Life-cycle assessment of four types of floor covering

0959-6526(95)00082-8

1. Cleaner Prod. Vol. 3, No. 4, pp. 201-213, 1995 Copyright 0 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0959-65269s $10.00 + 0.00

Life-cycle assessment of four types of floor covering Jose

Potting and Kornelis Blok

Department of Science, Technology and Society, Utrecht University, Padualaan 14, NL-3584 CH Utrecht, The Netherlands Received 12 September

1994; revised 27 July 1995; accepted 19 October 1995

Four types of floor covering have been investigated with respect to their environmental impact: linoleum, cushion vinyl, tufted carpet with a woollen pile and tufted carpet with a polyamide pile. The analysis relates to all stages in the life-cycle (from ‘cradle to grave’) and focuses on floor coverings for domestic use. The analysis is performed by means of the method for lifecycle assessment (Dutch approach). Each floor covering is assessed with regard to its environmental impact. This impact can be of various type: depletion of raw materials, cumulative energy requirement, global warming, acidification, tropospheric ozone creation, stratospheric ozone depletion, eutrophication, production of waste and human health. The inventory of environmental interventions (materials, energy requirements, waste and emissions to air, water and soil) was fairly complete. Most interventions relating to the processes that make up the life-cycle of the floor coverings in question could be quantified. A large part of the data is associated with the process energy requirement. In general these data are quite reliable. The results of the impact assessment for linoleum differs considerably from those for other types of floor coverings. Linoleum turns out to be the most environmentally favourable floor covering. It was not possible to differentiate between the environmental impact of cushion vinyl, tufted carpet with a woollen pile and tufted carpet with a polyamide pile. Copyright 0 1996 Elsevier Science Ltd. Keywords: life-cycle assessment; floor coverings; environment

Intruduction The annual sales of floor coverings in The Netherlands is about 65 x l@ m2. Almost 40 X 106 m2 is bought for domestic purposes. The remainder is used in buildings like offices and hospitals. Textile floor coverings or capets have by far the largest share on the Dutch consumer market. In particular tufted carpets with a polyamide pile (15 x 106 m2) and, to a lesser degree, tufted carpets with a woollen pile (4 x 106 m2) are popular. Also cushion vinyl has a considerable sale (5 x 106 m”). The share of other types of floor coverings is smalll. Little information was available about the environmental impact of the production, use and disposal of floor coverings. The aim of this article is to assess and compare the environmental impact in the entire lifecycle of the floor coverings with the largest share on the consumer market*: cushion vinyl, tufted carpet * This article is based on an earlier assessment and comparison of the environmental impact in the life-cycle of the floor coverings in question*. In this article some basic data have been improved and additional data have provided and therefore the conclusions resulting from this article are different from ref. 1

with a woollen pile and tufted carpet with a polyamide pile. Linoleum is also involved in the assessment because this floor covering is gaining in popularity at the expense of cushion vinyl. The assessment is made by means of the Dutch method for the environmental life-assessment of products2. The Dutch method is closely linked with the internationally accepted framework2s3. In this article we first describe the method and procedure followed. Thereafter we give main characteristics and environmental interventions in the life-cycle of the floor coverings in question. Next we estimate the contributions made by these environmental interventions to some important environmental problems. Then we compare the floor coverings with regard to their estimated environmental impact in order to discover the enviommentally most favourable floor covering. Thereafter we discuss the reliability of the results. The article ends with our main conclusions and recommendations. Methodology and procedure The Dutch method for the environmental life-cycle assessment of products consists of five steps2. The first

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Life-cycle assessment of floor covering: J. Potting and K. B/ok four steps and the procedure followed in each step are described below. The fifth step, the improvement analysis, is not reported in this article. Step I: Goal definition The life-cycle assessment of the floor coverings is carried out for the purpose of comparing the products with regard to their environmental impact. The analysis is restricted to floor coverings for domestic use in the current Dutch situation. The proportion of constituents of each type of floor covering varies within a certain range. Therefore in each category one typical product is defined. There are also differences in the functionality between the four types of floor coverings. The basis of equality (functional unit) is found in the function which the product has to fulfil and is defined as follows: ‘The amount of floor covering of good quality which is needed to cover one square metre of floor surface in a normal Dutch house over a period of 15 years’. Carpets in general feel warmer to the feet than do smooth floor coverings and smooth floor coverings in general are easier to clean than carpets. These differences in functionality, which are important determinants in consumers’ appreciation of a certain type of floor covering, are not incorporated in this definition of the functional unit. Step 2: Inventory analysis In the inventory the interventions relating to the processes that make up the life-cycle of a product are quantified. The life-cycle of a product consists roughly of four stages: (1) extraction and processing of raw materials, (2) product manufacture, (3) use of the product and (4) processing of the used product. Each of these stages is in the remainder of this article described in a section of its own. Each stage can be assumed to be an aggregate process which includes one or more subprocesses. Each process can be followed back (upstream) to its origins or forward (downstream) to its final end. The total of connected processes is called the product system. The product systems of the floor coverings are represented Figure I and eludicated in the remainder of this article. In Figure I the parts of the product chain that fall outside our system boundaries are indicated as pro-memory and also eludicated in the remainder of this article. The laying and cleaning of the product have been excluded from the assessment because it is impossible to generalize these aspects and because for domestic use vacuum cleaning appears to be the main method of maintenance for all floor coverings. Furthermore, only first-order (the actual processes) and second-order processes (energy production from primary energy carriers) are taken into account. Third-order processes (production of capital goods) and fourth-order processes (services) are not incorporated in the assessment.

