Solar Power isn't Feasible!

Solar Power isn't Feasible!
This cartoon was on the cover of the book "SolarGas" by David Hoye. It echoes the Sharp Solar slogan "Last time I checked nobody owned the sun!"

Saturday, June 7, 2014

Home Biogas for New York -- Where do we start, and what's next?




So you want to build a home biodigester?

In my opinion the best place to start here in the Northeast of the United States (where I am currently a visiting faculty researcher at Mercy College New York) is with a Solar CITIES IBC DIY system as a base digester and a modified ARTI floating drum as a gas capture/storage system.  I developed this in Germany at home, built one with my students at Mercy College in  New York and then built one at the  Kibbutz Lotan Green Apprenticeship Program.





Most recently we have built a two IBC home system  in New Paltz New York  in a basement, insulated and plumbed with PEX heating coils, to test throughout the winter (we have a similar twin IBC system at Mercy College which ran great all winter of 2013 indoors for a semester but was then moved outside with styrofoam insulation for the winter of 2014 and froze solid during the polar vortex months).

















We favor 2 IBC tank (twin IBC systems) because each IBC is one cubic meter in fluid volume and this permits a maximum gas output of 1000 liters of uncompressed biomethane each day when fed approximately 25 liters of ground up food waste at 35 Celsius.  1000 liters of biogas permits approximately 2 hours of cooking on a single burner at a medium flame height.  Since the reaction and production rate is temperature dependent and feedstock dependent (with an upper limit to how much you can feed) and both of these variables fluctuate, we have found that 2m3 is the best working volume for home biodigesters serving the cooking needs of 4 to 6 people.  Two IBC tanks fit nicely into basements and are quite safe as they are always filled with liquid (water and ground up food waste after initial start up with animal manure as a source of microbial innoculant).  We collect the gas in a floating drum outside the basement in the yard or porch where the liquid can be given anti-freeze properties by adding salt or other chemicals.   One can also collect and store more gas in PVC bladders or baloons as they do in China (Puxin sells them via the internet) or in truck inner tubes or even air mattresses.  To get the gas out then one needs a biogas pump, also sold on the internet from Puxin in China.


We at Solar CITIES favor jumping into the biogas field by building an IBC system because it is relatively inexpensive and robust, using ubiquitous found materials (used IBC tanks for between $135 to $175 each found on Craig's List, 2" and 1/2" PVC pipes, 2" inch and 1/2" Uniseals for tank penetration, PEX tubing for heat exchange, 2" inch and 1/2" PVC valves, elbows and unions, styrofoam insulation and stretch wrap.) 
A 2 IBC system can be built, labor excluded (we're assuming you "DIY" Do-it-Yourself with friends and make a party of it like we do!) for about $600 or $700 in parts, depending on how much plumbing you have to do (this doesn't include the food grinder which you should really have for effortless push button feedstock preparation, which adds another $150 to $250 to the cost, and possibly a sump pump if your installation area isn't below your sink).




The nice thing is that you get into the game and learn to appreciate the physics, engineering, chemistry and biology of biogas systems this way, and you can't lose because you are really creating a liquid compost solution, regardless of how much gas you get or what temperature (above freezing) you keep the biodigester at. And the liquid fertilizer that comes out is superior to aerobic compost in many ways (retains all nitrogen and micronutrients, is maintenance free, with no turning or lifting needed and easy transport in buckets or pipes and hoses).  So with a home biogas system you don't have to compost outside anything but twigs, leaves and branches and other woody material (whose aerobic disintegration is facilitated when biogas effluent is poured on it).
 

The Solar CITIES IBC Biogas system, which I've made an open source project* to encourage a community of biogas enthusiasts around the world to use collective intelligence to continue to improve, is one of the best ways for tinkerers to get involved in this evolving field of home waste-to-fuel-and-fertilizer production.  But while I will always want to continue training people in the construction and use of DIY home made systems, things are rapidly changing in the commercial biogas world.

*(at the bottom of this post are some of the materials you need to build your own Solar CITIES  style IBC based biodigester).

Overview of some Commercial Home Biogas Systems on the Market and on the Horizon

The world of home scale and intermediate scale biogas users is finally growing to the point where we are gaining traction not only at the tinkerer/bricolage level but in the marketplace at well.

Several home biogas companies are appearing outside of China and India (where there has been successful market penetration for some time now) and expansion is even occurring in the north temperate zones where seasonal temperature variations had previously discouraged people from taking an interest in this simple and effective technology (Northern European countries like Germany, Sweden and Denmark have been leading industrial scale biogas efforts for the past decade and a half, with million Euro facilities taking in both agricultural and municipal organic residuals; their size and thermal mass makes it feasible to utilize between 17% and 40% of the gas won each day to provide adequate heat in the colder months; it was generally considered that smaller scale systems located outdoors required too much investment in insulation and heating, and suffered too much heat loss due to surface area/volume ratio to make it worthwhile).

This equation is now changing.

