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Physics 140: Greenhouse Effect
Spring 2008
Homework #6, due Monday, May 5, 2008

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1) You want to buy carbon offsets to make your driving carbon-neutral. The offsets cost $10 per ton of carbon dioxide.
(a) (2 pts) How much would buying offsets add to the price of a gallon of gasoline? Assume that producing and burning a
gallon of gasoline emits 25.3 lbs of CO₂. Recall 1 ton = 2000 lbs.
(b) (2 pts) If you drive 12,000 miles per year and your car averages 30 miles per gallon, how much do
you have to pay in offsets per year?

2) In 1990, the carbon dioxide emission of the US was 5010.85 million
metric tons.
(a) (2 pts)If the Kyoto protocol target level of 7% reduction from the 1990
level were reached in 2012, what would the annual carbon dioxide
emission be in 2012?
(b) (2 pts) If this goal were to be reached by carbon capture and storage,
how much carbon dioxide would have to be sequestered annually in 2012?
(assume that the carbon dioxide emission of the US was the same in 2012
as in 1990 -- we wish!)
(c) (2 pts) Find a report on the Internet of a working demonstration carbon
capture and storage project, and find the amount of carbon dioxide
sequestered per year. Is it much greater, much less, or about the same
as the amount in part (b)?

3) Electric car carbon dioxide emissions
In driving an electric car, there are zero emissions "at the tailpipe," but
the emissions generated in the production of the electricity must be
taken into account.
(a) (2 pts)For a typical electric car, the electrical energy required is about 0.3 kWh/mile.
If you buy conventional electricity from PSEG, which results in emissions of
0.8 lbs/kWh, how much carbon dioxide is emitted per mile?
(b) (2 pts) For an efficient conventional car that gets 30 miles per gallon, how much
carbon dioxide is emitted per mile? Assume that producing and burning a
gallon of gasoline emits 25.3 lbs of CO₂.
(c) (1 pt) If you pay $0.16 per kWh, how much do you pay for the electric car
to go 30 miles? If gas is $4.00 per gallon, how much do you pay for the
conventional car of part (b) to go 30 miles? Compare and comment.

4) Green power
You are considering buying green power from PSEG to reduce
your carbon footprint. To get your power from wind and hydroelectric
sources costs an extra $0.059 per kWh.
(a) (2 pts) If your electric usage is 600 kWh per month, how much extra
would you pay on your monthly electricity bill?
(b) (2 pts) By how much would you reduce your carbon dioxide emissions,
in tons? Assume that conventional PSEG electricity results in
carbon dioxide emissions of 0.8 lbs per kWh, and that green power
results in zero emissions.
(c) (1 pt) How much would it cost you per ton of carbon dioxide to reduce your
emissions this way? Compare this to the $10/ton figure given in the
Problem 1. .