There is a Vice article that claims to have an accurate measurement of how many cows were killed to make the new UK five-pound notes.
The say it’s half a cow.
Ignoring that you can’t really kill just half of a cow, let’s look at their maths.
How much do cows weigh? Between 1,100kg for a male (bull) and 720kg for a female. So, on average, a cow weighs 910kg.
Not true. If you want the average weight of a cow, you need to remember that 50% of male cows are murdered before they become adults, so the average needs to take that into account.
It looks like Vice got their weights from Google, which says 1100kg for a male, and 720kg for a female.
Given a 2:1 female:male ratio, the average is more like (720*2+1100)/3=850kg per cow.
The body fat content of an average cow is 25 percent. Therefore, the amount of fat in an average cow’s body is 227.5kg.
Vice appears to take the word of this question‘s answerer when it states 25%.
So, 15% of 720Kg. Therefore, the amount of fat in an average cow’s body is 108kg, not 227.5kg. Less than half what Vice stated.
How many kilograms of this fat is contained in offcuts you could use to make tallow? About 40kg, according to a man at the James Elliott butcher in Islington.
Tallow is rendered from suet, which is made from the fat found around the loins and kidneys. So we can’t just use all the fat from the cow. According to the Oklahoma Department of Agriculture, about 4% of a cow’s weight is suet. That’s 28.8kg (720*.04), not 40kg.
How much tallow is used in one note, according to the Bank of England? “A trace”, which chemically means less than 100 parts per million, or 0.01 percent. A polymer consultant I called confirmed that the tallow present in a given polymer would be a fraction of a single percentage.
Again, where do they come up with these numbers? No references given.
First off, when some PR guy says “there’s just a trace”, they are not speaking as an analytical chemist. They are saying “stop asking. not enough per note to make a difference on a scale”.
They say that trace means less than 100ppm. But atmospheric CO2 is a trace gas, and that is 335ppm.
Here’s an actual definition of what “trace” means – 0.1%. That’s still a “fraction of a single percentage” as Vice said, but it’s ten times larger than the 0.01% they pulled out of nowhere.
New £5 notes weigh 0.7g, therefore there is roughly 0.00007 g of tallow present in one £5 note.
0.1% of 0.7g is 0.0007. Ten times larger than the figure Vice comes up with.
How many fivers are in circulation now, and therefore will be around by May of 2017, when all the old paper ones have been phased out? 329 million notes.
To work out how much tallow will be used in total in all of these fivers, we need to multiply 0.00007g by 329 million, which gives us 23,030g, or 23kg.
Again, multiply by ten. 329,000,000*0.0007g=230,300g, or 230kg.
And if you get about 40kg of tallow-worthy fat from the average cow, how many cows would you need to make every single £5 note in circulation?
Well, since it’s actually 28.8kg per cow… take the 230kg required, divide it by 28.8kg, and you get:
Not half a cow.
16 times larger.
You might say “yeah – but who cares? it’s a fucking cow!”.
Well yeah – people that say things like that are not going to be budged anyway.