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These environmental inputs (materials and energy) and outputs (waste and emissions to air, water and soil) of a process are referred to as interventions in the Dutch method. In a number of recent studiesM the energy requirement for the production of several materials was analysed. These data are used when possible because they are recent and reliable. The energy requirement for transport and the interventions relating to all process and transport energy requirements are calculated with help of Table I, unless there is a note to the contrary. The interventions in plastic production are mainly derived from ref. 7. These data are not so transparent, but are also recent, look reliable and are based on mass balances similar to those used for the energy analysis mentioned. The remaining interventions occurring in the life-cycle of the floor coverings in question are derived from scientific literature and interviews with producers and experts. Also ‘grey literature’ and formal requests that are covered by environmental legislation turned out to be very informative. All the environmental interventions in all processes are converted to the interventions per functional unit and represented in an aggregate table of interventions. Allocation is made on the basis of the economic value of the products. This article contains all data needed to come to the table of interventions. Only the data derived from ref. 7 are not represented because they are too comprehensive and easy to access. Step 3: Classification Environmental interventions have the potential to bring about several kinds of impact on the environment. In this study nine types of environmental impact are taken into account: depletion of raw materials, cumulative energy requirement, global warming, acidification, tropospheric ozone creation, stratospheric ozone depletion, eutrophication, human health and waste production. The contributions to depletion of raw materials (except for primary energy carriers) and stratospheric ozone depletion did turn out to be negligible. The method for estimating human health effects is of doubtful value (see Discussion section). Therefore these types of environmental impact are not mentioned in the remainder of this article. The remaining types of environmental impact are estimated as follows. The cumulative energy requirement is calculated by converting all energy requirements with the help of Table 2 to the use of primary energy carriers and then adding up the primary energy requirements. The contributions to global warming, eutrophication, acidification and tropospheric ozone creation are established by calculating the equivalent emissions with the help of Table 2. Non-hazardous waste and hazardous waste are calculated by adding together the contributions of the separate processes. Step 4: Evaluation The environmental profiles of the products have been compared in a qualitative way in order to discover

Life-cycle assessment of floor covering: J. Potting and K. B/ok

Fire

1 The production systems of linoleum, cushion vinyl, tufted carpet with a woollen pile and tufted carpet with a polyamide pile. The weights between parentheses are normalized to 1 square metre. The parts of the product chain that fall outside our system boundaries are indicated as pro-memory and elucidated in the remainder of this article. One functional unit of linoleum is 1.064 square metres, 1 functional unit of the other floor coverings is 1.995 square me&es

which

product

one. Because this step, in separate from international

is the most environmentally friendly of the inherent subjectivity involved in the Dutch approach evaluation is kept classification (in contrast with the general approach3).

Extraction and processing of raw materials Woollen yarn Wool for carpet manufacture is spun from so-called ‘carpet wool’. Sheep for carpet wool production have

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Life-cycle assessment of floor covering: J. Potting and K. Blok Table 1 The interventions in energy production and transport. The data about primary energy requirements in this table are derived from refs 56 and 57. The remaining data are all derived from the Dutch Central Bureau of Statistics (see ref.1 for references) Natural gas requirement (industry) (Nm? Primary energy requirement (MJ/unit) Carbon dioxide emission (kg/GJ) Nitrogen oxides emission (g/GJ) Sulfur dioxide emission (g/GJ) Carbon monoxide emission (g/GJ) VOC emission (g!GJ) Aerosol emission (g/GJ) Solid waste (g/GJ)

Electricity requirement (kwh)

31.65 56 W

9.3 71 135 92 3 0.5 3 77

Ga 4 -

Energy requirement in general (MJ) 1.00 59 92 ;: 13 5

Sea-going vessels

Inland shipping

On the road

(ton-km)

(ton-km)

(ton-km)

coast 0.09 Bulk 0.07 77 1230 1970 250 150 110

National 0.39 International 0.35 73 1170 79 700 70 70

3.89 73 1170 79 280 180 83

%trong variation for different industries. The nitrogen oxides emission is on the low side

Table 2 The equivalence factors used for calculating the contributions to eutrophication (NP), acidification (AP), tropospheric ozone creation (PCXP) and global warming (GWP)2 NP

AP

Hydrocarbons

PGCP

GWP,,

0.377

Carbon dioxide

1

Nitrogen oxides

0.13

Sulfur dioxide

0.70

1.00

Nitrous oxide

270

Ammonia

0.33

1.88

Aromatic hydrocarbons

0.761

Chlorinated hydrocarbons

0.021

Hydrochloric acid

0.88

Methane

0.007

Ethylene

1.080

Solvent

0.377

Aldehyde

0.443

Nitrogen

0.42

Phosphor

3.06

11

fleeces that contain longer and rougher fibres than normal. New Zealand is the main country of origin of such sheep. The growth of vegetable material, which is the main food of sheep, needs a supply of nitrogen (28.9 g/kg raw wool) and phosphoric anhydride (771.4 g/kg raw wool)*. The energy requirement for the production of fertilizers is relatively high: 41.3 UT/kg nitrogen and

