If they are nesting in the compost and you want to yse that compost this year the only way to do that is to kill the nest off. You could put a big glass jar over the entry and capture the workers as they leave for whatever they do, but that does not eliminate the queen, or the workers in the nest, who will simply produce more outside workers. Any reasonably intelligent person knows that pouring petroleum products on or in the ground today is a really bad thing to do, just as it was a really bad thing years ago but was not recognized as such.
Sevin (carbaryl) dust placed on something that would keep it from the compost but so the workers would have to walk through it on the way into the nest works because the workers take that stuff into the nest where it poisons every thing inside.
Of course another option is to simply leave it until next year because the wasps currently there will die this winter and the queens that do survive will find other nest sites, they will not reuse thae same site again.

Thanks Kimms, I'm headed out there in a few minutes, and may just have to decide to leave it. My system is a 3 bin system, and I'm worried about them getting into the other bins too. Would keeping the 3 bins wetter help?
Alberta

Keeping them hotter will help, by turning more often, and maybe they need to be wetter too. They should be moist to the touch.

I don't mess around with yellow jackets. I'd get a can of that wasp nest killer stuff, that shoots out a stream, and I'd go out at night when it was completely dark and blast it right into the opening of the nest. Not ideal for the compost but I'd still use it myself.

They'll get more aggressive as the season progresses, to the point where you won't be able to approach the other bins either.

My boss is trying to get rid of a yellowjacket nest in her dog run with an organic spray made from peppermint oil. She's been at it for a couple weeks now and meanwhile her dog can't stay in the kennel while she's at work, she has to leave him with neighbors. Don't waste your time, just kill the buggers, they'll not hesitate to kill you if they can. The wasp nest spray stuff works first time.

Yellow jackets are like the paper wasps and make their nests out of what looks kinda like paper, attached to something to keep it up where it is not touching the ground or other moist stuff. If you can see the nest and if it is where you can get clear access to spray it, the Raid Flying Insect spray is very effective at knocking them down immediately. Keep the spray going long enough to get them all and kinda soak the nest a little. I have never been stung using it, but it does take some nerve.

I have two cans of it around here to use on everything from flies to mosquitoes and wasps as needed. I do not bother any of the nests if they are not in the way or in a place where I, or someone else, is likely to get stung.
Bill P.

Update:
Yesterday hubby went out there, dressed in jeans, and long sleeves, there were about a dozen yellow jackets flying into the bin, and seemingly trying to find a way to get into the compost itself, such as I had witnessed the day before. He forked the compost out and they were swarming like crazy but did not attack him. I stood on the deck ready to run into the house (he was on his own). No nest was found, and he filled and refilled the wheel barrel with the compost at least 4 times, as I emptied it into surrounding beds. I think we lucked out and the yj's must have been just starting to build a nest or were looking to set up home for themselves and the queen. Thank you all for the answers above, its something I will now keep in mind if this happens again.
Alberta

The nest is likely a hole in the ground somewhere near the area or in the compost itself. Your husband may have covered the nest hole when forking out the compost and luckily spared himself a nasty swarm attack. I inadvertently placed a wheelbarrow next to a nest hole on Saturday and the yellowjackets attacked it for hours afterwards. I was stung three times on Friday when I inadvertently upset another bunch. They appear to be out in large numbers around here this summer. I once upset some paper wasps that were living, ironically, in an old abandoned pesticide sprayer at my grandparents' farm.

We once had a waspnest under our front door. We couldn't reach the nest, so to get rid of the wasps, we ran a vacuum-cleaner (canister type) with the suction hose taped down where the wasps walked into their entrance. As they walked from their landing spots toward their entrance, they got sucked up by the vacuum. To make sure they would not establish another nest, the area under the sill was sealed with silicone (or whatever it was). I was sorry to kill them; they had never done me harm, but we were afraid that they might get mad and attack someone some day....>lawsuit

I kind'a like wasps (aren't they excellent pollinators?), and so long as they exist peacefully in the yard, I let them be. But if they attack me, I get rid of their nest. Also, some wasps are beneficial predators: their larvae eat the larvae of Mexican Bean Beetle, see Jimster's post on the Legume forum (link below).

Diatomaceous Earth (DE) will also kill wasps so long as the DE remains dry and the powder gets on the wasps's bodies.

The lady with the wasps in her dog run might get ideas on how to use DE to rid her yard of wasps from this earlier post:

RE: Overrun with Houseflies
Thu, Jul 19, 07 at 14:24
Food-grade Diatomaceous Earth (DE) will kill the adult flies (and all other insects that get the DE powder on their bodies, including bees and other beneficials). DE works by dehydrating the insects. If you get DE on your hands, you'll see your hands get very dry.
When working with DE, you should wear a good face mask. In other words, don't breathe the powder.

You could put a layer of dry leaves, paper, or other carbon materials on top of your piles, and on top of this dry layer, sprinkle a thin layer of DE. The DE will kill the adult flies. For the DE to work, the DE will have to stay dry.

Whenever you add more greens to your piles, top them with a layer of dry materials, and top it all with DE. Your flies will croak if the DE stays dry.

So far as I know, food-grade DE is compatible with organic growing methods.

Peaceful Valley Farm and Garden Supply, Grass Valley, CA 95945, has 50 lb. bags of food-grade DE for $25 + shipping. (888) 784-1722

Don't use swimming-pool-grade DE; it contains other non-food-grade materials that are incompatible with growing foods.

I'm probably jinxing myself by posting this, but I've just been co-existing with the yellow jackets that visit my garden (I don't think their nest is back there, btw). I've noticed a huge difference in the housefly population since the yj's arrived this year. So until one of them takes offense to my presence, they're allowed to stay.