Socioeconomic concerns, the depletion of fossil fuels and other raw materials, and climate change, led people to pay greater attention to domestic and industrial wastes. Transforming waste materials into more useful products by reusing or recycling them, or converting them into an energy resource is of utmost importance. Many economic sectors (transportation, heat and power generation, industrial manufacturing, and construction) are focusing on new technologies to transform low-quality, no-cost materials into high-value products. Wastewater treatment using the microalgae has several advantages over conventional treatments: i) nitrogen and phosphorous can be converted into biomass without the addition of carbon source; ii) the discharged effluent into water bodies is oxygenated and obeys the discharge limits imposed by legislation; iii) high value products can be extracted from microbial biomass. The valorization of organic wastes (animal by-products, food residue, kiwi waste, glycerol) by anaerobic digestion is more attractive than other current treatment or disposal options.