product’s use and how it is treated at the End of Life. Figure 1 illustrates these stages and identifies the difference between “cradle-to-gate” and “cradle-to-grave”. The CO 2 e contribution of extracting, refining and blending the crude oil (cradle-to-gate) makes up a smaller value of greenhouse gases compared to its End of Life (cradle-to-grave). Although antioxidants have approximately twice the carbon footprint of mineral oil, they contribute a relatively small amount to the overall total since they are used at a small percentage in the formulation. Depending on what part of the world the used oil is generated, the contribution of CO 2 e at the End of Life is defined by what percentage is incinerated or re-refined. Different base oils may also contribute more CO 2 e to the overall product. For example, Polyalphaolefins (PAOs) have about twice the cradle-to-gate CO 2 e footprint as mineral oils. However, the End-of-Life of both products Research 4 Tribologie + Schmierungstechnik · 70. Jahrgang · eOnly Sonderausgabe 1/ 2023 DOI 10.24053/ TuS-2023-0026 1 Introduction Many companies utilizing rotating equipment have either initiated, or plan to initiate, decarbonization strategies. This is a process which reduces and compensates the emissions of carbon dioxide equivalent (CO 2 e), ultimately down to “Net 0”. Lubricants are an essential component in rotating equipment, so it makes sense to determine optimum ways of managing these fluids in the most sustainable way possible, which includes enhancing their performance. Life Cycle Assessment (LCA) is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a product and is the accepted tool to analyze the potential environmental impacts of products. It is therefore the optimum tool for measuring the sustainability of a lubrication program and comparing various products and strategies. The process of performing an LCA is defined in ISO 14040 and takes a thorough inventory of all the materials and energy required to make a product, calculating a cumulative potential environmental impact. Part of this calculation involves assessing various midpoint indicators, such as stratospheric ozone depletion, acidification, eutrophication, water scarcity and toxicity potential, but for the purpose of this paper, we’ll just focus on Global Warming Potential measured in CO 2 e. LCA is a useful tool for a variety of purposes. For example, how do you know if an electric vehicle will lower emissions compared to an internal combustion vehicle? What if the electric vehicle gets its power from a coal burning power plant? Doesn’t mining lithium and manufacturing batteries produce a lot of emissions? There are a lot of complexities with this question and the answer would not be possible without performing a cradleto-grave LCA. (Incidentally, there are many studies on this, and electric vehicles greatly reduce emissions over the life of the vehicle.) 2 Cradle-to-Gate vs Cradle-to-Grave When performing an LCA on a lubricant, one can look at various stages in the life of the product. Cradle-to- Gate represents the carbon impact of a product from its inception to the moment the product is ready for sale. This is the most common LCA done on lubricants, as manufacturers do not have control over the use of the product once it is sold. Cradle-to-Grave also covers the Managing Turbine Oils in a Sustainable Way Greg Livingstone, Ludger Quick, Jo Ameye* The majority of companies using rotating machinery have implemented decarbonization strategies that systematically analyze every part of their organization to try to adopt more sustainable practices. Lubricants are an essential component in rotary equipment, so it makes sense to find optimal ways to manage these fluids in the most sustainable way, including improving their performance. Life Cycle Analysis (LCA) is the recognized tool for assessing the overall environmental impact of a product from cradle to grave and is useful to compare different liquid management strategies. This paper outlines several ways in which turbine oils can be managed more sustainably by considering the life cycle assessment of different practices. Keywords rotating machinery, decarbonization strategies, Life Cycle Analysis (LCA), lubricants, cradle to grave, turbine oils Abstract * Mr. Greg Livingstone, Fluitec, Bayonne, USA Dr. Ludger Quick, Siemens Energy, Muelheim/ Ruhr, Germany Mr. Jo Ameye, Fluitec, Dordrecht Netherlands is the same representing a larger percentage. The overall CO 2 e contribution of a mineral turbine oil versus a PAO turbine oil is illustrated in Figure 2. Therefore, effort to extend the life of in-service oil will have a significant impact on lowering the total carbon footprint of a lubricant. It is also interesting to note that transportation plays a minor role in the overall carbon footprint. This is the case as long as lubricants are not being flown around the world. 