Transesterification Biodiesel 2 Esterification 2 Esters 2 Fatty acids 2 Fossil fuels 2 esterification 2 transesterification 2 Article 1 Betaine 1 Betaine methyl ester 1 Biodiesel production 1 Catalysis 1 Catalysts 1 Clean fuel 1 Comparatives studies 1 Complex fertilizer 1 Crude ester 1 Environmental problems 1 Fatty acid methyl ester 1 Feedstocks 1 Fertilisation 1 Fertilizers 1 Fuel oils 1 Heterogeneous base catalyst 1 Heterogeneous catalyst 1 Heterogeneous solid acid catalysts 1 High free fatty acids 1 Latin rectangles 1 Low grade 1