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Journal Article•DOI•

A through-life evaluation of end-of-life rolling stocks considering asset recycling, energy recovering, and financial benefit

Sakdirat Kaewunruen1, Panrawee Rungskunroch1, De’Von Jennings2•
University of Birmingham1, University of California, Irvine2
01 Mar 2019-Journal of Cleaner Production (Elsevier)-Vol. 212, pp 1008-1024
TL;DR: Analysis of compositions, materials, and the percentage of value adopted from the end-of-life rolling stocks found that those rates relate to the main components on rolling stock, which contained diversely characteristic to be reusable, recyclable or recoverable materials.
About: This article is published in Journal of Cleaner Production.The article was published on 2019-03-01 and is currently open access. It has received 21 citations till now.

Summary (5 min read)

Jump to: [1.1. Introduction] – [1.2. Objectives] – [2. Recycling and recovering process on end-of-life rolling stock] – [2.1. Recycling Process] – [2.2. Recovering Process] – [2.3 Main Components] – [2.3.1. Steel] – [2.3.2. Plastic (Polymers)] – [2.3.2. Glass] – [3.1 Methodology] – [3.2. Materials] – [3.3.1. Freight Trains] – [3.3.2. Passenger Trains] – [3.3.3. High-Speed Rail (HSR)] – [3.4 Future development on train compositions] – [4.1. Recyclability and Recoverability Rate of Rolling Stock] – [4.2. Net Present Value of Rolling Stock] – [4.4. The sensitivity analysis of MRF and ERF rates] – [Freight train] and [5. Conclusion]

1.1. Introduction

  • Global warming is the larger issue that needs to be corporate achieved by many countries around the world.
  • Manufacturing was reported as the largest producer of pollutant emission; for example, Great Britain has 16 of the 100 top polluting plants, showing a high damage cost from air pollution.
  • For human activities, which mostly include transportation, there are 700 million vehicles that are currently in use around the world and this number is predicted to increase to two billion vehicles by 2050 (Del Pero et al., 2015) .
  • As mentioned, human activities on transportation produce carbon dioxide into the atmosphere.
  • It has been claimed that the end-of-life of a single cargo railcar produces waste equal to 16-20 passenger vehicles, and passenger railcars generated waste equivalent to 48-57 passenger vehicles (Merkisz et al., 2014).

1.2. Objectives

  • There are four primary objectives of this paper.
  • The first is to break down and compare some raw materials that could be recycled, reused or should be properly managed such as disposal, landfill and incineration.
  • The second is to investigate the application of the raw materials in transportation construction.
  • The third is to identify a method of calculations for the net present value (NPV) of rolling stock materials.
  • It encourages reader genuinely understand the composing raw materials and the way to manage them after the end-of-life stage.

2. Recycling and recovering process on end-of-life rolling stock

  • With respect to the regulation the road vehicles-recyclability and recoverability calculation method document or ISO22628:2002 document, it provides the recyclability and recoverability rates to be an international standard.
  • Also, it includes re-use and recycling stages on the materials to be usable parts; in other words, the recyclability rate measures the fraction of total waste recycled and total wastes.
  • Network Rail (2017) mentioned that there are wide ranges of recycled rail parts and rail infrastructure such as panlock, fishplate, pad, screw, and insulators.
  • With respect to the reuse stage on rolling stock, some parts of end-of-life rolling stock can be reused rather than replaced; therefore, the reuse stage should be firstly concerned for reducing the end-of-life rolling stock wastes.
  • The apparently benefit of thermal energy recovery relates to reduce the CO 2 and various greenhouse gas emissions (Zhang, Worrell and Crijns-Graus, 2015) .

2.1. Recycling Process

  • Recycling is a process of treating or changing waste material into usable materials (Eurostats mullmagazine, 2008) .
  • The recycling process aims at increasing the quality and value of recycled products for decreasing the impact on the environment (Ravi, 2012) .
  • The benefit of the new design was not only the cost but also the reduction on environment impacts (Giorgetti et al., 2016) .
  • Regarding to measure the benefits and costs of waste management, the life cycle assessment (LCA) methodology is properly applied for evaluation (Craighill and Powell, 1996) .
  • There was many sources mentioned on the recyclability rate (R cyc ) and recoverability rate (R cov ).

