Can biobased lubricants, especially biodegradable ones, be used as food-grade lubricants? Are food-grade lubes biodegradable, and are they necessarily biobased? Its understandable that some people think of these terms as interchangeable. After all, food comes largely from plants and animals, so it is easy to imagine that lubricants made from them should be safe for incidental contact during food processing.
Lubricants marketer Schaeffer Manufacturing Co. says this isnt necessarily so. A document on the companys website states:
These lubricants are often thought to be interchangeable; theres an assumption that if its not harmful to food processing, then it should be acceptable for the environment. Adding to this confusion is the fact that food-grade lubricants and biodegradable lubricants have some similarities.
The similarities are obvious, but the distinctions between these categories are clearer if one pays attention to their definitions and to aspects such as origin and performance.
Biobased lubricants, also commonly called bio-lubes, are a category of origin since they are defined as lubricating oils or greases made from substances derived from living organisms. Bio-lubes include a number of methyl esters derived from corn, canola (rapeseed) and similar plants, as well as coconut oil and other tree-based oils.
Overall global lubricant demand is approximately 40 million metric tons per year. Biobased lubes make up 300,000 tons of that total, or about 0.75 percent. Market research firm Kline & Co. has projected the category will grow at a compound annual rate of 5 percent, while others have projected anywhere from 4 to 7 percent annual growth. All of those numbers exceed growth forecasts for the overall market, so bio-lubes are obviously seen as a rising trend.
Some biobased lubricants are used because rules or policies require the use of materials made from renewable resources-policies based on supply chain considerations. For example, the United States governments BioPreferred Program is designed to support agriculture and reduce dependence on petroleum. It requires federal agencies to procure items meeting minimum biobased ingredient content thresholds for 109 categories of products, including lubricants, unless any of several exemptions apply.
The European Unions Ecolabel program is designed to encourage sustainability and reduce carbon footprints as well as dependence on petroleum. It authorizes products in lubricants and other categories to bear an Ecolabel logo if they meet biobased content thresholds. Ecolabel standards include additional requirements that products have minimal impact when exposed to natural environments.
Biobased lubricants may also offer some performance advantages. Many plant oils have excellent lubricity and viscosity indices, although they generally do not perform as well in oxidative stability or cold-temperature characteristics. They also tend to be biodegradable, nontoxic and non-bioaccumulative.
Protecting the Environment
These latter three parameters all come into play when judging whether lubricants are acceptable for applications that may expose them to the environment.
Biodegradability is defined by standard industry methods in terms of how quickly materials break down. There are four categories:
Readily biodegradable substances that degrade at least 60 percent in 28 days, and for which that degradation occurs within 10 days of when it begins;
Ultimately biodegradable substances degrade at least 60 percent in 28 days, but with no requirement for a 10-day window;
Inherently biodegradable substances degrade more than 20 percent but less than 60 percent in 28 days;
Non-biodegradable substances degrade 20 percent or less in 28 days.
The characteristics that minimize the environmental impact of biobased lubricants make them popular for use as hydraulic fluids in certain applications, since these fluids are prone to leak or spill from hydraulic equipment, and many types of said equipment are used in mobile applications or environmentally sensitive areas. Biobased lubricants can also meet requirements for marine applications with oil-to-sea interfaces, such as stern tube oils, which lubricate propeller shafts on ships and tend to leak into the water. The same parameters are also sought for side rail greases on railways. These greases lubricate curves on railroad tracks to prevent wear on both the track and the locomotive wheel flange. They are applied automatically, often in remote locations, and could contaminate waterways when washed off by the elements.
Bio-lubes may also be sought for applications where human health is an issue, such as metalworking fluids, which can generate mists that are unhealthy for workers. This segment has largely transitioned to products composed of up to 70 percent water by weight. Base stocks derived from plant or animal sources can be the primary components of the oil phase in these blends.
David Sundin, owner of Tyler, Texas-based SVB Environmental Lubricants, said biobased lubricants have gained acceptance within industry and are recognized as having significant advantages in certain applications. However, they still are not ready for the most demanding applications, he noted in a recent interview, such as crankcase motor oils or applications with a lot of heat and pressure. But for many, if not most applications, bio-lubes can be used as one-to-one replacements for petroleum based products.
