Biodegradability and Compostability

Biodegradability and compostability are two different concepts, as laid down in the EU standards Enropean Norms (EN) 13432 [16], EN 14995 [17] and in the US standard, American Society for Testing and Materials D6400 [18]  

The inherent biodegradability of a plastic is inferred by stndying an actual biodegradation process, nnder specific laboratory conditions, and the conclusion that the plastic is biodegradable (i.e., it can be biodegraded) can be drawn from the test results [19]. It must be noted that a fully biodegradable plastic can show a very limited biodegradation if environmental conditions are not suitable (e.g., bioavailability). 

The waste hierarchy established by the European Commission in 1989 [20] laid down a priority order in waste management options  

In this scenario, compostable bioplastics can play a key role. Typical examples are waste bags for the collection of household waste, disposable catering items nsed in fast-food restaurants and agricultural mulch films. Bioplastics do not need separation but can be collected and treated in a homogeneous way with the other organic waste, making the system more efficient. 

The environmental benefits induced by the use of bioplastics in biowaste management, notably when composting or anaerobic digestion are the preferred options, are readily measurable with LCA, provided that the following scope aspects are considered  

Furthermore, we distinguish between induced primary degradation (macromolecule cleavage), materials dissociation, and final degradation of decomposition products to water, carbon dioxide, methane, and biomass [282], [935], [936], [937], [938], 

In the course of total biological degradation, microorganisms require extracellular enzymes to digest plastics and/or their molecular decomposition products. These enzymes essentially use oxidation and hydrolytic processes to break down the material into even smaller components, which can then be absorbed by the cell [940], [941], [1051]. However, the enzymes are too voluminous to penetrate the degrading material efficiently. Therefore, this process relies on surface erosion, or goes through a diffusion-controlled sequence in liquid carrier media, especially water. 

A material or materials mix is considered compostable, if, under defined conditions in a composting system, it is entirely transformed into COj, HjO, CH4, and biomass within a specified length of time, i.e., mostly during a composting cycle ranging from a few weeks to months [943]. For example, a tree trunk is biodegradable, but not compostable. 

In principle, biodegradability and compo stability of biopolymers and/or products made from them increase with simplified access for microorganisms to the molecules, thus enhancing metabolization. 

The standards for certification of compostable materials are discussed in more detail in the following sections. 

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Design the product so that only benign materials are left at the end of life - biodegradable and compostable materials with low eco-toxicity. 

Perhaps one of the biggest hurdles for the adoption of biodegradable and compostable materials has been the lack of kerb-side collection and municipal composting facilities, particularly in the USA and parts of Europe. Municipal composting would complete the circle for materials such as biopolymers, which start as natural renewable resources and degrade back to useable compost material. The wider development of a composting infrastructure would permit a realisation of the marketing benefits that seems to drive the adoption of sustainable materials. 

BioBag also supplies biodegradable and compostable film products for shopping bags, food packaging applications and for packing hygiene articles. 

Fortune Plastics is one of the top five plastic waste disposal bag manufacturers in the USA. In 2005, the company introduced COMP-LETE, a biodegradable and compostable waste disposal bag made from Novamont s Mater-Bi polymers. COMP-LETE has been certified by the US Biodegradable Products Institute. 

The Heritage Bag Company produces a biodegradable and compostable waste disposal bag under the trade name Bio-Tuf. The product meets ASTM D 6400 specifications for biodegradability and compostability. 

BioBag products meet all of the international standards for biodegradability and composting including ASTM D6400 specifications and EN 13432 2000. 

Earthcycle has developed a line of packaging specific for fresh vegetable and fruit. The packaging trays are water resistant and are available in two colours, natural fibre and vanilla. Other colours are available upon request, using vegetable dyes, so the biodegradability and compostability of the product is not jeopardised. 

The company is also in the process of developing a metallised NatureFlex film, which is currently undergoing independent testing in order to formally confirm its biodegradability and compostability. 

