ABSTRACTThe The The The synthesis of synthesis of synthesis of synthesis of fatty acid ethyl ester from chicken fat waste using ZnO/SiO fatty acid ethyl ester from chicken fat waste using ZnO/SiO fatty acid ethyl ester from chicken fat waste using ZnO/SiO fatty acid ethyl ester from chicken fat waste using ZnO/SiO2 2 2 2 heterogeneous catalyst was carried heterogeneous catalyst was carried heterogeneous catalyst was carried heterogeneous catalyst was carried out using t out using t out using t out using two wo wo wo----step procedures of acid pretreatment by esterification and transesterification of the pretreated oil. step procedures of acid pretreatment by esterification and transesterification of the pretreated oil. step procedures of acid pretreatment by esterification and transesterification of the pretreated oil. step procedures of acid pretreatment by esterification and transesterification of the pretreated oil. The first step reduces the high free fatty a The first step reduces the high free fatty a The first step reduces the high free fatty a The first step reduces the high free fatty acid in the oil to an acceptable level for transesterification using cid in the oil to an acceptable level for transesterification using cid in the oil to an acceptable level for transesterification using cid in the oil to an acceptable level for transesterification using concentrated sulphuric acid at a temperature of 60 concentrated sulphuric acid at a temperature of 60 concentrated sulphuric acid at a temperature of 60 concentrated sulphuric acid at a temperature of 60 o o o o C C C C during 1 h of reaction time. The second step was during 1 h of reaction time. The second step was during 1 h of reaction time. The second step was during 1 h of reaction time. The second step was transesterification of the preheated oil using silica promoted zinc oxide as heteroge transesterification of the preheated oil using silica promoted zinc oxide as heteroge transesterification of the preheated oil using silica promoted zinc oxide as heteroge transesterification of the preheated oil using silica promoted zinc oxide as heterogeneous catalyst. A three level, neous catalyst. A three level, neous catalyst. A three level, neous catalyst. A three level, four factorial box behnken design (BBD) of response surface methodology was used whereby the four factorial box behnken design (BBD) of response surface methodology was used whereby the four factorial box behnken design (BBD) of response surface methodology was used whereby the four factorial box behnken design (BBD) of response surface methodology was used whereby the biodiesel yield biodiesel yield biodiesel yield biodiesel yield obtained in the range of 56 obtained in the range of 56 obtained in the range of 56 obtained in the range of 56−88%and a second order quadratic polynomial regression model that established the −88%and a second order quadratic polynomial regression model that established the −88%and a second order quadratic polynomial regression model t...