Embed Size (px)
Citation preview
TEXTILE WASTE MANAGEMENT IN PRATO DISTRICT:
COLLECTING MODELS AND TECHNOLOGICAL OPTIONS FOR MATERIAL
RECOVERY
C. Bessi a, R. Meoni b, A. Canovai c, S. Casini d, S. Nesti e, G. Fabozzi e, R. Pagliocca f, G.
Tapparini f
a PIN S.c.r.l. Servizi didattici e scientifici per l’Università di Firenze, Piazza Giovanni
Ciardi 25 - 59100 Prato (PO), Italy, e-mail: [email protected]
b ASM S.p.A., via Paronese 104/110 – 59100 Prato (PO), Italy, e-mail: [email protected]
c REVET S.p.A., Viale America 104 - 56025 Pontedera (PI), Italy, e-mail: [email protected]
d Manifattura Maiano S.p.A., Via Maiano 207 - 50013 Capalle (FI), Italy, e-mail:
e Next Technology Tecnotessile S.r.l., Via del Gelso, 13 – 59100 Prato, Italy, e-mail:
f Programma Ambiente S.p.A. , via Paronese 104/110 – 59100 Prato (PO), Italy, e-mail:
Corresponding Author: C. Bessi, via Paronese 104/110 – 59100 Prato (PO), Italy,
Abstract
Due to the expansion of ready to wear industry in the industrial district of Prato, textile waste
management needs to implement efficient strategies to promote waste recycling.
This paper offers a series of environmental considerations on some experimental textile waste
management that have been carried out over the years in order to find an alternative to
landfill disposal, according to European Waste Framework directive (2008). Material recovery
tests were carried out through the use of synthetic and natural recycled fibers in the
production of building insulation panels. Other kind of treatments are now under evaluation:
the separation of synthetic polymers through particular hot fluids has to date developed on a
laboratory scale, waiting for the first industrial prototype. Finally SRF production test through
the use of textile waste they were carried out, in order to substitute coal in cement
production.
Keywords
Waste management, fabric waste, material recovery, textile waste
Introduction
Nowadays Prato is one of the largest Italian industrial districts and one of the most important
fabrics production site in the world. The evolution of materials technologies, together with the
progressively changing market demands led to a significant change both in industrial processes
and in the use of materials. Furthermore, new players joined the textile value chain, so since
the 90s a tailoring district, handled mainly by the Chinese community, has settled in Prato
industrial area. In this context the synthetic textile waste has become a new issue to be
addressed both from the collection and from the end of life management point of view.
There are different reasons for low recycling rate of waste textiles, that are related with the
different composition of textile goods being composed of various materials such as cotton,
wool, rayon, polyester, nylon, etc., making it difficult to separate the waste textiles. In order to
increase recycling rate of waste textiles and to reduce the final disposal waste volumes, a
recycling strategy, where the waste textiles are sorted by color have been proposed (Motoko
et al., 2013). Wang Y (2010) provides an overview on fiber and textile recycling, focusing on
carpets. Three different waste treatments have been proposed: melt processing by extrusion
that converts thermoplastic polymers into resin pellets, Dissolution/re-precipitation technique
aiming to separate the high value nylon from carpet waste and de-polymerization process
aiming to convert polymeric waste into monomers or oligomers that may be re-polymerized
into virgin-quality polymers. For all treatment, it is desirable or required to efficiently sort the
feedstock according to their composition.
At last, the energy content of the waste materials may be recovered by incineration, or
burning the waste materials. The calorific values of polymers are comparable with that of
heating oil and higher than that of coal. In this case the sorting pretreatment is not required.
Background
The Prato manufacturing district consists of 35,000 direct employees and 7,200 companies in
the sector, which produce 17 percent of Italian textile exports.
In postwar period, end of life textile management was the main driver for the development of
the textile district in Prato district, in Tuscany in central Italy: the recovery and recycling of
natural fibers has constituted the basis for the industry of yarns and fabrics.
Since 70s it takes place the full expansion of industrial activity: the emergence of the "fashion"
phenomenon on a mass level introduces an historical evolution on the clothing market (and
not only) with an increasingly request for differentiated, unstable and seasonal garments. In
recent years a fundamental asset change occurs: from wool-textile district (product oriented)
to fashion textile district (market-oriented).
