In addition, the biofuel studies were generally done with fed batch culture in order for the algae to maintain log phase growth and maximize yields, a process that may be expensive on a larger scale. The sludge produced in wastewater treatment plants may provide a potential nutrient source for algae in the production of biodiesel while simultaneously creating an ecofriendly recycling process for the byproducts of sewage plants. Over a 6-day period, "Auxenochlorella" was able to remove 59% of the total nitrogen, 81% of the total phosphorus, and 96% of the total organic carbon from the waste while maintaining a high lipid productivity rate. Higher biomass production can be accomplished with a heterotrophic/mixotrophic growth mix using wastewater and biodiesel-derived glycerol. The lipid content can be lower in wastewater than in a synthetic medium, however. Thus, cost-benefit analyses are needed to determine when nutrient addition may be required and beneficial to foster algal growth. The lipid-extracted biomass can be used for a multitude of functions: biogas production, a biofertilizer carrier, biofertilizer itself, biochar production, and an ingredient in animal feed. Microalgal-treated wastewater may not be flawless drinking water, but it could be more suitable for irrigation purposes. Additionally, if the wastewater after the microalga harvest is subjected to water-treatment protocols, it reportedly reduces the operational cost of the water-treatment process.