54 PHOTOSYNTHESIS 



with different raw materials. Table 6 is taken from the book of Monier- 

 W'illiams ; the values have been converted into U. S. gallons and liters. 



There are, of course, a great many more plants than those given in 

 Table 6 from which alcohol is produced, the plants used in different parts 

 of the world depending upon a number of different agricultural and eco- 

 nomic conditions. It is only the hexose sugars, d-glucose, d- fructose and 

 d-mannose that can be converted readily into alcohol by the enzyme of 

 yeast. Galactose is present in the products of hydrolysis of many plants, 

 but this sugar is fermented with difficulty. The pentose sugars which 

 comprise a considerable proportion of many plants are not fermented with 

 pure yeast. Recently other organisms have been found which convert 

 the pentose sugars into a variety of products, but this is not as yet carried 

 out on a large scale. 



The production of alcohol on a large scale has usually been consid- 

 ered from the economic viewpoint. Under present circumstances this is 

 essential and must include the many agricultural conditions related to soil, 

 climate, water supply, fertilizers, etc., as well as the factors of methods 

 of production, labor, transportation, markets, by-products, etc. The 

 problem therefore becomes an exceedingly complicated one. But here we 

 are, for the moment, not concerned with alcohol as competitive or even 

 supplementary to petroleum but rather with the perhaps somewhat specu- 

 lative idea of whether alcohol can replace petroleum, i.e. whether it can 

 serve as one of our principal sources of energy. 



In view of the fact that the raw materials from which alcohol can be 

 produced are all plant products the question immediately arises what 

 effect such a gigantic undertaking would have on the production of 

 foodstuffs. There is no sound indication that man will be able to derive 

 his food from any other source but the soil. So that if his means of 

 obtaining industrial energy is to be the same as that for obtaining food- 

 stuffs, the cjuestion is raised whether there will be a competition for 

 arable land to be devoted to food production on the one hand or fuel 

 production on the other. Boyd ®° has made an interesting analysis of 

 the possibilities of using vegetation as a source of motor fuel. The fol- 

 lowing figures give an idea of the situation : 



Average annual U. S. production of corn, 1913-1919, bushels. .2,740,000,000 



Average annual Acreage in corn, 1913-1919 106,000,000 



Alcohol from corn at 2.75 gallons per bushel 7,500,000,000 



Concerning this Boyd states: "The heating value of this amount of 

 alcohol is about equal to that of 5,000,000,000 gallons of gasoline. The 

 production of gasoline in the U. S. during 1920 was very close to this 

 amount, it having been about 4,900,000,000 gallons. The average acreage 

 in corn as given above is equal to 166,000 square miles, which is more 

 than four times the total area of Ohio. In view of the fact the possible 

 alcohol production from corn represents close to 60 per cent of the total 



"Boyd, T. A., Jouni. Ind. and Bug. Chcin., 13, 836-841 (1921). 