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6.9 MJ/kg phosphoric anhydride4T6*. The methane emission from sheep (due mainly to enteric fermentation) is 9.62 kglyr for one sheep9. A ‘carpet’ sheep produces on average 5.5 kg wool per year. The fleece of a sheep is contaminated with wool fat, sand and vegetable material (approximately 25%). Therefore, after the sheep are shorn, the raw wool is washed in the wool laundrya. The washing of wool (including drying) requires about 6.3 MJ process energy per kg washed woollo. After washing, the waste water is strongly contaminated with organic materials and detergents and has to be purified before it is drained off into surface water. The energy requirement per kg washed wool is 0.6 MJ for purification and 0.03 MJ for transport of active slib by lorry. After slib processing 21.4 g hazardous waste remains’. After washing, the wool is carded and spun into yam. During wool spinning about 100 g of waste per kg spun wool is produced. The energy requirement for carding and spinning is negligible in comparison with washing of wool and therefore is not included into the analysis. The distance covered when the raw wool is transported from sheep farmer to wool laundry and from wool laundry to the yarn producer is taken to be 500 km by lorry and 20000 km by bulk carriers. Styrene butadiene rubber

Styrene butadiene rubber (SBR) is a synthetic rubber made by copolymerization of butadiene and styrene. The base of each compound is crude oil. The energy requirement for the production of SBR from the raw materials is derived from refs 5 and 6 and amounts to 78.0 MJ/kg (43.3 MJ/kg feedstock requirement and 34.7 UT/kg process energy requirement). Only the carbon dioxide emission that is related to the process energy requirement is calculated with the help of Table * Feedstock requirement in this analysis is determined only for materials which comnete with regular primary energy carriers for energy production. ?herefore, in-contrast with refi2 and 6, the feedstock energy requirement for the production of phosphoric anhydride is put at zero

Life-cycle assessment of floor covering: J. Potting and K. B/ok

I. The interventions in copolymerization are assumed to be small compared to the interventions in the production of styrene and butadiene from crude oil. Therefore the remaining interventions in SBR production are put on a par with the interventions in the production of styrene and butadiene. These interventions are derived from ref. 7. Polyvinyl chloride

Polyvinyl chloride (PVC) is a polymer of the monomer vinyl chloride. Vinyl chloride originates from the raw materials crude oil and salt. The energy requirement for the production of PVC from the raw materials is derived from refs 5 and 6 and amounts to 57.2 MJ/kg (20.7 MJ/ kg feedstock requirement and 36.5 MJ/kg process energy requirement). Only the carbon dioxide emission relating to the process energy requirement is calculated with the help of Table 1. The remaining interventions in PVC production are derived from ref. 7. Polypropylene fabric

Polypropylene (PP) is a polymer of the monomer propylene, one of the products of the naphtha cracker (a crude oil distillate). The energy requirement for the production of PP from the raw materials is derived from refs 5 and 6 and amounts to 64.7 MJ/kg (42.7 MJ/ kg feedstock requirement and 22.0 MJ/kg process energy requirement). Only the carbon dioxide emission relating to the process energy requirement is calculated with the help of Table I. The remaining interventions in PP production are derived from ref. 7. Extrusion is a common way for production of yarn from PP. The process electricity requirement for extrusion is 0.45 kWh/kg (refs 4 and 6). Polyamide yarn

Polyamide (PA) is a polymer that exists in two forms: PA-6 and PA-6.6 The name refers to the number of carbon atoms of the monomers used: caprolactam for PA-6, hexamethylenediamine and adipic acid for PA6.6. Both polyamides can be produced in different ways, but originate from crude oil and natural gas”. The PA is ‘spun’by passing melted polyamide through a metal tag with small holes. The filament that is formed in this way is twisted onto a spool at great speed. This is how stretched filaments are formed. The filaments are further textured and joined together to form one yarn12. PA for carpet manufacture is mainly produced in Europe 13. The interventions in PA yam production are based on PA-6. The energy requirement for producing PA yarn from the raw materials is established by ref. 14 to be 170 MJ/kg (of which 81 MJ/kg is taken as feedstock requirement and 89 MJ/kg as

process energy requirement)*. The carbon dioxide emission relating to the process energy requirement is fully calculated with the help of Table 1. The other emissions related to the process energy requirement are only partly calculated with the help of Table I: for the spinning process, polymerization of caprolactam and the production of phenol from the raw materials (the cumulated process energy requirement is 62 MJ/ kg PA-6). The remaining interventions are based on the separate processes involved in the production of PA yarn from the raw materials. The interventions in caprolactam production from phenol, an intermediate product for caprolactam production, are derived from ref. 13. Phenol can be synthesized by toluene oxidation. The interventions in isolating toluene from a mixture of aromatic compounds, one of the products of the naphtha cracker (a crude oil distillate), are derived from refs 16 and 17. The cumulated emissions to air per kg PA-6 are: 2.1 g nitrogen oxides, 0.6 g sulfur dioxide, 0.1 g hydrocarbons and 5.2 g aromatic hydrocarbons. The cumulated emissions to water per kg PA-6 are: 19 g anorganic solvents and 16 g organic solvents. The cumulated hazardous waste production per kg PA-6 is 61 g. No data were available regarding the interventions in the production of aromatic mixture from crude oil. These interventions are put on a par with the interventions in the production of polyethylene from crude oil. The aromatic mixture and ethylene are both products of the naphtha cracker and the interventions in ethylene polymerization are assumed to be small in relation to the interventions in ethylene production. The interventions in polyethylene production are derived from ref. 7. Plasticizer

