This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Anaerobic Fermentation – 1”.
1. How many types of basic organic decomposition occur in Biomass energy conversion?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: There are two basic types of organic decomposition that can occur: aerobic decomposition (in the presence of oxygen) and anaerobic decomposition (In the absence of oxygen). All organic material, both animal and vegetable can be broken down by these processes.
2. Which decomposition process produces carbon dioxide and ammonia?
a) Aerobic decomposition
b) Anaerobic decomposition
c) Thermolysis
d) Thermal decomposition
View Answer
Explanation: Aerobic decomposition (fermentation) process produces carbon dioxide, ammonia and other small amounts of gases, heat in large quantities and a final product that can be used as a fertilizer. Aerobic decomposition is process of decomposition in presence of oxygen.
3. Which decomposition process produces Carbon dioxide and methane?
a) Aerobic decomposition
b) Anaerobic decomposition
c) Thermolysis
d) Thermal decomposition
View Answer
Explanation: Anaerobic decomposition will produce methane, carbon dioxide, some hydrogen and other gases in trace, very little heat and a final product with a higher nitrogen content than is produced by anaerobic fermentation process.
4. Anaerobic fermentation is how many staged process?
a) Single stage
b) Two – stage
c) 3-stage
d) 4 – stage
View Answer
Explanation: Anaerobic decomposition is a two stage process as specific bacteria feed on certain organic materials. In the first stage, acidic bacteria dismantle the complex organic molecules into peptides, glycerol, alcohol and other sugars. Than the second type of bacteria starts to convert these simpler compounds into methane.
5. In what PH range does anaerobic digestion occurs at best?
a) 6.8 – 8.0
b) 0 – 5.0
c) 2.3 – 4.5
d) 3.5 – 7.2
View Answer
Explanation: Anaerobic digestion will occur best within a PH range of 6.8 – 8.0. More acidic or basic mixtures will ferment at a lower speed. The introduction of raw material will often lower the PH (make the mixture more acidic).
6. Which amount is the ideal carbon-nitrogen ratio for the raw material into a biogas plant?
a) 30: 1
b) 20: 10
c) 5: 15
d) 1: 8
View Answer
Explanation: The bacteria responsible for anaerobic process require both elements, as do all living organisms, but they consume carbon roughly 30 times faster than nitrogen. Assuming all other conditions are favorable for biogas production, a carbon – nitrogen ratio of about 30: 1 is ideal for the raw material fed into a biogas plant.
7. Below which temperature the action off digesting bacteria decreases?
a) 16oC
b) 35oC
c) 28oC
d) 0oC
View Answer
Explanation: Anaerobic breakdown of waste occurs at temperatures lying between 0oC and 69oC, but the action of digesting bacteria will decrease sharply below 16°C. Production of gas is most rapid between 29oC and 41oC.
8. Which is the most suitable temperature for the production of methane in anaerobic fermentation?
a) 32 – 35oC
b) 18 – 26oC
c) 40 – 48oC
d) 10 – 15oC
View Answer
Explanation: A temperature between 32 – 35oC has proven most efficient for stable and continuous production of methane. Biogas produced outside this range will have a higher percentage of carbon dioxide and other gases than within this range.
9. Too nitrogen will cause ____________
a) Poisonous gases
b) Reduction in fertility of mixture
c) Reduction in quantity of mixture
d) Mixture to harden
View Answer
Explanation: Too much nitrogen will cause this to be left over at the end of digestion and reduce the quality of the fertilizer produced by biogas plant. The correct ratio of carbon to nitrogen will prevent loss of either fertilizer quality or methane content.
10. How much percentage of solid content is present in anaerobic digestion?
a) 8%
b) 2%
c) 32%
d) 50%
View Answer
Explanation: Anaerobic digestion of organics will proceed best if the input material consists of roughly 8% solids. In the case of fresh cow manure, this is the equivalent of dilution with roughly an equal quantity of water.
11. The central part of an anaerobic plant in an enclosed tank is known as ____________
a) Pit
b) Digester
c) Mixer
d) Feeder
View Answer
Explanation: The central part of an anaerobic plant in an enclosed tank is known as digester. This is an airtight filled with the organic waste, and which can be emptied of digested slurry with some means of catching the produced gas.
12. What is ADP stand for?
a) Adenosine terra phosphate
b) NADPH
c) Adenosine pyrophosphate
d) Adenosine tri-phosphate
View Answer
Explanation: Adenosine di-phosphate (ADP), also known as adenosine pyrophosphate (APP), is an important organic compound in metabolism and is essential to the flow of energy in living cells. ADP consists of three important structural components: a sugar backbone attached to adenine and two phosphate groups bonded to the 5 carbon atom of ribose.
13. What is C3H7O6P?
a) Glyceraldehydes’ 3-phosphate
b) 3-bisphosphoglycerate
c) NADPH
d) Tryptophan
View Answer
Explanation: Glyceraldehydes’ 3-phosphate, also known as trio-phosphate and abbreviated as G3P, GALP or PGAL, is a chemical compound that occurs as an intermediate in several central metabolic pathways of all organisms. It is a phosphate ester of the 3-carbon sugar glyceraldehydes and has chemical formula C3H7O6P.
14. Product of anaerobic decomposition involves ___________
a) Methane
b) Lactic acid
c) Oxygen
d) Alcohol
View Answer
Explanation: A second type of bacteria in secondary stage of anaerobic fermentation starts to form methane. These methane producing bacteria are particularly influenced by the ambient conditions, which can slow or halt the process completely if they do not lie within a fairly narrow band.
15. Solid remnants of the original input material to the digesters are called ________
a) Ordure
b) Egests
c) Digestate
d) Manure
View Answer
Explanation: Digestate is the solid remnants of the original input material to the digesters that the microbes cannot use. It also consists of the mineralized remains of the dead bacteria from within the digesters. Digestate can come in three forms: fibrous, liquor, or a sludge-based combination of the two fractions.
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