Algal-based biofuels have the potential to significantly impact the global use of petroleum-based fuel sources without competing with agricultural feedstocks. Chlorella vulgaris, a unicellular green alga with a high growth rate and limited nutritional requirements, can produce up to 42% lipids per dry mass under stress conditions, making it a promising biofuel feedstock. Of all lipid classes, triacylglycerols (TAGs) are most desired, as three moles of fatty acids are generated from every one mole of TAGs. The process of transesterifying these fatty acids results in the generation of a glycerol waste product with little economic value. With the exposure of mixotrophically grown C. vulgaris to exogenous glycerol, overall TAG production was increased, likely as a function of lipid cycling from cell membranes. Furthermore, with the use of isotopically labeled glycerol and GC-MS, it was determined that the exogenously applied glycerol was directly incorporated into the TAG backbone, a novel finding. Thus, using the glycerol waste product of TAG transesterification has the potential to increase the efficiency of algal biofeedstocks, both by recycling a previously unused waste product as well as increasing the high-energy TAG percent within the cultures.