 Hestia Home Biogas in the Oregon/Washington area of the U.S. which has been building home biogas units using concrete forms for several years, is launching a rotomolded 2m3 home biodigester this August that has a patented design enabling  lightweight  plastic (polyethylene)  units to be stacked for shipping with all parts inside.  They can be set up in a couple of hours.  The Hestia systems initial cost for early adopters will be about $2,495 for a basic uninsulated system and $2,895 for insulated systems with PEX heat exchangers designed for outdoor location in winter.  The heating can be done by vacuum tube or flat panel solar HW circulation, of any other source of hot water (gas burner, electric heated water, groundsource heat pump, recycled shower water) circulated through the radiant heating coils.  The systems are made to be as eco-friendly as possible, using a significant amount of  post consumer recycled plastic in the rotomolding and enabling insulation from recycled polystyrene (styrofoam).

(In a recent facebook post to our group Solar CITIES Biogas Innoventors and Practitioners ( https://www.facebook.com/groups/methanogens/) Hestia CEO and inventor Warren Weisman wrote:
"New York City area biogas enthusiasts, if you are interested in a premanufactured home biogas digester, our company Hestia Home Biogas will have our 2 cu.m. home units available in July, 2014 and we will have a distribution center in Brooklyn. Anyone willing to drive their own car and trailer/pick-up to pick up their unit will be able to save shipping.

The units are $2,495 for the uninsulated units and $2,895 for the insulated "Arctic Pak." Both come with a double burner Puxin stovetop and come fully assembled. You only need to add water once you place it within view of your kitchen window so you can see the inflatable top and know how much gas you have.

The digesters have a built-in pressure relief system that allows them to be left alone for days or weeks and safely release gas."

As the market grows and mass production kicks in the goal is to bring the units down to the $1000 price point that WTP surveys suggest will reach the late adopters and make household biogas a household name.


In Israel at present, where temperatures get quite hot in summer but where winter lows have included snowfall, the start-up company Eco-gas Home Biogas has launched commercial biodigesters for the home and small institution.  The units we visited in Mikhmoret with Envisaj Mercy Environmental Sustainability and Justice League students in January were 1 cubic meter, 2 cubic meters and 7 cubic meters in size; they build up to 12 cubic meters.  Originally they were using fiberglass for their home units; now they have patented a vinyl flexible digester design that is easier to ship and can be set up in a couple of hours.



The family units currently sell for about $2500 to $3000 for early adopters as they grow their market  but with mass production they estimate they will eventually get the costs down to below the $1000 price point.  Shipping the fiberglass and plastic units  outside of Israel previously limited the expansion of the market elsewhere but because the units now fold up into a rather small and lightweight  box they should be able to rapidly penetrate other areas. Insulation ideas are now in development to make these systems work in colder climates.

Across the continent of Africa, inventor and social entrepreneur Dominic Wanjahia has been rapidly expanding the business for his patented Simply Logic  Flexi Biogas systems from their home base in Kenya to a dozen other nations. Flexi biogas, as the name implies, provides PVC systems that can be rolled up with the installation pipes and put on the back of a motorbike or bicycle, making it easy to get them to a remote village at a low cost in rural areas, which has been the target area for the company. The whole system, including the hoop shade house for protection, is about $500.




In China and India, of course, we find the widest variety of market entrants into the small biogas field.

The Chinese Puxin 2.5 m3 household digester is the one that I have worked with and imported to the Philippines and to Iraq.

While the model above is intended for manual introduction of food waste,  another one of the models is intended as a septic tank replacement, to be plumbed to both the toilet and the kitchen sink (via a food grinder):


The cost of these systems, made originally from fiberglass but now increasingly Polyethylene, ranges from $1500 to $2500.  They are uninsulated as they are made for subtropical regions (Shenzhen, where they are produced, is near Hong Kong).  The difficulty in adopting them in the US is the cost of shipping, but a West Coast company is now meeting with the Puxin group in China to discuss bringing a large shipment in to the US to keep costs down.

In India there is the widest variety of home biogas systems available for the market.  Biotech India is one of the best known, with its innovative water seal for the floating drum.


With my students in Israel we visited a Biotech unit imported by Eco-gas Israel's Yair Teller. It performs well during the warmer months but is not insulated for winter; though the unit cost for the 2m3 family size is  fiarly inexpensive, once again importation and transportation fees have made it hard to catch on in markets outside of India.

Sintex, the Indian rotomolding company, has some new home biogas designs that look promising; again the uninsulated nature of the products, designed for tropical regions, and the size and thus costs of shipping, make them difficult to get momentum behind in the north temperate markets.


At the intermediate to institutional end of the scale, the India Company Green Elephant Energy's new Green Box, a standardized prefabricated system that can fit on a flatbed truck like a 40 foot container and dropped into place, pioneered at the Volkswagen plant in Mumbai, is emerging as a cost effective solution for handling 1 ton of organic "waste" per day.



The units cost between $100,000 and $150,000 and are currently distributed in the US by Hestia Home Biogas on the West Coast.  A spec sheet pdf describing their features and operation can be found here.

