Going Brown in order to go Green

[hill]

Watching survivorman the other night, he has a new show called, "Off the Grid" ... or something like that. 150 acres out in the wilderness, and he builds a home. One of the things (since they'll be doing their own farming) he looked into what was a toilet composter. I thought it was a joke, so I googled it:



This is a fancy one. Survivorman was looking at a primitave one where you haul your waste out to the composter in a bucket. And there are MANY models inbetween the fancy ones & the junkie ones. Sorry, I aint that green, to be hauling my own poo.



I enjoy a good compost for our gardening ... but c'mon now.

.

[jayman]

I need one of those for my cats. They put out a very impressive quantity of manure

[icarus]

I could write a book on composting toilets and there problems. They do indeed work, but they are indeed fussy. The one thing that they absolutely need to work well is heat! All the models that I have tested and used ( and there are several!) that claim that you can do it effortlessly without heat are bogus. In short, if the compost does not get and stay warm it won't evaporate enough water and it won't have enough biologic action to keep itself warm. Proper composting water content is that of a well wrung sponge.

I have designed and built tiny propane burners to install on off grid composting toilets so that they will work at all. Others have 120vac heaters in them, which require a significant power draw, ~500 watts to keep them going.

All in all, while I like the concept of a composting toilet, in my off grid house I have gone back to the simple pit outhouse. With a small handful of peat moss every week, some septic "bugs" and there is no smell and it reduces down to almost nothing. I will confess it is a bit bracing to tromp to the outhouse at -40 in the dead of winter, but you do get used to it!

Personally I wouldn't recommend any of the small scale indoor bucket type composting toilets. The larger ones with external tanks might be a better alternative.

The long and short of it is, a good well designed septic system using limited water (and separating grey water from black water!) is a very safe, healthy system. If you are are in the bush and can't do a real septic, consider an old fashioned pit outhouse. With full time use, it lasts ~10 years,, and then we just dig a hole a few feet away and move it, covering the old hole with the new holes dirt!

Icarus

[hill]

Oh lordy ... I never considerd the idea you'd have to make the poo nice and warm ... although some models that I looked up had a sort of rotisserie that slowly blended the waste, so fresh oxygen at the top of the pile would more quickly saturate the do do ... and accelerate the breakdown process.

[icarus]

Essentially composting toilets come in two styles. The "mouldering" type like the Clevis Multrum, or the "active" type. Mouldering types are closer to traditional outhouses in that they rely on slow degrading of material. It can take months or even years for the material to degrade. these types tend to work with anerobic biology. Active types need heat, temperatures ~100f to keep the biology active. These types work primarily work with aerobic bacteria. These types can compost material in a matter of weeks. Most of these types have some sort of air inducing stirring device. One big problem with all types is that you are constantly adding new, wet material on top of older partially or fully composed material.

As I suggested in the earlier post, while these can be made to work, they all require a fair amount of ongoing maintenance. I just found that maintaining one was way more trouble than it was worth.

Icarus

[hyo silver]

Brown and yellow has to turn into green eventually. Flushing excrement into the drinking water (rivers) and food supply (ocean) is not the hallmark of an intelligent species.

[Shawn Clark]

Icarus, that makes sense to me. As you say, if you are going to drive off that much water, you have to get the heat from somewhere, the phase change still takes nearly the same amount of energy. I've seen the same heat balance problem frequently in stripping columns for other materials--engineers often forget that and will try to strip off a solvent with a cold gas stream. It doesn't work very well without preheating of the gas--something that is missing from the aerobic composting system. Hard to see how it would work in a northern winter (although at least the air would be dry.) A dry climate in summer would be ideal.

[icarus]

Shawn,

Don't go getting all engineer on me again! (lol)

In fact the problems is exacerbated if you use even conventional toilets. IF you are considering doing something you MUST consider using a marine type toilet that uses about a cup of water.

If you use a toilet, and you use ~1.6 gallons on water, on top of perhaps what? 12 oz of human provided liquid you now have almost 10 times as much water to evaporate off. Having said that, SOME moisture is required, as the biology needs water (in the proper quantity) to thrive.

As for Hyo's comment. You are absolutely right, but what we have evolved to is we use water as a transport method for our waste. We evolved into this system because it was easy and it was cheap. The problem with this system (among others) is that we taint a huge amount of clean water by using it to move shit. If we were to separate grey water from black water, the shear volume of black water would be reduced significantly. Of course this would have to come with a significant infrastructure cost which we are unlikely to want to pay.

Secondly, nature has a huge capacity to clean itself up, given 1/2 a chance. Once again, if we don't overwhelm a system with excess flow or chemicals that kill natural bateria, nature will work quite well. As I have suggested before, a well designed septic drain field does a great job of cleaning the water put in it. (Getting rid of the solids are another matter).

There is no one right answer. The old axiom that the "solution to pollution is dilution" does indeed have merit IF there is proper designe and monitoring. For example, Victoria B.C has been chastised for dumping stage 2 effluent into the Straits of Juan De Fuca. Now it can be argued that this is crazy, but I also think that given the volume of effluent vs the volume of water flushing in and out of the straits every tide shift MAYBE it is ok. Remember, one animal's shit is another animal's food! Perhaps the hardest issue with human waste systems (aside from people deliberately dumping toxics in the sewers!) is the concentrations of heavy metals and drugs in our waste.

A University of Oregon study did large scale drug testing of various communities by testing the sewage. Interesting results!

Icarus

[Shawn Clark]

Yes, it is not at all feasible to think the water in a convention low flush toilet could be handled in composting. Even if one's poo were 100% dry charcoal briquets that were then lit to drive off the flush water, there is no way that they could drive off that much from their own combustion energy.

[ElectricZoom]

Yeah ive read about these in the past...

While I like "green" ideas an projects, I dont think this one is for me. And theres always the problems with it as others have mentioned...