We hear from Aaron Ainsworth, School of Engineering, University of Birmingham whose PhD project was funded by the Douglas Bomford Trust and EPSRC.
Back in March, I attended the 2026 AFCP Student Forum at Rothamsted Research. There I presented my recent work on the feasibility of some water-based lubricants made using plant carbohydrates. This was but a snapshot of what I’ve learned over my three years of PhD study. In this article, I’d like to share what I’ve learned and some of my findings thus far.
The importance of good lubrication
I’m a tribologist – that means I study friction, wear and lubrication. Lubricants are the lifeblood of machines. Without them, worldwide industry would quite literally grind to a halt. Right now, around a quarter of global energy is spent overcoming friction and replacing worn-out parts. The vast majority of lubricants in use today are derived from crude-oil. These petroleum oils are great at their job but come at the cost of being non-renewable, volatile prices, and low biodegradability.
Our reliance on petroleum lubricants only serves to the long-term detriment of agriculture. Every year, millions of tonnes of lubricant enter our ecosystems. Whether due to improper disposal or leaky machinery, the fact remains that current offerings cause lasting damage to freshwater and soil health. Land degradation such as this can increase greenhouse gas emissions, decrease soil arability, and increase crop price volatility.
What are the alternatives?
My research focuses on more sustainable replacements to these problematic oils, particularly in an agricultural context. It aims to assess a range of renewable bio-lubricants. From conventional examples such as vegetable oils, to more exotic microbial oils from fungi and bacteria. Each type has their pros and cons of course; there is no such thing as a universal lubricant. As for the agricultural focus, it’s multi-faceted. I wanted to consider lubricant applications such as universal tractor oils, transmission fluids and wet clutches, but also disseminate information about this lesser-known issue with the agronomic community (like I’m doing right now!).
Making more of waste
A major aspect of my PhD is waste valorisation. It’s the process of adding value to waste products via recycling or reuse. Many waste streams can be found around the farm such as animal waste and crop residues. When we consider the valorisation of crop residues, we tend to only think of their use for fertiliser and animal fodder. However, research shows that bio-lubricants can be extracted from many of these resources. For instance, vegetable oils from seed pods and nut shells, waste animal fats, or even water-based lubricants made from arable crop bi-products such as cereal husks, legume straw and fruit peels.
Following on from that, at the beginning of my project, I experimented with water-based lubricants made from apple seeds and apple wood clippings. They were simple solutions; however, they served as a bit of groundwork for me. Here at the University of Birmingham, I’m able to assess how well a substance reduces friction and wear in moving contacts using our range of tribometers (friction machines, see Figure 1), analytical microscopes and profilometers.
These initial studies, which were presented at the 2024 AFCP Student Forum, were inspired by previous studies using quince seeds. However, if you’ll excuse the pun, my apple lubricants weren’t very fruitful. They performed similarly in terms of friction and wear when compared to pure water, and considerably worse when compared to a conventional mineral oil.
While that may sound disappointing, the data and experience gained proved invaluable to my studies moving forward. In fact, it laid the foundation for the investigation I presented in March. The work looked at more water-based lubricants, this time using pectin and carrageenan. They’re both common gelling agents and thickeners used in the food industry. Carrageenan is found in red seaweeds and pectin is found in all land-based plants, being especially abundant in citrus fruit peels. It turns out that mixing them with water makes a noticeable improvement on its lubricating ability. I examined a variety of concentrations, from as low as 0.02% to 0.5%.
A range of experiments were conducted, from the usual friction tests to chemical analysis before and after being used, to viscometry (measuring thickness) and microscopic wear imaging (Figure 2). In short, I found that both substances lowered the amount of wear seen, especially so at higher concentrations, and carrageenan lowered the amount of friction measured too. Only the highest concentration of pectin tested did the same (Figure 3). They showed serious potential, so further testing is going ahead, including comparisons with mineral oil, testing under different conditions, and trying blends of the two substances.
The outlook
I realise this topic may have been quite different from the usual affair, but if we are to wean off petroleum-based lubricants, then I believe agriculture to be integral to that transition. A range of opportunities for growers and livestock farmers present themselves: whether it be cultivating new oil-bearing crops or rethinking how we best utilise our waste. The circular economy is a hot topic these days, and my field is no exception to its allure. An ideal future would be one in which farmers can convert their waste, either externally by selling it to recyclers or internally on the farm, into viable bio-lubricants that can then be utilised in their equipment.
My work is only a small piece of the puzzle of bio-lubrication, but I hope that by the end of it I can say that I have pushed the needle forward, even if only a little bit.
Lastly, I’d like to thank my supervisors Iestyn Stead and Karl Dearn for their guidance throughout my PhD. Also, a big thank you to the Douglas Bomford Trust and the Engineering and Physical Sciences Research Council (EPSRC) for funding this project.