Meanwhile, my not-for-profit organization Solar Cities Solutions (currently undergoing a name change) has imported into New York the Chinese Puxin steel mold concrete forms for building 4, 6 and 10m3 biogas systems from poured concrete.  The molds cost us about $10,000 with an additional  $5000 to $7000 for for add-on supplies and shipping and customs.  But the molds can be used hundreds of times.







 A 10m3 system made from the molds, assuming the molds are already paid for,  costs whatever the market price is for approximately 35 bags of cement and the necessary amounts of gravel and sand, plus the cost of a fiberglass gas holder (approximately $250) plus the cost of rebar and plumbing supplies, as well as labor and any machinery needed for construction not already on hand (we've built them using hand shovels and hand mixing of cement, but it is easiest with a backhoe and cement mixer).  In Brazil we paid approximately $3000 for each 10m3 unit including all labor and machinery; in the Philippines where all labor was donated and we did things by hand we were able to make a 10m3 for about $1500 (but it took longer).  We will be building on in Pennsylvania and another at the Permaculture Design Institute in Ellenville New York by October and testing insulation and heating and determining what the additional costs to make them perform well in the Northeast US will be.

Regardless of size or feedstock, the small scale biogas field is exploding, with many many options appearing that ultimately can ensure that ALL organic residuals, from toilet waste to yard waste to kitchen and cafeteria waste, to agricultural and market wastes, are no longer wasted but can be simply and effectively transformed from problems into solutions.  And why not -- a biodigester is simply a stomach and can be made from anything that holds water, literally.  So for people to say that small scale biogas "doesn't hold water" as a solution to our garbage problems is garbage.  When we conceive of a biogas system as a living animal whose microbiome simply treats organic material as it feeds, we see the world has plenty of room for these  rapidly evolving methanogenic and "fertilogenic" creatures at all scales -- a new addition to God's creatures, great and small.

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How to build your own Biodigester the Solar CITIES way:




The animation I made shown above (created in Blender 3D) will work as a general overview of the systems we now advocate.  It does however suffer from a couple of pre-revision mistakes.

1)  The first is that it shows the gas output as a half inch valve located directly on top of the IBC.  This works but leads to effluent spills when the gas is used up.  In all of our builds now we use a 60 cm 1/2 piece of PVC extending from a half inch uniseal mounted in the same location on top of the tank, but extending up above the height of the influent and effluent buckets. This way even when the gas is all gone and the buckets are full there is no chance for fluid to fill the gas pipe. Simple and effective.

2) We are finding that sometimes the 1/2 gas out pipe gets clogged with floating debris from the original horse or cow manure innoculation. While this can be fairly easily cleared by blowing back into the tube, we want to avoid all hassles. We now recommend using a 1 inch uniseal for the gas out with alength of 1 inch pipe rising up to the height of the bucket and a reducer to half inch before the valve, which can be half inch.  This way the pipe is less likely to ever get clogged.

3) Two IBCs are much better than one -- two cubic meters is more reasonable for producing good quantities of gas and by having two chambers, if one gets overfed and goes acid you still have a working system and can use the active tank to reactivate the inactive tank.

4) The animation doesn't show the PEX coils (100 feet rolls of red half inch PEX per tank) that we use as a heat exchanger to keep the tanks warm.  These we insert through the IBC caps using 1/2 inch uniseals and PVC; it would be better to use CPVC, which handles the heat (PVC deforms at around 80 degrees) but we haven't found CPVC in the right sizes so far, so we compromise.  Copper fittings would also be better but they are expensive.

5) The animation doesn't show insulation -- insulation is necessary to retain the heat (and you need to do warm water feeding when you feed).  We use styrofoam sheets and stretch wrap and sometimes bubble wrap but there is a lot you can use.  Just try to insulate the heck out of the tanks, particularly the tops (you don't have to worry much about the bottom as the IBC is on a pallette which creates an air gap.)

6) You don't have to build an ARTI style digester/floating gas holder to capture the gas. You can use used truck inner tubes and PVC balloons or bladders. The only problem there though is easily getting the gas out at a decent pressure.  We use the PVC bags and biogas pumps supplied by Puxin from China for optimal results. See http://puxinbiogas.en.alibaba.com/product/316977761-22043592/Bio_gas_storage_bag.html

If you do use a floating collector you can make smaller ones out of two trash cans (the Rubbermaid Brute cans work okay, but you'll have to cut the handles and tops off of the smaller telescoping one, and you won't get much more than 40 to 60 liters of gas storage at a time which equates to about 7 minutes of cooking; you would need four to do anything meaningful since it takes about a half an hours worth of stored gas  to do any significant cooking).

If I were you and you can't wait to bring a dedicated bag in from China,  I would use an air mattress!
Try for at least 200 liters of storage (that's your half hour of cooking as it usually works out to be 15 minutes for every 100 liters). You will still need either a pump or some weight to get the gas out -- I've used throw rugs and occasionally simply asked the kids to lie down on the gas mattress while I cook...

7)  If you make a floating gas holder you will probably have more reliable results for the central stabilizing pole using a bucket with cement to hold the pole. I didn't have cement/concrete when I built mine so I made the rickety metal stand out of galvanized plumbing pipe shown in the animation.
It works, but isn't ideal.

