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It has to be noted, that by including non-energy related CO2

emissions (+4.4 gigatons of CO2

greenhouse gases (GHG) like methane (N2 hexafluoride (SF6

Material footprint ), other O), sulphur ) hydrofluorocarbons, fluorinated

ethers, and perfluorinated compounds, as well as land use change (LUC), the total greenhouse gas emissions spiraled in 2019 to 59.1±5.9 gigatons of CO2eq.

! [9].

In a world of bits, bytes, and bitcoins, friction in moving parts and elements will still continue to dissipate energy into heat. The reduction of friction is not only a general issue or an issue for internal combustion engines, but also for electric vehicles, because reducing the friction in electric drivetrains extends the range of EVs.

Overall, friction reduction is a dominating subset of energy efficiency and as such well embedded in the sustainable development goals (SDGs) of the UN [10]. Energy efficiency can be found in SDG #7.3 “By 2030, double the global rate of improvement in energy efficiency” and SDG #13 “Take urgent action to combat climate change and its impacts”.

Compared to the CO2 issue, the public discourses

perceive the consumption of resources as only secondary in importance. Everyone is talking about climate change, but the term of sustainability remains vague. Where sustainability is concerned, industry, society and science share different viewpoints and constantly changing definitions. The 17 sustainable development goals (SDGs) of the UN give clarity here [11]. In modern societies, sustainability in association with the consumption of resources will be one of the most important global goals of the future. Material streams, consumption of resources and material hunger are subject to a growing socio-political discourse demanding to improve the eco-toxicological properties as well as scrutinising and optimising property profiles according to UN SDG sustainability criteria. Tribology affects the use and longevity of materials across all industrial sectors and consumer products and is not limited to mobility.

The hidden and complex interactions between wear protection and sustainability Longevity has no link to the technosphere of a circular economy, but extending the product life cycle subsequently decouples material consumption from economic growth and reduces waste streams.


Any raw material extraction and processing always impacts the environment. Global material streams represent the starting point for evaluations of the impact of resource consumption on associated embedded CO2

emissions of primary resources.

The material footprint from human activities in 2017 reached 92.1 gigatons of mass [12] plus 8.6 gigatons of recyclates [13] resulting in a material flow

of 100.6 gigatons, which inevitably contains CO2 emissions from extraction, processing and production (see Table 2). Fossil energy sources contribute only ~15% to the global material streams. Non-metallic minerals (building materials, mineral raw materials), such as sand, gravel and limestone, make up more than half of the total material extraction and may have no connections to tribology. Cement plays a significant role in this material stream (see Table 3). The consumption of cement for roads and highways was 33% US (2015) [14] and 22.4% in China (2019) of the total cement consumption [15]. Finally, the potential resource pools impacted by wear protection is at least 17.7 gigatons. The following levels of streams of engineering materials for 2017 need further studies and investigations to assign material streams going into applications and end-uses with tribosystems or those affected by tribosystems:

a. 17.720 gigatons (derived from data of the UN Resources Outlook 2019),

b. 9.120 gigatons of “metal ores” (UN Resources Outlook 2019, p. 43) [12],

c. 10.1 gigatons of “metal ores” (Circularity Report 2020, p. 18) [13] and

d. >6.642 gigatons of “engineering materials” (see Table 3).

Table 2: Global raw material extraction 2017

The impact of annual global consumption of around 40 million tons or 0.040 gigatons of lubricants is marginal within the global material streams, but can theoretically be fully sourced from renewables in view of the total volumes of biomass in-use.

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