ORGANIC WASTE COMPOSITION

Transcription

1 6961 Russell Avenue Burnaby, BC V5J 4R8 Phone: Fax: October 31, 2013 File No.: C Burke Van Drimmelen City of Surrey Engineering Operations th Street Surrey, BC V3S 3C8 Via ORGANIC WASTE COMPOSITION On October 1 st, 2012, the City of Surrey (City) commenced a new residential solid waste curbside collection service which included organic food waste with the existing yard and garden waste. The residential organic waste is presently sent to Fraser Richmond Soil and Fibre; however, the City s future plans include the construction of an organic waste processing biomethane facility which will accept all of the City s residential organic waste as well as a significant portion of industrial, commercial, and institutional (ICI) organic waste. The City s organic waste stream will comprise at least 50% of the overall feedstock for the facility. In order to determine the most suitable processing technology to maximize biogas production from the available feedstock, the feedstock must be characterized at a significant level of confidence. On November 7, 2012, TRI Environmental Consulting Inc. (TRI) was engaged to conduct a yearlong organic waste study (November 2012 to October 2013) with monthly sampling events for the City, in order to determine the composition and volatility of the residential organic waste stream. This technical memo summarizes the methodologies and findings for all work undertaken during this waste composition study. The samples originated from curb-side yard and food waste collection bins in each pilot neighbourhood. Each sample was sorted into 19 categories. The results were tabulated and the average and standard deviation for each category was calculated each month by taking into account the total weight of the material sorted. Photos of each sample and select waste categories were also taken, and select images are included at the end of this report. METHODOLOGY SAMPLE COLLECTION Organic waste was sampled from single family homes in the City of Surrey that participated in the waste collection service s pilot program, which ran for two years prior to full roll out across the City in October Expect Integrity Serving Since 1982

2 of These pilot areas consist of five separate neighbourhoods in the City, with each neighbourhood representing a separate collection day from Monday to Friday. Sourcing from these homes was chosen to provide a more accurate account of what the City s residential organic waste will be comprised of once the facility is operational, in approximately two years. The organic waste composition study first sampling event was in November of 2012 and monthly sampling was performed until October A city collection vehicle was used to collect organic waste from a set number of households from each neighbourhood over a five day period (one pilot neighbourhood per day for five days) each month. All organic waste was collected into the same vehicle over the five days, resulting in a mixed load of organic waste from the five separate neighbourhoods. The organic waste sorting was performed on the last day of the week after organic waste was collected from all five neighbourhoods. The total number of households collected from varied from month to month based on the expected tonnage of organic material based on historic organic collection data. A minimum of twenty homes per neighbourhood for a total of one-hundred homes per sampling event was the minimum number of homes collected from to obtain representative organic waste. In the winter months of January and February, organic waste was collected from one-hundred homes per neighbourhood for a total of fivehundred homes over the five days. Since the quantities of yard waste were much lower in the winter, more homes were required to ensure a minimum of 1.5 tonnes of organic waste was collected for composition analysis. Table 1 summarizes the number of homes collected from for each monthly sampling event. Sampling Day Table 1. Monthly Sampling - Total Number of Households Collected Historic Total Yard Waste Collected (4-year Monthly Average for ) [tonnes] Actual # homes collected from per day for monthly composition Actual # homes collected from over 5 days for monthly composition 23-Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct SAMPLE SORTING After the collection of organic waste over a five day period, the organic waste hauler would dump the entire contents of the load on the tipping floor at Surrey Transfer Station (STS) at Street, Surrey, BC. The load contents were spread to a nominal depth of 0.5 metres. Using a rough grid pattern, TRI Environmental Consulting Inc. 2