A wide range of plasticizers are used to improve the elasticity of synthetic material. Of these plasticizers diethylhexylphthalate (DEHP) is the most important. DEHP is produced by esterification of phthalic acid anhydride and alcohols, both originating from crude oiP8. The energy requirement for the production of DEHP from crude oil is established as 75.3 MJ/kg (59.2 MJ/kg feedstock requirement and 16.1 MJ/kg process energy requirement)5,6*11,17,19. Only the carbon dioxide emission relating to the process energy requirement is calculated with the help of Table 1. The remaining interventions in the production of DEHP from orthoxylene and olefines, both intermediate products for the production of phthalic acid anhydride and alcohols, respectively, are derived from refs 16 and 17. Per kg DEHP the emissions to air are calculated to be: 1.0 g nitrogen oxides, 0.2 g sulfur * Because ref. 14 does not distinguish between feedstock and process energy requirement, these are estimates. The cumulative energy requirement of ref. 14 is very similar to ref. 15. Because both sources are not very recent and several energy reductions have been effected in industry, the actual energy requirement for the production of polyamide can be somewhat lower

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dioxide, 0.7 g hydrocarbons, 0.06 g aromatic hydrocarbons and 0.002 g DEHP. The emissions to water per kg DEHP are calculated to be: 0.005 g DEHP, 1.2 g organic solvents and 0.01 g cobalt; 20 g hazardous waste is produced. The remaining interventions in the production of olefines and orthoxylene from the raw materials are put on a par with those of polyethylene. The interventions in polyethylene production are derived from ref. 7. Pigments Pigments are insoluble compounds that are used to colour a wide range of products. Many colours are derived by mixing different pigments. Titanium dioxide is a particularly important pigment, because it is the basis of many colours. Therefore, the amount of pigments used is largely determined by the amount of titanium dioxide20. There are two processes for the production of titanium dioxide from the raw material ilmenite: the chloride process and the sulfide process. The interventions in titanium dioxide production are based on the chloride process and involve a considerable energy requirement (70 MJ/kg) and a considerable amount of hazardous waste (2.3 kg/kg)21,22. The information on hazardous waste is taken from a rather old source22 and is outdated, according to ref. 23. However, no data are available that are more recent. Methylethylketone In general, except for the energy requirement, the interventions in the production of solvents are negligible in comparison with the interventions in the use of these solvents24. The energy requirement for the production of methylethylketone (MEK) from crude oil is established as 96.7 MJ/kg (40.2 MJ/kg feedstock requirement and 56.5 MJ/kg process energy requirement)5,6,11. Linseed oil Linseed oil is derived from the seed of the flax plant (oil flax). The main countries for the cultivation of oil flax are Canada and Argentina. A flax plant has a low nitrogen requirement and needs only a little fertilizer (35 kg/ha nitrogen, 17 kg/ ha phosphoric anhydride and 14 kg/ha potassium monoxide)25,26. The specific energy requirement for the production of fertilizers is relatively high: 41.3 MJ/ kg nitrogen, 6.9 MJ/kg phosphoric anhydride and 1.52 MJ/kg potassium monoxide4*6. The cultivation also needs a small quantity of pesticides (0.5 kg active compound/ha) 26. Approximately 20% of this amount is emitted to air2’. The energy requirement for reaping the flax is 0.65 MJlkg linseed2*. The emissions relating to this energy requirement are calculated with the help of the emission factors for transport on the road in Table I. The yield of linseed is 0.6 ton/ha (ref. 29). In most cases the straw is left unused on the land26.

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The best quality linseed oil is extracted by pressure from the linseed: 34% of linseed oil ($5OO/ton) and 64% of linseed cake ($2OO/ton) are obtained in this way. The only interventions in linseed extraction are minor losses (2%) and a small amount of energy required: 0.54 MJlkg30. The distance covered by transporting the linseed oil from Canada to The Netherlands is taken to be 1200 km by diesel train and 4600 km by international bulk transport. The energy requirement for transport by diesel train is 0.57 MJ/ton-km (ref. 5). The emissions relating to this transport are calculated with the help of the emission factors for inland shipping in Table 1. Jute Jute fibre originates from the jute plant. The main countries for the cultivation of jute are Bangladesh and India. After reaping, the jute fibre is opened by putting the jute plant in running water. The raw fibres are spun into yarn and then woven to a fabric. The interventions in the weaving process consist of a small electricity requirement (0.08 kWh/m2) and about 14 g/ m2 waste31. Because there are no data available about the interventions in jute cultivation and opening and spinning of the jute fibre, these interventions have been omitted from the analysis. The distance covered by transporting jute from Bangladesh to The Netherlands is taken to be 20000 km by international bulk transport. Ground wood The processing of wood in the sawmill in the south of Germany leads to large amounts of residual wood (about 50%). This residual wood is used for the production of ground wood. The grinding of wood requires only a small amount of energy (3.24 MJ/ kg) 32. The residual wood has a negligible economic value compared to the main products of the sawmill and therefore the interventions in wood production are not taken into account in this analysis. Ground limestone Limestone or calcium carbonate is obtained in socalled open mines in the north of France. The energy requirement for the extraction and grinding of limestone is quite low: 0.08 MJ/kg. The extraction and grinding of limestone causes a considerable amount of dust emission (72 g/kg)‘. Ground cork The production of cork stoppers in Portugal leads to large amounts of residual cork. This residual cork is used for the production of ground cork. The grinding of cork requires only a small amount of energy (1.62 MJ/kg)32. The residual cork has a negligible economic value compared to cork stoppers and therefore the interventions in cork production are not taken into account in this analysis. The distance covered by