In June 2004, Treofan introduced its new biodegradable and compostable Biophan film made from polylactic acid supplied by NatureWorks LLC. According to the company, Biophan offers exceptional transparency and gloss, the ability to transmit water vapour, and outstanding sealing properties. Biophan is also printable, resistant to oil, fat and alcohol, and is thermoformable. Biophan disintegrates completely into water and carbon dioxide within 45 days. 

Wemterra blown films are starch-based biodegradable and compostable materials. They are certified in accordance with DIN V 54900 (Germany) OK Compost and VGS-Tabel (including OK-Compost-Label, Belgium). Wenterra film is used for manufacture of bio-waste disposal bags and sacks. 

This report uses the American Society for Testing and Materials (ASTM) definitions of biodegradable and compostable plastics. 

Polymer films prepared by Hayes [3] consisting of bis(2-hydroxyethyl)tere-phthalate, lactic acid, tris(2-hydroxyethyl)trimellitate, ethylene glycol, poly (ethylene glycol), and the colorant titanium dioxide were both biodegradable and compostable. 

Over the past decade, researchers and citizen advocates have developed several tools to assist in decision making about plastics selection. The plastics pyramid (Fig. 5.1] developed by Thorpe and Van der Naalde in 1998 was an early attempt to visually display the life cycle hazards of different plastics to assist in materials selection. This ranking focused on the toxicity of the material, considering production hazards, use of harmful additives, hazards in use, and disposal hazards. In this pyramid, bio-based polymers form the bottom of the pyramid, indicating they are most preferable, as they are made from renewable resources, and theoretically are biodegradable and compostable (Rosalia et al., 2012]. 

Mater Bi ZlOlU/C, thermoplastic starch - poly-e-caprolactone, biodegradable and compostable, mainly for films and sheets no sensitivity to humidity, no ageing, high UV stability, high hydrolytic stability, from Novamont S.p.A. 

It should be noted though that this list includes biodegradable and compostable polymers. European bioplastics trade group predicted the annual capacity of 1.5 million tons by 2011 [16], a number that is very similar to the COPA/COGEGA estimate. 

The noncompliance of these products with the international norms of biodegradability and compostability, however, prevented significant market growth in Western countries. 

EarthSheU Corp. uses a combination of starch and limestone to make packaging products that are biodegradable and compostable. Products manufactured include cups, plates, bowls, sandwich wraps, and hinged-Ud containers. The company s foam laminate is produced by mixing the starch and limestone with water and fiber and placing it in a heated mold. Vaporization of the water foams, forms, and sets the product. The material physically disintegrates in water when it is crushed or broken. ... 

Poly(lactic acid) (PLA) is a thermoplastic polyester characterized by mechanical and optical properties similar to polystyrene (PS) and polyethylene terephthalate (PET). It is obtained from natural sources, completely biodegradable and compostable in controlled conditions as already stated in previous chapters. PLA offers some key points with respect to classic synthetic polymers, since it is a bioresource and renewable, while raw materials are cheap and abundant compared to oil. From a commercial point of view, a non-secondaiy approach, it can embellish with the word green so fashioned for the major stream consumers. Legislation can also help the commercial diffusion of biopolymers. As an example, a decisive leap has been made with the control of non-biodegradable shopping bags distribution in the European Commission and many of its member states. In addition, PLA has received some interest from the industrial sectors because of its relatively low price and commercial availability compared with other bioplastics. This is the veiy key point for any successful polymer application. In fact, the current price of commercial PLA falls between 1.5 and 2 kg , which is sufficiently close to other polymers like polyolefins, polyesters or poly(vinyl chloride) (PVC). Clearly, the PLA market is still in its infancy, but it is expected that the decrease in the production costs and the improvement in product performance will result in a clear acceleration in the industrial interest for PLA uses. It is estimated that PLA consumption should reach... 

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