transcription

1 Compost Maturity Testing in Ontario Cecily Flemming Standards Development Branch Ontario Ministry of the Environment and Climate Change (MOECC) Presentation for the 27 th Annual National Organics Recycling Conference

2 Overview Introduction Compost maturity Regulatory context Different respiration tests Purpose of studies / design and methods Findings / conclusions Ontario s direction and progress 2

3 Introduction Ontario had 3.6 million tonnes of food and organic waste in 2014 of which <40% diverted from landfill: 480,000 tonnes green bin waste 567,000 tonnes leaf and yard waste Ontario has 50+ compost facilities operating under environmental compliance approvals (ECA) New compost quality standards came into effect in 2015, including a new maturity standard 3

4 What is Compost Maturity? Compost is a stabilized humus that is a solid, mature product produced by an aerobic composting process Mature compost typically has an earthy smell Mature compost is required by CCME, CFIA, BNQ, many US and European jurisdictions Typically quantified by testing respiration (e.g., CO 2 evolution, O 2 consumption, Dewar heating) or biological tests (e.g., seed germination) 4 CCME - Canadian Council of Ministers of the Environment CFIA Canadian Food Inspection Agency BNQ Bureau de normalisation du Québec

5 Regulatory Context Maturity Standards Prior to 2015 Ontario producers had to demonstrate maturity: using any test method(s) of their choosing Or wait six months After July 1, 2015 new compost maturity standards: Minimum 21 days 40% moisture Numerical respiration rate of finished compost: < 400 mg O 2 / kg OM (dry wt) / hr or < 4 g CO 2 - C / g OM (dry wt) / day 5 OM - organic matter, on a dry weight basis by loss on ignition testing

6 Purpose of Maturity Studies Compost Maturity Study in 2014 To better understand how different maturity tests performed with mature and immature composts Move forward with a recommended method for MOECC Lab for compliance testing in Ontario Follow-up Studies: 2016/2017 Optimize new Oxygen Uptake Rate, OUR method (in our case, using the OxiTop manometric device) Validate new MOECC method against existing standardized methods (BNQ, CO 2 evolution) 6

7 Description of 2014 Compost Sites Site & Materials Sample Compost Method Status of Samples Days Curing Curing Set Up Site A C1 Gore Cover Immature 3 Gore Cover then SSO+L&Y C2 Mature 59 Windrows Site B C1 Tunnels Immature 3 Indoor Bays >4m SSO C2 Nearly mature 20 Site C C1 Tunnel Immature 1 Gore Cover then SSO+L&Y C2 Not yet mature 84 Windrows Site D C1 Outdoor Immature 1 Outdoor Windrows SSO+L&Y C2 Windrow Mature 25 ~2m Site H SSO+L&Y C1 C2 Outdoor Windrow All Highly Mature 90 Outdoor Windrows 7

8 Description of 2016/2017 Compost Sites Site Sample Compost Method Status of Samples Days Curing Curing Set Up Site A C1 Gore Cover Immature 3 Gore Cover then SSO+L&Y C2 Mature 59 Windrows Site D C1 Outdoor Immature 1 Outdoor Windrows SSO+L&Y C2 Windrow Mature 25 ~2m Site F C1 Outdoor Immature 180 Outdoor Windrows SSO+L&Y C2 Windrows Not mature 180 >6m Site G C1 Indoor Immature 7 Indoor Bays SSO C2 Tunnels Mature 25 Site J SSO C1 C2 Indoor Tunnels Immature Mature 7 28 Indoor Bays 8

9 Compost Sampling Scheme Sampled at 5 facilities: Total of 10 samples collected Pairs of mature and immature composts from each site Each sample was a composite of 10-grab samples Maturity Testing 5 Laboratories 4 types of respiration testing 9

10 Sample Collection Compost samples from ~1m depth Mixed by coning and quartering Shipped overnight Note that only some labs required shipping on ice 10

