Dian Hong wrote:What kinds of sawdust work best?
Fine sawdust of almost any type.
Even the allelopathic juglone in walnut sawdust should decompose adequately in the composting process, so it won't harm the growth of plants that the compost is used on. So use any wood's sawdust. The finer the better.
Where I am it's hard to get sawdust and I usually can only get something coarser, like shavings, or small shavings. Based on what I read in The Humanure Handbook
(Yay!!! 10/10 definitely recommend!), I've been trying to keep the coarse sawdust damp for as long as possible before using it. That seems to help it break down. I'm in an extremely dry climate so excess moisture is not a problem here.
Recently, I've been collecting coffee grounds from the cafes in the nearby touristy town. I was dumping them in the worm bin (which is separate from my composting toilet). Then I decided to mix some in with the coarse sawdust that had been sitting moist for many months and not changing color or evidently breaking down. It was maybe 2 or 3 kg (5-7 lbs) of dry espresso grounds mixed into about 50 liters of damp coarse sawdust/shavings. Just one day after mixing the coffee grounds in, the damp material was palpably warm to my hands. Yay! I hope I've finally found a way to break down the shavings a bit before using them as cover material in the toilet.
My toilet is not a bucket system. The region where i live in the Himalayas, composting toilets are traditional (though Jenkins would call them mouldering toilets). So when I built my house I designed it with a double-chamber composting toilet at the back. The ground floor, which is the two manure chambers built of stone with mud mortar, is separated from the wall of the house by a two foot gap (where I store the sacks of sawdust or autumn leaves). The upstairs, where the user goes, is attached to the upstairs of the house. I've put an exhaust fan pulling air out of the manure chambers, so smell doesn't come up into the user's room or the house. We used the first chamber for 2.5 years and then switched over to the second chamber. Another year later, I emptied the first chamber. There was a lot of dried out toilet paper on top, and a lot of intact wood shavings throughout, though no recognizable poop or poopy smell anywhere. So after that I have been trying to cap the manure pile in the closed-off chamber by dumping down on top: a large sack of crumbled leaves, a bucket of water once in a while, and used coffee grounds collected from town. And for cover material for the currently used chamber, I'm trying to get finer sawdust, and since that's difficult, I'm trying to break down the coarse sawdust/shavings before use by keeping them damp and now maybe by mixing in coffee grounds.