2.2. Recovering Process

  • Recovering is a process that turns materials back into what they were originally intended to be and/or into new purposes.
  • Waste recovering process aims at the utilization of waste thermal energy (Haddad et al., 2014) .
  • In the facts that, the wastes in the landfill were banned in some countries, i.e., Switzerland, Germany, Norway, Belgium, Sweden, and Denmark caused by the recovery rate was higher than other countries due to the wastes were directly sent to the recovery process.
  • In case of recovering on the end-of-life rolling stock, the wastes that mainly composed of elastomers and polymers (i.e. table, seat) will produce high recoverability rate, which will be mentioned on the material part.
  • Normally, the shredded materials can be classified in two types by using the magnetic properties as shredder heavy fraction or SHF (steel, iron, copper) and shredder light fraction or SLF (plastic, fibre, glass) (Delogu et al., 2017) .

2.3 Main Components

  • An intense analysis of the main components on the rolling stock has been focused on three materials; steel, plastic , and glass.
  • It relates with the study of Del Pero et al. (2015) that shows the material compositions on the metro train.
  • Besides, the collected data represent a component of three type rolling stock and type of material, which mainly composed of steel, mixed aluminium and steel, aluminium, and glass.
  • Hence, the recycling and recovering process of metals, plastics, and glass are analysed below.

2.3.1. Steel

  • The steel industries figured out an effective method to produce steel by using less energy and new materials more than 50 years ago.
  • Steel is well known for having an up to 100% recyclable rate for making new steel products.
  • If steel does not significantly lose its properties, it can be recycled over and over again (Kaewunruen, 2016) .

2.3.2. Plastic (Polymers)

  • Most plastics take thousands of years to degrade and also release chemicals into the atmosphere.
  • Regarding with the recovered and recycled wastes, the reports showed that an approximately 9.9 million tonnes of plastic wastes turned to be energy for manufacturing, household, and other purposes.
  • The main issue is the thermoset plastic can't be remoulded due to it contains long fibres that refer to advanced recycling processes such as thermal processes or mechanical recycling.
  • Therefore, the proper method on the plastic recycling process of the end-of-life rolling stock becomes significant in a role.
  • The second stage consists in downgrading the plastic into a product that uses lower property that a product from the primary stage.

2.3.2. Glass

  • Glass is a reusable material and, used glass can be broken down into cullet and mixed with sand, soda, and limestone before it is sent to the production process.
  • The raw materials require less than 10% of the all the energy obtained in glass production process (Kaewunruen, 2016) and the amount of CO 2 saved from the process is higher than the carbon dioxide emissions from the transportation of it in the process.
  • Also, one advantage of glass recycling processes is represented by the association of the European rail industry , which shows in the MRF rate is 66.7% and ERF rate is 33.3%, without any waste (, 2013).
  • In contrast, other sources have claimed that glass cannot be reused for any sources of energy; for example, many glass materials, such as windows, are made with fibre reinforced composites, which are difficult to make reusable (Sommerhuber, 2015; Guo et al., 2018) .

3.1 Methodology

  • The end-of-life rolling stocks cause large volume of wastes in the landfill not only in European countries but also countries around the world.
  • There are various methods used to calculate the lifecycle performance.

3.2. Materials

  • The hazardous elements need to be separated out first before transferring to further stages.
  • First, the specific information (e.g. materials and components of rolling stocks) needs to be listed.
  • As shown in table 1, the results of MRF (%) and ERF (%) of each material identify generic values between the recycling or recovery processes; for instance, metal has an MRF rate of 94%, which means it is proper to apply the R cyc rather than R cov .
  • Nevertheless, there are slight differences between practical and theoretical results; for example, safety glass and glass show a 100% residue rate from based on a few sources, such as Lawrence (2003) , ISO TC-267 (2015) , and Silva and Kaewunruen (2016) stated that they could be recycled up to 100% (Silva and Kaewunruen, 2016) .
  • Finally, the remaining materials or parts are directly forwarded to the shredding process, which is separation and recovery stage of metal materials and small parts.

