(625al) Production and Characterization of Biodiesel from Waste Lard

The diesel fuel consumption is very important, responding for nearly 60% of market share in fuels. Derived from fossil sources, the availability of diesel depends on the exploration of new petroleum reservoirs and on better use of the known ones. Although there is not a definite answer, it is likely that petroleum production rises to a maximum in a few years and then a decline period will take place. In this scenario, the development of alternative fuels from renewable resources, like biomass, has received considerable attention in all countries, mainly in Brazil due to its biodiversity. Biodiesel is an option in this situation. It is a mono-alkyl ester from fatty acids, like vegetable oils and animal fatties. It is produced by the transesterification of a triglyceride with a short chain alcohol, like methanol and ethanol, resulting in glycerol and esters.

Raw material characteristics are relevant factors in biodiesel production, when compared to process capital costs and energy consumption. At present, the most important raw material for biodiesel production is refined or semi-refined vegetable oil. Therefore, high production costs are expected most of the time, since the starting raw materials have a higher price than the produced biodiesel. When using refined oil, the raw material represents 70 to 80% of total cost process. Additionally, the use of food oils for biodiesel production is controversial.

Due to these disadvantages, several studies have been made to reduce costs on biodiesel production processes, such as the use of cheaper raw material. The use of wastes for biodiesel production has major advantages, since it does not compete with the food market, recycles waste and reduces production costs, therefore increasing biodiesel economic competitiveness. Examples of waste raw materials for biodiesel production are waste frying oils and animal fats like beef tallow, chicken fat and waste lard.

In this work, the production of biodiesel from waste lard was studied. Pork wastes, mainly consisting of fat and residual skin / meat and the lard separation was made by heating. The waste lard thereafter was transesterified with methanol and sodium methoxide (CH₃ONa) as the catalyst, in a batch reactor, for 1 hour, with a constant temperature of 50 ºC and stirred at 400 rpm.

The influence of methanol / lard mole ratio and of catalyst concentration on reaction yield was analyzed by the periodate method, which quantifies the formed glycerol.

A factorial planning analyzing two factors (mole ratio of methanol to lard and catalyst concentration) in two levels (5:1 / 7:1 and 0.50% / 1.00%) with a central point (6:1 and 0.75%) was used. The central point experiments were conducted in triplicate and the non-central points were carried out once.

Experimental results obtained in the transesterification reactions showed that the increase of methanol / oil mole ratio on reaction yield as well as the increase of catalyst concentration on reaction yield are positive. Reaction yields rose 10.95% on average when the mole ratio methanol / lard was increased. When catalyst concentration was augmented, reaction yields increased 5.45%, on average. These data show that the mole ratio effect is more meaningful than catalyst effect and these results are statistically meaningful, since the standard deviation was equal to 0.53%. Moreover, an interaction between methanol / lard mole ratio and catalyst concentration on reaction yield was observed. In the best operating condition, which consisted of a methanol / lard molar ratio of 7:1 and catalyst concentration of 1.00%, a 98.80% reaction yield was achieved. The biodiesel was further characterized – viscosity, flash point, acid value, density, copper corrosiveness, iodine value and cold clogging point. All these parameters followed Brazilian official regulations.