Now to the parts you need.

1) The first thing is of course two IBC tanks.  Find them on Craig's List for between $125 and $175 each, used; some people provide free delivery if you buy two or more so that works out nicely.

2) You need to order Uniseals.  Outside of Palestine and Israel I've not been to a hardware store that sells them (in Istanbul Turkey this past April we found some two inch rubber fittings that worked okay, but nothing for 1/2 inch or 1 inch). You can order them from Aussie Globe http://www.aussieglobe.com/uniseal1.htm and from Unites States Plastic Corp http://www.usplastic.com/catalog/item.aspx?itemid=89951,

You should order at least 12 2 inch uniseals, 5 1 inch uniseals and 15 1/2 uniseals.  If I were you I would also order 5 3/4 inch uniseals while you are at it. They come in handy for lots of things.  You aren't going to use them all, but in Israel at Kibbutz Lotan last January we destroyed a couple doing the installation and in New York a couple of weeks ago we found a damaged one in the shipment. They are rubber. Best to have extras on hand.

You will be using 4 of the 2"  uniseals for each of your IBC tanks (one for the inlet and one for the outlet of the tank and one for the bottom of the inlet bucket and one for the bottom of the outlet bucket) so that makes 8, and you will use one for the floating gas collector feed in pipe if you decide to build that.  That makes nine and leaves you with only three extra.

The inlet and outlet buckets will both need a half inch uniseal and the gas out will either use a half inch or a 1 inch or a 3/4 inch uniseal depending on how you decide to build. The PEX heat exchangers will each require two uniseals.   The gas holder will have two 1/2 inch uniseals. So figure that each IBC will use up 5 1/2 inch uniseals and the gas holder 2 and that leaves you with 3 extra.

You may (and probably should) use 1" uniseals for the gas out of the tanks (for the reasons I described above to prevent clogging), you would thus have 3 extra of those if you order 5.  And you can decide to do 3/4" as well... a lot of this depends on what size pipes and valves you can get, and if you can get reducers -- the smaller valves are much cheaper than the larger sized ones.  Much bricolage is based on compromise and whatever local materials are available!

3) You need at least four  5 gallon buckets (or larger; we used 10 gallon buckets in Israel; in Turkey we couldn't find ANY for sale if you didn't buy them with paint or something else in them, and in both Germany and Turkey many of the buckets that did store liquids were oval in shape and none had sealable lids).  The 5 gallon buckets at Home Depot are good, especially if you can get the Leaktite watertight screw lids that most Home Depots carry for $6.97. 
You can also get them from Amazon.com where they are known as Gamma Seal Lids, but they are more expensive (10 to 13 dollars)!
You are going to use one bucket on each IBC for the food waste to enter and one on each IBC for the slurry/supernatant/effluent to gather; these also act as hydraulic pressurizing  or "water displacement" systems to force the gas out; I designed it this way so the IBC could function somewhat like a Puxin 10m3 system in miniature. You end up storing the same amount of gas in the IBC as the liquid you can displace above the IBC so this gives you about 20 gallons (80 liters) of cooking fuel in the tank which can be between 10 and 13 minutes of cooking fuel.  Obviously the larger the buckets you use, the more gas you can store in the tank.

Note that if you are connecting your biogas system directly to the kitchen sink via the food grinder ("garbage disposal") you don't need an input bucket and if the rise of the pipe is tall enough (as it is when you build a system in your basement below the kitchen) you will still get water displacement through the pipes connecting the inlet of the tank to the upstairs sink. This is how we did it in New Paltz New York (see pictures at top of post).

4)  You will need at least 30 feet of 2 " PVC pipe ($7.49 each for a 10 foot pipe at Home Depot); each IBC uses about 10 feet -- approximately 5 for the feeding inlet and 5 for the outlet pipe, so that is 10 per tank, plus whatever you need to connect to your food grinder wherever it happens to be!).

5) Get 5 two inch elbows and 3 two inch T's. At least. You will need  2  two inch PVC elbows and 1 two inch PVC T to create the manifold for the feed in pipes connecting the twin IBCs together (2 elbows and 1 T) .  But then you need to connect this to your plumbing.  For this you usually need at least 3 more elbows and two more Ts.  The elbows are 90 cents and the Ts are $2.96 each unless you get the sanitary T's which are only $1.40 each and work just fine .

6) Get at least 4 2 inch PVC valves and 10 1/2 inch PVC valves.  You will want to valve each of the feeding pipes to each tank independently and valve the whole feeding system, and a bypass drain in case you don't want to feed your tanks for some reason.  And you need a half inch valve for each of the gas outlets and for each of the effluent buckets, as well as valving inbetween to the drain or garden. You can never have too many 1/2 inch valves I've found.  The 2 inch valves are about $13 a piece and the 1/2 inch valves are about $3 each. Make sure you get slip to slip valves and not threaded.

7) Get at least 20 feet of 1/2 inch PVC pipe for the effluent overflow. Also get about 10 feet of 1 inch pipe.

8) Buy a 1 inch to 1/2 inch reducer.