Synthetic fibers were developed mainly to supply the high demand for textile products. Rayon
and Nylon were the first ones to be developed and commercialized. Nowadays, textile fabrics
are manufactured from a unique type of fiber or from a combination of several fibers, natural
or synthetic, providing a huge variety of final products (Laredo dos Reis et al. 2009).
Quality and quantity of textile waste
As per other solid disposed material (i.e.), textiles waste can be distinguished between
industrial waste and consumer waste. Industrial waste arises either during the processing of
fibres or during the production of textiles and can be easily recycled. On the contrary,
consumer waste comes from the disposal of used garments and its reuse is more difficult since
it commonly consists of unknown fibre mixtures and often contains non-fibrous materials such
as buttons, buckles or other metal parts (Bartl et al. 2005).
Official data sources on waste management show a major disparity in the textile waste
production at national and local level: collected textile waste per capita per year is about 2.0
kg on a national basis; the value grows on a regional basis up to 3.3 kg and up to 14.4 kg at
Prato textile district (ISPRA, 2015), showing that textile manufacturing is strongly affecting the
composition of waste.
The textile industry in Prato municipality produces approximately 20,000 t per year of cuttings
and scraps. Nowadays, only 5,000 t per year is collected as a separated stream by the waste
management company and the study has been focused on that stream.
The remaining part is in the best case handled through private companies, but for the most
part is subject to illegal disposal or disposed together with unsorted urban waste: recent
analyzes have shown textile content within the unsorted waste up to 65% in industrial areas
(table 1).
Textile waste quality in Prato district (this parameter affects the recycling efficiency) is mainly
related with:
1. Waste composition: even if textile waste comes from industrial dedicated collection,
the contamination due to other materials has to be considered. In fact, it is common to
find situations, specially in Chinese community, where people lives within the
factories, so food waste or other urban waste can be found in textile scrap containers.
Besides, paper is used as carrier for garments tailoring. Normally the typical
composition of industrial textile waste is 80% textile, 15% plastic and paper, 5% other
waste.
2. Fiber composition: large variety of fibers present in textile waste is limiting textile
waste recycling: fibrous waste is composed by 30% nylon, 30% viscose, 30% polyester,
5-10% elastane, 5-10% according to Next Technology Tecnotessile estimations.
3. Net calorific value: Laboratory analysis on Prato textile wastes have established a
mean NCV value of 22,300 kJ/kg.
Table 1. Municipal unsorted waste composition in Prato district (Bessi et al., 2015).
Curbside collection system [%]
Public collection points [%]
Industrial areas collection [%]
Glass 1.75 3.40 0.63
Inert 3.41 1.21 0.08
Paper and cardboard 21.38 16.24 13.48
Kitchen and garden waste 17.01 29.10 4.79
Plastic 23.99 14.95 5.14
Textiles 8.00 17.51 69.32
Nappies 10.24 5.69 -
Metals 2.16 2.60 2.54
Wood 0.29 0.76 2.04
Other 7.44 5.36 0.04
< 10 mm 4.33 3.17 1.92
Collection
Currently, textile scrap disposal problem is one of the main challenges for Prato Textile district.
Often tailoring cuttings and other textile scraps are not even disposed but are abandoned on
fields or streets or in other hidden places (see figure 1).
Gradual transition to the curbside collection mode has been implemented to changing this
habit. It allows to remove road containers in order to reduce industrial waste disposal in the
urban collection system. Furthermore, a new textile collection dedicated system is being
promoted, trying to involve industrial activities in the proper waste management.
Figure 1: tailoring cuttings and other textile scraps sometimes are not correctly disposed but
are abandoned on fields or streets or in other hidden places.
Material and methods
Typically, recycling technologies are divided into primary, secondary, tertiary, and quaternary
approaches. Primary approaches involve recycling a product into its original form. Secondary
recycling involves processing a used product into a new type of product that has a different
level of physical and/or chemical properties. Tertiary recycling involves processes, such as
pyrolysis and hydrolysis, which convert the waste into basic chemicals or fuels. Quaternary
recycling refers to waste-to-energy conversion through incineration. All four approaches exist
for textile, plastic, and paper recycling (Laredo dos Reis et al. 2009).
In order to identify the best management solution both from the environmental and from the
economic point of view, these different approaches are being investigated. In particular, four
options have been considered for each approach:
1. primary approach: experimentation for plastic polymers recovery;
2. secondary approach: experimentation for the production of manufactured articles for
eco-building;
3. tertiary approach: experimentation for syngas / char / tar production in pyrolytic
systems. This treatment option is not included in this study since any kind of test is not
carried out yet;
4. quaternary approach: experimentation for the replacement of fossil fuels in cement
plant.
