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 It was unusual to see Joe out of the swamp. He approached me with the awkward, shuffling gait he uses on dry land as I was emptying some kitchen waste onto the compost pile and covering it with sawdust.
"Hi Joe," I called out. "What are you doing out so far from the swamp?"
"Hi yourself! I wanted to see this new-fangled compost bin you've set up. The critters[*] are talking about it, wondering how so much goes into it without it getting any bigger or smelling as much as they expect."
"So the critters are talking about my composting bin?"
"You bet! And I can see why. Look at this thing! Three separate bins in a row, each one over a meter square, constructed out of old shipping pallets. I was going to call it the Taj Mahal of composting bins, but it's too rickety and ugly for that. More like the Wal-Mart big box store of composting bins. Why, do you know that you can get perfectly acceptable composting on a small footprint by using a barrel as a single composting bin?"
"Why yes, Joe, I've heard of that," I replied. "Sure, I could miniaturize the composting bin, but I have space for something this size. And the space is useful - see how I'm storing sawdust in the two bins on the left?"
"Sure I see that! That's strange, too. What are you composting so much sawdust for?"
"I suppose I am composting it, but it's being used as an additive. I cover up what I add to the pile, to add carbon and to keep it from smelling."
"It sure works to keep down the smell," Joe commented, "just as the other critters said. Why, I was within 20 meters before I could tell whether you'd had beets or turnips last night."
"Twenty meters, huh?" I asked. "Well, either you have a lot keener senses than even I knew, or you got a whiff before I'd applied the compost. To the human sense of smell, this pile smells like wet pine sawdust, and that's it. But OK, super sniffer, was it beets or turnips?" I figured I'd get him with this question, since I'd just buried scraps from both vegetables in the compost heap.
"Last night, beets. Turnips were the night before, or possibly earlier. The turnip scraps were more decomposed. Besides, your sweat smells of beets today. I'll bet your pee is red, too."
"Right on all counts, Joe. Gee whiz, I should have known not to challenge your keen sense of smell."
Joe just grinned. But then he turned earnest and asked, "How come the pile smells so much like humans? I mean, I find the spots where your dog marks its territory, but this smells like a big ole human territorial mark, if you know what I mean."
"Ah, good question. And now we get to the core of the matter. I built the compost bin primarily to process waste from a new toilet I added to the house. The toilet is just a bucket that I add sawdust to in the house, so it doesn't smell. And I add more sawdust to it out here, again to cover it up and keep it from smelling. Like I said, we humans can't smell anything other than the sawdust, once it's covered up."
"So if other humans can't smell it, why are you marking your territory?"
"I'm not marking my territory, Joe," I said, trying not to sound exasperated, but my voice continued rising. "I'm recycling organic matter. Closing the nutrient loop. Living lightly on the earth. Being part of the solution, not the problem. Got it?"
I guess I did sound exasperated. I continued, more calmly, "You know the talks we've had about microflush toilets for blackwater recycling and toilets built for urine diversion [see EcoEng-Newsletter No. 1, 1999], so we can recycle nutrients from urine and feces back to agriculture?" He nodded. "This is the same principle, just a simpler application of it. It takes more frequent maintenance - I'm out here every week emptying the bucket, cleaning it, and spreading sawdust on top of it - but it cost less than ten dollars to build, and the maintenance doesn't cost me anything but 10-15 minutes time."
"I see," said Joe. He paused. "I think. You have this beautiful, newly renovated house that keeps the rain out and the heat in, using the latest in modern, environmentally friendly materials, and you crap in a bucket. Have I got that about right?"
"Well, yes. One of the bathrooms has a ceramic, urine-diverting toilet, so guests have an opportunity to use a water closet if they want. The other one was going to have a microflush, gravity-flow toilet. The toilets that use the least amount of water seem to be vacuum toilets, but they take electricity, and gravity works even when the power goes out. The thing was, when I was ready to install the microflush toilet, I learned that many users were dissatisfied with the current version of it. I'm not sure whether I'm going to try it anyway, or put in a vacuum toilet, or what. So, while I'm thinking the process over, I thought I'd try the sawdust toilet. I'd read about it in the Humanure Handbook - I bought the book, but you can read it for free online, if you want to check it out from the swamp. Thought the system was worth a try. The model I put together is very simple - maybe a little unstable, since the bucket is free standing rather than protected by a cabinet - but we haven't had any problems with it."
"So all that sawdust is for putting on top of the pile, just for smell purposes?"
"Partly for smell purposes, and partly to provide carbon to balance the nitrogen from the bucket. Each of us humans puts out about 4.5 kg nitrogen in our urine and feces each year, Joe. To get the carbon-to-nitrogen ratio ideal for composting, around 30 to 1, that calls for over 200 kg dry weight in sawdust each year, per person. That's assuming we're using this particular toilet 100% of the time, which, of course, we don't."
"That's a lot of sawdust! Sounds expensive."
"Around here, sawdust is cheap, if you know where to look. I fill up our trailer at a local 'sustainable harvest' sawmill for five dollars - that's over two cubic meters of sawdust. I'm hoping it will last us nearly a year, at our rate of use. But if you're somewhere where sawdust isn't readily available, other people have used lots of things - leaves or grass clippings or shredded paper. Whatever is readily available, breaks down relatively easily, and has lots of carbon."
"What do you do with the compost when it's finished? You don't spread it on your garden, do you?"
"I haven't finished any compost yet, Joe, and it's going to take quite a while to fill up one of these bins. When it's full, I'll let it compost a year or so and then decide. Joe Jenkins, the guy who wrote the Humanure Handbook, says he has monitored the internal temperature of his compost pile and found that it regularly reaches and stays at the 50 °C required for killing pathogens. Even after the pile has frozen in the winter, it thaws and heats up in the spring. So he confidently uses the compost in his garden. I probably won't be diligent about monitoring the temperature, so I'll probably use it on rose bushes or something."
Joe seemed satisfied. "I'm glad you're not sending all that wastewater to my swamp, and not draining the swamp, either, to get water to flush down that toilet. I'm going to go back and let the critters know why you have this big box store of compost bin here. And I'll check in with you after you've been carrying out buckets for a year, to see if you still want to keep using this system."
With that, Joe shuffled back to the swamp.
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