Nowadays, microalgae as renewable resources have wide applications in food, pharmaceutical and biofuel industries and has attracted particular attention. Biorefinery is recognized as a promising way to create a biomass-based industry that is capable of producing value added products and biofuels through various processes; in this regard, microalgae can be viable and economical raw materials for biorefineries. In this study, the microalgae Haematococcus pluvialis were cultivated and After studding its growth under favorable conditions, it was subjected to the stress of nitrogen deficiency with intense light to produce the antioxidant pigment astaxanthin, as a highly valuable pigment. The stress conditions were studied at two different temperatures of 26?C and 35?C to determine the effects of temperature on carotenogenesis. As a result, the pigment content at 35?C was 1.8 fold higher than that of the lower temperature (3.93% based on cell dry weight). The biomass was analyzed in terms of pigment and carbohydrate contents. The pigment was extracted using ultrasonic apparatus and acetone as a solvent. This process resulted in 81% solid biomass recovery used for biofuel production. After determining the total carbohydrate content, the biomass residue was first subjected to enzymatic hydrolysis. The hydrolysis efficiency of 97.2% over the total residual glucan was obtained. Then, the glucose released during hydrolysis was fermented by yeast Saccharomyces cerevisiae and yielded 0.44 gram ethanol per gram of glucose and 0.2 gram ethanol per gram of solid residue. Then, the residual solid remained after fermentation, the residual solid after pigment extraction and the raw algae sample of Haematococcus pluvialis were used for biogas production. The highest amount of methane produced was 232.2 ml/g volatile solid with 62.7% methane yield from residual biomass after pigment extraction. This study showed that the microalgae Haematococcus pluvialis is a proper candidate for astaxanthin as well as ethanol and biogas production in a biorefinery approach . Keywords: Microalgae, Haematococcus pluvialis , Astaxanthin, Ethanol, Biogas, Biorefinery
