I read that it takes "24 trees to produce one ton of paper", is this true, if so why?

Question

My back of the envelope calculations made me question this stat.:-

density of spruce wood = 450 kg/cm^3 (http://www.simetric.co.uk/si_wood.htm)

volume of a spruce tree = 300 cm^3 (http://en.wikipedia.org/wiki/Sitka_Spruce)

mass= 135,000 Kg, let's assume 100 tons.

24 trees equal 2400 tons of material

Hence, 0.04 % effecient ! That's an incredible wastage, surely this can not be correct...

Answer 1

I have seen a site that has said you are correct but I have also seen other sites say otherwise. I don't think tat it is correct. :-(

Answer 2

It's not correct.  How could anything have a density of 450kg per cubic centimeter?  Lead is only about 11g/cubic centimeter.

Ok after doing a little research I see where you got confused.  First, the volume you site is from a record-breaking tree.  That is not typical, and of course would produce more paper.

A somewhat average spruce has a volume of 16 cubic feet, which is .45 cubic meters.  At 450kg/m^3, that's 202.5 kg.  24 trees comes out to about 4850 kg.  So 24 spruce trees would be about 5.3 tons.

Remember also wood has a higher water concentration than paper.

Also, fix your units.  cm^3 is cubic centimeters.  Cubic meters are m^3.

I can't see your reference when you post dead links.

Answer 3

lol

Paper pulp today comes primarily from  farmed Aspen trees.  They grow fast and easy.  They are harvested every 5-6 years. They use 100% of the tree.  They are replanted they same day they are harvested.

Answer 4

The full sentence in the article you read states "It has been estimated that based on a mixture of softwoods and hardwoods 12 meters (40 ft) tall and 15-20 centimeters (6-8 in) in diameter, it would take an average of 24 trees to produce 0.9 tonne (1 ton) of printing and writing paper, using the kraft process (chemical pulping)."

So your answer is right there. They tell you the size of the trees they are talking about - Each tree would have a volume of about a quarter of a cubic metre and would weight about 120kgs. So 24 of them would weight a little under 3 tons.

Given that only the wood fibres are used in paper making and all the water, bark and soluble sugars and starches are discarded, the 33% yield sounds quite reasonable to me.