A Riviera Maritime Media webinar revealed market trends and assessed the technical and environmental advantages of bio-based lubrication and greases
Speaking during Riviera’s Bio-Lubricants: a perfect fit for new fuels? webinar, part of Marine Lubricants Webinar Week, RSC Bio Solutions technical business consultant Thomas To and Biosynthetic Technologies chief executive Mark Miller covered the history and the pros and cons of different types of bio-lubricants.
As Mr To explained, the term environmentally acceptable lubricant (EAL) was developed and introduced into legislation through the US Environmental Protection Agency’s (EPA’s) vessel general permit (VGP) in 2013.
The EPA legislation requires that all [commercial] vessels over 24 m in length use EALs when operating in US waters in all oil-to-sea interfaces.
Mr To said EALs are minimally toxic, non bio-accumulative (meaning they do not build up in the bodies of living organisms or proliferate up the food chain) and biodegradable.
Biodegradability, he said “is defined as greater than 60% degradation after 28 days,” a threshold which Mr To said was codified in ISO standards.
ISO standards, he said, categorise hydraulic fluid EALs by the chemical composition of their base oils, breaking them into four categories: HETG (triglycerides, vegetable esters), HEPG (polyalkylene glycols or PAGs), HEES (synthetic esters) and PAO and HEPR (polyalphaolefins and other synthetic hydrocarbons).
“These hydraulic fluids are listed in order of increasing stability and decreasing reactivity to oxygen or water,” Mr To explained.
Mr To said the chemical composition or “backbone of the base oil”, impacts key performance properties of the lubricants. Both triglycerides and synthetic esters have high degrees of instability because of their specific chemical structures – primarily hydrolytic instability and oxidative instability, he said.
“Even if the carbon-carbon double bond is removed by saturation, the ester group are still hydrolytically unstable,” Mr To said.
“PAGs are incompatible with all other fuels or seal materials, which is a real problem in the field,” he said.
Despite their instability, a poll of attendees suggested that those in the industry who opt to use bio-lubricants – a segment that has grown in response to uncertainty and unfamiliarity around alternative fuels – heavily favours synthetic esters (HEES). Almost three-quarters (72%) of respondents claimed to use HEES. While PAO and HEPR users made up 23% and triglyceride users comprised 5%, no one among the polled group identified as using polyalkylene glycols (PAGs).
Mr Miller acknowledged that bio-lubricants struggled to match traditional lubricants in some areas, but said his company’s mission is to change that.
“Typically, you’ll see that bio base oils struggle in a few areas. But we have created a couple of different prototype formulations that meet the ISO 15380 standard for hydraulic and stern tube fluids, 51517 for gear oils, as well as the China GB CKD specifications. We’re looking at global specifications for our products,” he said.
Mr Miller addressed the two primary areas of weakness for bio-lubricants as compared with petroleum-based lubricants, first discussing hydrolytic instability.
He said Biosynthetic Technologies has developed a test that takes a solution made up of 1% water and heats it to 82°C while stirring to measure the acid build-up, which impacts on hydrolytic stability of the fluid.
“We have been able to improve the hydrolytic stability, which will improve the life of the fluid [as well as performance],” he said.
The test methods, according to Mr Miller, typically see traditional esters breaking down very quickly, whereas group three base oils – petroleum-based oils made up of greater than 90% saturates and less than 0.03% sulphur with a viscosity index above 120 – and many PAOs show little in the way of acid-based breakdown.
The breakthrough, he said, was that his company had “created an HEES (hydraulic oil environmental ester synthetic) type product yet we’ve solved the hydrolytic instability”.
Mr Miller said Biosynthetic Technologies had also made progress on oxidative stability, “another area of traditional weakness of these esters”.
“We use a standard treatment of 0.5% phenolic 0.5% aminic antioxidant [on the ester-based oil],” he said. “And the estolides show top-of-class performance,” when compared with group three base oils, and low viscosity PAOs.
Attempting to “dispel some of the myths” of performance problems within bio-based hydraulic fluids as well as stern tube oils, Mr Miller said Biosynthetic Technologies had created a “VGP-compliant type of performance product utilising an eco-label capable additive system, the estolides, [and] a couple of unique base oils”.
“We looked at it in terms of the environmental performance, getting… the OECD 301 B biodegradability. This exceeds the 60% by a significant margin, up along the lines of 77%. And it’s classified as readily biodegradable,” he said. “One of the other things we like about it is typical biobased lubricants and VGP-compliant lubricants struggle with rust and reliability. And this formulation passed with flying colours,” Mr Miller said.
Biosynthetic Technologies has also made headway on gear oils for thrusters and similar applications in maritime, according to Mr Miller.
“We started tinkering with that using an eco-label capable formulation – 100% of the estolide base oil – and we were able to exceed the rust and saltwater corrosion protection and show excellent wear protection. Encouraged by that result, we went out to meet the [ISO] 51517 specification as well as the China GB specification,” he said.
The tests pitted the Biosynthetic Technologies lubricant against two commercially available synthetic, biodegradable, VGP-compliant gear oils.
“The estolide-based gear oil was able to meet all the performance requirements, again showing excellent oxidative and hydraulic stability. And this time, we put it into the micro-pitting test… and we got a first-time pass through the system,” Mr Miller said.
With 83% of those polled saying they currently utilise bio-lubricants, nearly 60% of poll respondents claimed to use EALs in all oil-to-sea interfaces as a preferred method of meeting VGP. Some 23% use air-gap seals, 7% claim technical infeasibility and some 10% said they avoid sailing in US waters to avoid compliance.
Citing “higher and higher goals for sustainability” throughout the industry, Mr Miller said Biosynthetic Technologies’ products were created with adherence to circular economic principles.
“We believe in circular economy. Our base oils are derived based on balancing social impact – looking to not compete with food for our bio-based content, we’re looking for the opportunity to create jobs through farming and agriculture,” he said, noting the company made efforts to ensure its products are net carbon negative “from gate to wake”.
Poll respondents listed environmental performance (9%) as the lowest consideration out of four options when it came to drivers of purchasing decisions. Price led the way at 43%, with quality and global availability coming in at 31% and 17%, respectively.
© 2023 Riviera Maritime Media Ltd.