Mechanical recycling, life cycle

This report discusses the options for feedstock recycling of plastics waste, including aspects of the environmental and economic pros and cons relating to feedstock recycling in comparison with incineration or mechanical recycling of municipal solid waste, based on a number of life cycle assessments. Particular reference is made to the experience of the TNO-CML Centre of Chain Analysis.485 refs. 

F. Perugini, U. Arena and M. L. Mastellone, A life cycle assessment of mechanical and feedstock recycling options for management of plastic packaging wastes, Env. Progress, 24(2), 137-154 (2005). 

The arthropods present us with an intriguing range of biomineralization mechanisms that suits their peculiar bodily needs and functions. Biomineralization activities change on demand during their life cycle and clearly have been modulated to maximize a particular form and function. Sequestering and recycling of calcium for hardening their carapaces, an essential part of their defense mechanism. 

The products can also be recycled after use for second time and they can even be hydrolyzed back into lactic acid which is the basic monomer. Nevertheless, the recycled lactic acid can be re-introduced into the polymerization process of PLA. The last possibility is to introduce PLA into the natural life cycle of aU biomass where it degrades into carbon dioxide and water. Thus, the diversity of PLA becomes obvious as it can be recycled and also decomposed like all other organic matter. Besides that, it will do no harm if burned in an incineration plant or introduced into a classical waste management system (Jacobsen et al. [1]). The typical values of mechanical properties of PLA are displayed in Table 11.1. 

While the effects of material and processing variations on polymer properties are quite well-documented [7-10], reliable prediction techniques for the evolution of properties during the service life of a part are still lacking. In a typical application, a polymer component may be simultaneously subjected to mechanical, thermal and chemical stresses suA that the characterisation of the durability of such a part is a complex task. Polymers retain memory of preceding life-cycle steps so the durability not only depends on what happens during service, but also on what happened before, during manufacture (Figure 2.5). Hence, the durability of recycled plastics will depend on the full history... 

After the actual reaction, a separation process to obtain a pol mier of a certain purity and state follows. Usually, thermal and mechanical imit operations are applied. Pol miers may include residual monomer and solvents which are often difficult to remove. Special consideration has to be given to this subject in the polymers industry in a perspective of life-cycle impact of the products. In the context of the IPPC Directive, the focus is on the minimisation of the emissions of monomers at the industrial site [27, TWGComments, 2004]. Separated monomers, mostly as gases, can be directly returned to the process, returned to the monomer unit to be prepared for purification, transmitted to a special purification unit, or flared off Other separated liquids and solids are sent to a centralised clean-up or recycling unit. Additives needed for processing or for protection may be added to the polymer at this point. 

Cnd-of-life options for plastics are important factors that influence the life cycle assessment (LCA) of plastics. Disposal options for plastics are to mechanically recycle the plastic, chemically recycle the plastic, compost the biobased plastic, burn the plastic into energy, or bury the plastic in a landfill. 

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