Restaurant grease recycling questions

Not sure if any of you have experience with this, but so far for me it seems the buyers are greasing me up.
First buyer paid $.12/# when they paid.
2nd buyer said they would pay $.15/#, but only are paying $.10/#.
Wondering what is a fair price?
& i also am double checking the math & the conversions are confusing.
our grease is classified as yellow grease, & majority says it weighs 7.6 lbs/gallon. True?
Buyer measures grease in tank with a dang tape measure an gives us inches of grease. Now i need to figure out how much an inch of grease in our tanks weigh. hopefully google can locate info on this double walled tank, otherwise it will be pretty hard to do the math.

Measure the inside diameter of the tank, I'm assuming it's a cylinder. Volume of a cylinder is Base x Height.

Base of a cylinder is PI x Radius squared.

Radius = 1/2 diameter

So, (1/2 diameter)(1/2 diameter)(3.14) = Base

Base x Measured height is volume in cubic inches. Convert cubic inches to gallons.

If it's not a cylinder, same equation works. Base x Height. Or, length x width x height.


Also, a gallon of water weighs 8.34 pounds. Fats are less dense than water, so that 7.6 sounds like it could be right.

If you can't get the inside measurements, try this method I've used calculating volumes of tanks for spraying crops. Measure the depth of grease in the tank, pour in a known quantity (say 5 gallons for ease of figuring) and measure again. Divide gallons poured by inches increased even if fractional and you get gallons per inch. Weigh the grease you pour in and divide by the gallons to get lbs per gallon. Then just multiply lbs/gallon x gallons/inch and you have lbs/inch of tank.

Tanks are rectangular & gets wider at the top. Can only get the vertical measurement on the inside.
Pnutfarmer thanks that is a clever method. I dont actually handle the grease, but i may be able to coordinate with the cooks & try & get them to call me when they dump next. Then i could try your method, but it may be too much of a hassle trying to set that up.

Odd he pays buy inches but has a price per pound
The pound is the standard for filling fryers that could help you. If your fryer is a 45 lb capacity and you put it in the tank after it is used with a tape you should be able to get a rough idea.
when you add and it goes up 5 inches then 45lb/5 in will give you 9 lb an inch then 9 x .12 or 1.08 an inch
good luck

The measurement of weight should be taken a different parts of the angle to get an idea of weight difference per in when the surface area increases.
I'm sure if you volunteer to put the grease in yourself you will find no objection:)

Thanx guys, now I have a head ache.

happyscraper - Walk it off, you'll be fine :)

Even if offered to me for free don't think I would get involved in grease recycling. Just too nasty a mess for me...

Im not sure how big grease recycling is in your part of the country but over here in the north eastern US the companies literally fight for the grease. There are many biodiesel companies that will buy as much as you have but some want to buy by the lb and others by the gallon. While it is a messy business there must be money to be made because some make you sign a real binding contract because there are other companies that just drive around and try to pay a nickle more and suck the grease out of a competitors tank. There is an index of what yellow grease goes for http://www.ams.usda.gov/mnreports/lswagenergy.pdf. Good luck