This topic contains 41 replies, has 13 voices, and was last updated by Anonymous 5 years, 1 month ago.
May 14, 2008 at 1:29 pm #472
I see incineration mentioned for waste disposal in the online book, particularly in regards to human solid waste, due to the pathogens involved.
May 14, 2008 at 6:38 pm #1995
- However, I don’t see any reason why an incinerator would be required at such a high energy cost
- Human solid wastes don’t have to be incinerated, they simply have to be sterilized.
- This requires far less input energy than actually burning material with such a high moisture content.
- It could quite probably be accomplished via irradiation- a technique, BTW, which has many adherents in the meat processing industry.
- Essentially, just microwave it in volumes small enough to be thorough.
I´m not sure I understand the problem. If it´s organic, and it sinks, can´t you just run a sewer pipe/hose down some distance past the counterweight and flush it down? Are the sea creatures really adversely affected by human waste (pathogenic or otherwise)?
If you use existing infrastructure (fuel burner for heat/electricity) to burn it, will it still be expensive?May 14, 2008 at 8:04 pm #1998
“If it´s organic, and it sinks, can´t you just run a sewer pipe/hose down some distance past the counterweight and flush it down?”
- Well, as they outline in the book, there are serious political repercussions to being seen as a polluter, and there are existing regulations about dumping waste at sea.
- Shit floats.
- Water has a steep depth/pressure gradient. The coutnreforce from pressure quickly overcomes gravity.
“Are the sea creatures really adversely affected by human waste (pathogenic or otherwise)? “
- What happens when we flush raw sewage into a river?
- It kills fish, chokes the river with algal and other growth, it poisons terrestrial mammals the length of the watershed. Unless you want to live in a swirl of your own waste, dive in it, and harvest your food from it, I think you need to examine this issue moore closely.
- Ships which flush their organic waste into the ocean don’t stay in one place long enough to see appreciable effects from it.
- It is also diffused so that they are not dumping as much in one spot and the concentration doesn’t build up as much.
- Lastly, they mostly carry their own food and are not dependent upon fishing and farming in a pool of their own waste for months to years at a time.
“If you use existing infrastructure (fuel burner for heat/electricity) to burn it, will it still be expensive?”
- The military field expedient for disposing of human shit is to build a “toilet” over a metal barrel cut in half. When the barrel gets mostly full, they stir in diesel fuel and light it on fire. It’s got a high moisture content and is not flammable on its own. You’ve got to process it somehow to get it to burn.
- Diesel costs money. Any other incinerator system has to have some kind of energy input, and the short of the matter is that it takes more energy to burn shit than you receive in heat and energy coming out of it naturally.
- So, yes, it is expensive in terms of energy, which typically translates into expensive in terms of money.
- If you dual-purpose some kind of existing heating system, it now takes more fuel or electricity than it would have taken to provide the heat alone, and quite probably, more complex (expensive) design to handle the extra input (human waste) that doesn’t add anything to it’s efficiency.
On the other hand, there are solid wastes other than human feces, that have properties which make them a net plus for energy generation- either by burning (net plus on calories) or in combination with some biological processes, can be turned to further energy production. Human waste and other organic waste can be turned to methane production, perhaps. You still get some rather unpleasant biologically hazardous outputs, but these could also be sterilized by irradiation and they are further down the process towards being composted soil by the point you’re done with them.
May 19, 2008 at 3:43 pm #2090
- Of course, even composted, biologically inactive (irradiated) material cannot necessarily just be dumped into the water around your seastead, as just adding particulate matter and nutrients to the water will have side effects, some potentially positive and some potentially negative. So you still have the problem of disposal, but now you have a product which may have at least some low value/ton that could be traded, sold or used somewhere. And if you’re creating artifical land, it may be useful in growing your real estate.
Waste is always a stinky issue but there are some very constructive ways of dealing with it. Simply burning human waste is not a sustainable option. It may be sterile but its just as filthy.
