Re: Can the wood pulp from one tree can make approximately 400 newspapers

Thank you for the interesting question, Shannon. I have often looked at a 
tree and wondered how much paper could be made from the tree. 

When you try to answer a question like how many newspapers can be made 
from a tree, you have to make some assumptions about how big the tree is 
and how much a newspaper weighs. I will make a couple guesses and answer 
your question. 

First, I will list the assumptions I have made in solving the problem, 
then I will work through the solution. 

1.	The tree is 60 ft tall and has an average diameter of 9 inches. 
This is a fairly small tree, but one that is somewhat typical of a pulp 
wood tree. 
2.	The average newspaper weighs 0.5 kg. 
3.	The newspaper is made from mechanical pulp, which uses no chemical 
treatment to remove lignin or other components of the tree during the 
pulping process. (For more information about the manufacture of paper, 
please see the following answer:  http://
www.madsci.org/posts/archives/jun2000/961075580.Ch.r.html.) 

Next, I will mention some of the values I will use to calculate the 
results. Note that some of these numbers are approximations and I have 
gathered most of the numbers from notes from classes I have taken. 

1.	The density of wood is 540 kg/m^3. 
2.	A tree is 50% wood and 50% water.
3.	The yield from a mechanical pulping process is 95%.

Now, for the calculations: The tree would have a volume (V=3.14*r^2*h) of 
26.5 ft^3, or 0.75 m^3, which would give a tree the weighs (0.75*540=) 405 
kg. Since 50% of the tree is water we have 202.5 kg of actual wood. After 
pulping, we will have (0.95*202 kg =) 192 kg of pulp from our tree. Since 
each newspaper weighs 0.5 kg, we can make (192/0.5 =) 384 newspapers from 
our tree. 

It looks like the tree in this example could make about 400 newspapers. 

Keep in mind that I have made several assumptions the may not be true in 
every instance. Some trees will be as big as 1 cubic meter rather than our 
tree, which was 0.75 cubic meters so you could make more newspapers from 
that tree. Also, some newspapers will be lighter or heavier than the 0.5 
kg I assumed in the calculation, which would also change the number of 
newspapers able to be made.