For the first time, an efficient simultaneous trans/esterification process for biodiesel synthesis from waste goat tallow with considerable free fatty acids (FFAs) content has been explored employing an infrared radiation assisted reactor (IRAR). The impacts of methanol to tallow molar ratio, IRAR temperature and H2SO4 concentration on goat tallow conversion were evaluated by response surface methodology (RSM). Under optimal conditions, 96.7% FFA conversion was achieved within 2.5 h at 59.93 wt.% H2SO4, 69.97 degrees C IRAR temperature and 31.88:1 methanol to tallow molar ratio. The experimental results were also modeled using artificial neural network (ANN) and marginal improvement in modeling efficiency was observed in comparison with RSM. The infrared radiation strategy could significantly accelerate the conversion process as demonstrated through a substantial reduction in reaction time compared to conventionally heated reactor while providing appreciably high biodiesel yield. Moreover, the in situ water removal using silica-gel adsorbent could also facilitate achieving higher FFA conversion to fatty acid methyl ester (FAME). Owing to the occurrence of simultaneous transesterification of triglycerides present in goat tallow, overall 98.5 wt.% FAME content was determined at optimal conditions in the product biodiesel which conformed to ASTM and EN biodiesel specifications. (C) 2013 Elsevier Ltd. All rights reserved.