I am greatly honored to present this Keynote address. My focus, even after sixty years, continues to be on the future of phycology, even though I now present mainly from the past. I am delighted to see biological and physical scientists and engineers coming together in the field of Applied Phycology. Our working together will result in many benefits for mankind. There is no doubt that Applied Phycology has a great future because it has the potential for more efficient use of solar energy than conventional agriculture, and because it is poised to reach still unimagined goals through both genetic and ecological engineering. As an engineer I have focused mainly on large algal mass culture systems and the efficient use of solar energy in wastewater treatment (Oswald, 1962, 1963). But now I can envision such future triumphs as the introduction of genes for sulfur amino acids into the presently deficient Spirulina genome. I am fascinated by Dr Bailey Green’s crusade to minimize energy use and greenhouse gas emissions using algae-based sewage treatment (Green, 1998), by Dr Joseph Weissman’s commercial production of shellfish fed mass cultured algae, and by Dr John Benemann’s vision of achieving very high productivities through physiological and genetic manipulations of the photosynthetic apparatus (Benemann, 1990), to mention just three examples currently underway by former students and colleagues. All of these and many more advances have resulted from combining biological and engineering knowledge. As a young civil engineer I was greatly surprised when I learned that the growth of one unit dry weight of algae is accompanied by release of over one and one half times as much dissolved molecular oxygen, a process powered by virtually free solar energy. How to use this low cost dissolved O2 in wastewater treatment and life support systems has consumed much of my, and many of my students’, ingenuity during the past half century. Over these years my main area of research has been the design and operation of largescale cultures of microalgae that grow commensally with bacteria in rich organic media such as domestic sewage or some industrial wastes. Not only is solar energy and the resulting ‘photosynthetic oxygenation’ nearly free, but also the nutrients in the wastewaters are free and often ideally suited for algal mass cultures. In these waste treatment ponds we only exert minimal control over the algal species that grow, but we can impose some limits through pond operations such as residence time, depth and mixing. For reasons best known to the algae themselves, we often find species of Chlorella, Scenedesmus, and Micractinium, although species of Euglena, Chlamydomonas and Oscillatoria may occur in ponds with excessive loadings or long residence times. In these wastewater-fertilized systems the role of algae is primarily for production of O2 to support bacterial growth, although nutrient uptake, adsorption of heavy metals and, indirectly, disinfection are also important functions of the algae in these systems. In the following I highlight some of the benefits of growing microalgae in wastewaters (Oswald 1978).