My compost pile consists of weeds, grass clippings and leaves from various trees, including maple. It has been about three years since it was last fully turned. For a couple years , and even before, I noted a white powdery substance when I dug into the pile a bit. Now, on doing a full turning I see quite a lot of this white powder. I once got service from a pathologist at OSU Pant Pathology Lab. and I would be willing to pay for chemical analysis if no simpler identification is possible.
Washington County Oregon
Thank you for your question. The white powdery substance you are seeing is probably a fungus, an important part of the soil microbe system that reduces plant tissue back into nutrients that can be made (by other plants) into new plants. If you don't water, turn, and add the right components to compost, the fungus takes over. You can remedy the issue, and you don't need any pathology test, by following the guidelines here: https://www.oregonmetro.gov/tools-living/yard-and-garden/composting