Tribology Trends – Green Tribology

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Part 2: Green Tribology: Pioneering Sustainable Solutions

In modern industries, few threads are as essential as tribology. From the gears that propel our vehicles to the turbines generating our power, tribology underpins the functionality of countless mechanical systems, ensuring optimal performance and longevity. It intersects with three primary sectors: transportation, power generation, and manufacturing. Within these industries, machinery of all kinds relies on tribology to maximise profits. New materials, lubricants, and designs are continually being developed to reduce wear caused by corrosion and friction, all with the overarching goal of decreasing costs and improving profits.


What is Green Tribology?

Now, imagine tribology with a green twist. That’s Green Tribology, a specialised branch focused on reducing the environmental impact of how materials interact. It’s like giving our machines an eco-friendly makeover. Amidst the pressing challenge of global climate change, exacerbated by a growing population and its escalating energy demands, tribology stands as a powerful solution in reducing greenhouse gas emissions. By drawing inspiration from nature and utilising sustainable materials and energy sources, Green Tribology aims to make industrial processes more environmentally friendly. It’s not just about reducing friction and wear; it’s about doing so in a way that minimises harm to the planet.

Green tribology has three main principles [6] aimed at ensuring limited impact on the environment and human health. These three principles are biomimetics* and self-lubricating materials and surfaces, biodegradable and environmentally friendly lubrications, and renewable and/or sustainable sources of energy. [5]

*Imitating the models, systems, and elements of nature in order to solve complex human problems.


Why is it Important?

Amidst mounting environmental urgency, Green Tribology assumes critical importance. Its relevance extends beyond mere efficiency gains; it holds the potential to curb greenhouse gas emissions and foster sustainable development. As highlighted by researchers Kenneth Holmberg and Ali Erdemir in their work, Influence of Tribology on Global Energy Consumption, Costs, and Emissions, a significant portion of global energy consumption is attributed to inefficiencies in tribological contacts. Specifically, about 23% of current global energy consumption arises from tribological inefficiencies. Within this figure, approximately 20% is spent on addressing friction issues, while the remaining 3% is allocated to remanufacturing worn parts and spare equipment due to wear and wear-related failures. [1]

The stakes are high, but so too are the potential benefits. Embracing Green Tribology could lead to substantial energy savings and a notable reduction in carbon emissions. Projections suggest that within eight years, energy losses due to friction and wear could decrease by up to 18%, with a potential reduction of 40% within fifteen years. These savings, particularly prominent in transportation and power generation, offer not only environmental benefits but also significant economic advantages. [1]


Industry Applications

  1. Revolutionising Transportation: Green Tribology is revolutionising the transportation sector by reimagining the role of friction and wear in vehicle efficiency. Beyond conventional approaches, such as aerodynamics and engine optimisation, Green Tribology explores innovative solutions like advanced lubricants, optimising wheel-rail interfaces and surface treatments to minimise frictional losses. By reducing resistance within engines and mechanical systems, Green Tribology not only enhances fuel efficiency but also extends the lifespan of critical components, contributing to reduced emissions and lower operating costs [1].
  • Driving Sustainable Manufacturing: In manufacturing, where efficiency and productivity are paramount, Green Tribology is driving sustainable practices that prioritise environmental responsibility without compromising performance. By introducing eco-friendly lubricants, such as bio-based and water-based formulations, Green Tribology minimises the environmental footprint of machining processes while optimising performance and reducing maintenance requirements. Furthermore, advances in surface engineering and material science enable manufacturers to develop wear-resistant components that withstand harsh operating conditions, leading to increased productivity and reduced resource consumption [1][2].
  • Empowering Renewable Energy: Green Tribology plays a pivotal role in unlocking the full potential of renewable energy sources, such as wind and solar power. By optimising the performance and reliability of critical components, including bearings and gears in wind turbines and solar panel tracking systems, Green Tribology maximises energy conversion efficiency and minimises downtime. Through advanced lubrication technologies and predictive maintenance strategies, Green Tribology ensures the long-term viability of renewable energy infrastructure, facilitating the transition towards a cleaner and more sustainable energy future. With every advancement, Green Tribology reinforces the importance of renewable energy as a cornerstone of environmental stewardship and energy independence [1][2].

Principles of Green Tribology

Green Tribology, anchored in fundamental principles, strives to mitigate environmental impact while enhancing machinery efficiency and reliability. These principles, informed by interdisciplinary research, encompass various aspects of eco-friendly tribological practices. Let’s explore key concepts, drawing insights from referenced sources and incorporating additional material:

1. Biomimetics: Nature serves as an inspiration for biomimetic designs in engineering, aiming to reduce friction and wear. By studying biological systems such as animal joints or lotus leaves, engineers develop surfaces and materials with reduced friction and self-lubricating properties, thus minimising reliance on conventional lubricants [1][4].

2. Self-lubricating Materials: In response to environmental concerns associated with conventional lubricants, Green Tribology advocates for the adoption of self-lubricating materials. These materials possess inherent lubricating properties, achieved through surface modifications or intrinsic characteristics, thereby reducing friction and wear without relying on environmentally harmful lubricants. Examples include polymers impregnated with solid lubricants like PTFE (polytetrafluoroethylene) or MoS2 (molybdenum disulfide), composite materials with embedded lubricating particles, and surface coatings with low friction coefficients, such as DLC (diamond-like carbon) coatings and plasma-based treatments [1][2].

