Introduction

5.1.1 Petro Polymers and Biopolymers: Remarks on Environmental Impact

The worldwide consumption of polymeric materials and plastics rises annually by around 7 to 10%. Total consumption in 2000 was approximately 200 million tonnes (t), which corresponds to nearly 30 kg per capita, with an average of 80 to 100 kg in industrialized countries and 2 to 20 kg in emerging countries and countries in transition.1 More than 98% of plastics are based on fossil feedstocks (crude oil), the reserves of which are predicted to last for only approximately 80 more years.2

Public concern about the environmental consequences bound to the production and consumption of various materials and products is increasing. These effects occur at every stage in a product's life cycle — from the extraction of the raw materials through the processing, manufacturing, and transportation phases, ending with use and disposal or recycling.3

At the occasion of the World Conference on Ecology in 1992 in Rio de Janeiro, the United Nations Framework Convention on Climatic Change was signed. With the Kyoto Protocol in 1997, industrialized nations undertook the initiative of reducing greenhouse gas (GHG) emission at least 5% below the amount of 1990. The European Union (EU) committed itself to cutting GHG emissions to 8% below the level quoted by the year 2008.4

In 2003, the consumption of polymer for plastic applications in Western Europe was approximately 40 million tonnes. Many plastics applications involve a consumption time of less than 1 year; after that, the vast majority of these plastics are discarded as waste. If fossil-based plastics were to be replaced by starch-based polymers, it is estimated that CO2 emissions could be reduced by 0.8 to 3.2 t per t of material produced.5

Recent EU legislation increasingly requires the recovery of plastic waste through recycling, composting, or energy recovery. The plastics industry mostly recycles its own in-plant scraps, and although commercial-scale plastics processing has been available for many years, postconsumer plastics recycling is still very limited. Moreover, if recycling is to offer true environmental benefits, whatever the material involved, several factors must be taken into account. Most broadly, the manpower and economic resources used to collect, sort, and recycle must be less than, or at least comparable with, those used to produce virgin materials. Sufficient demand from end-market users for the recycled material is also a vital prerequisite, and a key factor for marketing these products is that the use of recycled materials does not compromise product safety or performance.1

Organic recycling is a specific recycling option for biodegradable waste, i.e., for biodegradable or compostable materials. It diverts biodegradable waste from landfills, preventing emissions of methane that represent a very powerful GHG generated in anaerobic conditions by landfills. Composting technologies, used for the disposal of food and yard waste that account for 25 to 30% of total municipal solid waste, are particularly suitable for the disposal of biodegradable bioplastics and plastics from fossil feedstock, together with soiled or food-contaminated paper.

The term "biopolymer" and hence the converted plastic items (bioplastics) refers to natural products that are polymeric in character as grown or can be converted to polymeric materials by conventional or enzymatic synthetic procedures.6 Thus, under that heading, one can include natural polymers used as direct feedstock for plastic production as well as artificial polymers, such as those obtained by chemical modification of preformed natural polymers or by polymerization of monomers deriving from renewables.7 Total demand for biodegradable polymers in the U.S., Europe, and Japan was 20 kt in 1998, valued at $95 million.8 The European market for bioplastics, resulting from the fruits of 15 years of technological development, is

Environmentally Deg Biobased Polymeric M

Environmentally Deg Biobased Polymeric M

FIGURE 5.1 Main options for the production of environmentally degradable biobased polymeric materials and plastics.

FIGURE 5.1 Main options for the production of environmentally degradable biobased polymeric materials and plastics.

growing slowly but steadily. According to the industry association (International Biodegradable Polymers Association and Working Group — IBAW), the bioplastics usage in 2004 amounted to 50 kt. Compostable rubbish bags and starch-based loose packing material constitute the major part. The IBAW estimates that one-tenth of all plastics applications in Europe could be satisfied by modern bioplastics, a figure that corresponds to approximately 5 million t of polymers. However current worldwide production capacity only amounts to 300 kt,9 which is 0.15% of the overall present production of plastics.

Traditional natural polymeric materials are represented by polysaccharides (cellulose, starch, chitin, alginic acid, ulvans, xanthanes, guar gum), proteins (fibroin, keratin, collagen, and the polynucleotides RNA and DNA), natural rubber, lignins, and vegetable oil binders. Fibrous material derived from renewable crops, their byproducts, or their industrially processed wastes can be considered a good source for the formulation of polymeric blends and composites based either on synthetic and natural components (hybrids) or on only natural components, which we name "nat-cos" for quick identification (Figure 5.1).1011

Biopolymers, unless heavily modified, are biodegradable by definition and can be composted, thus promoting an environmentally compatible waste-management system. Biopolymers are derived from renewable resources and therefore produce no net increase in atmospheric CO2 balance as part of a sustainable material cycle.

5.1.2 Petro Polymers and Biopolymers: Economic Considerations

In industrial production, sustainability must be achieved, but with awareness that business will fail unless some minimum profit margin is guaranteed. New bioplastics should be introduced as more appropriate options in cases where the degradation constitutes a plus in specific applications by defraying the cost inherent in managing

TABLE 5.1

Energy Content in Agricultural Plants

Plant

Wheat Barley Potato

Energy (MJ/kg)

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