56 P. M. COOK 



production of Chlorella. To make a system successful it first must 

 be technically feasible and, second, it should give a fair return 

 per dollar of investment and operating cost. A system uf large 

 shallow tanks v^^as visualized in v^'hich growdi vi'ould be allov^ed 

 to proceed for a period of time and the contents then harvested. 

 A further development from this vi^ould be a series of tanks, 

 each successively larger, to permit more efficient utilization of 

 Hght, space, and equipment. Careful analysis of data on the 

 growth of Chlorella clearly showed, however, that growth was 

 most rapid during a short portion of the life of a batch culture. 

 This indicated that for maximum production, the culture should 

 be grown under conditions optimum for its most rapid growth 

 and highest yield. Therefore, a continuous system was visualized 

 in which conditions were maintained constant at the point for 

 maximum production. Without experimental data, however, it 

 was virtually impossible to accurately estimate costs of producing 

 Chlorella and it was clear that no estimate could be made of the 

 value of large-scale cultures without considerable reseach. A sur- 

 vey of the literature had shown that Dr. Jack Myers (Myers and 

 Clark, 1944) had developed a laboratory apparatus that would 

 maintain constant conditions and that studies could easily be 

 made with this equipment to determine optimum conditions for 

 growth. In addition to the importance of this technique for basic 

 scientific studies, Dr. Myers has made a significant contribution 

 in showing the technical feasibility of a continuous system. By 

 holding conditions of culture constant and also by studying the 

 effects of varying conditions on the growth of Chlorella, he has 

 thrown new light on the mechanism of photosynthesis. His work 

 provided strong evidence that a large-scale continuous system 

 maintainmg constant conditions was technically feasible. 



The importance of maintaining a continuous system is easily 

 seen. Sunlight, in order to be used most efficiently, must be inci- 

 dent upon a culture in which optimum conditions for photosyn- 

 thisis are maintained. These conditions exist in a "batch culture" 

 (one grown over many days, starting with a small inoculum and 

 being harvested at a high population density), for only a limited 

 period of time. In agriculture there is an extremely inefficient 