In this first phase of the investigation, processes are briefly described, then a preliminary
environmental comparison between the four recycling approaches has been carried out, since
some data are still pending in order to assess a complete LCA study.
Environmental and process performance information are organized according to the generic
input / output formulation (see figure 2), without considering technology peculiarities. Some
of them are patented technologies, so it is currently not granted a full disclosure.
Figure 2: Environmental balance generic scheme. The environmental parameters (air, water,
energy) are considered both for the investigated process and for the pre-treatments required.
Polymeric separation (primary recycling approach)
A patented system for the recycling of textile scraps is under investigation. A pilot plant is
under construction and its results will influence further decisions on waste management.
The technological process allows, thanks to a non-invasive process, to separate the
thermoplastic fibers from the natural ones. In other words, from any fabric with any fibrous
composition, it is possible to separate polyester, nylon and elastomers from the natural or
artificial fibers such as wool, cotton, viscose, hemp, etc.
The advantage of this new technology consists in the fact that the thermoplastic materials are
recovered and transformed directly into 100% pure powders or granules, which can in turn be
reused in industrial processes of plastic molding. The remaining natural and artificial fibers
instead, still in the form of the original fabric, can be opened and reused in the processes of
traditional textile spinning and the production of nonwovens.
The process is implemented through machinery and systems comparable to industrial washing
plant, for the part relating with fiber material separation.
The process takes advantage of some of the characteristics of the fluids being used which
allow to operate at temperatures of fusion of the thermoplastic polymers: fluids don’t
chemically dissolve the polymer but are only a media to bring them to their melting point. The
process is performed at a specific temperature in order to melt he various types of polymers in
a selective way without any alteration of the material structure and without the formation of
fluid/polymer mixtures.
Production of building insulation panels (secondary recycling approach)
A local company has produced a heat-insulating and sound-absorbing panel from recycled
textile fibers, sterilized at 180°C and processed without the use of water and chemicals. The
proximity between textile wastes production and Panel Production involves environmental
benefit, already studied by the manufacturer in their own carbon footprint studies (Iraldo et
al., 2014).
The process begins with fraying, a mechanical operation type realized by electricity -powered
machines that turns the fabric scraps in suitable fibers to be process in further steps. The
second step is mixing. The different fibers must be mixed to avoid the presence of non-
uniformities in the finished product. In this phase some products (for example, mothproof
products or fire retardants) can be added. In the end, the last step is panel production: this
phase includes several steps in succession such as compaction, carding, thermo-bonding and
cutting.
Figure 3: building insulation panels production steps. Sorted textile cuttings, frayed material,
finished product ready for construction industry.
SRF Production (quaternary recycling approach)
According to new regulations on waste preparation for combustion, the waste management
company in Prato performs some tests on waste mechanical treatment flows to verify it can be
classified as Solid Recovered Fuels (SRF) and thus used for energy production in cement
industry. High quality textile wastes could be exploited as fuels for non-dedicated facilities,
such as cement plants or power plant, in substitution of coal (Bessi et al., 2015). Considering its
high NCV value, some refining treatment on this waste stream has been performed in order to
meet cement plant burning system requirements: in fact, particle size is the most limiting
factor for textile SRF production, as the waste is highly resistant to the shredding mechanical
action. Its pre-treatment with cutting machines showed that SRF quality increased, even if SRF
production per hour is lower than expected.
Figure 4: SRF from textile waste. In order to meet cement plant burning system requirements,
high refining process is necessary.
Results and discussion
A preliminary evaluation of the input/output related with some of the recycling strategies
described above (Insulation panel and SRF) has been carried out, including all the production
steps since waste sorting.
In Table 2 and Table 3, input and output data for waste management and material re-
processing have been listed. Environmental resources, such as water and energy, demands for
polymer separation process is higher than re-processing. In fact, it is a wet process that
required large amount of water an energy (referring to 1 kilogram of final product, water: 1.17
m3*kg-1, energy: 3.20 MJ*kg-1, chemicals: 0.11 kg*kg-1).
Panels production is showing the highest energy consumption value (9.81 MJ*kg-1 of final
product), since recycled material value chains mainly involve electricity powered processes.