Life-cycle assessment of floor covering: J. Potting and K. B/ok transporting cork from Portugal to The Netherlands is taken to be 2320 km coastal trade. Glass fibre fabric A glass fibre fabric (55 g/m2) consists of 75% glass libre and 25% binding agent. Because there are no data available about the interventions in the production of coating, these interventions have been omitted from the analysis. Glass fibres for glass fibre fabric are obtained by melting a mixture of sand, limestone, soda, borium oxide and a small amount of other raw materials33. The energy requirement for raw material extraction is established at 0.4 MJ/kg glass4y6. The remaining interventions in raw material extraction are unknown and therefore these processes have been omitted from the analysis. The molten glass is ‘spun’ by passing the mixture through a metal tag with small holes. The filament formed in this way is twisted onto a spool at great speed. During twisting a coating is applied to the filament. The interventions in glass fibre production are derived from ref. 33. Per kg glass fibre the emissions to air are: 0.3 g dust, 2.2 g nitrogen oxides, 320 g carbon dioxide, 0.1 g carbon monoxide, 1.7 g sulfur dioxide, 0.01 g hydrocarbons, 0.1 g formaldehyde, 0.01 g phenol, 0.01 g dichloroethylene, 0.1 g hydrochloric acid, 0.01 g ammonia, 3.9 g diboronpentoxide, 1.4 g fluor and 0.01 g lead and zinc. The emissions to water per kg glass fibre are: 0.1 g inorganic solvents, 53 g hydrocarbons, 0.3 g fluor, 0.0002 g heavy metals and 0.01 g cobalt. The process energy requirement is 5.5 MJ/kg glass fibre. The weight of glass fibre fabric is 55 g/m2. The interventions in glass fibre weaving consist of 1.6 MJ/ m2 natural gas requirement and about 9% waste.

Product manufacture Linoleum

Linoleum consists of a very hard layer of linoleum compound on a backing cloth of jute. Linoleum for domestic use has a weight of 2300 g/m*. The linoleum compound is a mixture of linseed oil (27%), colophonium* (8%), limestone (lo%), ground wood (lo%), ground cork (10%) and pigment (5%). Linseed oil and colophonium are oxidized and then mixed with the other ingredients. This mixture is pressed with a roller onto a woven backing of jute (250 g/m*). The still very soft floor coverings are hung in big loops and dried for two or three weeks. After drying the linoleum is cut to measure and then finished with a

* NO data are available about the interventions in the production of colophonium (a resin from pine trees). Nevertheless in ref. 34 these interventions are estimated to be small (especially in relation to the interventions in the production of the other materials). Therefore these interventions have been omitted from the analysis

acrylate dispersion layer? (8 g/m’). The cutting waste is recycled into the process of linoleum manufacture25T36. The process energy requirement for linoleum manufacture is estimated at 10.6 MJ/m2 natural gas and 1.5 kWh/m2 electricity. The remaining interventions in linoleum manufacture consist only of emissions to air and are derived from refs 36 and 37: 4.6 g hydrocarbons, 2.7 g solvents and 0.7 g dust. The distance covered by transporting the materials to linoleum manufacture is 80 km national inland shipping for ground cork, colophonium and linseed oil, 660 km by lorry for ground wood (southern Germany) and 500 km by lorry for limestone (nothern France) and pigments (western Germany)38. Cushion vinyl

Cushion vinyl consists of several layers of foam vinyl on a non-woven layer of glass fibre. The average weight of cushion vinyl is 1700 g/m’ 39. The foamed layers are mixtures of polyvinyl chloride (50%), plasticizer (30%), limestone (15%), stabilizers (3%), pigments (0.3%) and some other additives. The mixture is applied as a liquid mass on the non-woven layer of glass tibre (55 g/m”) and then led through several ovens. In the meantime a design is applied (most often by deep pressure by means of a solventS). Finally the product is cut to size. The cutting waste is recycled into other products35,39. The process energy requirement for cushion vinyl manufacture is established to be 8 MJ/kg vinyl layer40. The interventions of the process energy requirement and the remaining interventions in cushion vinyl manufacture are derived from refs 35 and 39. Per square metre the emissions to air are: 0.3 g nitrogen oxides, 685 g carbon dioxide, 2.9 g carbon monoxide, 0.2 g hydrocarbons, 8.4 g solvents, 0.01 g ammonia, 0.3 g hydrochloric acid and 0.2 g dust. The hazardous waste production is 29 g/m2. The distance covered by transporting all materials to the cushion vinyl manufacture is taken to be 250 km. Tufted carpet with a polyamide pile or woollen pile

About 85% of all carpets are made by the tufting process. The tufted carpets in question have a polyamide pile (600 g/m*) or a woollen pile (950 g/m’) and further consist of 120 g/m2 polypropylene used for the backing cloth and 430 g/m* styrene butadiene rubber and 1100 g/m2 limestone used for the adhesive and the foam backing41. Manufacture of tufted carpet can be split into three

t The interventions in the production of solvents are expected to be negligible in proportion to the interventions in the use of these solventP. Therefore, and because of the small quantity used for linoleum manufacture, the interventions in the production of acrylate dispersion lacquer have been omitted from the analysis $ According to ref. 35 MEKMIBK (in a prooortion of &X0/20)is used as solvent for vinyl floor covering m&ntfacture. Because no data were available about MIKB (methylisoketone butyl) the total use of solvent is assumed to be MEK (methylethylketone)

