From the Lump database at Nakedwhiz...http://www.nakedwhiz.com/lumpdatabase/lumpbag6.htm
Scrap Lumber Pieces?: Nearly 100%
"We have received two separate reports that ceramic insulation from the kilns used to make Cowboy charcoal has been found in bags of Cowboy products. The ceramic insulation was found in Whole Foods and Wild Oats charcoal, both of which are made by Cowboy. Both individuals who found the insulation in the charcoal contacted Cowboy and Cowboy indicated that the material is indeed ceramic insulation. The insulation has been described as "cotton fluff" and "like fiberglass insulation". Cowboy told both individuals that the material is harmless. One individual contacted an EPA toxicologist who indicated that this material is "is probably as carcinigenic as asbestos" and should not be allowed to contaminate the product. As always, we want to be sure you understand that we are not qualified to judge the information provided by Cowboy or the EPA toxicologist. However, we strongly encourage anyone using Cowboy or one of the other brands supplied by Cowboy to carefully examine the charcoal when they add it to their cookers. Be on the lookout for foreign objects, especially anything that looks like fiberglass insulation. It may be harmless or not, but it doesn't really cost you anything to be on the lookout and remove it if you should find any."
"We recently purchased a bag of Cowboy lump for use in our burn time comparison test. We are a bit distressed to say that we found a sheet of plywood in the bag:
We wrote to Cowboy for an explanation and after 3 follow up emails to customer service, they finally responded. The bottom line is that they say that none of their suppliers makes plywood so Cowboy doesn't know how the plywood could get into their supply stream. We continue to receive stories of odd things found in bags of Cowboy lump. This is the first truly bad item we personally have found, but the stories do concern us. At this point, short of rating this charcoal as simply unacceptable, we highly recommend that you keep an eye on what comes out of the bag before you let it get into your cooker."
PS If you have a Brookshires grocery locally, their "Picnic" brand of lump charcoal rated very highly and is usually on sale.