On the contrary, SRF production process requires the lowest energy per unit of product.
Moreover, not being necessary the pre-selection of the material, is also the process that
creates less residual waste.
Table 2: Environmental input-output process balance per 1,000 kilograms of textile waste.
Polymeric separation
building insulation panels
SRF
PRETREATMENT
(Manual sorting) (Manual sorting)
INPUT kg 1,000 1,000 -
Energy demand MJ - - -
Water demand m3 - - -
Chemical demand kg - - -
Discard kg 200 200 -
PROCESS
INPUT kg 800 800 1,000
Energy demand MJ 875.5 7,851 144
Water demand m3 2,400 - -
Chemical demand kg 80 - -
OUTPUT
Product kg 750.4 800 900
Discard kg 49.6 - 100
Wastewater m3 2,480 - -
Table 3: Environmental input-output process balance per kilogram of product.
Polymeric separation
building insulation panels
SRF
Energy demand MJ*kg-1 1.17 9.81 0.16
Water demand m3*kg-1 3.20 - -
Chemical demand kg*kg-1 0.11 - -
Residual Waste kg*kg-1 0.33 0.25 0.11
Further studies will be carried out considering environmental concern/benefits related with
the different proposed approaches.
Conclusion
Waste disposal requires constant creation of new landfill spaces, which is in contradiction to
the environmental goals, including ecosystem protection. Significant effort has been devoted
to the reduction, reuse, and recycling of the waste materials.
In particular synthetic fibre residues create a substantial concern regarding a sustainable
recycling strategy. Today this material is disposed through landfill only as the calorific value is
too high for waste incineration. Landfill disposal is also problematic as the capacities are
declining and costs are rising. In contrast natural fibre would provide more options for material
recycling if collected separately which is a future objective.
In view of this, waste management company of Prato is looking for new technologies that offer
a pathway towards the sustainable recycling of synthetic fibre residue from the local garment
industry.
Experience in material recovery through the use of textile waste in the production of insulation
materials for construction industry have already been carried out. Despite the encouraging
results, due to the excellent characteristics of the panel which performance is completely
comparable to classic insulating materials, however the housing crisis together with the limited
knowledge of builders did not yet allow a stable production.
Other treatment trials are undergoing. A first process consists in the separation of synthetic
polymers through particular patented fluids that allow to operate to the melting temperatures
of the individual polymers. This process has to date developed on a laboratory scale, waiting
for the first industrial prototype.
Direct environmental performances relating to such processes are very different: energy and
water requirements are substantial, in addition a considerable effort in manual pre-sorting
operations, which should be influential during the economic feasibility assessments.
A second technology option consists of energy recovery through fossil fuels replacement in
industrial facilities. In particular textile, thanks to the high NCV, can be used for SFR production
for cement plants. Partial replacement of non-renewable energy in combustion process for
clinker production produces a positive energy balance. Though required specifications in terms
of size and moist content has to be guaranteed.
The present study was prepared at an early stage of recovery technologies experimentation.
Further experiments will provide data for the next life cycle assessment studies.
References
Bartl A, Hackl A, Mihalyi B, Wistuba M, Marini I (2005): Recycling of fibre materials. Process
Safety and Environmental Protection, 83(b4): 351–358
Bessi C, Lombardi L, Meoni R, Canovai A, Corti A (2015) Solid recovered fuel: An experiment
on classification and potential applications. Waste Management vol. 47 part B, 184-194
Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on
waste and repealing certain directives.
Iraldo F, Fontanelli A, Nucci B (2014) Studio LCA (Life cycle assessment) di pannelli isolanti per
edilizia prodotti da Manifattura Maiano SpA.
ISPRA (2015), Rapporto Rifiuti Urbani, edizione 2015. Rapporti n. 230/2015
Laredo dos Reis JM (2009): Effect of Textile Waste on the Mechanical Properties of Polymer
Concrete. Materials Research, Vol. 12, No. 1, 63-67, 2009
Motoko U, Teruo K, Ttsuya S (2013). Study on recycling system of waste textiles based on
colour. Journal of Textile Engineering (2013), Vol. 59, No. 6, 159 - 164
Next Tecnologies, Dell’Orco e Villani. Innovative patented system for the recycling of textile
scraps
Wang Y (2010) Fiber and Textile Waste Utilization. Waste Biomass Valor (2010) 1:135–143
