Ecological and economic evaluation of a novel glycerol based biocide-free metalworking fluid

Worldwide, huge amounts of mineral oil containing metalworking fluids (MWF) are applied for industrial metal machining. Future challenges in the field of lubricant usage are to overcome the consumption of finite resources and to solve problems like compatibility of MWFs to human health and environment as well as laborious deoiling and costly disposal. In this context, ecological and economic properties of a novel glycerol/water-based MWF are introduced. Investigations revealed that if a proportion of ≥35% of the biostatic trihydric alcohol glycerol was present in the MWF, the addition of biocides for fluid protection was unnecessary. Technical grade glycerol, a renewable by-product from the biodiesel market, proved a sufficient purity for application. Compared to common MWFs, the cleaning of metal surfaces just by rinsing with water was distinctly facilitated because of the water solubility of all fluid components. A disposal of the MWF at the end of service life or the wash waters had not to be considered because of the microbiological degradability of the organic components of the diluted MWF. The novel glycerol-fluid is available for energetic or even material recovery which contributes to cost reduction and covers the aspect of sustainability. Concerning the costs of application of the novel MWF in industrial production processes, the fluid even nowadays appears to be competitive to many common mineral oil based lubricants.