A multistage anaerobic digester for treatment of wastewater including complex organic polymers, includes a hydrolysis stage converting the complex organic polymers received at an inlet to solubilized monomers at an outlet; an acidogenesis stage, coupled to the outlet of the hydrolysis stage, converting the solubilized monomers into intermediate products at an outlet of the acidogenesis stage; an acetogenesis stage, coupled to the outlet of the acidogenesis stage, converting the intermediate products into simple molecules at an outlet of the acetogenesis stage; and a methanogenesis stage, coupled to the outlet of the acidogenesis stage, converting the simple molecules to an end product, the end product including a quantity of methane and a quantity of carbon dioxide.