ETHYL ALCOHOL FROM WOOD WASTE. 

 EFFECT OF TANNIN AND BARK. 



53 



Various mixtures of spruce and spruce bark were cooked under 

 the usual conditions of 7.5 atmospheres of pressure, 125 per cent 

 of water, and 2.5 per cent of sulphuric acid based on dry weight. 

 The results are given in the following table: 





Cook 



No. 



Total 

 sugars 

 (per cent 

 of origi- 

 nal dry 

 weight). 



Per cent 

 of total 

 sugars 

 fermen- 

 table. 



Alcohol yields. 





Per cent 

 of origi- 

 nal dry 

 weight. 



Gallons 



absolute 



per dry 



ton. 





84 

 87 

 85 

 88 



22.11 

 19.60 

 22.49 

 17 07 



70.38 

 69.47 

 60.04 

 31.95 



7.457 

 6.765 

 6.364 

 2.730 



22.55 



91.5 per cent of wood, 8.5 per cent of bark 



74.5 per cent of wood, 25.5 per cent of bark 



All bark... 



20.46 

 19.25 



8. 25 







From the result it is seen that as much as 25 per cent of spruce 

 bark may be mixed with the wood without appreciably decreasing 

 the yield of alcohol. Other barks were not available in sufficient 

 quantity to determine the practical limits to which they may occur 

 in waste mixtures without appreciable effect. Commercial experience 

 however, has shown that not more than 10 per cent of the total of 

 yellow pine may be bark without seriously affecting the yield. Spruce 

 bark has long been used in Europe as a tanning material and has 

 found favor because of its high sugar content, which in the "mellow- 

 ing" or fermentation and acidification of the tanning liquors produced 

 a comparatively large amount of acid and was therefore used as a 

 plumping agent. 



The tannin present shows no inhibitory action toward yeast growth, 

 for even sugar liquors produced from red and white oak gave normal 

 fermentation and fermentation efficiencies. In commercial practice 

 other factors have been found, such as long cooking periods with 

 increased formations of acids, acetone, and aldehydes, which influence 

 yeast growth and fermentation much more than does the tannin 

 found in the sugar liquors usually produced from mill waste. 



EFFECT OF CATALYZERS OTHER THAN SULPHURIC ACID OR IN ADDITION 



THERETO. 



As indicated previously, Korner, Cohoe, and others have attempted 

 the production of sugar and alcohol from wood with the use of hydro- 

 gen peroxide, potassium dichromate, and potassium persulphate 

 as hydrating and oxidizing agents in addition to sulphuric acid, and 

 these investigators have also recommended the use of hydrochloric 

 acid. The experiments at the Forest Products Laboratory have 

 been only preliminary to an investigation of the field, but they have 

 confirmed several known facts besides establishing several new ones. 