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processes: tufting, dyeing and backing. The tufting process is in fact a sewing technique. The backing cloth is passed through a sort of multi-needle machine (the tufting machine). Each needle contains a yarn, which is pricked through the backing cloth to form a pile. In the tufting process about 1% of yarn is wasted42. In the next step the semi-finished product is dyed in a dye bath (unles the yarn was already dyed: woollen fibre is often dyed and then mixed with undyed fibres in a ratio of 3:7 before spinnings). After dyeing, the waste water is contaminated and has to be purified before it is drained off into surface water. The energy requirement per m2 polyamide carpet is 0.08 kWh electricity for purification and 0.03 MJ for transport of active slib by lorry. Furthermore, per m2 polyamide carpet 1.2 g dye stuffs are emitted to water and after slib processing 22.4 g hazardous waste remains. The energy requirement per m2 woollen carpet is 0.05 kWh electricity for purification and 0.01 MJ for transport of active slib by lorry. Furthermore, per m2 woollen carpet 0.6 g dye stuffs are emitted to water and after slib processing 12.2 g hazardous waste remainsl. When the tufts are formed, they are simply held in the backing cloth by friction. The backing of the dyed semi-finished article is coated with an adhesive in order to keep the piles in place and then a foam backing or a secondary backing (a fabric of jute or polypropylene) is applied. For the analysis a carpet with a foam backing is taken. Finally the carpet is finished by cutting off a small strip (5.5 cm of which 1.5 cm is backing cloth only) from each side and a 4 m broad carpet is the result43. The process energy requirement for carpet manufacture is 8.2 MJ/m2 natural gas and 0.5 kWh/m2 electricity44. The remaining interventions in carpet manufacture are derived from ref. 45 and consist of hazardous waste (2.6 g/m2) and emissions to air (0.1 g tetrachloroethylene, 0.06 g styrene and 0.003 g ethylene). The distance covered by transporting all materials to the carpet manufacture is taken to be 500 km.

Incineration generally results in considerable emissions to air of carbon dioxide and vapour. The carbon dioxide emissions are based on the carbon content of the materials: 3310 g/kg styrene butadiene rubber, 2340 g/kg polyamide, 3145 g/kg polypropylene, 1420 g/ kg polyvinyl chloride, 2710 g/kg diethylhexylphthalate and 440 g/kg calcium carbonate. For renewable materials the fixation of carbon dioxide during growth is equivalent to the emission of carbon dioxide by incineration of the materials. Therefore, the emission of carbon dioxide from the incineration of renewable materials is considered to be zero. Some other emissions are released to the air and a non-flammable remnant remains. These emissions are quantified by using emission factors per kg incinerated unspecified material: 0.5 g dust, 1.5 g hydrocarbons, 2.0 g carbon monoxide and 0.3 g (thermal) nitrogen oxides47,48.An additional emission of nitrogen oxides and sulfur dioxide has been established for wool and polyamide on the basis of the nitrogen content of these materials and the emission reduction in incineration: 185 g nitrogen oxides per kg polyamide and 205 g nitrogen oxides and 4 g sulfur dioxide per kg of wool48,49. In the same way the emission of hydrochloric acid has been calculated as 250 g per kg incinerated polyvinylchloride‘@. Additives, pigments and quicklime (CaO; combustion product of limestone) are considered to be non-flammable. The heat producted by incineration is used for electricity production (efficiency of 15%). In this way energy production and related emissions in a conventional energy production plant are avoided. For each floor covering the energy credit for incineration is calculated on the basis of the heat of combustion of the various materials: 18 MJ/kg polyvinylchloride, 36.6 MJ/kg diethylhexylphthalate, 28.7 MJ/kg polyamide, 44 MJlkg polypropylene, 43 MJ/kg styrene butadiene rubber15 and 15 MJ per kg unspecified organic material of natural originso.

Product use Although the technical lifetime can be longer, on average floor coverings are used for about 8 years. This period is the accepted time-of-use of carpets and cushion vinyP9@. According to ref. 38, the time-ofuse of linoleum is 15 years. After the first use floor coverings are almost always disposed of. The most important reason for throwing away the used floor covering and buying a new one seems to be a removal. When the floor coverings are laid about 6% is wasted in the cutting process. About 45% of this waste is incinerated and 55% is landfilled. The interventions in incineration are described in the following section.

The classification

Waste processing Used floor coverings are disposed of as ‘large’domestic waste. In the current Dutch situation about 60% is landfilled and 40% is incinerated.