3 organic waste from randomly selected areas was shovelled into bin containers by TRI staff, and subsequently identified and weighed. A target sample weight of approximately 100 kg was used for each sample. The truck number would be recorded, and the contents of the load photographed. The sorting was performed by two sorters including the sort supervisor. The sorters received training in the sort method, so that identification of each waste item on the sort table could be made and the item placed in the appropriate bin for a total of 19 categories. The sort supervisor and all sorters received health and safety training to manage hazards associated with sorting waste as well as site-specific hazards. All workers were required to have up-to-date tetanus shots. The categorization of items was generally straightforward. Selected photographs were taken of the samples. For this study, TRI performed QA/QC by first weighing the selected sample prior to sorting. After the sort was completed, all categories were weighed and the total weight calculated. All samples final weight was within 3 % of the starting weight. TOTAL SAMPLES COMPLETED In total, the organic waste composition study will complete 12 monthly sampling events, with five samples completed each month for a total of sixty samples completed over a one year period, as shown in Table 2. This sampling plan is designed to capture the seasonal variation in organic waste composition. Table 2. Total Samples Completed Sampling Day Samples Completed 23-Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Total 60 The uncertainty range for the monthly dataset using five samples per month is based on the sampling statistics generally used for waste characterization studies 1,2. Table 3 calculates the number of samples required when allowing for a 90 % confidence interval with the corresponding uncertainty ranges and 1 CCME., April 30, Recommended Waste Characterization Methodology for Direct Waste Analysis Studies in Canada, 39 pp. 2 Ministry of Water Land and Air Protection (MWLAP), November, Procedural Manual for Municipal Solid Waste Composition Analysis. TRI Environmental Consulting Inc. 3

4 standard deviations between samples assuming the desired confidence interval of 90 %, and 5 samples, with a two-sided t-value of Table 3. Number of Samples for Desired Uncertainty Range Uncertainty Range % (+ or - ) Standard Deviation Between Samples 11% 23% 46% 10% % % The CCME waste characterization methodology uses the equation outlined below to determine the number of samples required to achieve a precision objective. However it is an iterative process, as the expected standard deviation has to be known. It is important to note that precision objectives cannot be met for all waste categories due to the high variability for some categories. Formula to determine the number of samples for desired uncertainty range: where: n i = the number of samples to collect for the i th waste category t = the t-statistic for the desired confidence level and the number of samples s i = the estimated standard deviation for the i th waste category; and, d = the precision requirement (i.e. one half the range of the confidence interval). The number of samples and houses that have been collected from in this study was designed to allowing for a 90% confidence interval with a corresponding uncertainty range and variance of approximately 10% between samples for most categories, assuming that the five pilot neighbourhoods are a good representation of the expected organic waste to be collected from single family homes in the City of Surrey two years after the program has been implemented. MOISTURE SAMPLING = Moisture samples were completed quarterly (November 2012, February 2012, May 2013, August 2013) for each organic waste category. After the organic waste was sorted, all materials of the same category were combined and mixed to form an aggregated sample for each category of organic waste. Approximately 2-5 kg of material from the aggregated sample representing each category was collected into sealed Ziploc bags and were placed in a cooler and delivered to a laboratory under a Chain of Custody the same day. The laboratory would use the entire sample to perform the moisture content analysis following ASTM method Method D2216 for moisture content analysis. Moisture is reported in percent (of the sample wet weight). The calculation is as follows: % = ( h ) ( h ) ( h ) TRI Environmental Consulting Inc. 4

5 Total moisture content for the mixed sample was calculated by accounting for each category s percent contribution to the total waste stream. SUMMARY OF RESULTS SEASONAL TRENDS A summary of all results for all the percentage organic waste composition is presented in Table 4. Raw data for all categories and samples are provided in a Microsoft Excel format spreadsheet that will be sent along with this memo. Figure 1 depicts the seasonal changes in percentage composition of the residential organic waste stream. 100% Figure 1 - Organic Waste Composition -% Breakdown 90% Total % of Organic Waste Stream 80% 70% 60% 50% 40% 30% 20% 10% 0% Nov-12 Dec-12 Jan-13 Feb-13 Mar-13 Apr-13 May-13 Jun-13 Jul-13 Aug-13 Sep-13 Oct-13 Yard Waste Kitchen Waste Gross Contaminants Net Contaminants (minus compostable materials in plastic bags) Net Contaminants TRI Environmental Consulting Inc. 5