3. Biodegradable Lubricants: Addressing the ecological impact of conventional lubricants, Green Tribology promotes the use of biodegradable alternatives. These lubricants, such as vegetable-based oils, synthetic esters, polyalkylene glycols (PAGs), and bio-based greases, break down naturally into non-toxic components over time, minimising environmental impact, particularly in applications prone to leakage or contamination [1][2].

4. Renewable Energy Sources: Non-renewable energy sources contribute to carbon emissions in tribological systems, prompting Green Tribology to advocate for renewable alternatives. Solar, wind, and hydroelectric power are championed to drive machinery, significantly reducing environmental footprint. By harnessing clean and sustainable energy sources, tribological operations align with principles of environmental stewardship [1][2].


concept idea eco power energy. wind turbine on hill with sunset

5. Advanced Coatings and Lubricants: In addition to the foundational principles, Green Tribology explores advanced coatings and lubricants to further optimise tribological performance. Diamond-like carbon (DLC) coatings, for instance, exhibit exceptional durability and friction-reducing properties, enhancing machinery efficiency and longevity. Other examples of advanced coatings and lubricants include nanostructured coatings, and graphene-based lubricants, and synthetic lubricants formulated to meet stringent environmental standards, offering superior performance while minimizing environmental impact [1][2].

By embracing these principles, Green Tribology strives to achieve a harmonious balance between industrial efficiency and environmental sustainability. Through biomimetic designs, self-lubricating materials, biodegradable lubricants, renewable energy sources, and advanced coatings and lubricants, tribological systems operate in synergy with the natural world, minimising resource consumption, pollution, and ecological impact.

Explore further insights into the challenges and implications of Environmentally Acceptable Lubricants (EALs) in maritime lubrication practices by delving into our study review titled ‘The Impact of Environmentally Acceptable Lubricants (EALs) on Stern Tube Bearings.’ Click here.


Challenges in Green Tribology

The pursuit of green tribology is underscored by the imperative to address environmental concerns while enhancing the efficiency and sustainability of tribological systems. Both the paper, A Green Approach to Tribology by Kandile and Harding [3], and the work by Nosonovsky and Bhushan [4] shed light on the multifaceted challenges encountered in this endeavour.

  1. Integration of Fields: Green tribology encompasses various disciplines, including biomimetics, micro structuring, biodegradable lubrication, and self-lubrication. However, achieving synergy among these fields remains a significant challenge. Without integration, green tribology risks being perceived as a disparate collection of research topics rather than a cohesive scientific and technological domain [4].
  2. Technological Synthesis: The development of methodologies to synthesise biomimetic approaches, micro structuring techniques, and novel lubrication strategies into cohesive tribological solutions is essential. Collaborative research efforts are needed to explore the potential synergies between these approaches and their applications in sustainable engineering and energy production [4].
  3. Assessment Metrics: The absence of standardised metrics to assess the environmental impact of tribological technologies poses a barrier to progress. Drawing insights from green chemistry, there is a need to develop quantitative measures that can evaluate the sustainability credentials of tribological solutions effectively [4].
  4. Global Integration: Green tribology holds promise as a catalyst for addressing pressing global challenges, such as climate change and resource scarcity. However, its integration into broader scientific and policy frameworks is essential to realise its potential impact on a global scale [4].
  5. Economic Viability: The economic feasibility of green tribology solutions is a critical consideration for their widespread adoption. Balancing research and development costs with potential environmental benefits is essential for industry buy-in and long-term sustainability [3].
  6. Educational Initiatives: Raising awareness and fostering interdisciplinary collaboration are vital for advancing green tribology. Education and outreach efforts can help bridge knowledge gaps and cultivate a culture of sustainability among researchers, industry stakeholders, and policymakers [3][4].
  7. Lifecycle Analysis: Comprehensive lifecycle assessments are needed to evaluate the environmental footprint of green lubricants throughout their lifecycle. Factors such as raw material sourcing, production processes, and end-of-life disposal must be considered to ensure overall environmental benefit [3].

Addressing these challenges requires concerted efforts from researchers, industry stakeholders, policymakers, and the broader community. By overcoming these obstacles, green tribology can realise its potential to mitigate environmental impact, conserve resources, and drive sustainable innovation in tribological practices.


To sum up

The exploration of green tribology heralds a transformative approach to industrial practices, aiming to mitigate environmental impact while optimising efficiency. By adhering to the principles of green tribology and leveraging innovative solutions, industries can revolutionise their operations, reduce carbon emissions, and promote sustainability. However, addressing the challenges inherent in green tribology is essential for its successful implementation. Through collaborative efforts and a commitment to overcoming obstacles, industries can unlock the full potential of green tribology, ushering in a future marked by environmental responsibility and technological innovation.


References

[1] Holmberg, K., & Erdemir, A. (2017). Influence of tribology on global energy consumption, costs and emissions. Friction, 5(3), 263–284. DOI: 10.1007/s40544-017-0183-5

[2] Shaha, R., Martinib, A., Woydtc, M., & Wongd, H. (2020). Green Tribology. Tribology in Industry, 42(4), 592-596. DOI: 10.24874/ti.2020.42.04.12

[3] Kandile, N. G., & Harding, D. R. K. (2019). A Green Approach to Tribology. In Surfactants in Tribology, Volume 6. CRC Press.

[4] Nosonovsky, M., & Bhushan, B. (2010). Green tribology: principles, research areas and challenges. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 368(1929), 4677–4694. https://doi.org/10.1098/rsta.2010.0200