Corn stover contains both cellulose and hemi-cellulose. Cellulose can be convert
ID: 870289 • Letter: C
Question
Corn stover contains both cellulose and hemi-cellulose. Cellulose can be converted by pre-treatment to glucose and then by yeast (S. cerevisiae) to ethanol as follows: Hemicellulose in corn stayer contains a large amount of xylose, a S-carbon sugar, which can be liberated by pre treatment. Yeast can?t digest xylose, so a bacterium (Z. mobilis) has been used to convert the xylose into ethanol as follows: 1. How much ethanol (gallons per acre) can be theoretically made from the corn stover? 2. How does this compare with ethanol from corn grain? Assumptions: Assume corn stover is 37% glucose and 20% xylose. Molecular weights: glucose 180; xylose = 150, ethanol = 46. . Only 75% of the glucose and 50% of the xylose in stayer can be extracted and converted to ethanol. 1 gallon of ethanol = 6.586 lbs 2.0 dry tons (4,000 lbs) of stover is harvested from one acre. Assume corn grain yields 2.8 gal of ethanol per bushel and 175 bushels per acre.Explanation / Answer
400lbs corn stover => 37% glucose -> 4000*0.37 = 1480lbs Glucose
amount of mole: n = m/M = 1480lbs/180 = 8.22 only 75% can be extracted -> 8.22*0.75 = 6.16 (actual amount of glucose)
n(glucose) = 2n (EtOH)
n(EtOH) = 6.16*2 = 12.33
m = n*M = 12.33 * 46 = 567.3 lbs
Xylose: 20 % of 4000lbs = 800lbs
n = 800/150 = 5.33 only 50 % can be extracted -> 5.33*0.5 = 2.66
3n (xylol) = 5n (EtOH)
n(EtOH) = (2.66/3)*5 = 1.6
m(EtOH) = 1.6*46 = 73.6lbs
total amount of Ethanol: 73.6+ 567.3 = 640.9 lbs
1gal = 6.586lbs -> 640lbs/6.586lbs *1gal = 97.3 gal/acre corn stover
in corn grains: 2.8 gal/ bushel and 175 bushel/acre -> in 1 acre: 2.8gal* 175 bushel = 490gal/acre
you can get much more ethanol from one acre of corn grains than from the corn stover