Use of Biowaste-Derived Biosurfactants in Production of Emulsions for Industrial Use

This study reports on the use of soluble biobased organic substances (SBO) with emulsifying properties in the production of oil-in-water emulsions for industrial consumption. One of the potentially interesting applications is in formulation of metalworking fluids, which typically consist of oil-in-water emulsions used in metal manufacturing industries. Soluble biobased substances were collected from urban food and gardening wastes in a waste management plant located in a densely populated area in North Italy. The biowastes were fermented under anaerobic and/or aerobic conditions and then treated chemically to yield four different SBO samples, which were characterized for chemical composition, solution behavior by water surface tension measurements, and ability to form stable 10% oil-in-water (O/W) emulsions. Experiments were carried out to evaluate the hydrophilic−lipophilic balance of emulsions with surfactant concentrations in the 2−8% (w/w) range. Stable emulsions were obtained with at least 3% (w/w) surfactant concentrations. All SBO samples presented the characteristics necessary for acting as emulsifiers, when compared with conventional emulsifiers. According to rheology, particle size, and centrifugation tests, SBO samples isolated from composted biowastes performed better than samples isolated from the digestate of anaerobically fermented biowastes. The product ash content and/or isolation process also affect the emulsifier performance. The effects of the biowaste source, chemical composition, and surface activity on the emulsifier performance were evaluated, indicating the feasibility of attaining stable emulsions with environmental benefits.