9) Buy PVC primer and glue

10) Buy two rolls of 100 foot 1/2 inch PEX tubing and buy connectors to connect with 1/2 inch PVC.

11) Get two wheelbarrows worth of gravel and/or small stones/volcanic rock/bits of concrete/zeolite, whatever you can put at the bottom of the tanks in a layer about 10 cm deep for the microbes to live on.

12) Get at least 200 kg (like an oil drum or two worth) of  fresh cow or horse manure for the startup innoculant of methanogenic microbes.

13) Get at least 4 1/2 inch threaded to 1/2 barbed brass nipples.

14) Get at least 4 1/2 inch female slip to female threaded connectors that you can screw the brass barbs into.

15) Get at least 30 feet (10 meters) of 5/8" outer diameter clear plastic hose to carry the gas. You can get 100 feet for $16.

16) Get at least 10 6 packs of polystyrene insulation panels at $7.25 each. This is for the sides of the tank.  If you spend more you can get better insulation; this is the cheapest suggestion.  You want to keep heat in!

17) Get a roll of stretch wrap (1000 feet for $22.97 usually does the job, but it doesn't hurt to get more)

18) Get at least two packs of rigid foam insulation for the top of the tank at $11.98 each. This stuff won't crack when you put things on top of the tank as inevitably you will!

There will be variation and you will probably have to make several runs to the hardware store to complete your installation, but this gets you going.  I will update this post with more details as time permits.

Saturday, May 24, 2014

Sh*t happens. We can deal with it.




Most northerners don't know sh*t.

Most of us don't understand sh*t.

But I know my sh*t.

I know my sh*t, not because I'm a “professional”, but because I try things at home. And when something works for me at home, then and only then do I take it "on the road" and work on implementing what works for me in other communities around the world .  Rather than having the hubrus to "think globally" and then act locally (which always seemed backwards to me!) I "think locally" and then, by solving my own problems and openly sharing the results - the successes and failures - with my worldwide social network through our facebook group "Solar CITIES Biogas Innoventors and Practitioners" (http://facebook.com/methanogens) we find that in fact we are acting globally. We get to know our sh*t together, collectively, iteratively, through trial and error and shared experience rather than hearsay, fiat and decree.




I know my sh*t, not because I'm an “expert” but because I take care of my own sh*t. I've been building and using my own composting toilets and biodigesters for more than 15 years.In my apartment in the Los Angeles Eco-village I started getting into deep sh*t with the paint bucket toilet system found in Joseph Jenkins Humanure Handbook (you can get the entire book free here. It has all the data you need to understand how easiy it is to safely deal with humanure, a.k.a. "sh*t"). Since then I've strived  to avoid letting the results of my consumption become somebody else's problem.

Sometimes, like everybody else, I'm full of sh*t. But when the sh*t goes down, it is quickly and safely recycled into the precious life giving organic matter it was intended to be. That way the sh*t never hits the fan. Mine doesn't get distributed over hell and high water, giving hell to others. My sh*t can never be a source of filth and disease, odor or infirmity. My sh*t stinks like everybody else's upon production, but because of the way I treat it at home it never releases its thiols/mercaptans and phenols and sulfuric compounds to the environment and will never attract flies or permit the transmission of cholera, dysentary, typhoid or E. coli contamination. What goes on in Vegas stays in Vegas, and what goes on en mi casa will never affect tu casa. I don't give my sh*t away to nobody. You'd have to fight me to steal my shi*t. I take care of my sh*t. Most northerners don't.

Southerners used to understand sh*t. Probably many northerners too. But south of the border, down Mexico way, and in all of the countries between the tropics of capricorn and cancer, the recycling of shit was so fast that it rarely posed a problem prior to the absurd human and “pest species” population growth that characterized the 20th century. After all, every animal that lives and that ever lived (and the tropics had the lions share of every phylum) sh*ts in its environment, and none had waste treatment plants. Fish and aquatic mammals sh*t in the very water they drink, and that we drink too, but their sh*t is so quickly taken up as food by other organisms that it rarely if ever permits the accumulation of pathogenic microbes in threatening quantities. Our own sh*t, released into an environment rich in biodiversity, also became immediate feedstock for plants and animals and fungi. And when we concentrated in certain places, as long as we kept our sh*t out of our immediate drinking water supplies, it posed no threat. Safety came from efficient cycling. As long as we didn't overwhelm the absorbtive capacity of a given ecosystem dealing with sh*t was easy.

I had a teacher once who chided those of us in the eco-village movement for thinking we could use natural processes to deal with sh*t in tropical countries. In the late 1990s we showed her a video of the John Todd Living Machine that I had learned about at Harvard in 1980 when I visited the New Alchemy Institute on Cape Cod (I and my Mercy College students visited a functioning version of the technology called the “Eco-Machine” at the Omega Institute in New York a couple of weeks ago). My professor told us “you can't apply these biological processes to the tropics and sub-tropics; you will end up killing people”. When we asked why, she said “you obviously have no understanding of the ecology of the south, in hot humid environments disease runs rampant. Bacteria grow everywhere. Flies will breed like... well, like flies. These living machines will be a disaster”

The outdoor wicking beds at the Eco-Machine at the Omega Institute with returning cattails and other constructed wetland plants emerging after the spring thaw.  These wicking beds, we were told on our recent visit, are the heart of the effective waste-water treatment that goes on at Omega in New York. By summer time this will look like a naturally wetland, thick with greenery  The inside part in the building  is the sexier "finishing" part of the process, but the beautiful vegetated gravel pits are where the real heavy lifting occurs, eliminating any problems that so called "black-water" might cause.  The inside section helps to eliminate the problems associate with the more difficult issue in waste water: soaps and detergents, NOT sh*t.