11 Laboratories and Test Methods TEST CO 2 Evolution (TMECC B) BNQ Respiration (BNQ/CAN ) BOD (BOD3182) Modified BOD Test (Method by Dr. Paul Arnold) LABORATORY 1. A&L Canada Labs, London, ON and 2. SGS Agri-food Lab, Guelph, ON 3. Centre de Recherche industriel du Quebec (CRIQ), Quebec City 4. MOECC Lab Services, Toronto 5. Acadia University, Wolfville NS 11

12 Respirometry- CO 2 Evolution Rate (TMECC B) Measured CO 2 evolved from compost mass in sealed jar 25 g moist compost added 4 30 o C Static method (no mixing) Used an NaOH trap (30mL) Titrated trapped CO 2 daily Calculated Ave. rate in mg CO 2 -C/g OM /day NaOH CO 2 No Mixing Compost 12

13 Respirometry- BNQ Method (CAN/BNQ Part I-2005) Measures CO 2 produced 20 g compost in 1L 18 to o C Scrubs CO 2 in caustic Constant mixing (stir bar) Converts ml pressure drop from CO 2 loss into O 2 Unit mg O 2 /kg OM /hr 13

14 O 2 Consumed (ml) BNQ Respirometer (cont d) Pressure drop in ml CO 2 converted to O 2 based on 1:1 mol stoichiometry Respiration ml O 2 consumed Respiration (mgo 2 /kg OM/hr) Unit reported in O 2 respiration rate per hour Time in hours 14

15 Modified BOD Respiration Method (Acadia University Dr. Paul Arnold s method) Measures O 2 consumption with optical dissolved O 2 meter 50 g compost in 20 L 3 day 25 o C Dynamic - Constant Mixing Re-aerated vessel if O 2 level drops below to 1.5 mg/l Routinely aerated for 30 min every 8-hr (or 1 hr every 4 hr for immature samples) Ave. rate in mg O 2 /kg OM /h 15 Now available by BNQ: Method CAN/BNQ Part II-2016

16 Modified BOD Respiration Method (cont d) Dissolved O 2 readings were plotted over a period of 3 days O 2 uptake rates were based on: Average of the 3 highest consecutive rates (slope in mgo 2 /L/hr) for each 8-hr interval for mature compost (represents 24 hr), or, Average of 6 highest slopes, for each 4-hr interval for immature compost samples Additional tests were run on these samples at Acadia Univ., not shown e.g., Dewar self-heating test; Solvita index; Contact Dr. Arnold for details Sample of dissolved oxygen output courtesy of Paul Arnold 16

17 Sample Cured days Maturity Test Results Status % H 2 O A&L Lab CO 2 evol A&L Lab O 2 conv c CRIQ O 2 Acadia BOD O 2 Standard (>40%) (<4.0 a ) (<400 b ) (<400 b ) (<450 b ) A-C1 3 Imm A-C2 59 Mature B-C1 3 Imm B-C2 20 Imm C-C1 1 Imm C-C2 84 Imm D-C1 1 Imm D-C2 25 Mature H-C1 90 Mature H-C2 90 Mature a mg CO 2 -C/g organic matter(om, dry wt,dw)/day; b mg O 2 /kgom dw/hr c Convert mgco 2 -C/gOM/d to mgo 2 /kgom/hr by x 32g/mol/12g/mol x 1000g/kg/24h/d

18 Comparing Maturity Tests Resolution power between tests is more obvious with less mature composts No such thing as false +ve Similar results for mature composts CO 2 evolution test data converted to O 2 18 Converted mg CO 2 -C/g OM/day to mg O 2 / kg OM/hr by x 32 g/mol/12 g/mol x 1000 g/kg/ 24 hr/d

19 Converting CO 2 evolved to O 2 consumed Stoichiometry assumed 1:1 for converting CO 2 vs. O 2 However, actual stoichiometry is up to 1 : 1.16* O 2 consumption is O 2 used to make CO 2 and other oxidized products, e.g., NO 3, SO 4 Oxidation without nitrification is*: C 10 H 19 O 3 N O 2 10 CO 2 + 8H 2 O + NH 3 With nitrification O 2 consumed is higher*: C 10 H 19 O 3 N O 2 10 CO 2 + 9H 2 O + NO 3- + H + Therefore O 2 consumed in Modified BOD Test is higher; hence, BNQ standard for O 2 uptake = 450 mgo 2 /kgom/hr) 19 * Stoichiometry and equations provided by Dr. Arnold, Acadia University