6 Date of Organic Waste Characterization Table 4. Organic Waste Composition - % Breakdown 23-Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct-13 YARD WASTE 1 Green grass clippings 0.4% 0.1% 0.0% 1.1% 18.8% 31.6% 8.7% 47.9% 0.3% 39.7% 62.3% 2.4% Grass clippings 2 Brown grass clippings 0.0% 0.0% 0.0% 0.0% 20.4% 0.5% 43.4% 2.3% 51.5% 4.8% 0.0% 3.1% 3 Green leaves 1.3% 3.8% 5.8% 2.5% 1.6% 1.2% 0.5% 20.9% 0.6% 0.0% 0.2% 7.6% Leaves 4 Brown leaves 64.4% 27.3% 15.7% 17.7% 8.3% 0.2% 7.5% 3.5% 2.7% 0.1% 2.0% 36.3% 5 Green vegetation 3.8% 2.2% 0.4% 1.7% 0.4% 41.5% 12.7% 6.7% 9.3% 30.8% 19.5% 5.8% Other vegetation 6 Brown vegetation 2.6% 0.6% 2.0% 33.3% 0.1% 0.8% 4.5% 0.0% 9.1% 5.2% 7.3% 2.7% 7 Sticks and branches 2.2% 12.1% 4.7% 14.3% 12.1% 6.9% 3.2% 3.1% 8.3% 4.7% 1.0% 24.3% 8 Wood 0.0% 0.0% 0.1% 0.6% 10.3% 0.4% 0.2% 0.4% 0.1% 2.6% 0.5% 2.0% Yard Waste 74.8% 46.1% 28.5% 71.2% 72.0% 83.1% 80.7% 84.8% 81.9% 87.9% 92.8% 84.2% KITCHEN WASTE 9 Backyard compostable 14.7% 24.4% 59.0% 15.6% 11.7% 4.6% 5.0% 9.1% 8.7% 5.4% 2.2% 2.5% Food scraps 10 Non-backyard compostable 1.8% 14.0% 2.5% 2.2% 6.0% 1.4% 2.0% 2.1% 2.9% 2.5% 1.4% 0.7% 11 Soiled paper 3.4% 11.7% 8.1% 7.7% 7.2% 7.6% 4.8% 1.7% 4.2% 2.2% 3.0% 2.9% Kitchen Waste 20.0% 50.1% 69.6% 25.5% 24.9% 13.7% 11.8% 12.8% 15.9% 10.1% 6.6% 6.1% CONTAMINANTS 12 Plastics 0.1% 0.6% 0.9% 0.3% 0.2% 0.7% 0.1% 0.0% 0.1% 0.1% 0.0% 0.3% 13 Glass 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 14 Metals 0.0% 0.1% 0.0% 0.1% 0.0% 0.0% 0.2% 0.0% 0.0% 0.0% 0.0% 0.1% 15 Dirt / stones 0.3% 0.1% 0.0% 0.0% 0.3% 0.0% 6.9% 1.1% 0.7% 0.6% 0.0% 6.4% 16 Pet waste 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 17 Garbage in plastic bags 0.0% 0.0% 0.0% 1.1% 0.0% 0.1% 0.0% 0.0% 0.0% 0.1% 0.0% 0.2% Compostable materials in 18 plastic bags 3.7% 2.8% 0.0% 1.8% 2.5% 2.2% 0.1% 1.2% 1.5% 0.9% 0.3% 2.2% 19 Other contaminants 1.2% 0.2% 1.1% 0.0% 0.1% 0.1% 0.1% 0.0% 0.0% 0.3% 0.2% 0.4% Gross Contaminants 5.3% 3.8% 1.9% 3.3% 3.1% 3.2% 7.5% 2.4% 2.3% 1.9% 0.6% 9.7% Net Contaminants (minus compostable materials in plastic bags) 1.6% 1.0% 1.9% 1.6% 0.6% 1.0% 7.4% 1.2% 0.8% 1.0% 0.2% 7.4% TRI Environmental Consulting Inc. 6

7 Yard waste formed the bulk of the residential organics waste stream in all months except for December and January; in December, yard waste and kitchen waste approximately comprised the organics waste stream equally, while in January, kitchen waste formed the bulk of the organics waste stream. The portion of contaminants in the organics stream remained fairly consistent through the months at less than 10% of the overall organics stream. Standard deviation values were generally larger in the fall/winter months for yard waste and kitchen waste (October to March) than the spring/summer months (April to September). Yard Waste The percentage of yard waste in the total organic waste stream ranged from 28.5% to 92.8% over the months. Changes in the portion of yard waste generally followed expected trends in seasonal vegetation growth: the lowest point was in January, then increasing in percent composition through the spring and summer green months to a peak in September, and decreasing again through the winter months. Figure 2 depicts the secondary and tertiary percentage composition of the yard waste portion through the year. TRI Environmental Consulting Inc. 7

8 Figure 2 -Yard Waste Composition -% Breakdown 100% 90% 80% Total % of Organic Waste Stream 70% 60% 50% 40% 30% 20% 10% 0% Certain secondary and tertiary categories formed the bulk of the yard waste for certain months of the year: green grass clippings in April, June, August, September, brown leaves from October to January, brown grass clippings in May and July, other green vegetation in April and other brown vegetation in February. Kitchen Waste Green grass clippings Brown grass clippings Green leaves Brown leaves Green vegetation Brown vegetation Sticks and branches Wood Yard Waste The percentage of kitchen waste in the total organic waste stream ranged from 6.1% to 69.6% over the months. Figure 3 depicts the secondary and tertiary percentage composition of the kitchen waste portion through the year. TRI Environmental Consulting Inc. 8