The inside of a John Todd style Eco-Machine or Living Machine at the Omega Institute in New York.  It uses plants, fish, snails and microorganisms to create clean water from toilet wastes and washing and cleaning wastes, treating both "black water" and "grey water".



She was well intentioned but ignorant of the facts. In fact the rapid growth of all organisms made possible by the warmth and wetness of the southern latitudes makes living machines much more effective there than in the north. If disease is spreading in the south it is because, following the “western” model of development, people have radically diminished the transformative capacity of the ecosystem by cutting down forests, altering watersheds, monocropping, spreading poisononous herbicides and pesticides, impoverishing biodiversity, overfishing, poisoning lakes and streams and rivers and oceans with soaps and detergents, causing eutrophication and hypoxia. Under these conditions, along with the extra warmth and wetness, can pathogenic and pestulent creatures experience out of control population explosions? Si, se puede! But those same conditions also give complex ecosystems an edge, enabling the establishment of regimes that make short work of errant “bad guys”.

 It is for this reason that waste water treatment using the schmutzdecke system (a German description of a natural process that occurs in ponds in the warmer latitudes) works so well in the south. In a schmutzdecke system a rich population of interrelated organisms (microbes, algae, protozoa, water insects) is cultured above a slow sand filter and contaminated water is dripped in slowly enough that it doesn't disturb the complexity of the aquatic ecosystem. This shmutzdecke (which means “dirty layer” and needs to be about 20 cm deep) actually cleans the dirty water by eating all the pathogens. Residual microbes are trapped by electrostatic and mechanical forces in the fine sand layer (which needs to be at least 75 cm deep for proper effectiveness).


When I tried making one at home in Germany it worked pretty well in the summer but stopped working in the winter. Of course. And while it appears to take care of bacteria that can cause disease (development agencies are using them effectively in Afghanistan) it does nothing to eliminate the awful smell and taste of greywater. My experiments with my Shmutzdecke system convinced me that if anything, dealing with soap is much harder than dealing with sh*t! And I would have continued my experiments except that living in the north made it so hard to harness the biology properly. No wonder northerners are so down on biological treatment – we rarely get a chance to see it work. Hence the culture of chemical extermination we've created and promulgated around the world.

The author experimenting with his own home scale schmutzdecke system. Video here.


So-called Western culture, (which, given the rotation of the Earth along a north-south axis, and the distribution of major landmasses above and below the equator, is a misnomer), has evolved an unfortunate fecophobia that is coupled with a certain conversational smugness that inhibits rational discussion of sh*t. The fact that I feel compelled to use an asterix in place of the letter I in the word is testimony to the taboo we have in our society – I don't want to risk offending anybody by calling the result of eating by its vernacular.

Later on in this essay I will resort to using Latin descriptions like 'feces” or “fecal matter” but parsimony suggests that when writing expositions like this it is better to use four letters (even if one of them is a symbol) instead of five or eleven. Westerners are supposed to be appreciative of efficiency.

Anyway, the society in question is really northern hemisphere society, not western. The native Americans were as west as you can get from England and many of their members told the anthropological psychologist Erik Erikson that they found the European practice of crapping into rivers and streams an abomination. Indigenous peoples around the world were the inventors of some of the first composting toilets; Eriksson reportd that the native American habit was to do your business in the forest, as far from bodies of water as possible, so that the insects and worms could quickly recycle it back into the forest. Does a bear sh*t in the woods? You betcha!

I am asserting that perhaps northerners didn't get sh*t and its transformative properties (with the very very notable exceptions of people like Joseph Jenkins and the Austrian artist/artchitect/activist Hundertwasser whose "Shit Culture Manifesto" should be on every development program's reading list)  because they didn't understand biology and how to deal with winter. Sh*tting on snow leaves a prolonged and unsightly mess, particularly when accompanied by the yellow stain of urine, and it is a mess that will last for months until the spring thaw. At that time biological systems are struggling to re-establish themselves and it is easy for ecological systems to get out of kilter. If the sh*t is too concentrated in an area and there isn't enough biodiversity hopping to balance the flow of nutrients, the “bad guys” can predominate. How much more convenient to sh*t in a river and let the lumps of digested food waste become somebody else's problem. “Not in my backyard” became “why not in everybody elses?”. The tragedy of the commons reared its ugly sh*tty head … as well as the tragedy of the less fortunate downstream.

