Production of biogas from greenhouse residues, outcome of intensive greenhouse vegetable cultivation, was investigated in this study. Plackett-Burman design (PBD) combined with central composite design (CCD) was employed for the optimization of thermal-H2SO4 pretreatment of greenhouse residues to obtain maximum biochemical methane potential (BMP). The effects of operational parameters; acid concentration, initial solid content, reaction time, reaction temperature and mixing speed on sCOD and sSugar were studied with PBD. The acid concentration and reaction temperature were found to be effective on sCOD and sSugar results. CCD was used for further optimization and the above-mentioned parameters were investigated in detail. A cost driven approach was preferred for the first optimization based on sCOD and sSugar. Acid concentration was minimized, whereas reaction temperature, sCOD and sSugar were maximized. For the second optimization based on BMP, desired goal was selected as maximum BMP, while reaction temperature and acid concentration were set within ranges. In the first optimization, pretreatment with 2.59% H2SO4 concentration at 100 degrees C reaction temperature yielded a maximum production of sCOD and sSugar. sCOD increase (%) and sSugar concentration were found as 75.80% and 28.63 mgGlucose/gVS, respectively. In the second optimization, pretreatment with 0% H2SO4 at 78 degrees C reaction temperature resulted in maximum BM P production. The amount of biogas production obtained was 274.1 mLCH(4)/gVS under these conditions. The enhancement of BMP compared to untreated raw material (231.3 mLCH(4)/gVS) was found as 18.5%. (C) 2011 Elsevier B.V. All rights reserved.