20 Results Comparing Tests in 2014 BNQ Respirometer and Modified BOD tests gave best performance: Highest numerical values for O 2 consumed by biomass (BOD) Clearly failing immature composts and with a high resolution CO 2 evolution test performed adequately: Gave the lowest comparative respiration results Failing most immature composts Lower resolution and results subject to % moisture (i.e. false ve) One immature sample passed all tests: Possibly due to sample conditions (very hot sample) or Perhaps test duration too short for microbial activity to start up 20

21 Compost Maturity Observations BNQ Respirometer and Modified BOD tests are dynamic methods that minimize many errors: Mixed well, oxygenated, saturated No dead zones, gas exchanged maximized CO 2 method gave lower rates: not reliable in overly dry compost (e.g., 25% moisture) European OUR test was also considered going forward (OxiTop) OxiTop manometer system 21 OUR Oxygen Uptake Rate Test (e.g., Ireland s maturity standard)

22 MOECC Moving Forward 2016/17 Oxygen Uptake Rate (OUR) with OxiTop I.S. EN :2011 (NSAI) Measures CO 2 via pressure 3 g compost (~2 g OM)/ L 20 o C for 5-7 days (run in Duplicate) Add ph buffer, nutrients, and nitrification inhibitors NaOH pellets trap CO 2 Dynamic test (const. stirring) Convert CO 2 results to mg O 2 units Electronically logs pressure drop 22 NSAI - National Standards Authority of Ireland

23 Samples Maturity Testing Results & 2017 Days Cured Status % H 2 O A&L CO 2 A&L Lab O 2 conv c MOECC OxiTop O 2 CRIQ BNQ O 2 Standard (>40%) (<4.0 a ) (<400 b ) (<400 b ) (<400 b ) A-C Imm A-C Mature A-C Imm A-C Mature D-C Imm D-C Mature F-C Imm F-C Mature G-C Imm G-C Mature G-C Imm G-C Mature J-C Imm J-C Mature J-C Imm J-C Mature a mg CO 2 -C/g organic matter (OM, dry wt) /day; b mg O 2 /kgom dw/hr c Convert mgco 2 -C/gOM/d to mgo 2 /kgom/hr by x 32g/mol/12g/mol x 1000g/kg/24h/d

24 2016 & 2017 Results Comparing Maturity Tests BNQ is best performance; OUR (OxiTop) is intermediate e.g., compost too dry CO 2 Evolution test data converted to O 2 Meets standards 24 Converted mg CO 2 -C/g OM/day to mg O 2 / kg OM/hr by x 32 g/mol/12 g/mol x 1000 g/kg/ 24 hr/d

25 Conclusions OUR test performance (using OxiTop system) : Dr. Arnold s Modified BOD test gave highest rates, followed by BNQ Test OUR was similar to BNQ respirometer test or slightly lower values OUR out-performed CO 2 evolution test in most cases CO 2 evolution gave lowest rates: Under-estimated respiration in some immature composts Most often low in composts that were too dry (e.g., <30% H 2 O) Water adjustment and equilibration time critical when performing the test OUR (with OxiTop) was selected for MOECC: Standardized, inexpensive, small scale automation (10 tests), small size Completing method validation for MOECC compliance 25

26 Questions? Thank You! Thanks to eight participating municipalities and compost producers in Ontario Acknowledge all laboratories for their analytical work Grateful to Dr. Paul Arnold, Acadia University, for in-kind Modified BOD testing and many helpful discussions Thanks to Dr. Stefanie Maedler, MOECC Lab Services Branch, for OUR test development work with OxiTop For more info contact: Standards Development Branch, Ontario MOECC 40 St. Clair Ave. E., Toronto Ontario M4V 1M2 26