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Recycling of materials must become an important design parameter
V IEWPOINT
m
John Hayes is a consultant and freelance journalist specializing in the plastics industry.
Recycling o f m a t e r i a l s m u s t b e c o m e an important design parameter The J a n u a r y 1991 issue of the UK C o n s u m e r ' s Association p u b l i c a t i o n Which advises conservation conscious readers t h a t having milk delivered in r e t u r n a b l e one p i n t glass bottles by a m i l k m a n driving a n electric float uses less energy in total t h a n buying milk in disposable cartons. These have a total energy cost for materials, m a n u f a c ture a n d filling of 350 megajoules per carton. The c o m p a r a b l e figure for a bottle, a s s u m i n g t h a t it has a life of t e n deliveries, is said to be 142 megajoules, even t h o u g h bottles are initially more energy expensive to make a n d are also heavier to t r a n s p o r t . The significance of all this seems to be t h a t we should s t a r t looking at energy conservation a n d recycling in a b r o a d e r context, i n c l u d i n g the way in which the p r o d u c t is used, i n s t e a d of a s s u m i n g t h a t recycling p e r se m u s t be a good thing, r a t h e r like taking exercise or eating apples. The Association of Plastics Manufacturers in Europe (APME) lists 26 post c o n s u m e r recycling schemes in o p e r a t i o n in t e n E u r o p e a n n a t i o n s at present. Not surprisingly, most involve collecting food containers, domestic waste a n d packaging. Of the 26 million t o n n e s of plastics c o n s u m e d each year in Western Europe, some 8 million t o n n e s ends u p in m u n i c i p a l solid waste (MSW). Most of t h a t is either i n c i n e r a t e d or d u m p e d into landfill sites. Only a b o u t 1% of domestic plastics scrap is recovered because of c o n t a m i n a t i o n , cost of collection a n d difficulty in sorting. Recovery of w h a t are generally categorized as 'technical specification' plastics is m a i n l y restricted to p o s t - p r o d u c e r or post-converter waste where polymer c o n t e n t a n d physical p r o p e r t i e s are readily identified. But with volatile p e t r o l e u m prices a n d the p r o s p e c t of events in the Middle East rocking the feedstock supply, s h o u l d we n o t try h a r d e r to r e c o v e r h i g h e r e n e r g y v a l u e p o l y m e r s from finished products? A u t o m o b i l e s are p r i m e candidates n o t only because of the weight of plastics p e r vehicle (between 60 a n d 80 kg for small cars a n d more on some u p - m a r k e t models) b u t also because of the variety of polymers. W h e t h e r one s u p p o r t s the 'greenhouse' theory or regards it as a n o t h e r e x a m p l e of conservationist o v e r - r e a c t i o n , t h e r e is no d e n y i n g t h e p o l l u t i o n c o n t r i b u t i o n of cars a n d commercial t r a n s p o r t . One calculation e q u a t e s every litre of p e t r o l e u m fuel b u r n t with a b o u t 2.3 kg of carbon dioxide, c a r b o n monoxide, h y d r o c a r b o n s a n d o t h e r toxic n a s t i e s released to the atmosphere. Short of b a n n i n g a u t o m o b i l e s completely, a suggestion favoured by some residents of p a r k i n g m e t e r - s t r e w n , t r a f f i c - c o n g e s t e d a r e a s of o u r
REINFORCED PLASTICS FEBRUARY1991
cities, t h e s o l u t i o n w o u l d a p p e a r to lie in improving c o m b u s t i o n a n d power t r a n s m i s s i o n systems a n d reducing the dead weight of the vehicle. Polyester composite p a n e l s have reduced body weight, s h r u n k engine sizes a n d improved fuel performance on a n u m b e r of goods a n d passenger vehicles a n d the process is likely to continue. But w h a t h a p p e n s w h e n those vehicles reach the e n d of their service life? C u r r e n t car shredding practice is i n t e n d e d to c o m p a c t metal n o t to sort different plastics, m a n y of which even the experts