3 Comparing Lubricant Sustainability There are many factors that go into measuring the sustainability of a lubricant. Figure 3 illustrates these various factors and pathways to make the lubricant more sustainable. Using a comparison like this, it is possible to compare the sustainability of various lubricants and lubrication practices. Keep in mind that each category can be converted to kg CO 2 e, except for environmental performance, which is its own category. Biodegradability performance, bioaccumulation results and the oil’s toxicity rating are important aspects of the sustainability of the oil, but those qualities must be directly compared since they are on a different scale. Based on this spectrum, the ultimate sustainable lubricant would be one that is plant-based (oleo sourced) and Research 5 Tribologie + Schmierungstechnik · 70. Jahrgang · eOnly Sonderausgabe 1/ 2023 DOI 10.24053/ TuS-2023-0026 Figure 3: Factors influencing the sustainability of a lubricant Figure 2: Cradle-to-gate CO 2 e comparison between mineral and PAO turbine oils Figure 1: Stages of a Lubricant’s Life ples illustrate that the product with the highest cradleto-gate carbon footprint is not necessarily the one with the lowest carbon footprint once a cradle-to-grave analysis is completed. 4.1 Case Study 1: Avoiding a “Varnish Flush” Maintaining a turbine oil with low varnish potential has many financial benefits for a power plant. In addition to increased availability and reliability, one may avoid having to do a “varnish flush” in between oil changes. Flushes are both energy and volume intensive which accumulates to a sizeable carbon footprint. Fluitec has invented a solubility enhancing technology called DECON which decontaminates lube oil systems in between oil changes. Among other benefits, the technology allows rotating equipment users to avoid having to do a varnish flush in between oil changes. The following case examines the sustainability impact of adding 3 % DECON to an in-service turbine oil to avoid having to perform an oil flush. In this example, we use a gas turbine oil with a 5,000-gallon reservoir and an eight-year life span. The Fluitec Value Impact Calculator adds the cost and carbon footprint of adding DECON to the fluid and measures the value of not having to perform a flush during the next oil change. The results can be viewed in Figure 4. By using DECON and avoiding having to perform a lube oil system flush, this turbine can avoid generating 18 metric tons of CO 2 e per year. A calculation like this would be challenging without performing a cradle-to-grave LCA. As with most sustainable lubrication practices, avoiding a Varnish Flush also saves considerable money for the power plant as well. Research 6 Tribologie + Schmierungstechnik · 70. Jahrgang · eOnly Sonderausgabe 1/ 2023 DOI 10.24053/ TuS-2023-0026 made from renewable energy; one which is readily biodegradable, non-toxic and doesn’t have bioaccumulation; one which provides a long service life and improves the energy efficiency of the system it is lubricating; and finally at the end of this ideal fluid’s life, it is re-refined or re-used in another application. Also, for a sustainable lubricant to be practical, it needs to be fully compatible with the application, including materials of construction and contamination ingression. For example, an oleo-based ester may tick all the boxes but may shrink system seals and hydrolyze due to high water contamination, making it unsuitable for a specific application. 4 Lubricant Sustainability Case Studies Following are two examples of comparing the sustainability of different lubricants by using LCA. The exam- Figure 4: Example of the high carbon footprint involved in lube oil flushing and how maintaining a low varnish potential in your turbine oil reduces your carbon footprint 4.2 Case Study 2: Replenishing Turbine Oil Antioxidants instead of performing an oil change Antioxidants are sacrificial components in turbine oil formulations. The life of a turbine oil is largely dictated by the rate of antioxidant depletion, with the condemning limit by most OEMs and industry bodies stating that action needs to be taken when the antioxidants reach 25 % of their original value. The traditional approach when the life of the antioxidants has been consumed and the oil is at the end of its life is to drain, flush, and recharge the system with new turbine oil. However, this consumes outage resources and is expensive so many plants have considered simply replacing their antioxidants instead. Custom made antioxidant concentrates can be added to turbine oils in situ, provided the correct up-front, qualification tests are performed to certify compatibility. This emerging practice has been done successfully in hundreds of turbines and is a cost-saving alternative to the old model of dump and replace. It seems that this would also be environmentally beneficial, however, to quantify this, an LCA is required. Below is an example of large frame cogeneration system with single shaft configuration. Since this system is in Eastern Europe, a whole new set of assumptions are required compared to the first case study. Transportation and the percentage of oil that is rerefined versus incinerated are two examples. Figure 5 shows the results of adding an antioxidant concentrate (DE- CON AO) to the in-service oil. In this case, over 200,000 kgs CO 2 e are estimated to be saved over a 10year period, which translates to more than 75 kgs CO 2 e per day. The power plant also benefits from cost savings, waste reduction and other advantages. 