Can we make more sustainable choices in lubricants?

Foodgrade lubricants are products developed specifically for the food industry to reduce the risk of contamination during the production process and ensure maximum safety. Classically, the choice is between mineral or synthetic oils, both of which have less favorable origins. But then again, with vegetable oils, the operating range remains limited. Can cooking oil be a more environmentally friendly alternative?

Lubricants have enabled significant improvements in technology by reducing the natural wear and tear of mechanical parts. But in the food industry, lubricant manufacturers face additional challenges. There, lubricants must, on the one hand, reduce oxidation despite sometimes high or low temperatures and, on the other, inhibit the growth of bacteria, yeasts and fungi. In addition, they must allow safe contact with food for certain applications. In other words, they must minimize the risk of migration of hazardous substances into the food and must also not alter the organoleptic profile of food. Three well-known categories apply: H1 (incidental contact with food is possible), H2 (used for machinery and equipment where contact is ruled out) and H3 (stainless, soluble lubricants).

Mineral, synthetic or vegetable

Food grade lubricants have two main ingredients. The main ingredient is mineral, synthetic or vegetable and is responsible for the product's properties. Mineral oils are derived from petroleum and are the most widely used. They can have different viscosity grades and their strengths include thermal stability and resistance to oxidation. Synthetic oils are chemically processed and have higher thermal stability than mineral oils. They are often used in applications with extreme temperatures or heavy loads. This category includes polyalphaolefins (PAO), polyalkylene glycols (PAG) and esters. Vegetable oils are biodegradable but have less thermal stability and oxidation resistance than the former. Viscosity also depends on the type of plant from which they are extracted and can be affected by the temperature at which they are processed. Finally, we find additives in them. These improve the properties of the lubricant. They include, for example, antioxidants to prolong life, antifoaming agents, antimicrobials and anticorrosives. 

Oxidation stability as a concern

Research today is increasingly focusing on organic and ecological alternatives. Vegetable oils are the focus of interesting studies because of their ecological sustainability. However, they require extra care in storage and disposal. The main challenge is their oxidation stability, which can lead to the formation of undesirable compounds and the accumulation of deposits in the environment. To solve this problem, specific additives must be used in the formulation. Some materials may be incompatible and react chemically, causing elastic or plastic parts to deform or break down. This can lead to failure or corrosion of seals and equipment or reduced performance over time. Vegetable-based oils often have lower operating temperatures than mineral or synthetic oils, so they may have limited use under extreme operating conditions.

Cooking oil as an alternative?

The widespread use of mineral lubricants has broadened the debate on environmental impacts and led to the assessment of their alternatives. One of these is cooking oils. Unlike petroleum-based oils, these oils offer improved viscosity and tolerance to high temperatures, along with reduced volatility. Another factor that makes this oil attractive is its competitive price compared to other oils, its ability to produce energy with it and its more limited environmental impact. Another scenario is non-edible oils, such as rubber and castor oil. These oils are cheap as raw materials, but require specific technologies for their extraction and separation of unwanted impurities. 

Still more expensive

Although it is estimated that they can significantly replace petroleum products in particular, lubricants of organic origin are currently more expensive than mineral and synthetic oils. Doubts do remain about the energy efficiency of their production, along with poor hydrolytic stability. As a result, they are not very resistant to moisture and show reduced fluidity at low temperatures. We must also take into account another factor: the extraction of natural oils varies according to the climate, temperature and nutrients of the plants of origin. Thus, it is difficult to get stable products in terms of properties, which are also influenced by the extraction method. Further studies will be needed to ultimately improve the properties of vegetable oils, focusing on the possible conversion from wild to commercial crops, genetic interventions to obtain specific functions, and the development of chemical modifications and blends to obtain stable, ecological, high-performing and safe products.