Peanut butter is sticky. It takes several gallons of hot soapy water to wash it out so that it is ready for recycling.
Is there a better way to do this?
I have found that using hot, hot water from the faucet helps to soften the peanut butter and loosen it from the jar's edges and surface. Often times I will fill it with hot water and let it soak for 10-15 minutes or so, and then return to the jar and empty it. Then, using hot water I use the sprayer nozzle from my sink to maneuver within the jar and remove all of the leftovers.
Have a dog?1 Give it to him/her. The dog will love the treat, since it provides a bit of a puzzle. Most of the larger breeds have very long tongues, capable of reaching inside of the jar.
And.. of course, in the end, you'll be left with a licked-clean jar!
1. Don't have a dog? Give it to a friend that does, and ask them to recycle it when done
As AllisonC pointed out, a few PEANUT BUTTERS, ESPECIALLY THE ONES THAT ARE SUGAR FREE, may use a sweetener called Xylitol. This is lethal to dogs. Check your labels!
To help you get the remainings more easily out of the glass, there are silicone scrapers available in different shapes and sizes. They work quite well. Actually it works a lot better than you could do with a knife or spoon. Afterwards it should be clean enough for recycling.
Here's an image:
For the purposes of recycling glass you don't need to wash it perfectly clean. A small amount of fat doesn't do much harm to liquid glass (probably it will just burn and be gone at some point).
Here's a quote from a website on the topic:
Small amounts of food left don’t interfere with the glass and steel recycling process. Scrape all the solid food scraps out of jars and cans and then put them in the recycling bin. If you’re concerned about having left over food in the bin you can lightly rinse out your jars and cans. Using left over washing up or rinsing water is best as there’s no point wasting good water just to wash recycling.
If the jars are to be reused by some food producer (e.g., returnable containers) they will have better and more efficient cleaning processes than you have for cleaning their input material.
If you want to reuse the jar yourself, that's a different story though.
First, fill the jar with warm water and then use your fingers to wipe as much peanut butter as you can off the inside surface. (Don't spend more than a few seconds on this; it's not necessary to get all the peanut butter off at this point.)
Then empty the jar and fill it up a bit more than halfway with hot water and maybe a little dish soap. Screw the lid onto the jar, hold it securely, and shake it vigorously, turning it once or twice in the process. Ten or twenty seconds of agitation should very quickly dislodge all the remaining peanut butter. (In rare cases you may need to repeat the process with fresh hot water.)
First, use the jar properly empty.
When using the peanut butter, push the bits sticking to the side of the jar down into the main amount in the jar. If you do this regularly, you will not get a sticky residue on the sides, but an almost empty jar.
You can get out the bits left in the bottom with a spoon rather than a knife, making it a bit easier.
What you are left with just needs a rinse or a normal wash.
(You can also look for a different kind of peanut butter, one that is not as sticky, as is the most popular kind where I live.)
Easiest and fastest way to clean out ANY jar for recycling...
2-3 WET paper towels with liquid dish soap. Use your elbow grease and just wipe the jar, the paper towel will pick up enough left over food to make it recyclable.
Recycling doesn't have to be a tedious job that requires 10 minutes of soaking. They just don't want people throwing in stuff that spoils and causing issues with he rest of the recyclables. Do a quick wipe and rinse, the thicker the paper towel the more it will pick up, quick fast and easy...