9 Figure 3 - Kitchen Waste Composition -% Breakdown 100% 90% 80% Total % of Organic Waste Stream 70% 60% 50% 40% 30% 20% 10% 0% Backyard compostable Non-backyard compostable Soiled paper Kitchen Waste Backyard compostable food scraps comprised over half of the kitchen waste in six out of twelve months, and comprised at least one-third of the kitchen waste during the other months of the year. TRI Environmental Consulting Inc. 9

10 Contaminants The percentage of contaminants in the total organic waste stream ranged from 0.6% to 9.7% over the months; if compostable materials in plastic bags were discounted, the percentage range decreases to 0.2% to 7.4%. Figure 4 depicts the secondary and tertiary percentage composition of the contaminant portion through the year. Total % of Organic Waste Stream 20% 19% 18% 17% 16% 15% 14% 13% 12% 11% 10% 9% 8% 7% 6% 5% 4% 3% 2% 1% 0% Figure 4 - Contaminants Composition -% Breakdown Other contaminants Compostable materials in plastic bags Garbage in plastic bags Pet waste Dirt / stones Metals Glass Plastics Gross Contaminants Net Contaminants (minus compostable materials in plastic bags) Net Contaminants With the exception of the month of January, compostable materials in plastic bags were present in all monthly samples. The spikes in the percentage of dirt/stones in May and October were attributed to a large piece of concrete (patio stone) in one sample and larger quantities of dirt from large plant pots in May, and large quantities of chicken manure in October. Other contaminants include diapers in TRI Environmental Consulting Inc. 10

11 November 2012, snow and tetra pack containers in December 2012, rubber in February, leather and textiles in March, non-compostable paper, a juice box, and an asphalt shingle in April, candle wax and textiles in May, a clay pot in June, painted wood in August, textiles in September, and bird carcasses in October. Glass and pet waste were not encountered in any of the sampling events. A grid sampling technique is used after the load is dropped off, and although the load is mixed, there are sometimes pockets of material in the pile that end up in one sample and not the other. For this reason five samples are taken from the entire load. The overall averages are accurate, and the standard deviation is indicative of the varied nature of the sample, where one group of houses could predominately have leaves, while another group of houses predominately has food waste. The number of samples and houses that have been collected from in this study was designed to allowing for a 90% confidence interval with a corresponding uncertainty range and variance of approximately 10% between samples. A large confidence interval does not necessarily indicate that the data is unreliable; instead it could indicate that the data from a particular sector is highly variable depending on the source, with different sub-sectors producing different types of organic waste. MOISTURE SAMPLES The results of the moisture samples collected quarterly (November 2012, February 2013, May 2013, and August 2013) are presented in Table 5. During some sampling events, there were no materials from specific categories present as noted in the table. The results presented are calculated on a wet weight basis. Moisture for all compostable material was between 21-78% with an overall average between 61% and 72% depending on the season. The moisture content average is calculated taking into account the organic waste composition as some organic waste categories are present in larger quantities than others and will contribute more to the overall average moisture content. Reference moisture data obtained from four different sources are tabulated in Table 5 and compared to moisture sample results. Note that reference data was not available for sticks and branches, other brown vegetation, and soiled paper (all sources are for clean paper). It is notable that the moisture contents measured for brown leaves and brown grass clippings are significantly higher than the values cited in literature; this may be due to the wet climate of the BC Lower Mainland or contact with food scraps, which tend to be moist. TRI Environmental Consulting Inc. 11