find it difficult to identify purely by visual inspection. Recycling economics are very sensitive to the cost of collecting a n d s e p a r a t i n g wastes as the organizers of schemes to recycle polyethylene terephthalate (PET) soft drinks bottles have discovered. T h e r e are a b o u t 12 d i f f e r e n t g r o u p s of t h e r m o p l a s t i c s a n d four or five different thermosets in the bodywork, trim a n d u n d e r b o n n e t c o m p o n e n t s of most m a s s p r o d u c e d vehicles. At the top of the scale the ser~es 7 BMW is estimated to c o n t a i n a b o u t 1000 plastic c o m p o n e n t s in nearly 600 different compounds. The list l e n g t h e n s steadily for most vehicles, with appreciable growth d u r i n g the last ten years in the use of polyamides, p o l y u r e t h a n e (PUR) a n d polyesters. The weight of PUR per car now averages a b o u t 22 kg with increased p o p u l a r i t y of reaction injection m o u l d e d (RIM) b u m p e r s a n d other large body components. But PUR a n d polyesters, like other thermosets, are n o t easily recycled. There are c h e m i c a l t e c h n i q u e s which can be used to reduce t h e m to basic m o n o m e r s b u t the economics are poor. Even the so-called 'commodity' t h e r m o p l a s t i c s such as polyvinyl chloride (PVC) a n d polypropylene (PP), which together a c c o u n t for some 23 kg per average car, may n o t be a viable p r o p o s i t i o n for recovery except in easily accessible trim a n d large components. A complete r e t h i n k of design philosophy is needed, for m a j o r domestic a p p l i a n c e s as well as cars, to help disposal at the end of their service. They m u s t be easier to dis-assemble. Coding or some other m e a n s m u s t make it easy to identify the types of plastics used a n d these m u s t be selected according to suitability for recycling or for energy-recovery potential, as well as for their first use physical properties. We are r u n n i n g out of time ..... as well as out of space to bury o u r r u b b i s h a n d discarded equipment.
John Hayes m
m
John Hayes is a consultant and freelance journalist specializing in the plastics industry.
Recycling o f m a t e r i a l s m u s t b e c o m e an important design parameter The J a n u a r y 1991 issue of the UK C o n s u m e r ' s Association p u b l i c a t i o n Which advises conservation conscious readers t h a t having milk delivered in r e t u r n a b l e one p i n t glass bottles by a m i l k m a n driving a n electric float uses less energy in total t h a n buying milk in disposable cartons. These have a total energy cost for materials, m a n u f a c ture a n d filling of 350 megajoules per carton. The c o m p a r a b l e figure for a bottle, a s s u m i n g t h a t it has a life of t e n deliveries, is said to be 142 megajoules, even t h o u g h bottles are initially more energy expensive to make a n d are also heavier to t r a n s p o r t . The significance of all this seems to be t h a t we should s t a r t looking at energy conservation a n d recycling in a b r o a d e r context, i n c l u d i n g the way in which the p r o d u c t is used, i n s t e a d of a s s u m i n g t h a t recycling p e r se m u s t be a good thing, r a t h e r like taking exercise or eating apples. The Association of Plastics Manufacturers in Europe (APME) lists 26 post c o n s u m e r recycling schemes in o p e r a t i o n in t e n E u r o p e a n n a t i o n s at present. Not surprisingly, most involve collecting food containers, domestic waste a n d packaging. Of the 26 million t o n n e s of plastics c o n s u m e d each year in Western Europe, some 8 million t o n n e s ends u p in m u n i c i p a l solid waste (MSW). Most of t h a t is either i n c i n e r a t e d or d u m p e d into landfill sites. Only a b o u t 1% of domestic plastics scrap is recovered because of c o n t a m i n a t i o n , cost of collection a n d difficulty in sorting. Recovery of w h a t are generally categorized as 'technical specification' plastics is m a i n l y restricted to