Tribology in CO2 Emission

Introduction

The role of tribology in CO₂ emission is not directly visible, however, it can be due to friction losses causing energy crisis and failure in machine elements leading to consuming more resources. There are various other factors of friction, wear, and lubrication that can be improved in industrial machinery applications reducing CO₂ emission into the atmosphere. It is important that all the measures and guidelines should be followed by the industries to protect this planet from global warming and stabilize greenhouse gas emissions. The annual CO₂ data is shown in Fig-1.

Fig-1 The annual statistics of the CO2 emission [1]

The increasing concerns for a sustainable environment with more efficient and green sources as fuels for transportation and industrial activities are seen in the past decade. These concerns can be related to tribology as friction is one of the most energy-consumed factors in the world, it consumes around one-fifth of all energy used worldwide. And the amount of energy used in transportation to reduce this friction is around one-third of its total consumption. Hence, tribological aspects such as friction and wear should be improved to increase the efficiency of the machine elements thereby maintaining energy sustainability.

Transportation is one of the important sectors of energy consumption, and developing a systematic approach to saving energy in this sector is important. There are several research which focuses on studying the impact of friction and wear on the energy and environment in transportation. Improvements in the lubricants, tribological materials, and suitable economic practices could be used to solve this issue. One of the examples is internal combustion engine-driven transportation and their energy losses are shown in Fig-2. Most transportation uses internal combustion engines, in the case of passenger cars, only 21% of energy is used to move the car, and the rest is wasted as energy loss. This loss distribution is schematically shown in Fig-2. Hence, there is a need the increasing the efficiency of transportation mediums by more energy-saving designs and using the right materials for saving energy thereby decreasing CO₂ emission.

Fig-2 Breakdown of energy use for ICE-driven passenger cars, tank-to-wheel calculation [2]

Reducing friction and wear

Advancements in tribology knowledge

The tremendous advancements in tribology such as the knowledge of science and engineering of sliding surfaces, thin coating films, surface modification techniques to improve lubrication, etc have resulted in reducing friction and wear losses. These solutions have resulted in reducing friction by orders of magnitudes and they are dependent on various techniques and also the development of new materials. The lubrication and the type of lubricants for various applications have also increased with more advanced component designs and improving the research among nanotechnology, biomimetics, etc.

Advancements in coating and lubrication

The understanding of self-lubricating materials and their growing applications in various sectors have proven their impact on reducing friction. The increase in thin layer coating and methods to deposit these coatings have also developed to increase its efficiency in various applications. The improvement in diamond-like carbon coatings is one of the successful examples of ceramic coatings used in friction reduction. Along with the coating, traditional lubrication with mineral oils and the development of synthetic oils have increased. Various properties of these oils such as viscosity, nano additives, and other anti-wear and friction additives have been reported to improve friction.

Advancements in surface properties

The studies on the structural properties of the materials in improving the load-bearing capacities have shown their impact on reducing friction in various applications. The surface tribological properties are improved using the techniques to reduce the surface roughness impacts on sliding by surface texturing. Textured grooves, dimples, or protrusions have been shown to improve lubrication efficiency.

Advancements in superlubricity

The condition of zero friction on any surface interface is superlubricity and achieving this could save a lot of energy avoiding friction at the interface. Research on self-lubricating materials such as MoS₂, WS_2, etc has been shown to improve the frictional properties of the surface. Along with this, research is also conducted to develop 2D lubricants with nano-diamond particles at the interface to improve frictional stability.

Fig-3 Advancements in Tribology [3]

Conclusion

The importance of the relationship between tribology and CO₂ emission has not been seen recognized yet. This connection is very important to be identified in order to save the energy loaded due to friction and increase sustainability. It is estimated that saving 30-40% of frictional loss could save 2.66-4.93 gigatons of CO₂ emission per year [4]. Hence it is important to develop different techniques to reduce friction and wear by developing tribological advancements with respect to lubrication, coating, and new materials.

Reference

[1] https://ourworldindata.org/grapher/annual-CO2-emissions-per-country

[2] Holmberg, K. and Erdemir, A., 2019. The impact of tribology on energy use and CO2 emission globally and in combustion engine and electric cars. Tribology International, 135, pp.389-396.

[3] https://engine.iium.edu.my/tribo-man/

[4] Woydt, M., 2021. The importance of tribology for reducing CO2 emissions and for sustainability. Wear, 474, p.203768.