The UK festival scene has seen the welcome introduction of composting toilets in recent years. Im not saying we should all have boxes filled with sawdust on our seasteads but we should remember that there is no waste (with the exception of plastics) that cannot be turned into something usefull.
I would say that a system incorporating biological breakdown of waste in a contained environment would be the best. The waste could then be more easily re used in composts for soil based grow systems or integrated into hydroponic nutrient systems. The bacteria/plant model of dealing with waste is both ancient and efficient and with some tweaking can be made to work in almost any environment.
(please forgive any typos and spelling mistakes)May 19, 2008 at 3:47 pm #2091
There is no waste including plastics that can’t be turned into something useful. But there are many types of waste that cannot be economically turned into soemthing useful.May 19, 2008 at 4:04 pm #2092
Thanks for that… It was there inside me but I just didnt get it out in the right way hehe.
I meant to type: (with the exception of plastics which can be more difficult to recycle) but my mind was running way from me.
Heres a link to the Humanure Handbook which gives a really good grounding in the art of composting human waste.May 20, 2008 at 10:44 am #2114
A good way of doing the initial sterilizing of human waste before sending it to a bacterial composting chamber would be UV sterilisation.
Powering UV lamps requires electricity that we may want to save for some other job. There is however a widely available alternate source of UV in sunlight. Do you think it would be feasible to filter sunlight so that you are only left with UVA and UVB. I am envisaging something similar to a solar water heater except that the panel has waste pumped through it and the only light reaching the waste is UV filtered off from sunlight.
After this UV sterilisation the waste can be passed to a series of digestion chambers where it would be treated using traditional bacterial based composting techniques.
Of course I am unsure as to weather sunlight provides enough UV to sterilize quantities of faecal matter but its worth a look.May 20, 2008 at 11:15 am #2115
May 20, 2008 at 2:18 pm #2118
- I forgot about this thread, sorry about the late reply.
- Shit floats huh? Ok, that I agree wouldn´t be very nice.
- A river is hardly comparable to the ocean in this regard, so I´m not convinced it´s a real pollution problem (assuming that everything you release is biodegradable). I´d guess you´d have to ban farting in the atmosphere as well if you want to ban pooping in the ocean, to be consistent. But then again, who said international law has to be consistent, right…
- I agree it´s a political problem.
- I agree it will cost resources (diesel/electricity/whatever) to burn it. But everything costs money, including sewers and water cleaning plants in cities. The question is whether it is prohibitively expensive or not.
- Setting up a regular sewage treatment plant could perhaps be possible of course.
UV sterilizes a lot of bacterias and virii quite nicely, but it doesn’t penetrate deeply. You would have to spread the fecal matter extrememly thin and probably physically turn it several times in some sort of process. It would also take LOTS of room, and be unpleasant in the meantime. Composting takes time, and has the danger of leakage before natural biological processes have time to render pathogens in the fecal matter harmless.
- Microwave radiation will penetrate right through it and will sterilize it quite thoroughly in much larger bulk.
- Yes, it is a use of electricity, but dealing human waste is one of your most important enviro-health concerns. I can think of few higher priorities for electricity
- most other lagre uses of electricity in terrestrial life can be achieved by alternate means- cooking, heating, cooling can be achieved with combinations of systems, many of which are passive
This doesn’t eliminate the need for composting and otherwise disposing of solid waste, it just kills the pathogens. So it makes the process safer and shortens the cycle.May 20, 2008 at 2:45 pm #2119
The composting temp of > 65C for 8+ hours kills pretty much everything pathogenic. Allegedly odorless.
You’ve got plenty of carbon from food wastes.
So, yeah, I think possibly quite useful.May 20, 2008 at 3:30 pm #2123
- “The composting temp of > 65C for 8+ hours kills pretty much everything pathogenic.”
