Effects of High Temperature & Pressure Pretreatment Process on Methane Production from Cyanobacteria

In this study, <i>Desertifilum tharense</i> cyanobacteria, which has energy generation potential, was firstly isolated from the water sources from Denizli/Turkey, the culture-specific parameters were identified, characterization analyses were performed, and the production in photoreactors under laboratory conditions was performed. <i>D. tharense</i> cyanobacterium was subjected to a high temperature–pressure pretreatment process (HTPP) to increase methane production efficiency, and the pretreatment process was optimized for methane production. <i>D. tharense</i> had a total carbon (C) content of 50.2% and total organic carbon content (TOC) of 48.9%. The biochemical methane potential (BMP) of the raw <i>D. tharense</i> sample was measured as 261.8 mL methane (CH₄) per gram of volatile solids (VS). In order to investigate the effects of HTPP and to determine the optimum process conditions, Central Composite Design (CCD) approach-based Response Surface Methodology (RSM) was used. BMP values of the samples treated with HTTP were measured in the range of 201.5–235 mLCH₄ gVS⁻¹ and lower than the raw sample. These results revealed that the HTPP is not suitable for the production of biofuel methane from <i>D. tharense</i>. The optimization of the HTPP was carried out by Design Expert software. For maximum BMP production, the software proposed a reaction temperature of 200 °C and a reaction time of 20 min as optimum conditions. With the proposed model, it was estimated that 227.1 mLCH₄ g VS⁻¹ methane could be produced under these conditions, and 211.4 mLCH₄ g VS⁻¹ methane was produced in the validation experiment. It was determined that <i>D. tharense</i> cyanobacterium could be used as a suitable biomass source for methane production. However, it was not necessary to use the HTTP as a pretreatment process prior to the methane production.