There were those, of course, who did try to contain their sh*t, but most northerners, sh*tting into an outhouse pit or ditch, trying desperately to hide the “shame” of their defecation, never seem to have figured out that they could simply use a bit of insulation (straw would have done fine, sawdust and ashes are the norm, grass and green leaves are even better) to line their pit, do their business, and then throw some more straw or grass or leaves on top, increasing the carbon to nitrogen ratio to the point where exothermia sets in, creating a thermophilic compost pile that rapidly turns sh*t back into soil (the original source of sh*t, transduced through plants to animals to sh*t and back to soil again through solar energy). When it comes to the basic biology of soil formation, most northerners apparently never got the memo, and where sh*t wasn't being flushed away into rivers and streams causing deadly outbreaks of cholera and dysentary and typhoid and E. coli poisoning, more or less contained outhouses all over stank to high heaven, the stink attracted numerous flies, and contamination of ground water become a historical life threatening problem. It never had to be that way.

Of course I can't indict all northerners. In the Himalayas in Nepal I visited plenty of traditional Sherpa villages on our National Geographic expeditions where they have been doing composting toilets for thousands of years – forget digging a ditch (the soil is too rocky and frozen), the clever Sherpa built toilets elevated above a stone chamber filled with rhododendron leaves, and provided piles of rhododendron leaves next to the toilet hole for “flushing” with the pleasant smelling cover material and used the heat of decomposition to partially warm their houses. But then, nobody really considers the Nepalese northerners or westerners. With both terms we really mean “the descendents of the Europeans” and it is, I believe, our cultural hegemony that makes dealing with sh*t so messy.

Northerners don't know sh*t. We've created a culture of flush and forget, relegating the transformation of sh*t nto non-sh*t to a few engineers , most of whom have been schooled in chemical obliteration as the solution to everything. Disinfection is the mantra of the northern world in response to the workings of biology at the digestion or “production' end of the tube that is the human animal, just as pesticide and herbicide and fungicide and sterilization is the mantra at the consumption end of the tube. Kill everything you can before you put your food in your mouth and kill everything you can when the results come out (and don't forget to use mouthwash and antibiotic soaps and take your antibiotic pills to disinfect your whole body in the in-between while you are at it!).

In these troubled times, with the legacy of historical colonialism and the nightmare of neo-colonialism still impeding self-determination in southern countries, the north-south vector of development aid and “expertise” is a most unfortunate thing. Because most northerners don't understand how small a problem sh*it really is, and how easily solved, the descendants of the colonized in tropical and sub-tropical countries, where proper temperatures and biodiversity can turn sh*t back into soil in a matter of days, emulate the sh*tty practices of their colonizers, having forgotten how easy it was and is to avoid all the problems sh*t entails and actually make of it a value added enterprise.

Sh*t looms large in the consciousness of Euro-American culture, particularly North American culture, like the shadow of a hand puppet that looks like a giant marauding bear on the wall until you have the courage to turn around and see it for what it really is – a really precious feedstock for the very process of life, rich not only because of its chemical constituents but because of the very bacteria and other microbes (Archaens aka “methanogens” – a life form distinct from and much more ancient than bacteria that transsubstantiate sh*t into recoverable energy in the form of methane).

An illustration of the difficulty most northerners (and most of their descendants, wherever they may live after the conquest) have with understanding sh*t comes from my recent work in Brazil where we are trying to solve grave waste management and sanitation problems. I will be blunt and politically incorrect and say that most of the white people I work with around the world really believe that sanitation is a difficult technical issue that requires long processes of technical study and huge investments to solve. They look to investment intensive and massive centralized waste-water treatment plants for the answer to the filth that flows into the lagoons and bays of Rio de Janeiro. They frown uncertainly when it is suggested that all the sh*t related problems can be dealt with much more simply and effectively using small anaerobic digestors and wicking gravel beds and compost bins or aeration tans. They balk at the idea of open constructed wetlands and the use of banana trees for transpiration and nutrient uptake, somehow offended by the idea that sh*t can be taken care of without the use of chemical weapons – “germicides” like chlorine (the famous chemical in the deadly mustard gas of World War I). The thought that organic material and chlorine combine to form carcinogenic compounds that persist in the water barely crosses their minds – as long as we “obliterate” the invisible enemy they call “germs” we can let the hospitals deal with the suffering of the survivors of our “carpet bombing” strategy for disinfection.


Constructed wetland for treating toilet waste built by the community at the Alemao Verdejar Favela in Rio Arguably much prettier than a septic tank or waste water treatment plant.

Another view of the constructed wetland at the Alemao Verdejar Favela in Rio

Constructed wetland at the Alemao Verdejar Favela in Rio

The Constructed wetland at the Alemao Verdejar Favela in Rio built by the community uses a bed of used automobile tires and gravel cemented into place and planted with banana trees and other vegetation.  It processes toilet wastes from the community creating fertile soil while the banana trees transpire and evaporate the liquids.


Constructed wetland at the Alemao Verdejar Favela in Rio

A hand made mini kitchen biogas system designed and  built by Solar CITIES on a travel grant from Solar Cities Solutions in Alemao Verdejar from a Rotoplas tank.

