Your Questions About Sustainable Energy Without The Hot Air

Robert asks…

How many 75-gallon barrels of waste corn oil should be collected for 1 entire year? moreinfo below?

Methane (CH4), or natural gas, is commonly used all over the world as a source of energy and fuel. Many homes in the United States combust methane to generate heat for hot water heaters, central air heaters, and is used extensively in gas powered stoves and ovens. Currently methane is mass-produced in a variety of different ways, many of which are not sustainable or environmentally friendly. Many people have started producing their own methane in a variety of different ways. Even though most of these methods are not very efficient, they can be somewhat sustainable if reclaimed or waste materials are used from local sources. One way to “home-brew” methane in a decently sustainable way is to collect waste vegetable oil from various local restaurants and “pyrolyze” it with high heat (typically ~700 K) in the presence of oxygen. Pyrolysis is a very similar chemical reaction to combustion; however, it differs in the types of products it makes.

Corn oil, a commonly used vegetable oil at fast-food restaurants, is composed of approximately 65% by mass linoleic acid (HC18H31O2) and 35% by mass oleic acid (HC18H33O2). In reality there are many other components of corn oil, but these are the main ingredients. The un-balanced reactions below show the pyrolysis of linoleic and oleic acids, respectively, in the presence of oxygen.

HC18H31O2(l) + O2(g) CH4(g) + CO2(g) + H2O(g) + H2(g)

HC18H33O2(l) + O2(g) CH4(g) + CO2(g) + H2O(g) + H2(g)

This year approximately 580. kg of methane in the home was used for heating, hot water, and stove/oven use. How many 75-gallon barrels of waste corn oil should be collect to produce methane for 1 entire year? The density of oleic and linoleic acids are very similar, you may assume both are 0.90 g/cm3. Additionally, you may assume the percent yield of methane production from corn oil pyrolysis is 100% (in really it is much smaller). To make this problem easier, you may assume 65% of the methane produced comes from linoleic acid and 35% of the methane produced comes from oleic acid.

admin answers:

President Bush thought this process was some sort of answer.

Wrong!!

It does a number of things that make it impractical.

1. It prevents people from being fed. Every acre that you put into corn production for inefficient SUV’s is 1 acre that cannot be used for feeding starving people, including some Americans.

2. It takes a huge amount of energy to change either of those two hydrocarbons into a simple chemical like CH4 is frightening to calculate. 700o is about 500oC which is hotter than a kitchen oven gets and that is not a trivial consideration.

3. Can you imagine 330 million people all running around to get wasted cooking oil? I can’t either.

4. Not 100% efficient?? My, what is the efficiency?

OK I’m done with my rant. Sorry. I can’t see how you can do this problem without knowing some Chemistry. I think I’m in the math section. I would say we have to balance the equation and proceed, but it scares me to think you may not know enough to go on. There are an infinite number of ways to balance this thing. Here’s one.

HC18H31O2(l) + 12.5O2(g)  6CH4(g) + 12CO2(g) + 3H2O(g) + H2(g) If this is the actual process, it means that 1 mole of linoleic acid produces 6 moles of Methane.

So the mass of the methane is 580 kg * 0.65 = 377 kg
The number of moles of methane = 377000/16 = 23562 moles of methane.
That means that you need 3927 moles of linoleic acid. Just how many grams is that?

1+18*12 + 31 +2*16 = 280 grams per mole

3927 * 280 = 1099560 grams
1099560 / 0.9 = 1221733 cc I take you are using US gallons in this.

1000 cc = 1 L
1221733 cc = x Liters = 1221 L

There are 3.78 L in a US gallon

1221L/3.78 L/gal = 323 gallons

1 barrel = 75 gallons
x barrels = 323 gallons

x = 4.31 barrels.

I’ll give you the second equation balanced. You can work out the rest of it for yourself. Just follow my numbers.

HC18H33O2(l) + 11O2(g) ==> 6CH4(g) + 12CO2(g) + 4H2O(g) + H2(g)

Edit
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Sorry, I thought you were posting from the United States. My rant holds true for any country that produces corn.

Paul asks…

How might an introduced plant species kill native plant species? ?

A. An introduced plant’s rapid growth can deprive native plants of sunlight.
B. An introduced plant’s rapid growth can deprive native plants of food.
C. An introduced plant can cause soil loss from erosion.
D. An introduced plant’s rapid growth can deprive native plants of oxygen.

2. What is one of the greatest threats to biodiversity on Earth?
A. habitat destruction
B. loss of drinking water
C. decrease in food supply
D. pollution

3. In which biome is biodiversity most threatened?
A. tropical rain forest
B. grassland
C. taiga
D. wetland

4. The Alaskan pipeline is raised up on “legs” in areas along caribou migration paths. Why was it built this way?
A. to prevent damage to the pipeline by caribou
B. to prevent harm to the caribou by the pipeline
C. to prevent habitat fragmentation
D. to prevent caribou from migrating to the wrong habitat

5. Why might an introduced animal species overrun native species in an ecosystem?
A. Its population size is smaller than those of native species.
B. It is more energy efficient, so it eats less food.
C. It is a predator of the native species.
D. It often has no natural enemies.

6. What does the Endangered Species Act do?
A. It provides food for endangered species.
B. It protects organisms that are near extinction and their environments.
C. It protects populations of animals from predators.
D. It protects endangered plant species only.

7. Which term describes the practice of managing resources so that current needs are met without harming future generations?
A. species introduction
B. sustainable development
C. habitat fragmentation
D. biomagnification

8. Why does clear cutting lead to a loss of biodiversity?
A. Lumber companies kill the animals in an area when they cut trees.
B. An entire ecosystem is destroyed when all the trees in an area are cut down.
C. Too much sunlight enters the area after the trees are cut down.
D. Tree seedlings cannot be produced.

9. Which of the following techniques can help prevent populations of slow-growing fish from being depleted?
A. fishing gear review
B. rotation
C. fishing bans
D. harvest reduction

10. Which law regulates emissions from automobiles and industrial factories?
A. Clean Water Act
B. Endangered Species Act
C. Clean Air Act
D. National Environmental Policy Act

admin answers:

1.) A & B
2.) A
3.) I am not sure. The answer may be C or D even though A gets the most publicity.
4.) C – Actually the Alaskan pipeline is on legs to prevent the hot oil from melting the permafrost of the tundra.
5.) D
6.) B
7.) B
8.) B
9.) C or D
10.) C

Do check my answers against your text and class notes, because I may not be completely right, according to your class.

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