Summary

It is essential to reduce the environmental impact of railway, to make the railways more environmentally conscious. LCA, Life Cycle Assessment, was advocated as a tool to measure the environmental damage inflicted by industries, but it has not been established. We attempt to apply this method positively to railway area in identifying the relevant issues and problems. Sleepers, trolley wire and rolling stocks have been chosen for case study objects. Because of imperfection in basic and equitable data on the objects for manufacturing, it cannot be concluded but it is thought that long life time and waste disposition of trolley wire and sleepers are important. Sound-absorbing materials recycled as residue of burned waste, the ballast mat and slab mat made of recycled rubber from used tire are notable examples of which railway parts made of recycled materials in Japan. At this moment, it is obvious that the materials for railways must be harmless, easy to recycle, long-life and lightweight. To boost the effect of reducing the environmental impact of railway, not only material improvement, but also systematic designing is vitally important.

Key Words : Environment, Material, Railway, Recycle

1.Introduction

As the global environmental issues become serious, it becomes necessary to reduce the environmental impact of railway, which is smaller than those of other transportation systems, to make the railways more environmentally conscious, which means that in the field of materials or ecological materials, their impacts must be considered they have small impacts on the environments. They can be more finely classified as follows; (1) recyclable material, (2) recycled material, (3) biodegradation material, (4) very long life material, (5) material replacing toxic material and non-reclaimable material, (6) high natural affinity material such as wood and apatite, and (7) material made from renewable resource.

2.Environmental Impact of Railway in Japan

Energy consumption by transportation sector accounts for 23% in total Japanese energy consumption in 1990. Out of this 80 million kl in oil is about 70% greater than that of 1973, which marks the first oil shock. After this, energy consumption by industrial sector remains on almost the same level, but those by transportation and private sector have been increasing. Fig.1 shows energy consumption of each sector in Japan of 1973 and 1990, as converted to oil. The CO₂ emission of transportation sector is 22.5%, almost the same as the share of energy consumption, in 1989. Industrial sector accounts for 49.8% and private sector for 27.6%.

The shares of transportation system, aviation, shipping, railway and car, in energy consumption and transportation mass are shown in Fig.2. It is clear that the energy efficiency in railway transport is better than those of others. So it is important that the railway plays an appropriate role in transportation sector. If the share of railway transport increases, the energy consumption and CO₂ emission of transportation sector will reduce and further total volumes in Japan will also reduce.

Another serious and urgent environmental problem in Japan is disposition of industrial solid waste. In Japan, total mass of industrial solid waste per year amounts to about 400 million tons in 1990. The biggest waste is sludge. Table 1 shows mass of waste from several principal manufactured goods. The scrap weight of rolling stocks per year may be about 1/100 of scrapped cars. Total mass of waste from railway, including construction and maintenance of tracks and so on, is much greater than scrapped rolling stocks. The final disposal sites are very few in Japan, so it is very important to reduce the mass of disposition and to promote recycling.

3.Materials used in Japanese Railway and their Environmental Impact

Railway is composed of many kinds of parts and components, such as station, rolling stock, rail, bridge etc. and the serving conditions and required performances are very diverse. They are divided into two major groups of the wayside installations and the rolling stocks. The former is represented by railway track, structure, electric equipment etc. These are long and big, and their total life times amount to 50 to 100 years. They are maintained at each place. The latter, rolling stocks’ life expectancies are 20 to 40 years and they are maintained in the workshops.

We are trying to study Life Cycle Assessment (LCA) to know the environmental impacts of railway sector. As the case study objects, sleepers, trolley wires and rolling stocks are being inspected. The study results of rolling stocks are introduced as the other presentation in this congress [1.T.Nagatomo, T.Miyauchi, H.Tsuchiya,1997].

Sleepers are used in large amounts and they are made of PC concrete , wood, composite or iron. These are used to fit each characteristics, for example composite and wooden sleepers are used on steel bridges because of their sound-absorbing capabilities. From a view point of environmental impact, PC concrete sleeper mainly used in Japan because of its low cost and long life time, and its problem is how to dispose the waste sleepers. Wooden sleeper is mainly made of southern wood but it does not rely on the same sort of trees. Some trees are easier to cultivate and to convert into money, after cutting, but they are not sustainable resources. Composite sleeper is estimated to have very long life time, but the way of its waste disposal is not established yet.

