Carpentry and Woodworking - Carving a very large hole

I am trying to build a large sawdust bowl out of a Birch tree log. After every project I finish, I sweep up and throw away all of the sawdust on the floor. I was thinking I could use this sawdust in my fireplace rather than using so much natural gas. I want to carve a bowl out of a large Birch tree log I recovered off my property. I am at a loss on how to carve out a smooth bowl from fresh Birch. Any help would be appreciated.

I often gather up my sawdust [in the winter] in plastic grocery bags and throw it in my wood stove [in the shop]. I don't know that it would work well with an open fireplace - definetly not if you have gas logs!! I usually put the saw dust in my compost pile the rest of the year.

I've never made a bowl but I always thought they were usually made on a wood lathe with special attachments.

Don't put sawdust in a gas fireplace.

Only way to make bowls I've ever seen was on a lathe, but that doesn't make it the only way.

I have to separate my shavings from regular wood to pt. Wifey uses the regular in her chicken laying boxes.

Not sure how big of a large tree you have but you look at carving blades that attached to a right angle grinder. They are designed for wood removal.

You could do the rough work with a chain saw but seems like a bit dangerous just to save the shavings.

I like the black bag idea though.

Try and adz, but I question using sawdust in the stove or fireplace, it is VERY explosive.