This 1986 study has been provoking some interesting discussions in another thread. In the interest of keeping that one on topic, I'm starting a new one here. The study in question is here: http://www.arb.ca.gov/research/apr/past/a3-122-32.pdf Continuing with our discussion already in progress... [quote author="Battenkiller" date="1294357162"]Yes, the green wood needed more air to achieve maximum burn rates, he even says so in the text. However, the overall efficiency numbers don't lie. There was not a significant loss of sensible heat up the flue due to the extra air being introduced. Yes, some dilution effect is evident, especially is the open stove, but that doesn't support anecdotal evidence of massive amounts of creosote deposition in residential chimneys venting stoves burning green wood. Just the opposite is reported here, and the dilution effect is clearly aiding this... to the benefit of green burners everywhere. [/quote] True. And I think I found the reason why the "green" oak burned better than expected (in addition to what you wrote further down about the moisture content being less than what we might think of as green), with less air than one would expect. Look at table 5-2, Summary of Fuel Load Properties, see the Avg. Piece Mass. For the green oak it hovers around 1.1kg, or 2.4 lbs. That is a very small piece of wood. Most here would consider that large kindling. It would be in the same size range as a 2x4. In the airtight stove, the load was six of these pieces. Put pieces that small on a live 20% charcoal bed and it is not going to be difficult to burn a 38%MC load like that. The largest pieces were used in the Blaze King - about 2.5kg, or 5.5 lbs. All the other stoves burned pieces half that weight, four to six pieces at a time. I'd bet my boots than almost nobody on this forum regularly loads their stove only with pieces that small - we're talking maybe a 3" diameter round or split. That's about the size of wood I use in the X33, because the firebox is very shallow. I think much of that too is explained by the piece size. Also, the thing I find most significant about the Oregon weighting is not so much the uncertainty factor, but the heavy weighting of lower burn rates. Throw out the lowest burn rate tests, and results improve dramatically for all of the non-cats. I didn't know the rarer metals could be recovered in recycling. Is it a high percentage recovery? There's no denying the effectiveness of cats, especially for round-the-clock burners. They're not well suited to my heating needs so I've never used one - odd, perhaps, in 30+ years of burning, but true. There's a place for both in the scheme of things. It's a pleasure to be able to delve in to the depths of things with you.