Materials Waste in
Materials Waste in thousand tons 80000 70000 60000 50000 40000 30000 20000 10000 0 US Municipal Waste 2010 63% Paper/ Paperboard 3% Food Waste 53% Yard Waste Recovered | Landfill / Incineration Data source: US EPA 2010 Municipal Solid Waste Report Figure 1: Recent historic recovery of municipal organic waste via recycling or compost [1] Yeatman C.: Biogas Experiences and Ethanol Prospects, Oxford Farming Conference, 2007, pp. 1-12. [2] Edelmann W, Baier U, Engeli H.: Environmental aspects of the anaerobic digestion of the organic fraction of municipal solid wastes and of solid agricultural wastes, Water Sci Technol. 2005;52(1-2):203-8. [3] Darby, Debra: Innovation with a Marine Focus: New Film Products for Marine and Anaerobic Digestion, bioplastics MAGAZINE, 05/11, 2006 pp. 32-33 yield can be highly variable based on feedstock and operating conditions. However, a typical yield for food scraps may be about 265 m 3 /t and almost 1000 m 3 /t for fat and grease. This compares with biogas yields in the range of about 25 (cow) to about 80 (chicken) m 3 /t for manure [1]. Grass clippings and yard waste would likely be in the range of 150-200. Except for materials high in lignin (e.g. wood waste), most natural organic materials are readily degraded with Anaerobic Digestion. Somewhat surprisingly, most compostable bioplastics do not degrade quickly in Anaerobic Digestion, especially at lower temperatures. A study [2] using life cycle assessments (LCA) has shown that Anaerobic Digestion of municipal organic waste is clearly superior to both composting and incineration. A key contributor to the improved LCA is the energy recovered with Anaerobic Digestion (as biogas), compared with the energy input required for turning/aeration of compost. Incineration also recovers energy, but this benefit is offset by greater emissions (of CO 2 and other gaseous combustion products) and the ash waste which may be concentrated in toxic heavy metals. Most (non-recyclable) municipal organic waste now goes to land fill or incineration, with minor amounts diverted to home or industrial composting. Data from the US, for 2010 (Figure 1) show that only about 3% of food waste was recovered (through composting). Recovery of yard waste was considerably better (at about 57%). In comparison, about 63% of paper and paper board was recovered through recycling. Thus, municipal organic waste (especially food waste) is a large, favorable, and mostly untapped source of raw materials for Anaerobic Digestion. Implementation of Anaerobic Digestion would show numerous environmental benefits over current disposal methods and provide a clean source for renewable energy. Based on these benefits, many communities are now exploring Anaerobic Digestion as a preferable option. One concern in many countries is the collection infrastructure and logistics, including the availability, cost, and performance of waste bags. PHA Advantages for Anaerobic Digestion EcoWorks ® AD, by Cortec Corporation, St. Paul, Minnesota, USA, first described in a previous issue of this magazine , is ideally suited for expanding the use of Anaerobic Digestion for disposal of municipal organic waste. EcoWorks AD is made from Mirel P5001 PHA (polyhydroxyalkanoate), which degrades rapidly and completely in Anaerobic Digestion (demonstrated by ASTM D5511). This means that debagging of waste is not necessary for feeding of materials into the Anaerobic Digestion system, and it is compatible with a wide range of operating conditions (high or low solids, high or low temperature). EcoWorks AD has good mechanical properties, including high tear and impact strength (table 1). Unlike some other compostable/ degradable bags (especially paper bags and some starch bioplastic blends), EcoWorks AD does not become weak or sticky when it gets wet. EcoWorks AD can be made in a range of sizes and thicknesses, to accommodate commercial (e.g. large bags for restaurant or food service waste collection) or residential (e.g. counter top food scrap bins, yard waste bags) applications. 44 bioplastics MAGAZINE [02/12] Vol. 7
Materials Property Test Method Units Typical Value Caliper ASTM D6988 µm 44.45 Breaking Factor Tensile Strength at Break Elongation at Break Yield Strength Tear Strength Dart Drop Impact Resistance Puncture Resistance MD 0.70 ASTM D882-02 kN/m TD 0.63 MD 15.98 ASTM D882-02 MPa TD 13.94 MD 594.26 ASTM D882-02 % TD 567.84 MD 8.85 ASTM D882-02 MPa CD 11.43 MD 4332.75 ASTM D1922-06a mN CD 3044.37 ASTM D1709-04, grams 147.29 Test Method A MIL-STD-3010, N 6.65 TM 2065 * Typical properties represent average laboratory values and are not intended as specifications but as guides only. is working with Metabolix to continue development and production of EcoWorks AD. The product expands Cortec’s portfolio of bioplastic products while growing the market for the Mirel brand bioplastic. Cortec is now manufacturing EcoWorks AD bags and film, along with the companion brand EcoOcean, at its Advanced Films division in Cambridge Minnesota, USA. Plans are underway to also manufacture the product at the EcoCortec subsidiary in Beli Manaster, Croatia in the future. EcoWorks AD is targeted to be price competitive with other compostable bioplastics, yet provides the superior benefits described above. www.cortecvci.com www.mirel.com Table 1: Typical Properties Eco Works AD Further environmental benefits of EcoWorks AD include: • Suitable for use in home compost. EcoWorks AD will degrade at the lower temperature (even ambient temperatures) of home compost bins compared to commercial compost facilities. • It will biodegrade in marine (ASTM D7081), soil, and fresh water environments; reducing long term effects of inappropriate disposal (litter). Its ability to biodegrade in marine environments provides coastal areas with a technological “safety net” for coastal and marine preservation. • It contains 77% biobased carbon content (ASTM D6866) and has been awarded USDA Biopreferred designation for Waste Bags • Meets ASTM D6400 standard for compostable plastics. In municipal composting facilities, EcoWorks AD breaks down faster than most other compostable bioplastics, allowing faster composting cycles and/or less ”plastic” residue visible in the compost product. Shaping the future of biobased plastics The combination of mechanical and degradation properties of EcoWorks AD create the opportunity for a more environmentally friendly plastic shopping bag. If provided by retailers, consumers would use the bag to transport their merchandise home. Then the bag could be used to collect home waste for disposal via Anaerobic Digestion, home composting, or collection for municipal composting. EcoWorks AD represents a collaborative development between Cortec and Telles. With the recent termination of the Telles joint venture, the ownership of the Mirel brand and technology has reverted to Metabolix. Cortec www.purac.com/bioplastics bioplastics MAGAZINE [02/12] Vol. 7 45
