The establishment of an algal biofuels industry is dependent upon the development of a robust process scheme that successfully integrates major processing steps such as cultivation, harvesting, oil extraction and fuel conversion in a cost-effective manner.  Developing a low cost harvesting step is considered to be one of critical steps in producing algal biofuels that are cost competitive with petroleum-based fuels.  Alkalinity-induced autoflocculation has been explored as a process method for harvesting and concentrating microalgae.  At a sufficiently high pH cations such as Mg++ and Ca++ can be precipitated as salts thereby trapping microalgal cells within a salt precipitate. As a result the interstitial space of the forming floc is composed of precipitated salts, whose added density may considerably increase the settling rates of microalgae. The method is likely to be broadly applicable to different algal species which may not aggregate well using traditional flocculating agents such as alum and ferric chloride. The overall process consists of mixing during alkaline addition, followed by a coarsening period that produces shear-limited precipitates, and then quiescent sedimentation. During sedimentation, further flocculation occurs as visibly larger flocs settle. The sedimentation rate and concentration factor were measured for different microalgal species grown under various culture conditions. In preliminary experiments with Chlorella vulgaris, a 60-fold increase in settling rate could be achieved with pH-induced flocculation relative to single-cell settling alone. These initial experiments suggest that the sedimentation rate can be increased with increased precipitation; however, the settled solids volume also increases, which reduces the final concentration factor.