p o s t - p r o d u c e r or post-converter waste where polymer c o n t e n t a n d physical p r o p e r t i e s are readily identified. But with volatile p e t r o l e u m prices a n d the p r o s p e c t of events in the Middle East rocking the feedstock supply, s h o u l d we n o t try h a r d e r to r e c o v e r h i g h e r e n e r g y v a l u e p o l y m e r s from finished products? A u t o m o b i l e s are p r i m e candidates n o t only because of the weight of plastics p e r vehicle (between 60 a n d 80 kg for small cars a n d more on some u p - m a r k e t models) b u t also because of the variety of polymers. W h e t h e r one s u p p o r t s the 'greenhouse' theory or regards it as a n o t h e r e x a m p l e of conservationist o v e r - r e a c t i o n , t h e r e is no d e n y i n g t h e p o l l u t i o n c o n t r i b u t i o n of cars a n d commercial t r a n s p o r t . One calculation e q u a t e s every litre of p e t r o l e u m fuel b u r n t with a b o u t 2.3 kg of carbon dioxide, c a r b o n monoxide, h y d r o c a r b o n s a n d o t h e r toxic n a s t i e s released to the atmosphere. Short of b a n n i n g a u t o m o b i l e s completely, a suggestion favoured by some residents of p a r k i n g m e t e r - s t r e w n , t r a f f i c - c o n g e s t e d a r e a s of o u r
REINFORCED PLASTICS FEBRUARY1991
cities, t h e s o l u t i o n w o u l d a p p e a r to lie in improving c o m b u s t i o n a n d power t r a n s m i s s i o n systems a n d reducing the dead weight of the vehicle. Polyester composite p a n e l s have reduced body weight, s h r u n k engine sizes a n d improved fuel performance on a n u m b e r of goods a n d passenger vehicles a n d the process is likely to continue. But w h a t h a p p e n s w h e n those vehicles reach the e n d of their service life? C u r r e n t car shredding practice is i n t e n d e d to c o m p a c t metal n o t to sort different plastics, m a n y of which even the experts find it difficult to identify purely by visual inspection. Recycling economics are very sensitive to the cost of collecting a n d s e p a r a t i n g wastes as the organizers of schemes to recycle polyethylene terephthalate (PET) soft drinks bottles have discovered. T h e r e are a b o u t 12 d i f f e r e n t g r o u p s of t h e r m o p l a s t i c s a n d four or five different thermosets in the bodywork, trim a n d u n d e r b o n n e t c o m p o n e n t s of most m a s s p r o d u c e d vehicles. At the top of the scale the ser~es 7 BMW is estimated to c o n t a i n a b o u t 1000 plastic c o m p o n e n t s in nearly 600 different compounds. The list l e n g t h e n s steadily for most vehicles, with appreciable growth d u r i n g the last ten years in the use of polyamides, p o l y u r e t h a n e (PUR) a n d polyesters. The weight of PUR per car now averages a b o u t 22 kg with increased p o p u l a r i t y of reaction injection m o u l d e d (RIM) b u m p e r s a n d other large body components. But PUR a n d polyesters, like other thermosets, are n o t easily recycled. There are c h e m i c a l t e c h n i q u e s which can be used to reduce t h e m to basic m o n o m e r s b u t the economics are poor. Even the so-called 'commodity' t h e r m o p l a s t i c s such as polyvinyl chloride (PVC) a n d polypropylene (PP), which together a c c o u n t for some 23 kg per average car, may n o t be a viable p r o p o s i t i o n for recovery except in easily accessible trim a n d large components. A complete r e t h i n k of design philosophy is needed, for m a j o r domestic a p p l i a n c e s as well as cars, to help disposal at the end of their service. They m u s t be easier to dis-assemble. Coding or some other m e a n s m u s t make it easy to identify the types of plastics used a n d these m u s t be selected according to suitability for recycling or for energy-recovery potential, as well as for their first use physical properties. We are r u n n i n g out of time ..... as well as out of space to bury o u r r u b b i s h a n d discarded equipment.
John Hayes m