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The environmental interventions in the life-cycle of the floor coverings in question are given in aggregate form in Table 3. The data concerning the environmental interventions are used to estimate the potential contributions of the four floor coverings to environmental impact. The results are represented in Table 4. It is necessary to make some comments with respect to these figures as there may be differences between the impact calculated in this way and the expected actual impact. Tufted carpet with a woollen pile makes a high contribution to eutrophication, global warming, tropospheric ozone creation and non-hazardous waste. Some interpretative remarks are needed here. The extremely high contribution of the woollen carpet and the contribution of linoleum to eutrophication are mainly determined by the need for fertilizer during sheep farming and cultivation of oil flax. Sheep

Life-cycle assessment of floor covering: J. Potting and K. B/ok Table 3 The environmental interventions (expressed per functional unit) in the entire life-cycle of linoleum, cushion vinyl, tufted carpet with a woollen pile and tufted carpet with a polyamide pile (PA). The (raw) material consumption is represented in the product systems in Figure 1 Linoleum

Vinyl

Wool

PA

Cumulative energy requirement (MJ)

feedstock requirement process energy requirement natural gas electricity other transport-sea transport-coasters transport-inland shipping transport-road

11.4 11.2 12.8 0.6 0.1 0.05 3.2

97.5

48.4

154.3

29.4 -10.1 83.3

16.3 -1.1 69.9 7.4

16.3 -1.2 151.0

3.3

16.0

9.0

Waste(g) non-hazardous hazardous Emission to the soil (g) nitrogen phosphor Emissions to air (g) dust carbon dioxide carbon monoxide nitrogen oxides nitrous oxide sulfur dioxide hydrocarbons solvents methane ethylene aromatic hydrocarbons DEPH styrene clorinated hydrocarbons tetrachloroethylene formaldehyde aldehyde phenol fluor hydrochloric acid ammonia mercury lead and zinc diboronpentoxide pesticides

1480 400

3420 590

2040 600

84 487

56 12

32.9 2560 4.6 8.3 3.6 7.3 2.8

2770 645

164.7 8500 15.1 213.7 0.4 24.8 22.2

38.5 9100 13.5 13.0 1.0 12.0 31.1 16.8

5060 0.005 0.06

163.4 13400 16.1 106.7 0.4 6.3 31.0

0.005 6.8

0.002 0.1

0.1

0.3

0.3

0.0002

0.0002

0.3 0.001 0.01 0.001 0.1 170.5 0.03 0.0005 0.001 0.3 0.2

Emissions to water (g) dyestuffs suspended particles inorganic soluble matter (other) organic soluble matter chlorinated org. soluble matter oil phenol fluor mercury diethylhexylphthalate cobalt heavy metals

farming takes place in New Zealand and cultivation of oil flax in Canada and Argentina, where eutrophication is not a problem. If the contribution of fertilizer is not taken into consideration, the contribution to eutrophication becomes relatively small for the woollen carpet (28 g P0,3--eq./fu) and linoleum (1 g P0,3--eq./fu).

0.1 75.7 7.0 0.03 0.6 0.01 0.04 0.000 0.006 0.01 o.OOtN2

1.1 0.002 33.0 0.2

2.4 0.002 87.1 19.9

0.4 0.004 0.001

0.8 0.02 0.002

About 75% of the contribution to tropospheric ozone creation can be attributed to the methane emission during sheep farming. Tropospheric ozone creation, the result of reactions of nitrogen oxides and volatile organic compounds (VOCs) under the influence of U.V. light, is very much influenced by

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Life-cycle assessment of floor covering: J. Potting and K. B/ok Table 4 The environmental profiles per functional unit of linoleum, cushion vinyl, tufted carpet with a woollen pile and tufted carpet with a polyamide pile (the scores for linoleum with a time-of-use of eight years are represented in parentheses) Cushion vinyl

Linoleum Cumulative energy requirement (in MJ) Feedstock requirement Process energy requirement Global warming (GWP,oo: in g carbon dioxide equivalents) Eutrophication (in g phosphate equivalents) Acidification (in g sulfur dioxide equivalents) Tropospheric ozone creation (in g ethylene equivalents) Waste (in g) Hazardous waste Non-hazardous waste

91

26ii 60 400 1500

!2%{

48

Polyamide carpet

2 170 18

64:: 1550 170 44

154 175 13 500 14 80 17

600 2000

600 3400

650 2800

9::

10 4

Woollen carpet

the amount of nitrogen monoxide in the troposphere. In thinly populated and rural areas like New Zealand, where the amount of NO (and VOCs) is very small compared with industrialized areas, tropospheric ozone creation is also expected to be very small. The POCP factors of ref. 2 do not distinguish between different background levels of NO (and VOCs). The methane emission during sheep farming also contributes considerably to the estimated global warming (80%). The contribution of methane to global warming, expressed as the amount of carbon dioxide which is expected to cause the same effect over a given time period, is strongly determinded by the time horizon chosen: GWP,,=35 carbon dioxide equivalents, GWPloo = 11 carbon dioxide equivalents and GWPSOO=4 carbon dioxide equivalents*. However, for all time horizons the contribution to global warming of the woollen carpet remains high due to the methane emission.

vinyl together make the largest contribution to nonhazardous waste and maybe also to tropospheric ozone creation. The polyamide carpet has the largest cumulative energy requirement, but the woollen carpet and cushion vinyl together have the largest contribution to acidification. In short, one cannot draw conclusions about which of these floor coverings is environmentally preferable without weighing up the various types of environmental impact, one against the other. This goes beyond the scope of this article. It is not possible to put the remaining types of floor covering in order of preference with regard to the environmental impact. The time-of-use of linoleum is estimated to be 15 years, whereas the other floor coverings are expected to have a time-of-use of 8 years. Even if the time-ofuse of linoleum is assumed to be 8 years, this has no important influence on the comparison. It is then only the contribution of linoleum to hazardous waste which becomes larger than that of the other floor coverings.