3.3.1. Freight Trains

  • Freight trains usually transport materials and goods and they are much more economically efficient when transporting goods in bulk over long distances compared to transporting freight on the road.
  • By carrying the optimal volume of goods over long distances, the freight trains are competitive than other transportation.
  • Calculating the R cyc and R cov of the rolling stocks, the equations 1 and 2 are applied respectively.
  • Various important factors like m and m [S].

3.3.2. Passenger Trains

  • The recycling process of passenger rolling stock is more complicated than for freight rolling stock because not only are the structures of commuter trains composed of various materials, but their structures are also separated into multiple units.
  • Passenger trains contain self-powered railcars or locomotives and trailers or coaches (Kaewunruen, 2016; Lee et al., 2010) .
  • The composite material such as lightweight alloys applied on car body aiming to reduce the GHG emission (Rezaei et al, 2007) .
  • The report also found that the global CFRP market was expected to increase over 35% as its benefits on the environment.
  • In fact, the majority component of the rolling stock is made out of aluminium, but its dimension and shape at the end-of-life are incompatible with the recycling process.

3.3.3. High-Speed Rail (HSR)

  • HSR is designed to support high velocities above 250 km/h and, it is operated on specific tracks.
  • Normally, HSR is the most efficient rolling stocks type for supporting customers' requirements regarding increasing conveniences, saving travel time, and enabling new areas when the distance for a trip is in the range of 300 to 1,000 km (Kojima and et al., 2017; MLIT, 2017) .
  • As they are supporting high velocities, mostly components of HSR are made with lighter materials such as silicon carbine and polypropylene for minimizing drag forces as can be seen in Fig. 6 .
  • The HSR's car body is made out of mixed aluminum and steel rather than pure steel as the freight train's car body as can be seen in Table 7 .

3.4 Future development on train compositions

  • As follow various aspects to enhance the railway system, to changing on material composition and adding innovations has been interested.
  • Cost and energy saving, lightweight, high stress, and high modulus were essential key ideas to replace new materials.
  • Reducing body weight, high strength, corrosion resistance and vibration resistance are strong points making CFRP over steel and aluminium.
  • Also, the study on the replacement of CFRP in rail car body in Korean Tilting Train express (TTX), which found that the energy cost was reduced as a reduction in rail carriage weight (Castella et al., 2009) .
  • Therefore, the pyrolysis method, which is one of a thermal treatment process, is highly suggested to apply to the CFRP recycling process for splitting carbon fibre out of the waste (Das, 2011; Khalil, 2017) .

4.1. Recyclability and Recoverability Rate of Rolling Stock

  • This research has analysed in depth the recyclability rate (R cyc ) and recoverability rates (R cov ) of three types of rolling stock (freight, passenger, HSR) based on calculations related to their components, via equations 1 and 2.
  • In contrast, the calculation of the recovery rate of batteries was 98%, whereas the industry data claims that they are 50-70% recoverable (Silva and Kaewunruen, 2017) .
  • The reason is that batteries could be recharged and mostly reused if they are in excellent condition.
  • The recyclability rate was only 61.4% due to some parts of the HSR were made out of composite materials and other lightweight materials, which were not properly recycled as heavy scrap materials.

4.2. Net Present Value of Rolling Stock

  • The rolling stocks become crucial assets for railway organisation, which take the majority cost of investment.
  • This study needs to evaluate the value of rolling stock along its lifetime during operation until the end-of-life time.
  • Besides, a discount rate parameter is used to evaluate the costs and benefits over the period.
  • Likewise, the result of HSR shows the R cyc and R cov rates at 61.4% and 73.9% respectively conforming to the mainly components as steels, which shows the MRF values at 94%.

4.4. The sensitivity analysis of MRF and ERF rates

  • As mentioned in section 4.3, the MRF and ERF rates are fundamental factors that directly effect on the R cov and R cyc values.
  • In the fact that, the MRF and ERF values can be differ depend on the potential of manufacture's recycle and recovery processes.
  • The benefit of this section is to indicate the result of sensitivity analysis, which provides the possible range of R cyc and R cov on individual materials.
  • On the other hand, secondly, varying in the ERF value precisely changes on R cov only.

