City of Orillia Biodegradable Bag Study
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CITY OF ORILLIA BIODEGRADABLE BAG STUDY December 2003 Solid Waste Management Division TABLE OF CONTENTS 1.0 INTRODUCTION .........................................................................................1 2.0 BACKGROUND...........................................................................................1 2.1 CERTIFICATION OF COMPOSTABLE BAGS .......................................................1 2.2 POTENTIAL FOR COMPOST CONTAMINATION ..................................................3 2.3 MUNICIPALITIES IN ONTARIO TESTING BIODEGRADABLE BAGS.........................4 2.3 BAG BRANDS STUDIED.................................................................................5 3.0 GOALS AND OBJECTIVES........................................................................6 4.0 METHODOLOGY ........................................................................................6 4.1 BAG STRENGTH TRIAL .................................................................................7 4.2 WINDROW TRIAL .........................................................................................7 5.0 RESULTS AND DISCUSSION ....................................................................8 5.1 BAG STRENGTH TRIAL .................................................................................8 5.1.1 Yard Waste Bags ................................................................................8 5.1.2 Kitchen Waste Bags............................................................................9 5.2 WINDROW TRIAL .......................................................................................10 5.2.1 BIOSAK® Bags.................................................................................10 5.2.2 BioBag® Bags...................................................................................11 5.2.3 BioTrue Bags ....................................................................................12 6.0 SUMMARY AND CONCLUSIONS ............................................................12 7.0 RECOMMENDATIONS..............................................................................13 REFERENCES ...................................................................................................13 LIST OF TABLES TABLE 1: American and European heavy metal limits for compostable plastics as well as limits for compost in Ontario................................................................3 TABLE 2: Product information for certified bag brands.........................................5 LIST OF FIGURES FIGURE 1: Logo indicating that plastic product is certified compostable under ASTM D6400-99. ............................................................................................3 FIGURE 2: Results for yard waste biodegradable bag strength trial.....................9 FIGURE 3: Results for kitchen waste biodegradable bag strength trial ..............10 LIST OF PHOTOS PHOTO 1: Biodegradable yard waste bags in the storage compartment..............7 PHOTO 2: Windrow preparation with bags ...........................................................8 PHOTO 3: In tact BIOSAK® yard waste bag in a windrow pile after seven weeks ......................................................................................................................11 PHOTO 4: Fragment of BioBag® yard waste bag in a windrow pile after six weeks............................................................................................................11 PHOTO 5: BioTrue yard waste bag in a windrow pile after one week.................12 1.0 Introduction Currently residents of the City of Orillia are asked to place their yard waste in a clear plastic bag, a rigid container, or bundled and tied. The bags are opened and emptied by collection staff into the collection vehicle. The price charged by the contractor for this service is likely to increase appreciably with the new contract starting in July of 2004. Use of biodegradable plastic bags would facilitate yard waste collection in that the bags would not have to be opened or emptied by collection staff, and hence, would minimize the collection price charged for this service. The purpose of this study was to determine how well three brands of certified compostable (biodegradable) bags performed both as a collection medium and in the City’s windrow composting operation. The brands tested include BIOSAK® (W Ralston Inc.), BioBag® (BioCompostable Technologies Inc./Polar Gruppen), and BioTrue (BioTrue Biodegradable Film Products Inc./Farnell Packaging). 2.0 Background Over the past decade a fair amount of research has been undertaken in Europe and North America regarding biodegradable plastics. When these products first came on the market in the 1980’s, they were made by mixing polyethylene with starch. Such products were labelled biodegradable when in fact after the starch broke down, plastic (polyethylene) fragments still remained (EPIC, 2001). This led to confusion as to whether these materials were doing what the manufacturers claimed they were supposed to do. Currently there are newer biodegradable plastic products on the market which do in fact completely break down. These products are made from such materials as polyester, starch, and derivatives from vegetable oil. There is a notable difference in terminology regarding a compostable versus a biodegradable plastic. A biodegradable plastic will break down into carbon dioxide, water, and biomass (humus material). A compostable plastic refers to a plastic that breaks down in a composting environment as fast as the surrounding material and leaves no visible, distinguishable or toxic material. A compostable plastic is not necessarily a biodegradable plastic since inorganic materials may be left behind. A new certification process, however, ensures that designated compostable bags are in fact biodegradable. 2.1 Certification of Compostable Bags In 1999 after eight years of study, the American Society for Testing and Materials (ASTM) developed a new series of tests and criteria to designate plastics as 1 compostable. This designation is found in ASTM D6400-99 “Specifications for Compostable Plastics.” In order for a plastic to meet these standards it must: 1.) Biodegrade – Be converted rapidly to carbon dioxide, water and biomass at the same rate as kraft paper and other compostable materials; 2.) Disintegrate – Not be visible or need to be screened out after composting; 3.) Be safe for the environment – Produce no harmful by-products or hinder the ability of the compost to support plant growth The ASTM tests measure biodegradability, disintegration, and ecotoxicity and are measured as follows. A known quantity of active compost and test material (i.e., the sample plastic) are placed in sealed flasks (as is the case with blank and control materials). Temperature, oxygen, and moisture are maintained in these flasks at optimum levels to sustain microbial activity. Biodegradation is determined by measuring the amount of carbon dioxide produced by the degrading plastic over a 180 day period (Narayan and Mojo, No Date; Stevens, 2002). The percentage of the material which is mineralized is based on the measured levels of carbon dioxide produced. A conversion ratio of 60 percent or more is considered a pass, and is based on mineralization of kraft paper. Disintegration is measured by sieving the residue material left behind after the biodegradation test. The product passes this test if less than 10 percent of the residue material remains on a 2 mm screen. Once again, kraft paper is the reference material. This test ensures that any non-degraded pieces left over would be indistinguishable in the compost. Ecotoxicity is determined by measuring plant growth and germination for different concentrations of the resulting compost mixed with soil. If plant growth and germination are significantly lower (statistically) than those of the control compost, the material will not pass this test. In addition to these three tests, the plastic material must undergo chemical testing to ensure the product meets pollutant limits. This will be addressed in the next section. Plastics which meet these standards can be affixed with the “Compostable” Logo from the Biodegradable Products Institute (BPI) as displayed in Figure 1. 2 FIGURE 1: Logo indicating that plastic product is certified compostable under ASTM D6400-99. 2.2 Potential for Compost Contamination Compost produced at the Waste Diversion Site regularly meets metal and organic chemical concentration limits set out in Schedule B of the landfill’s Provisional Certificate of Approval No. A25061 and Table 1 of Ontario Regulation 101/94 for regular use compost. By meeting these limits, the City’s compost can be sold to the public. As such, it is essential that if biodegradable bags are to be incorporated into the City’s composting operation, they do not add any sources of contamination to the final product. The compostable bag certification process ensures that the three brands of bags tested will not reduce the quality of the compost the City produces. As well as meeting the ASTM standards, these bags also meet European standards for compostable plastics (EN 13432). The heavy metal limits set out in the European standards are more stringent than those set out in the ASTM standards. ASTM heavy metal limits are based on 50 percent of the legal limit for soils in the United States. European limits are based on 50 percent of the quantities normally found in compost. Table 1 lists heavy metal limits under the ASTM D6400-99 standards,