hello,
wood shavings/sawdust do rob the soil of nitrogen if just added fresh . But they are perfectly ok to use in a compost heap ,depending on how much you have . The thing with shavings/sawdust is that it takes a long time to rot down and will use available nitrogen during that time making it unavailable for plants . The way round it is to mix it with animal manure (chicken manure is ideal ) and plenty of stuff rich in nitrogen ie grass cuttings, comfrey leaves, stinging nettles or any green veggie type stuff. As with any compost keep things even and well mixed, this will make the best compost .If there is a high shaving mix it will take longer to rot down , but it will rot . You can also add plenty of urine to it as well . If the shavings are quite dry soak them with a 20-1 mix of wee and water . The wee can be any type human or whatever...lol but I have heard tell that mens wee after they have been to the pub is best ...Wee is a very good activator for any compost heap . Hope that helps a bit ....
cheers
Russ