Answer: You can always sift out the larger pieces and use them as mulch, so that is not a problem. However, as with any compost of essentially unknown origin, you might well be concerned about the ingredients. Although the majority of organic material added should be quite safe, there is always some level of risk of finding a patch with a heavy dose of uncomposted black walnut leaves that would be toxic to plants or an imperfectly composted section full of weed seeds, or perhaps a patch with diseased material that had not quite heated sufficiently during the composting process and is thus still potentially capable of infecting your garden. There is also a possibility of chemical or other residues depending on what other homeowners have used in their yards and whether or not municipal sludge or other ingredients are added during the composting process. Since this is a government sanctioned program, you might ask them if they have done any tests on the finished compost or have any thoughts on its suitability to vegetable garden use. I have gladly used municipal leaf mold (rotted leaves) on my ornamental plants, but I prefer to use my own homemade compost in the vegetable garden because I know exactly what is in it.
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