56 PHOTOSYNTHESIS 



fermentation and similar processes. From the waste molasses of the 

 sugar industry alone there are some two hundred million gallons of 

 alcohol produced annually. However, in the utilization of such surplus 

 and waste materials for large scale production a number of difficulties 

 are encountered. The supplies of such materials are often uncertain and 

 irregular, so that operation of a plant is overtaxed at one time and idle 

 at another. Storage of a great deal of such waste material is often im- 

 possible or expensive, which has made the continuous operation of the 

 distilleries impossible. One of the requisites for the successful operation 

 of an industry of this kind seems to be that the supply of the product is 

 continuous or synchronous with the demand, thus obviating the expense 

 and hazard associated with the storage of enormous quantities of alcohol. 

 With seasonal crops this has been exceedingly difficult to accomplish. 



Probably the most promising waste material of vegetable origin is the 

 cellulose from the lumber industry. Such material answers many of the 

 requirements of a source of fuel : it is easily produced and its supply can, 

 with proper management, be continuous. The chemical methods for 

 hydrolyzing the cellulose to fermentable sugars are, in principal at least, 

 very simple and the waste products from the fermentation process can 

 be returned to the soil to maintain its fertility.®^ Although this problem 

 has been the subject of much intensive research there is still much to be 

 done to assure good yields of alcohol. At present there are obtained 

 from 15 to 25 gallons of 95 per cent alcohol from a ton of sawdust which 

 is about 50 per cent cellulose or a yield of approximately 35 per cent of 

 the theoretical amount. The increase in these yields is dependent upon 

 the development of the chemistry of the processes involved. 



Whether there is sufficient waste cellulose available to supply the needs 

 is very difficult to ascertain. It has been estimated that there are approxi- 

 mately 5,000,000,000 cubic feet of waste in the woods and at the mills. 

 .Assuming a cubic foot of wood to weigh 30 pounds this would be 75,- 

 000,000 tons which at 20 gallons of alcohol per ton would yield 1,500,- 

 000,000 gallons of alcohol. This quantity represents about one third of 

 our present motor fuel requirements. In all probability the quantity 

 of waste material could be increased and it is also to be exp>ected that the 

 yield of alcohol can be increased. P)y making what appear to be rather 

 generous allowances for increase in waste material by various means, 

 Hibbert calculates that about 75 per cent of present requirements can be 

 cared for. Calculations of this nature are. of course, of limited value, 

 as they do not include the various economic factors of labor, transporta- 

 tion, interest charges, etc., which usually are the determining ones. But 

 such approximations as can be made, even in their most sanguine aspect, 

 do not assure a continuous supply of fuel in quantities to meet present 

 petroleum consumption. 



There is one other factor which may play a very important role in 



"Sherrand, E. C, Chem. Age, 29, 53 (1921). Hibbert, H., Journ. Ind. and Eng 

 Chem., 13, 841 (1921). 



