Excercises

Question 1

Which energy carriers are produced in mineral oil refineries besides diesel and gasoline (petrol)? Indicate 3.

Answer 1

LPG (propane, butane), kerosene, light fuel oils, heavy fuel oils

Question 2

Which are the 2 leading nations in global bioethanol production and which are their major domestic feedstock crops used for bioethanol production?

Answer 2

• USA (1P), corn (1P) - brazil (1P), sugar cane (1P)

Question 3

a, Explain the term “second generation bioethanol”. b, Indicate 2 major technical hurdles of second bioethanol technology and give brief explanations.

Answer 3

A, Bioethanol produced from lignocellulosic biomass B, Major hurdles – optional answers: - complex pre-treatment for disintegration of feedstock required to enable bioconversion -enzyme costs are still high, since demand of enzymes is high  enzyme activities have to be improved and costs for enzyme production have to be reduced - performance of pentose fermenting microorganism has to be improved (mainly for fermentation of xylose from hemicellulose) by bioengineering to achieve high yields of bioethanol -reduction of process steps for enzymatic hydrolysis & fermentation – target: consolidated bioprocessing -economy of scale requires large scale plants –> supply of feedstock for large scale plants may be a hurdle

Question 4

Production of BtL-fuels via the Fischer-Tropsch-pathway.

a, Describe in headlines the production of Fischer-Tropsch-fuels from wood.
b, By which means can the yield of FT- diesel fuel be enhanced?

Answer 4

Solution:

• *A,**
• gasification of wood 1 P
• cleaning of gasification gas 1 P
• gas conditioning 1 P
• FT-Synthesis 1 P
• separation of the oil phase to get a diesel, wax and petrol fraction 1 P
• *Optional credits for intermediate steps, e.g.:**
• Grinding of feedstock
• pyrolysis
• cooling /washing of FT raw product

B, Hydrocracking of waxes, H2-import, Low temperature process

Question 5

Discuss the benefits and drawbacks of using algal oils based fuels for
transportation.

Answer 5

Solution - possible arguments:
Benefits:
-algae production requires no agricultural areas  food for fuel conflicts can be
avoided
-high biomass & biofuel yields per acreage possible (yet requires high
performance bioreactors!)
-drop-in-fuels may be produced, e.g. by HVO technology
Drawbacks:
-Still poor energy efficiency, mainly due to high energy demand for downstream
processing
-still high costs of fuel production
(-technology still under R&D)