Those look a lot like Tree Oysters (
Pleurotus ostreatus), which are a delicious and edible species. But the picture is small and I can't be 100 percent certain (just 95%). I would suggest making a spore print, and getting a second and third opinion before eating them. Consult a few books and websites. Oysters are fairly easy to identify and there are few deadly look-a-likes.
I don't know if there are any Mycological Societies where you live but if so they are a great resource of local experts.
Here's a photo of some oysters that I grew:

oyster gills by
frankenstoen, on Flickr
If those are indeed oyster mushrooms, you might wish to keep and water that firewood, rather than burn it!