Continued from page 22 Figure 1. Degrees of biodegradation.
Comparing the different base oils available, esters are the base oil of choice to deal with the readily biodegradable requirement. However, not every ester is readily biodegradable. The degree of biodegradation highly depends on the molecular structure of the ester. In general, biodegradation decreases with increasing chain length and branching of the carboxylic acid used to prepare the ester. Due to the variety of possible combinations of carboxylic acids and alcohols or polyols, esters are the most versatile base oil and properties can be tailor-made. Vegetable oils usually show low thermal and oxidative stability and accordingly can’t be used directly in every application. Therefore, they are chemically modified to improve their properties or esters based on petrochemicals are used to serve even the most demanding applications. However, biodegradation is independent of the origin of the raw materials, but solely depending on the molecular structure of the ester.
As mentioned above, renewable substances are not required by the EU Ecolabel anymore. However, the term bio-based or bio-lubricant can be used if the biobased carbon content is 25% or higher. If renewable ingredients derived from palm oil or palm kernel oil are used, the sustainable production needs to be certified.3
Palm oil mainly comprises palmitic (C16) and oleic acid (C18:1), palm kernel oil mainly comprises lauric (C12), myristic (C14) and oleic acid (C18:1). Furthermore, palm kernel oil is the only commercial source of caprylic (C8) and capric (C10) acid next to coconut oil, though the latter is nearly exclusively consumed in nutrition. Accordingly, esters or other derivatives using these acids most likely need a certification of sustainable production. Alternatives based on petrochemicals exist. They show comparable properties and can be readily biodegradable as well, e.g. esters using pelargonic acid (C9) produced by OXEA and others.
As described above, current regulations are requiring readily biodegradable substances rather than biobased ones. This differentiation does make sense taking into account that not every biobased substance is readily biodegradable. Therefore, the use in applications with potential loss to the environment may be limited. Furthermore, it’s important to notice that biobased substances are not necessarily sustainable. Conditions under which these substances are obtained and related problems have to be taken into account as well (e.g. deforestation related to palm oil, food vs. fuel debate). In a holistic approach, sustainability comprises environmental (e.g. minimising waste and emissions) as well as economical (e.g. creating jobs) and social (e.g. good working conditions) aspects.
References 1 DIN SPEC 51523 : 2011 2
https://www.epa.gov/npdes/vessels-vgp 3
https://eur-lex.europa.eu/eli/dec/2018/1702/oj 4 V. Bouillon, Lube Magazine 2018,148, 24-27. 5
http://ec.europa.eu/environment/ecolabel/ products-groups-and-criteria.html
This decision is part of the EU’s efforts
to protect the environment and combat deforestation of tropical rainforests. As only 19% of global palm oil production is currently certified by the Roundtable for Sustainable Palm Oil (RSPO),6
the origin of
corresponding derivatives should be checked. The natural fatty acid distribution (as triglycerides) in palm oil and palm kernel oil is shown in table 1.
LINK
www.oxea-chemicals.com
6
https://rspo.org/ 7 M. Bockisch (ed.): Fats and Oils Handbook, AOCS Press, Urbana/IL 1998.
Table 1. Fatty acid composition of palm oil and palm kernel oil.7
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LUBE MAGAZINE NO.150 APRIL 2019
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