No wonder, I wouldn't use spruce essence for anything you want to drink
The spruce addition is easy enough - a quart of fresh or frozen Sitka spruce tips at 60 minutes. I went to a talk on spruce beers at the NHC in Vegas, it was awesome. Pete Devaris is from the Great Northern Brewers, he knows a lot about them. Some things I remember:
Spruce tips should be fruity and somewhat citrusy, not piney
You want to use only the bright green tips of the tree, and taste them before you use them. One tree can taste great while one right next to it can be nasty.
Once you find good trees you can go back to them year after year to harvest, and there will be even more tips in their place.
Sitka spruce tastes the best, and the further North it is growing the better it tastes.
Measure by volume, not weight - they are more or less the same size, but the water content varies too much.
If you want, you can boil the tips by themselves and either add that to the pot or use it as mash water. I found it easy enough to just throw them in the boil.
I'm sure there are other ways of making spruce beers, but I found that following these guidelines from Pete made an excellent, excellent beer - if you like spruce tips. Oh, I should also mention that the tips that I used for that batch are ones that he mailed me. Well worth the price, I haven't gone looking for local tips.