We report an economically- and environmentally-promising microalgae biorefinery pathway, which uses catalytic pyrolysis with HZSM-5 catalyst to convert whole microalgae into aromatic hydrocarbons. This process produces valuable petrochemicals and ammonia, the latter of which can be recycled as a fertilizer for microalgae cultivation. We tested samples of lipid-lean green microalgae, Chlorella vulgaris , at various reaction temperatures and catalyst loads. We also tested samples of lignocellulosic biomass, red oak, for comparison. Our results demonstrated that catalytic pyrolysis of microalgae produces better aromatic yields and better aromatic distributions than catalytic pyrolysis of red oak. The maximum carbon yield of aromatics from microalgae was 24%, while that from red oak was 16.7%. Moreover, catalytic pyrolysis of microalgae produced more monocyclic aromatics than were produced by catalytic pyrolysis of lignocellulosic biomass. Microalgae present many advantages as a feedstock for biofuel. With the promise catalytic pyrolysis offers for solving some of microalgae's disadvantages, microalgae biorefineries move one step closer to economic and environmental feasibility. Catalytic pyrolysis of microalgae converts protein-rich microalgae into green aromatics, while nitrogen in protein is released in ammonia and recycled for algae growth.