Sustainable biolubricants developed from agricultural waste

Traditional lubricants are usually made from petroleum products and non-biodegradable thickeners or additives, which can be harmful to the environment. This raises the need to find alternatives made from other renewable and biodegradable products, so that they maintain their functionality, but with less impact.

Taking this into account, a team from the Chemical Products and Processes Technology Centre (Pro2TecS), attached to the University of Huelva in Spain, has developed a product for lubricant applications made from wheat cellulose pulp and castor oil, derived from agricultural waste. Manuel Trejo Cáceres, María Carmen Sánchez and José Enrique Martín Alfonso have found that this waste can be used as a thickener or additive for oils and bitumens, as an alternative to conventional ones. The resulting products are less toxic and less harmful to the environment than those normally used in the industrial sector. They also propose a mixture that can be used to pave places such as roads, made from this same agricultural waste. In this way, they obtain more sustainable products than the usual ones.

“Our aim was to propose an alternative that would take advantage of and reuse agricultural waste, in line with the new Andalusian industrial policy, in accordance with the principles of the circular economy model ‘less raw materials, less waste, less emissions’,” José Enrique Martín, professor of Materials Science at the University of Huelva, explained to Fundación Descubre.

To obtain cellulose pulp from wheat straw and waste, researchers used the Kraft chemical process, which consists of applying caustic soda to the waste and heating it until its fibres become a semi-solid paste. This process is used, for example, for the production of paper.

Using this paste, the scientific team carried out an exhaustive study of the main variables that affect its chemical modification: temperature, reaction time and the ratio between reagents. As occurs in the tests of culinary recipes, this allowed them to check how much heat they had to apply, the time it took to take effect and how the properties of the final product changed once mixed with the fluids.

In this way, over the course of a year of experimentation, they obtained a range of different pastes with different chemical modifications and were able to verify which ‘recipe’ worked best and what each one was used for.

Dispersion formulated with modified wheat cellulose paste and castor oil suitable for lubricant applications. (Photo: University of Huelva / Fundación Descubre)

The experts add that the modified paste can be used as a thickener or additive to develop lubricating greases or binders. “Under normal circumstances, these substances would not mix well. What we have done is improve their chemical compatibility so that the mixture is more stable and homogeneous, also providing other functional properties,” says Manuel Trejo, a researcher from the University of Huelva.

The study is titled “Assessment of the acetylation process of wheat straw pulp as a sustainable rheological modifier for non-polar fluids” and has been published in the academic journal Cellulose.

The next step for the researchers from the Pro2tecs group will be to improve the functional properties of the paste by modifying its physical properties and adding other chemical groups that will give rise to new products with improved properties. (Source: Fundación Descubre)