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Estimating volumes of food waste and other organics for composting

  1. 1. Estimating volumes for composting
  2. 2. You’re thinking about diverting food waste and other organics from disposal to composting. The big question is ... where to begin?
  3. 3. When not offered as part of a municipal service, commercial hauling and composting services are usually based on fees charged by the ton.
  4. 4. Before you can get quotes from contractors and other service providers, before anyone can talk collection strategies or space requirements for your own facility, you’ve got to get a handle on generation volumes and convert those volumes to tons.
  5. 5. Your goal is to determine how many tons of compostables are being generated each year, whether a municipality, household, college, factory or business park.
  6. 6. Then you can begin the planning process and start to gather cost estimates.
  7. 7. There are a number of routes available for determining annual volumes of organic wastes. Each has advantages and disadvantages. Here are some ideas to get your project started:
  8. 8. Develop estimates based on published norms and averages. ROUTE 1
  9. 9. The largest component of the MSW stream is compostable: • 14.9% food • 26.6% paper and cardboard • 6.2% wood • 13.3% yard trimmings ≥ 61% (NOTE: Some non-identified organics currently classified as textiles, plastics and other, plus gypsum board, are also compostable using a high-rate process. As much as 70% of the global waste stream is compostable.) SOURCE:
  10. 10. Solid waste generation rates for households, schools, hotels, etc. SOURCE:
  11. 11. SOURCE: ReFED_Technical_Appendix.pdf More solid waste generation rate estimates
  12. 12. 10 gal = 20 lbs. 20-32 gal = 60 lbs. 45-64 gal = 120 lbs. 96 gal = 180 lbs. Contact your waste hauler or city/county solid waste division for specific sizes or weight limits for your community. SOURCE: cleanscapes/bothell/your-three-carts/ Maximum cart weight examples
  13. 13. Multiply the size of your container by these weights: • 1 cubic yard of food waste is 1,070 pounds or about .5 tons • 1 cubic yard of mixed paper is 875 pounds or .44 tons • A 40 cubic yard roll-off filled with flattened corrugated cardboard weighs 1 ton (50 pounds per cubic yard) Contact your waste hauler or city/county solid waste division for specific container sizes and weight limits for your community. SOURCE: swmb/css/documents/vol-to-weight-conversion.doc Weights by the cubic yard
  14. 14. Calculation example - households 500 households, each generating (1) 10 gallon/20 pound organics cart per week 20 lbs. per week x 52 weeks = 1,040 lbs/year/household divided by 2000 lbs. per ton = .52 tons per year (TPY) per household .52 tons x 500 households = 260 tons of organics generated by those 500 households per year
  15. 15. Calculation example - college 1 college of 35,000 students generating 1 pound per student per week = 35,000 lbs. per week x 52 weeks = 1.82 million lbs. per year / 2000 lbs. per ton = 910 TPY 910 TPY x 61% (organic fraction of the MSW stream) = 555.1 tons of organics generated by the college per year
  16. 16. Calculation example – fast food 1 restaurant with 16 employees generating 200 lbs. per employee per week = 16 x 200 = 3,200 lbs. per week 3,200 lbs. per week x 52 weeks = 166,400 lbs. per year / 2000 lbs. per ton = 83.2 tons per year (TPY) 83.2 TPY x 61% (organic fraction of the total MSW stream) = 50.8 tons of organics generated by the restaurant per year
  17. 17. PROS: Fast, cheap, easy CONS: If your community, office, school, etc. varies significantly from the average, results will not be representative. RECOMMENDED FOR: Low volume generators (the total volume of any “error” will be a small amount). For everyone else, rough estimates only. ROUTE 1
  18. 18. DIY waste audit ROUTE 2
  19. 19. 1. Take statistically representative, random samples 2. Sort and weigh 3. Calculate annual tonnage
  20. 20. SOURCE: 2009 UHBristol Clinical Audit Team – Version 3. This resource discusses clinical audits, but suggests a number of sampling methods to improve randomization and reduce sampling bias. What’s a representative sample?
  21. 21. 1. Take statistically representative, random samples 2. Sort and weigh 3. Calculate annual tonnage
  22. 22. • Separate the sample from the total waste stream. • Sort the contents (paper, plastic, metal, food, etc.). • Weigh the results in each waste category if conducting a full waste stream audit. Otherwise, just weigh the compostables and average the results to develop generation rates per audit unit, i.e., per person, cart, classroom, etc.
  23. 23. Common compostables*: • Food scraps, culls and plate waste • Paper and cardboard, including dirty and waxed • Grass, yard waste and other vegetation • Unpainted/untreated wood and gypsum board If intended for processing at a modern, high-rate facility you may also include*: • Meat, bones, dairy • Compostable plastics • DAF sludge and other food processing by-products • Municipal drinking water and wastewater treatment sludge *Verify acceptance with composter
  24. 24. 1. Take statistically representative, random samples 2. Sort and weigh 3. Calculate annual tonnage
  25. 25. Calculation example If the sample representing one week’s worth of garbage resulted in 10 pounds of separated organics: 10 pounds x 52 weeks per year = 520 pounds per year 520 pounds/2000 pounds per ton = .26 tons of organics per year
  26. 26. DIY audit postscript Sometimes, a local college or university will have a professor, student, or class looking for a research project. Your waste audit might be a perfect for their needs. This win-win can provide you with quality data for a low-to-no investment in time or dollars. Check with departments related to engineering, environment, hospitality, health, etc.
  27. 27. PROS: Requires a little time, but not much money. Can be carried out by one person or as a group project. CONS: Is only as accurate as the volunteers. Training to help sorters identify compostables recommended. RECOMMENDED FOR: Almost anyone. NOT RECOMMENDED IF: There are safety concerns, like toxic constituents. ROUTE 2
  28. 28. Professional waste audits ROUTE 3
  29. 29. If the waste stream is too large or too complex for a do-it-yourself project, you may have to call in the Big Guns.
  30. 30. For municipalities and other high-volume waste generators requiring more exact figures than sampling or calculation can provide, or when the waste stream contains toxins or other components that make DIY assessments inadvisable, a professional waste audit or waste characterization study may be the best route.
  31. 31. Professionals may charge by the hour or by the contract. But if you are in an area where tipping fees for composting are less than for disposal, the audit may pay for itself many times over in the form of reduced costs for waste management services.
  32. 32. PROS: Can be the most accurate method. Requires no training, volunteer mobilization or outreach program development. CONS: Will require a budget. RECOMMENDED FOR: Sizeable and/or toxic waste streams where the expense of professional expertise and equipment is warranted. ROUTE 3
  33. 33. Some online tools for DIY waste audits: PERMISSIONS Links to and presentations of this slide show for the purpose of outreach and education are encouraged. But it cannot be edited or altered in any manner and must be used in its entirety. CREDITS Production costs for this presentation have been underwritten by McGill Environmental Systems. ©McGill Environmental Systems of N.C. Inc. All rights reserved. Read the WhitePaper: Food waste diversion – it’s time to pursue alternatives that make environmental and economic sense View more titles related to food waste diversion and composting. to-conducting-classroom-waste.html