The web book cited in your link says:
- “Survival times of pathogens in soil are affected by soil moisture, pH, type of soil, temperature, sunlight, and organic matter. Although fecal coliforms can survive for several years under optimum conditions, a 99% reduction is likely within 25 days in warm climates (see Figure 7.1). Salmonella bacteria may survive for a year in rich, moist, organic soil, although 50 days would be a more typical survival time. Viruses can survive up to three months in warm weather, and up to six months in cold. Protozoan cysts are unlikely to survive for more than ten days. Roundworm eggs can survive for several years.”
And I think when you’re talking about adding carbon to help compost, it typically is in the form of cellulose: wood fibers, paper (same thing, really), leaves, straw.May 20, 2008 at 5:27 pm #2128
If you could rapidly raise the temperature to 65 degrees 8 hours should be enough to steralize a small volume. Take for example everyones favourite pathogen rich meat: Pork. If you roast a pig on a spit the entire hunk of meat needs to have reached a temperature of 65 centegrade for ten minutes to be safely eaten rare. Pork can harbour most of the dodgy bacteria and worm eggs that an unhealthy human would. If a temperature of 65 is good enough for pork then there is no reason why it shouldnt be good enough for feaces. Allowing compost to reach these temperatures through natural processes does take quite a while so artificial heating would be needed.
The microwaving idea is pretty good but my main concern with it is that it requires specialist components that may not be so easily replaced. More simplisting solutions that involve augmentation of natural processes would seem more affordable and effective than being reliant on hi tech spares that require special manufacturing processes. A microwaving component could be made quite small and efficient. If such components were used I would see them being a similar size to the commercial UV sterilization equipment that is currently available.May 20, 2008 at 10:34 pm #2134
Vacuum drying is more efficient than heat drying, and once dried it does burn. Also, dried feces don’t stink. Of course, proper septic composting would likely be more efficient and also produces useful fertilizer as well as methane for gas stoves and fridges.May 21, 2008 at 9:47 am #2161
It’s also important to consdier batch sizes. In my gardening experience, it takes a pretty big pile of compst to raise internal temperatures much. The problem I see with it:
- where to store it for that long
- how much can we afford to store at a time
- are we constantly adding to it, or do we reach a discrete volume, and then leave it be while starting a new batch. constantly adding to it means we are never certain exactly when it is safe
- how many batches do we need to have in simultaneous “production” to handle our feces dispoasal needs
And finally, not quite so much of a problem- what to do with it when we’re done making it safe?
Microwave technology is not really so complex. It’s no more complex than the transmitters needed for radio/sattelite communications or radar.. Microwave ovens work by:
- A microwave oven uses microwave radiation to heat food. In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz). Radio waves in this frequency range have an interesting property: they are absorbed by water, fats and sugars. When they are absorbed they are converted directly into atomic motion — heat. Microwaves in this frequency range have another interesting property: they are not absorbed by most plastics, glass or ceramics. Metal reflects microwaves, which is why metal pans do not work well in a microwave oven.
In addition, microwave ovens are fairly efficient because most of the energy used is directly absorbed by the object being heated. Not a lot of waste heat is generated (waste heat is not only a loss, but sometimes requires secondary systems to deal with.)
Given that the average kitchen microwave oven doesn’t much exceed 1000 watts, a microwave generator of a few kilowatts would probably be sufficient for fairly large discrete amounts of sewage. For one thing, it will be largely water, which is what primarily reacts to the 2.5 GHz frequency range. It’s reasonably consistent density (no bones to absorb, block, deflect the radiated energy.) Given a known wattage microwave generator, and an average density close to that of water, the formula to figure out how long to microwave a given volume of waste to raise it’s temperature a given amount (say to 65C) should be pretty easy to compute.
May 21, 2008 at 11:21 am #2168
- Amusingly, your radio/radar tech may also be your sanitation engineer.
That’s in soil. We’re not talking about in soil. We’re talking about in composting environments, where the thermophilic bacterial heat the pile past the point where their competitors for food can survive, kill them, including the pathogens, and then have the remaining food supply all to themselves.
Quite different from slow rotting in soils.
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