Freight train

  • The distinctive point is the R cov value slightly differ from R cyc on the freight train and passenger train but, it obviously changes on HSR.
  • The main reason is because the HSR contains with high recoverable rate materials that represent at R cov 12.5%.
  • Therefore, the sensitivity analysis of ERF value on HSR shows obviously different between R cyc and R cov lines.

5. Conclusion

  • Railway has become essential transportation effecting on human life; however, the end-of-life rolling stock was turned into waste and left in landfill.
  • As supported sustainable development, this research provides fundamental information about rolling stock and its main components and includes waste management processes like recycling and recovering.
  • The methodology and component analysis illustrates that the properties of materials directly affect the R cyc and R cov .
  • The results show that HSR has a maximum NPV of around £45,441,934 at a 10.00% discount rate with calculations based on 30 years of rolling stock life in services.
  • This not only saves energy but the amount of waste in landfill is also reduced.

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Frequently Asked Questions (18)
Q1. What are the contributions in "University of birmingham a through-life evaluation of end-of-life rolling stocks considering asset recycling, an energy recovering, and financial benefit" ?

This 10 paper evaluates efficient and feasible approaches to recovering and recycling wasted rolling stocks. In this 12 article, all compositions of the three types of rolling stock are studied, with the results of the recyclability and 13 recoverability rates being used to inform their productive treatment at the end-of-life. 14 The distinctive point of this research is an analysis of compositions, materials, and the percentage of value 15 adopted from the end-of-life rolling stocks. Finally, the two key recommendations for further design on rolling 22 stocks are provided regarding the proper selection of materials and the method to enhance efficiency of recycling 23 and recovering process. 

Reducing body weight, high strength, corrosion resistance and vibration resistance are 18 strong points making CFRP over steel and aluminium. 

the recycling processes should apply after the end-of-life to save energy, reduce waste 32 in landfills, and decrease toxic gases emissions. 

The recovery rate 40 of a fuel tank on a freight train, for example, was found to be only 33%, whereas industries claim to have data that 41 shows that around 80%-98% of fuel tanks can be recovered (UNIFE, 2013). 

In the UK, the shredded waste of plastic represented at 41 9.4% - 16.8% by mass of total shredded scraps (Ambrose et al., 2000; Cossu et al., 2014; Miller et al., 2014). 

12 For human activities, which mostly include transportation, there are 700 million vehicles that are currently in use 13 around the world and this number is predicted to increase to two billion vehicles by 2050 (Del Pero et al., 2015). 

CFRP is widely used in transportation industries (i.e. electric 19 vehicle, aircraft) since 2012 and expected to cover 200,000 tons per year in 2020 (Dauguet and et al. 

In 2012, there was 25.2 million tonnes of plastic wastes across European countries; nevertheless, it was 26 only 60% of the wastes could be recovered or recycled. 

8 Manufacturing was reported as the largest producer of pollutant emission; for example, Great Britain has 16 of 9 the 100 top polluting plants, showing a high damage cost from air pollution. 

In case of recovering on the end-of-life rolling stock, the wastes that mainly 13 composed of elastomers and polymers (i.e. table, seat) will produce high recoverability rate, which will be 14 mentioned on the material part. 

The end-of-life rolling stocks cause large volume of wastes in the landfill not only in European countries but also 13 countries around the world. 

the pyrolysis method, which is one of a thermal treatment process, is highly suggested to apply 27 to the CFRP recycling process for splitting carbon fibre out of the waste (Das, 2011; Khalil, 2017). 

44 Regarding the four stages of the plastic recycling process, the primary stage, which involves reprocessing plastic 45 into a product with similar properties with a raw plastic material. 

the remaining materials or parts are directly forwarded to the shredding process, which is separation 10 and recovery stage of metal materials and small parts. 

The 1 HSR’s end-of-life rolling stock showed the highest energy recovery rate among three type of the end-of-life rolling 2 stock at 12.5%; in other words, some parts can be burned down and turned into energy. 

12 13 As follow various aspects to enhance the railway system, to changing on material composition and adding 14 innovations has been interested. 

Some research identifies that the 15 loss on quality and dilution comes from the contamination on the end of life vehicle i.e. the copper is mixed with 16 steel (Nakamura and et. al. 2012). 

The thermosets, another type of plastic, also used in rolling stock but, the recycling 35 process of thermoset plastic is complicated than other plastic types.