This study investigates the year-round production potential and quality of biodiesel from wastewater treatment high rate algal pond (WWT HRAP) biomass and how it is affected by CO2 addition to the culture. The mean monthly pond biomass and lipid productivities varied between 2.0 +/- 0.3 and 11.1 +/- 2.5 g VSS/m(2)/d, and between 0.5 +/- 0.1 and 2.6 +/- 1.1 g/m(2)/d, respectively. The biomass fatty acid methyl esters were highly complex which led to produce low-quality biodiesel so that it cannot be used directly as a transportation fuel. Overall, 0.9 +/- 0.1 g/m(2)/d (3.2 +/- 0.5 ton/ha/year) low-quality biodiesel could be produced from WWT HRAP biomass which could be further increased to 1.1 +/- 0.1 g/m(2)/d (4.0 ton/ha/year) by lowering culture pH to 6-7 during warm summer months. CO2 addition, had little effect on both the biomass lipid content and profile and consequently did not change the quality of biodiesel. (C) 2016 Published by Elsevier Ltd.