I bought some kidney suet from a meat processor. I also had them grind it up because I didn't want to chop it up myself...it cost more, but was worth it to me.
Here is a 5lb.bag of ground kidney suet:
I measured out 2.5lbs. because I don't have a large stock pot and wasn't sure if the pot I had would be big enough to render 5lbs.:
I used hot water, and filled to same level as the fat. I'm not sure if I needed to add any salt because there was no odor, but I did anyway. I used 2 tsp. :
Bring to a boil. Keep a close eye on it because it will rise!
Once it starts boiling, turn heat down and reduce to a simmer. This picture was taken after simmering for 20 minutes (still not getting any foul smells...smells like soup to me):
Total time simmering was 30 minutes. I put cheesecloth in a colander and drained, VERY slowly as it's VERY hot. When everything was drained, I took a spoon and mashed the meat chunks to get more liquid out:
A yellow liquid when it's all drained. Let it cool off before putting into fridge overnight:
This is what it looked like the next day. I used a sharp knife to break the seal and pull the tallow out (the remaining liquid underneath, I flushed down the toilet).
A disc of tallow:
This is the underside which was covered in pellets, as best as I can describe them. I used a sharp knife to flick them off and gave it a quick rinse under the faucet. After rinsing, used a paper towel to blot dry:
I cut the tallow into chunks, put them in a labelled freezer bag, then into the freezer to store. (I ended up with about 2lbs. of tallow)