I think you would be better with a compost pile, like a pile of organic matter that is not actual wood based. Wood and bark in my experience brake down a lot slower than say leaves and other greens. If you could get a halfway aged manure from somewhere and make a pile of it, this would provide the most heat. Ive seen manure piles literally steaming in subzero days , ive also heard that they sometimes produce such temps that they self ignite, dunno if its true thought, i see it as a possibility in a hot summer day perhaps ...