Methyl or ethyl esters were produced from lard and restaurant grease by lipase-or base-catalyzed reactions. Before esterifying, some renewable substrates (lard and restaurant grease) should be manipulated through acetone fractionation or on a chromatography column packed with an adsorbent to obtain maximal reaction rate. Because lipase activity was hindered by excess amounts (more than 1 mol) of methanol, each 1 M methanol was added sequentially after 24 h of reaction. Through a three-step reaction, 74% conversion to tallow-methyl ester was obtained. However, a porous substance, such as silica gel, improved the conversion when more than 1 M methanol was used as reaction substrate. When a 1:3 (fractionated lard/methanol, mole ratio) substrate was used, the conversion rates (i.e., extent of conversion) were 2.7 (24 h) and 2.8% (48 h). However, with 10% silica gel in the reaction mixture, the conversion rates increased to 25 and 58%, respectively. Regenerated restaurant grease (FFA removed through column chromatography) was further converted to esters by alkali-catalyzed methanolysis. After 24 h of reaction, 96% conversion was obtained, while only 25% conversion was observed from crude grease. Alkyl esters produced in this study could be used for fuels, potentially as biodiesel.In the early 1930s, vegetable oils were tested on diesel engines as fuel. However, the high viscosity of vegetable oil, compared to petroleum-derived fuels, caused the engines to malperform, impeding their application as engine fuel. Nevertheless, concerns about petroleum shortages and environmental issues have continuously promoted the development of "alternative fuels" from vegetable oils, animal fats, and even restaurant grease (1-3).Monoalkyl esters of fats and oils are known as biodiesel (BD), which can be used as a blend with conventional petroleum fuels. Oils are esterified with alcohols (alcoholysis) to overcome the high-viscosity problem as engine fuel. In diesel engine performance and emission tests, a 20% blend of alkyl ester with No. 2 diesel fuel (BD-20) reduced emissions of particulate matter (−26.8%), carbon monoxide (−72.8%), and total unburned hydrocarbons (−73.2%) (4). Therefore, BD is one of the alternative fuels regarded as environmentally friendly.Lard is an inexpensive co-product of the meat-packing industry that could be further converted to value-added products such as BD. However, the relatively high contents of saturated fatty acids (SFA) in lard result in the poor coldtemperature properties of its alkyl ester. To improve coldtemperature properties, the content of SFA in lard could be reduced through a fractionation process before esterification. As a consequence of this procedure, BD from fractionated lard resists forming crystals at low temperatures, thus improving cold-temperature properties. Restaurant grease would be another renewable source for BD production. During cooking, especially deep-frying, oils are hydrolyzed into FFA and degraded by complex chemical reactions. As a result, abused cooking oils contain ...