The evaluation

Discussion

The reliability of the environmental profiles is reasonable to good, which justifies the comparison of the floor coverings in question*. Linoleum makes the smallest contribution to almost all types of environmental impact. This floor covering is considered to be the most environmentally favourable one. It is more difficult to compare the remaining floor coverings. Tufted carpet with a woollen pile makes the highest contribution to eutrophication, global warming, stratospheric ozone creation and non-hazardous waste. However, as argued in the previous section some of these contributions (eutrophication, tropospheric ozone creation and non-hazardous waste) may be estimated to be much less severe than the calculated values may suggest. Taking this into account, tufted carpet with a polyamide pile and cushion

The inventory of environmental interventions in this article is fairly complete, especially in the light of the restricted availability of relevant data in the literature that is publicly available. The consulted sources are considered as reasonably to very reliable. Only for a few processes in the product systems of the floor coverings in question are no data about interventions available. For some of these processes the unknown interventions are estimated on the basis of comparable materials. This estimate is seen as reasonably reliable. With regard to some other processes (like jute culture and colophonium extraction) the interventions are unknown and have therefore been omitted from the analysis. These interventions, however, are expected to be small. The amount of hazardous waste related to titanium dioxide production is probably outdated. Unfortunately no data are available that are more recent. The interventions relating to the process energy requirement and the waste processing were calculated with the help of emission factors. Emission factors may also be very helpful for estimating the environmental interventions in landfilling. Emission factors (such as those for incineration, landfilling, energy production)

* In the report’, on which this article is based, a preference was stated for floor coverings with a woollen pile as the second-best choice from an environmental point of view. However, in that report the emission of methane due to sheep farming had not yet been taken into account. Because of that the contribution made by the woollen carpet to global warming and stratospheric ozone creation is considerably higher than in the original report

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Life-cycle assessment of floor covering: J. Potting and K. Blok need to be standardized (and regularly updated and validated) in order to improve the reliability and comparability of results of various studies. The laying and cleaning of the floor coverings have been omitted from the assessment because these aspects cannot be generalized and because for domestic use vacuum cleaning appears to be the main way of maintenance for all floor coverings. Nevertheless, it should be noted that, for example, the energy requirement for vacuum cleaning can be considerable. The energy requirement for vacuum cleaning over a period of 8 years is estimated to be 120 MJ/m* 51. This is comparable to the cumulative energy requirement for the woollen carpet and cushion vinyl. Compared with linoleum and cushion vinyl, carpets have relatively large insulating properties. The insulating properties of floor covering may lead to energy savings due to reduced heat demand during the use of the product. The energy savings for an insulated floor are estimated roughly at 4-21 MJ for linoleum and cushion vinyl and at 2242 MJ for carpets (per functional unit). Incorporation of the insulating properties of floor coverings in the assessment is expected to lead to a decrease in the net cumulative energy requirements and contributions to global warming (especially as far as the textile floor coverings are concerned). For non-insulated floors the effect is even larger. Although the comparison of the floor coverings is not expected to be largely influenced by the results, this assumption needs to be validated. This study has proved that the method for environmental life-cycle assessment is a practicable one. In spite of this, further development of the method is still very important in order to improve the transparency, uniformity and validity of environmental product assessmenP*. An improvement in the calculation of the potential environmental impact is needed most. In life-cycle assessment studies generally no attention is paid to the place where an emission is released. This lack of differentiation in the inventory may lead to unacceptable error in the impact assessment. This is especially true with regard to potential human health effects, but also holds for acidification, tropospheric ozone creation and eutrophication. An example can clarify this. According to the current methods for impact assessment a solvent emission due to product manufacture into outdoor air is calculated to lead to the same effect on human health as an equivalent solvent emission due to product use into indoor air. However, in the first case the actual effect may be negligible due to dilution. Improvement analysis of the floor coverings is not reported in this article. However, many kinds of improvements can be made in the life-cycle of each floor covering 1,53. Improvements in the product’s lifecycle with respect to the energy requirement will lead to gradual reductions in the energy requirement. Improvements with regard to emissions however may in some cases lead to a sudden, large reduction, This is nicely illustrated by the improvement that has been

made in cushion vinyl manufacture. During the time this study was being carried out an 80% decrease in volatile organic compound emission was achieved by the introduction of emission reducing measures. These kinds of improvements can have an important influence on environmental profiles. Further improvement analysis (also with respect to effectiveness, cost and technical constraints) is desirable. The environmental impact in the life-cycle of the selected floor coverings has also been assessed in an indicative ways4.55. Both authors reached the same conclusion as in this article, namely that linoleum is the most environmentally favourable floor covering. They also concluded that cushion vinyl is the most environmentally unfavourable floor covering. They based that conclusion on the fact that there are safety risks associated with the production and transport of chlorine. Risk aspects have not been considered in this study.

Conclusions and recommendations The most environmentally favourable floor covering is linoleum. Further conclusion about a sequence in environmental favourability of the remaining floor coverings are not possible. This study has proved that the method for environmental life-cycle assessment is practicable. In spite of this, the method still needs to be improved, especially with regard to impact assessment of human health, eutrophication, acidification and tropospheric ozone creation. Although improvement analysis was not one of the aims of this study, with respect to each floor covering important improvements do seem possible. Further improvement analysis (also with respect to effectiveness, cost and technical constraints) is desirable.

Acknowledgement This investigation was initiated and funded by the science shops of Utrecht University. Many people assisted with this investigation. We would like to thank everybody for their help and in particular the science shops.

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