Trolley wire has been made of copper, and it is easily recycled, but in recent years composite wires, which have high tension and are good for high speed train operation, have been developed and come into practical use. They are CS trolley and TA trolley. CS trolley is composed of steel core wire and copper wire. TA trolley is composed of steel core belt and aluminum wire. Steel core is employed to improve the strength of trolley wire. To recycle those composite wires, we must separate steel core from copper or aluminum on extra work.

Because of imperfection in basic and equitable data on the objects for manufacturing, it cannot be concluded but it is thought that long life time and waste disposition of trolley wire and sleepers are important.

In the case of rolling stocks, there is a tendency to increase use of plastic materials for weight reduction. For example, about 1 ton of plastics is consumed in new type commuter train. It will be necessary to evaluate total environmental impacts. The merit of lightening is reduction of energy consumption and the demerit is treatment of waste plastics.

The rolling stocks which have aluminum alloy body, have been increasing for weight reduction. For the sake of making it easy to recycle aluminum body, it is necessary to standardizing the grade of aluminum alloy, although it may slightly increase the weight.

4.Basic Concept of Recycle and Reuse in Railway

Basic concept of recycle and reuse in railway is to reduce the amount of raw materials and wastes. For example, in case of developing a new product, it is demanded to try to use recycled or reused raw materials, especially which come from railway system. It must be considered that new products in railway, whose raw materials are materials originally used in railway. In addition, in railway services, there are lots of wastes generated from passengers, such as lunch boxes, bottles, magazines and so on. Regarding to these wastes, recycle and reuse must be promoted within railway system (Fig.3). Some examples are given as follows.

4.1 Railway Crossing Plate Made of Recycled Polymer Materials [2. N.Aihara, M.Suzuki, N.Mifune, T.Sakamoto, Y.Hashimoto,1996 ]

Recycled Polymer Crossing Plate (RPCP) is made of recycled polyethylene, which comes from electric branch wire protector(Fig.4), pipe guard in civil engineering, cable cover and so on. These materials are made of almost pure polyethylene(PE). In the first step, abolished materials are crushed into small particles. These small particles are purified by means of the specific gravity method. Then pure small particles are put into a metal mold and shaped by heat and pressure. Because of its light weight and elasticity of RPCP, installation and handling of RPCP is easier and faster than that of stone or concrete crossing plates. Moreover RPCP is easy to cut and bore holes therein in order to fit into crossing. RPCP has great durability against ice-water degradation, because of its elasticity and electric non-conductance. In addition, noise and vibration reduction performances are also expected. Installations of RPCP are illustrated in Fig.5.

4.2 Environmentally Ecological Noise Absorber (EENA)[3, M. Hansaka, K. Kubomura, K. Ando, N. Mifune, K. Kudo,1996]

Hard residue particles are generated from municipal solid waste. They are crushed into 2~5 mm in diameter. Hard residue particles in such sizes are named Environmentally Ecological Noise Absorber(EENA). EENA mostly consists of crushed pottery and glass (Fig.6). Metals, such as steel and copper, salinity and other impurities are removed in production process. EENA is recommended for use as noise absorber in railway track. Noise reduction properties of EENA are shown in Fig.7. At almost all frequencies from 250 to 4000Hz, acoustic absorptivity of EENA in 100 mm thickness is superior to that of 400 mm thickness of ballast (crushed stone). Fig.8 shows the installation of EENA packed in fiber bags.

4.3 Ballast Mat and Slab Mat

Ballast Mat and Slab Mat are used as vibration and impact isolators on ballast track and slab track. Raw materials of Ballast Mat and Slab Mat come from rubber tires of automobiles.

5.Concluding Remarks

At this moment, it is obvious that the materials for railways must be harmless, easy to recycle, long-life and lightweight. To boost the effect of reducing the environmental impact of railway, not only material improvement, but also systematic redesigning of components and systems is vitally important.

[1]T. Nagatomo, T. Miyauchi and H. Tsuchiya : Preliminary Investigation for Life Cycle Assessment (LCA) of Shinkansen Vehicles, WCRR’97,(1997)

[2]N. Aihara, M. Suzuki, N. Mifune, T. Sakamoto and Y. Hashimoto,: 7th ISWA Int. National Congr. And Exhib.,II-166,(1996)

[3]M. Hansaka, K. Kubomura, K. Ando, N. Mifune and K. Kudo : 7th ISWA Int. National Congr. And Exhib.,II-170,(1996)