What woods can be safely used to flavour/age beer?

Over the weekend I kept thinking about this and I have done a bit more digging and found this article from bear-flavored.com, in which they speak about brewing with 4 different woods and discovered this company Black Swan Cooperage who make barrels and aging additions out of 8 different woods listed below:

• Cherry - Butter brickle, ripe cherry, fresh grass, meringue, light fried bread/Belgian waffle
• Hard Maple - Maple candy, light spice-nutmeg, cinnamon, syrup, bread/bakery, cream hint of cocoa
• Hickory - Honey, BBQ, hickory smoked bacon, apple sauce, cocoa coconut Red Oak
• Red berries, toasted marshmallow, light grass, baking bread, butterscotch
• Sassafras - Vanilla, Sage/Spice, Root Beer, Mint
• Soft Maple - Yellow cake, light smoke, banana, nut, toasted bread, hint of orange spice
• White Ash - Campfire, marshmallow, light grass, rising bread dough, light sweetness (adds different mouth-feel dimension)
• White Oak - Vanilla, toasted coconut, cinnamon, pepper, sweet baked bread, caramel
• Yellow Birch - Toffee, butterscotch, honey croissant, light lemon, tropical fruit

I also found this thread on beeradvocate:

"While I haven't experimented with Cypress in beer, I have brewed with a variety of other conifers such as white pine, douglas fir, long leaf heart pine, and red cedar. None have been promising; all have imparted nuances of turpentine and/or other unfavorable chemicals. "

and

"I have handled yew wood plenty without a skin reaction, and that wood can kill you if ingested."

In addition I found a list from a wood working site of toxic woods4 which other users have flagged up and looks very informative. The two that leap out of the list as avoids are Yew and Oleander both marked as Direct Toxin potency 4 out of 4.

I would stick to the wood chips that are available from your homebrew supplier. There is a large selection available.

One may be temped to cut up an old liquor barrel or cubing a known safe species of wood. But care needs to be taken not to contaminate the wood with the cutting tool, saws have coatings and oils etc. The chips made for brewing have been processed with a clean shear so they are contaminate free.

Many woods intended as builing material have been treated, or at least been processed with saws and plainers that drink oil. That's not to say you can't find decent maple or oak at your lumber store. Just use caution.

You may be interested in Wood Toxicity and Allergen Chart presented at The Wood Database. With very important warning:

Just because any given wood is not listed on the chart, does not mean that it is completely safe to use. It simply means that adverse reactions have not been reported as of yet.

That said, there is over 200 kinds of wood in this one source. More in others. And that's only about wood, no say about wood smoke for smoked grain, spruce tips, et cetera. Listing all wood-related dangers is far too broad for QA format.

Only reliable way is to research particular kind you think you want to use it, and the way you want to use.

That said, some choices are known as safe.

Oak is usually OK, but don't use raw. Way too much tannins. Either use roasted oak, or chips from a barrel that had stronger alcohol maturing in it. That way tannins will either be thermally neutralized or washed out. Similar precautions about other leafy tree woods, if they have tannins in significant amount and are not on toxicity lists.

For conifers, and some leaf trees, there is an issue of resin. Some resins are poisonous. Most have bad taste. Succinic acid, acetylsalicylic acid and others may be found in amounts that can ruin the taste. Or not, depends on kind of wood, season it was cut, way it was treated when it dried, and so on.