5 Other Strategies to Manage Oils in a more Sustainable Way There are multiple other lubricant management strategies that can lower the carbon footprint of your lubricant program, including: • Selecting the best performing oil for your application resulting in longer drain intervals and lower maintenance costs. • Implementing an Oil Analysis Program to optimize the drain intervals of your oils. Keep in mind that not acting when oil analysis warrants it, not only increases maintenance costs but can also dramatically increase your carbon footprint. • Avoiding Varnish. In addition to failed components, deposits can create an insulating layer on bearing surfaces resulting in higher temperatures, lowering the energy efficiency of the system. Research 7 Tribologie + Schmierungstechnik · 70. Jahrgang · eOnly Sonderausgabe 1/ 2023 DOI 10.24053/ TuS-2023-0026 Figure 5: Value Calculator of using DECON AO instead of performing an oil change References Livingstone, G. (2023). Measuring and Attaining Sustainable Lubrication. Precision Lubrication Magazine. https: / / precisionlubrication.com/ articles/ sustainable-lubrication/ Bieker, G. (2021). A Global Comparison of the Life-Cycle Greenhouse Gas Emissions of Combustion Engie and Electric Passenger Cars. The International Council of Clean Transportation. European Climate Foundation and the Climate Imperative Foundation. Fehrenbach, H. (2005). Ecological and Energetic Assessment of re-refining used oils to base oils. Institut für Energieund Umweltforschung GmbH (IFEU), a study commissioned by GEIR-Groupement Européen de l’Industrie de la Régénération. Fluitec. (2022). Life Cycle Assessment. Bayonne, NJ: Fluitec International, LLC. Life Cycle Assessment. (kein Datum). Von Wikipedia: https: / / en.wikipedia.org/ wiki/ Life-cycle_assessment abgerufen Muralikrishna, I. a. (2017). Life cycle assessment - an overview. Science Direct Topics. Environmental Management Science and Engineering for Industry. Raimondi, A. e. (2012). LCA of Petroleum-based lubricants: state of art and inclusion of additives. The International Journal of Life Cycle Assessment, DOI: 10.1007/ s11367-012-0437-4 , 987-996. Taylor, R. e. (2005). Lubricants & Energy Efficiency: Life Cycle Analysis. Life Cycle Tribology. (2017). Tribology Opportunities for Enhancing America’s Energy Efficiency. Advanced Research Projects Agency - Energy at the US Department of Energy. Wernet, G. B.-R. (2016). The ecoinvent database version 3 (part I): overview and methodology. The International Journal of Life Cycle Assessment, 1218-1230. Young, J. E. (2020). Energy Efficient Industrial Lubricants: Reducing Energy Consumption with Industrial Lubricants. Pennsylvania Statewide Technical Reference Manual - Work Paper. Research 8 Tribologie + Schmierungstechnik · 70. Jahrgang · eOnly Sonderausgabe 1/ 2023 DOI 10.24053/ TuS-2023-0026 • Re-refining an Oil at the End of its Life. Creating a circular economy with your lubricant at the end of its life by re-refining instead of incinerating will reduce the carbon footprint of your lubricant program. • Minimizing Contamination Ingression. Studies have shown that contamination is responsible for as much as 70 % of premature machinery failures. Deploying a strong contamination control program not only saves significant operational costs but will also reduce associated carbon footprint. 6 Summary As the saying goes, “If it doesn’t get measured, it doesn’t get managed”. In the case of achieving sustainable lubrication, using cradle-to-grave LCA principles allows you to measure and improve the sustainability of your lubricant program. This paper illustrates how to perform these calculations, and as the case studies illustrated, the initial carbon footprint of the lubricant does not necessarily mean decreased sustainability. Performing these LCA studies allows users to easily identify areas for improvement and can quantify the benefits. These calculations can also shed some light into the practices which should be negated to assist in the decarbonization efforts, such as lube oil flushing as illustrated in Case Study 1. The carbon footprint of lubricants may seem small, especially if one does not consider “product use” in LCA equations. However, tribology in general can have a tremendous impact on lowering society’s carbon footprint. A report to ARPA-E in 2017 calculated that 24 % of energy can be saved annually through tribology efforts. Measuring these efforts start with cradle-to-grave Life Cycle Assessments.