Production and Testing of Butyl and Methyl Esters as New Generation Biodiesels from Fatty Wastes of the Leather Industry

Climate changes caused by the greenhouse effect make it necessary to look for new sources of energy. One of them is waste of a biological origin. They are often difficult to dispose of and such a process can be expensive. Increasingly, they are used to produce biofuels that can replace petroleum-based fuels. They are also an alternative to food-based biofuels. The aim of the work was to propose a method of using fatty waste generated in a plant dealing with tanning animal skins and to evaluate the properties of the produced biofuels. The authors decided to use this waste to produce biodiesel. A patented reactor and technology developed by one of the co-authors was used for this purpose. Two alcohols, butyl and methyl, were used to produce esters in the transesterification process. Animal fats butyl esters (AFBE) and animal fats methyl esters (AFME) have been produced. A high efficiency of the transesterification process was obtained. It amounted to 99.2 (wt.%) for AFME and 98.9 (wt.%) for AFBE. The physicochemical properties of AFBE and AFME biodiesels, diesel fuel, and mixtures of these biodiesels and diesel fuel were tested. Most of the tested properties of AFBE were more favourable than those of AFME. The produced AFBE in relation to AFME was characterized by better cetane number, heat of combustion and calorific value, density, dynamic viscosity, kinematic viscosity, and flash point. For example, the kinematic viscosity for AFBE was 3.6 mm2/s and for AFME 4.1 mm2/s. In contrast, the calorific value of AFBE biodiesel was 39.2 MJ/kg, and that of AFME biodiesel was 38.4 MJ/kg. The use of butanol from the point of view of the properties of the produced biodiesel turned out to be more advantageous in relation to methanol. Due to the fact that the production uses waste fat, the produced biodiesels can be regarded as second-generation biofuels. Producing biodiesel from waste is a way to utilize waste and is beneficial in terms of environmental protection. It can be a way to increase the share of biofuels in the energy balance of regions where large amounts of fat waste products of animal origin are available