Various man-made ingredients, some of them petrochemicals, can also be used to make lubricants that offer similar green attributes. Polyalphaolefins are non-toxic and, to varying degrees, biodegradable, as Ken Hope, global PAO technical services manager for Chevron Phillips Chemical, explained.
Lower-viscosity PAOs are more biodegradable, he said during a telephone interview, so 2 centistoke PAOs are readily biodegradable, 4 cst PAO is inherently biodegradable, and higher viscosities are less biodegradable. PAOs are used in applications that involve environmental and health concerns, such as environmentally acceptable lubricants, as defined by the U.S. Environmental Protection Agency, and metalworking.
Polyalkylene glycols also come from the petrochemical industry. Some of these fluids are also biodegradable and non-toxic and meet requirements of environmentally acceptable lubes, according to a 2016 article in Tribonet, an online resource from the University of Twente in the Netherlands.
Some synthetic esters are derived from plant or animal oils, but some are made of petrochemicals, and these can also be biodegradable.
Hope noted that lube formulators wanting to make environmentally acceptable products dont have to choose between biobased and non-biobased materials.
Oftentimes you can find a blend of both, he said. For example, a biobased material might suffer from poor oxidative stability or poor low-temperature performance, and blending with PAO improves those characteristics. By the same token, you could take a 9 cst PAO, which is at the upper limits of low-viscosity PAOs, and blend them with a high-oleic ester and end up with a lubricant that is quite a bit better for biodegradability than the PAO would have been by itself.
Keeping Food Safe
Unlike biobased products, food-grade lubricants are defined by performance. Specifically, they are designed to be non-toxic and to have no taste or odor, in case they come into contact with food. The industry recognizes three categories of food-grade lubes:
H1 for products used in food-
processing environments that present the possibility of incidental contact with food;
H2 for lubes used in locations of processing plants where there is no possibility of contact;
H3 for lubes, typically edible oils, used to prevent rust on hooks, trolleys and similar equipment.
Deciding whether there is a possibility of food contact is tough, so many plant operators err on the side of safety and select H1 over H2. Some go even further and require their lube suppliers to have NSF Internationals ISO 21469 certification, which involves on-site audits of the lubricant manufacturing facility.
The categories were originally created by the U.S. Department of Agriculture and defined in terms of materials and amounts of those materials that could be used in each. Today private organizations such as Ann Arbor, Michigan-based NSF run certification programs based on updated lists.
Most vegetable oils are non-toxic and are on the list of ingredients permitted for H1, said Benjamin Garmier, vice president of Renewable Lubricants in Hartville, Ohio. But you have to look at the additive packages, too, and-for example-certain antioxidants that would be used in non-food-grade biobased lubes may not be on the H1 list.
By the same token, some food-grade lubes would not meet the requirements of environmentally acceptable lubricants. People assume that products that are safe for incidental contact with food consumed by humans will also be safe for other organisms, Garmier said, but the rub is often that the microscopic organisms involved in toxicology tests cannot survive the quantities of lubricant they would encounter from spills.
Usually [food-grade products] fall down on the toxicological side, Garmier said. That and biodegradability, because food-grade doesnt require biodegradability, so why would you formulate for that if you dont have to?
Lubricants that meet requirements of both food-grade and environmental standards are actually rare, Garmier said. Renewable Lubricants makes two: an ISO 46 hydraulic fluid and an ISO 32 oil used in air tools.
From my experience in Europe, when people are looking for NSF-registered lubricants for incidental food contact, they are not looking for environmentally friendly products, said Marc Aluma, global business unit manager and chemical engineer for Industrial Quimica Lasem, which produces H1 lubricant components. For food processing, the application is enclosed, and so any leakage is under control.
There are important differences between food-grade, biobased and biodegradable lubes. Each is defined on a different basis and has different, if overlapping, purposes. Bio-lubes represent a large class of products made from once living feedstocks. Biodegradables are products that meet certain test protocols primarily designed to minimize environmental damage. Food-grade products are for a specific set of applications.
Caitlin Jacobs contributed to this article.