Materials Maxi-Use
Materials Maxi-Use Agro-Food Processing Waste for Truly Sustainable Bioplastics By Elodie Bugnicourt Oonagh Mc Nerney Innovació i Recerca Industrial i Sostenible (IRIS) Castelldefels, Spain Andrea Lazzeri Center for Materials Engineering University of Pisa Pisa, Italy Bioplastics are largely derived from feedstock such as crops and vegetable oils. If such pure feedstock competes with food sources, it reduces to some extent the true sustainability of the resulting bioplastics. Polylactic acid (PLA), for example, is the most widely used bioplastic and, in spite of progress in both research and industrial fields, it is still typically made by the polymerisation of lactic acid produced by microbial fermentation of sugars from corn, wheat, beet, etc., which for the most part are not derived from waste. Moreover, in terms of competing with many standard plastics, the properties of PLA are not sufficient for certain applications. There is undoubtedly a gap in the market for bioplastics that possess better barrier, thermo-mechanical properties and/or processability and that are obtained through a holistic sustainable approach with feedstock that do not compete with our food supplies. To this end, the bioplastics industry needs to tap into new raw material sources from agro-food residues that are in abundant supply, are cost-effective, and indeed to date pose waste management and environmental challenges. Recent research has been concentrating on an integrated environmental approach to bioplastic production known as Maxiuse, whereby each stage, from sourcing to disposal, is considered in a complementary way to establish cost effective, sustainable solutions. The methodology is characterised by reuse along every stage of the process, whereby a useful application for each of the compounds is investigated with a view to maximising resources to the full, thereby bringing positive impacts in terms of sustainability Fig 2: Maxi-use of foodstuff wastes from the olive oil industry to produce PHA bioplactics for packaging (Picture courtesy IRIS) 32 bioplastics MAGAZINE [04/11] Vol. 6
and profitability along the value chain. Wastes from agro-food processing can be used as raw material inputs for plastics in the packaging field, among other applications. The ability to recycle or compost the material at the end-of-life helps to redress the problem of growing and persistent volumes of land and marine waste, as well as reducing dependence on conventional fossil fuel-based resources. This Maxi-use approach has been the basis for the ideation of a project called WHEYLAYER [1]. that commenced in November 2008 and whereby whey (fig 1), a by-product from the cheese industry, is valorised into a value-added bioplastic for food packaging. Indeed, coatings obtained from whey proteins can be applied onto standard carrier films to obtain multilayer films with excellent barrier properties. The resulting oxygen barrier properties are several orders of magnitude greater than that of polyethylene (PE). Whey-based coatings have reached oxygen transmission rates (OTR, Q 100 ) as low as ranges of 1 cm³/m² d bar and water vapour transmission rates (WVTR, Q 100 ) at ranges of 2 g/m² d (Q 100 refers to the barrier properties normalised to a layer of 100 μm thickness), thus making them good candidates to substitute synthetic barrier films such as ethyl vinyl alcohol copolymer (EVOH) [2]. Another key success factor is the degradability for whey-based coatings using selected enzymes and Fig 1: Whey (Picture courtesy IRIS) bioplastics MAGAZINE [04/11] Vol. 6 33