12 Literature Source/Date of Moisture Analysis Table 5. Average Moisture Content Values from Literature CCME 1 Cornell 2 Wilson 3 NPTEL 4 Nov Feb Sample Results* May YARD WASTE 1 Green grass clippings 75.2% 82% 25-35% - 69% 75% 76% 61% 70% Grass clippings 2 Brown grass clippings - 9% % 64% 69% 3 Green leaves % - 69% 70% 61% - 67% Leaves 4 Brown leaves % - 73% 55% 47% - 58% 5 Green 69% 62% 62% 60% 69% - 57% 70% 66% Other vegetation 6 Brown % 67% 62% 42% 60% 7 Sticks and branches % 51% 34% 42% 45% 8 Wood 15% % % 21% Yard Waste Moisture Content 72% 59% 66% 61% 64% KITCHEN WASTE 9 Backyard compostable 78% - 78% - 76% 76% 61% 78% 73% Food scraps Non-backyard 10 compostable 39% % 56% 51% 44% 53% 11 Soiled paper % 72% 41% 61% 60% Kitchen Waste Moisture Content 73% 73% 51% 66% 66% Aug Total Moisture Content 72% 63% 64% 61% 65% * Moisture Results are calculated on a wet weight basis [1] Recommended Waste Characterization Methodology for Direct Waste Analysis Studies In Canada, Prepared for: CCME Waste Characterization Sub-Committee by SENES Consultants Limited, April pp. 30 & 34 [2] Cornell Natural Resource, Agriculture, and Engineering Service. On-Farm Composting Handbook; appendix A, table A.1. NRAES-54. Copyright May Retrieved from [3] Wilson, David Gordon (ed.), Handbook of Solid Waste Management, [4] NPTEL. Environmental Engineering and Waste Management. Ch. 8 Waste Characteristics. Yearly Avg TRI Environmental Consulting Inc. 12

13 STUDY LIMITATIONS The data collected and analyzed for each sampling period is from samples collected over one week. The results presented are a snapshot of the organic waste composition. The study was conducted from specified homes from the City of Surrey in a pilot area that has been part of the organic waste collection system for approximately two years. The waste composition is expected to be highly variable throughout the year as the amount and composition of yard waste varies depending on the season. CLOSURE AND PROFESSIONAL STATEMENT TRI Environmental Consulting Inc. prepared the foregoing memo for the exclusive use and information of the City of Surrey. The information and data were collected and compiled in accordance with the general level of care and skill normally exercised by environmental science and engineering professionals practicing under similar circumstances. During the preparation of this report, TRI has relied on reports, data, studies, specifications, documents and other information provided by others. TRI has taken care to verify the information provided where possible, but makes no warranty as to the accuracy of the reports, data, studies, specifications, documents and other information prepared by others and accepts no responsibility for information contained in them. Any use by a third party of the foregoing report, or any reliance upon or decisions made by a third party based upon them, are the sole responsibility of such third parties. TRI Environmental Consulting accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions taken based on the foregoing report. Thank you for choosing TRI for this Project. Should you have questions concerning this memo, or if you require additional information, please contact the undersigned at or at tauseef@tri.bc.ca. Sincerely, TRI Environmental Consulting Inc. TRI Environmental Consulting Inc. Leandro Torrella, RPBio., BSc., EPt Field Supervisor Yihting Lim, EIT, BASc Project Manager TRI Environmental Consulting Inc. Tauseef Waraich, MSc., P.Ag, EP General Manager TRI Environmental Consulting Inc. 13

14 PHOTOS TRI Environmental Consulting Inc. P h o t o s

15 City of Surrey Entire Sample Load November 2012 Entire Sample Load December 2012 Entire Sample Load February 2013 Entire Sample Load March 2013 Entire Sample Load April 2013 Entire Sample Load May 2013 TRI Environmental Consulting Inc. Photos

16 City of Surrey Entire Sample Load June 2013 Entire Sample Load July 2013 Entire Sample Load August 2013 Entire Sample Load September 2013 Entire Sample Load October 2013 Yard Waste Green Grass Clippings (May 2013) TRI Environmental Consulting Inc. Photos

17 City of Surrey Yard Waste Brown Grass Clippings (Sept 2013) Yard Waste Green Leaves (Jan 2013) Yard Waste Brown Leaves (Dec 2012) Yard Waste Green Other Vegetation (Oct 2013) Yard Waste Brown Other Vegetation (Dec 2012) Yard Waste Sticks and Branches (July 2013) TRI Environmental Consulting Inc. Photos

18 City of Surrey Yard Waste Wood March 2013 Kitchen Waste Backyard Compostable Food Scraps Jan 2013 Kitchen Waste Non Backyard Compostable Food Scraps (Apr 2013) Kitchen Waste Soiled Paper (July 2013) Contaminants Plastics (Dec 2013) Contaminants Metals (Dec 2013) TRI Environmental Consulting Inc. Photos

19 Contaminants Dirt/Stones (May 2013) Contaminants Garbage in Bags (Feb 2013) Contaminants Compostable Materials in Plastic Bags (Oct 2013) Other Contaminants Glove (Jan 2013) TRI Environmental Consulting Inc. P h o t o s