In this post, we will consider the emissions of a brake system. While we have previously discussed the topic of brake dust and it’s likely solutions (and indeed, how it remains a hot topic today), this post will introduce the idea of life cycle analysis for brake systems. We will look at how such analysis could be applied to a simple brake part, and discuss the practicalities of a circular economy approach to braking.
Circularity of a Brake System
When we think of a road vehicle, or any of the various systems that go into a vehicle, we tend to consider the Life Cycle of the vehicle in terms of our own direct experience – namely in developing a new component or system as part of the product emergence process, or using vehicles in our own daily lives. Most of us have experience of using a vehicle, and those of us who own a vehicle have direct experience of purchasing replacement parts. Some of us probably have direct experience with what it takes to create the individual parts that form part of a vehicle system, and the supply chain that is required to send a vehicle to a dealer show-room. Others of us may have direct experience with what happens at the other end of the vehicle’s life, and how the vehicle systems are dismantled to be dealt with in an appropriate manner. In recent years, the end of life treatment has significantly altered, with new industrial sectors emerging to specialise in creating value through component and system reconditioning and reuse. Therefore, amoung us, there may be those that have bought a replacement part or re-threaded tyre for a vehicle. Legislation in this area has supported the normalisation of vehicle recycling and many working components are stripped from an end of life vehicle for reuse prior to eventual material recycling.
But if we wish to consider the life cycle of a brake system, we need to widen the scope significantly beyond the primamry use of the vehicle, to consider what it means to create the materials and components, assemble the systems and finally what it takes to reuse or recycle the components after the use phase. We will need to consider the balance between creating a clean and robust brake system during use, and what design and technology decisions we make to create such a system might impact the world at large. We will see that component reuse makes a significant impact on the overall environmental footprint of our system.
Life Cycle Analysis
The life cycle analysis (LCA) of a brake part should consider the environmental impact of all 3 major phases of the parts existence, namely; part creation, part usage, and part disposal. These include the resource and energy impact of gathering of raw materials, manufacture of the individual sub-components and assembly into the final component, through the usage and eventual safe disposal of the part, in line with local practice. As you can imagine, the LCA for a single component could vary significantly based on any one of these 3 major phases. Consider a relatively simple brake hose component. The brake hose may be produced in a supplier’s plant for a single OEM, and dispatched to several OEM assembly locations, each serving different regional or global markets. The environmental impact of the hose will be different for each assembly plant, and differ further for each region it is finally used in. The usage of the brake hose, and it’s treatment at end of life can vary greatly.
Therefore, to create a meaningful analysis of a brake component, it is necessary to set some context and boundaries for any analysis. This definition also allows for a meaningful usage phase to be established, such as a component or vehicle service life. For some brake components, a service schedule will exist, but others will stay with the vehicle throughout the full life, barring technical failure.
Once we have a meaningful definition of the component, we consider the three major phases in more detail. During part creation, we are concerned with extraction of raw materials such as metals, rubbers or plastics. We also consider environmental impacts such as energy consumption, habitat destruction and pollution associated with gathering our materials.
Next we consider the manufacture of the part. Here, we access the energy and material inputs, the emissions of our process and it’s supporting processes, and any waste that is generated. Later, during vehicle assembly, we should also consider these elements in integrating our part into the vehicle.
Once we have created the part, we must transport it to the assembly plant, and of course afterwards to the eventual market. Obviously, the emissions and energy usage here is of interest in our analysis.
Next comes the usage phase, and the component will share a portion of the overall vehicle energy usage. Any maintenance activity on the component or vehicle should also be considered. In the case of a brake system in a vehicle, it is likely that multiple powertrain variants are covered by a single brake system specification, so a single variant should be declared in the scope.
Finally, we can consider the end of life. Typically, this will mean disposal of the part, with a significant proportion of the raw material being recycled. End of life vehicle legislation has a significant impact here, setting minimum quantities for recycling, as well as enabling the reuse of many major vehicle components in aftersales.
Relevant standards in the area include ISO 14040 and 14044 for principles, framework and requirements for conducting an LCA, while ISO 14067 is helpful for establishing carbon footprints of products, providing guidance and requirements for quantifying and reporting greenhouse gases from the life cycle. SAE J2881 provides guidance on the development of life cycle inventory analysis specific for the automotive sector, for both vehicles and components, and can enhance the approaches outlined through the ISO standards.
Reuse and circular approaches
If we consider again our brake hose, then for a single use part, we would expect that a high performing brake hose would minimise its material impact, be simple to manufacture with a low energy input. Transportation of the finished part to the assembly plant should be as dense as possible. We would want a part that’s easy to assemble and should survive for the life of the vehicle. At the end of the useful life, we would want to recover as much material as possible while minimising energy overhead. At each stage, we can consider aspects to reduce the complexity of the part, but a key decision that would significantly impact the life cycle analysis is whether we can re-use the part in some form at the end of life. If this is possible, it saves raw material, manufacture and recycling from the original process, and is the most significant decision point available when considering LCA.
Reuse of a brake hose (or brake component) may be possible in the scenario of a recycled vehicle donating second life aftermarket parts to another vehicle of the same model (or platform, in the case of a large OEM), but this scenario is only relevant in few cases where a component has failed on an otherwise serviceable vehicle, and a donor vehicle has recently been recycled to offer parts. (My car has a worn brake hose, and I find a local scrap yard has a suitable End of Life vehicle which could donate a similar vintage hose).
To truly offer component re-use, then the component design itself must transfer from one vehicle generation to the next, meaning any example of the component could be stripped from an End of Life vehicle, and fitted to a new vehicle. In the case of a brake hose (assuming it stays with a vehicle for the full service life – and given the service life of a single vehicle may span multiple decades) integrating a 15 year old component design into a new platform is unlikely with today’s approaches. While the function of the brake hose is likely directly comparable between vehicle generations, any change in axle kinematics, steering, bump travel or even neighbouring component package will likely preclude design compatibility, and therefore component reuse. Some brake components maybe capable to be renewed during service exchange, for those components which are replaced at regular intervals. For the majority of braking components, full reuse is unlikely to be possible, without significant reworking of the donor part.
If we can’t fully re-use a component, then can we recover elements of the component for re-use in a later vehicle? Or can we easily minimise the efforts involved in material recovery, such that the link between end of life of one component and the raw material of the next component is enhanced?
In the next post, this topic will be explored, together with some live examples of both component reconditioning and material re-use. Further to this, we will explore how brake emissions during the usage phase have a direct influence on the those emissions we must consider during manufacture and end of life.