The hand-made  Solar CITIES Rotoplas mini biogas system for kitchen waste with a food grinder donated by Insinkerator corporation to assist in the biodigestion.

On the left is a three drum vermicomposting system that the favela had already installed in the kitchen. Behind it is the hand-made  Solar CITIES Rotoplas kitchen digester prototype built by T.H. Culhane and Luis Felipe Vasconcellos when T.H. was visiting on a trip funded by Solar Cities Solutions  in the summer of 2013 to explore larger Puxin type community digesters for treating toilet and food wastes in Niteroi and Rio. An Insinkerator food grinder sits in the foreground which will be used to feed the digester.


Ironically, some of the most dreaded consequences of improperly processed sh*t actually aren't so hard to manage. Yes it is true that one of the weeks I was in Nigeria building biodigesters for schools and hospitals with former president Obasanjo to help turn sh*t into safe fuel and fertilizer, 900 children died due to a cholera outbreak in the city of Lagos when a sewer pipe broke and fecal material contaminated the drinking water supply. Also, flooding in the city while we were there due to plastic bags filled with food waste clogging the sewer drains backed up fecal laden water into the streets. All of this death and misery could have been avoided if both sh*t and food waste were routinely placed into biodigesters. But what is far too infrequently told outside of medical clinics in the “third world” is that cholera and other water-borne illnesses aren't really the danger they appear to be and are readily treatable. The reason for so many tragic deaths from fecal contamination is usually dehydration. Babies, children and the elderly will get cholera or shigella from contaminated water and these organisms produce toxins that inhibit water retention so that they can pass through the body and back into the water to complete their life cycle. The body responds through diarrhea, eager to flush the invaders out. If the diarrhea is not deposited back in the water, the infection dies out. If the body of the host is kept hydrated with a solution of electrolytes (the right sugars and salts) the infection can run its course without mortality. Millions and millions of lives can be saved by simple interventions of rehydration and monitoring.

 If sh*t is causing nightmares in developing countries it has more to do with our lack of investment and attention in proper affordable and available medical treatment than the true danger of the pathogens in sh*t. Most of them are much more benign than the pathogens that can result from organisms dining on our food waste – the plagues of Europe were the result of improper treatment of high-energy organic residuals preyed upon by flea bearing rats, not improper treatment of sh*t. Airborne infections, like influenza and other viruses carried by absurd concentrations of domestic animals (avian flu, swine flu etc.) are what I fear most when I travel, along with salmonella and other forms of food poisoning, almost all the result of a paucity of diversity in our food supply and our tendency to crowd animals and plants of the same species together. Death by proximity to another person or animal scares the sh*t out of me. I can avoid most of the diseases and problems sh*t brings by boiling or purifying my water and washing my fruits and vegetables and, if necessary, hydrating myself when I get ill. Diarrhea I can deal with.

For my part, having lived and worked in areas with poor sanitation for many years, I've never had such a phobia for feces. Fecophobia, which is extant in the north, doesn't seem to be a part of the “threat level orange” response of most people in the south because, as mentioned, most sh*t degrades rather quickly in a landscape filled with worms and insects and fish and reptiles and birds and mammals and a trillion different kinds of protozoa and bacteria and archaea that we haven't even begun to identify (all of which are sh*tting too, every day). The scarab beetle, sacred to the ancient Egyptians, is actually the dung beetle, and one of the reasons it was sacred is because of how quickly and effectively it carried off our sh*t and turned it back into life giving soil.

I can never forget living in the jungles of Borneo for a year on a Harvard University research team in the mid 1980s and marvelling nights when I squatted over our dung pits in the forest near our huts watching the ruby red eyes of the dung beetles magically approach as soon as I had done my business. With a gentle whir of their wings they would dive bomb between my legs, quickly roll up a ball of sh*t larger than themselves and then take flight, whizzing up and out with a tickle of air on my bum, taking the gift of my sh*t to their lairs to cultivate with the aid of fungi into food for their larvae.

On other occasions in Borneo we found ourselves in pools of flowing water where it was actually appropriate to sh*t in the water because hungry fish were waiting and as soon as you dropped your load they snatched it up in a flurry of writhing scales and fins. This interest by fish in human feces was well noted by Indonesians; in Sumatera we visited a restaurant built over an artificial fish pond that had bird cages also suspended over the pond. The birds were there to feed the fish with their feces, but on inspection I noticed that the toilet for the human patrons also discharged directly into the pond. I was told that the fish we were eating were also fed by us. Cooked properly, they assured me, it was quite safe. I'm not sure about that (even I have my limits when trying to suspend disbelief) but I finished my meal and I didn't get sick, nor did anybody else.

In a Dyak village in Kalimantan Timor I dined with a tribal chief whose hut was built on stilts in two stories with the bedroom and bathroom on the second floor. The toilet was a hole in the slotted wooden floor underneath which the chief's “babi hutan” or forest pigs lived. They ate all our sh*t and we in turn dined on them, and so the cycle completed itself.

During visits to Quitos, Ecuador and the Meskital slums of Guatemala city I used composting toilets that I built using the Jenkins “Humanure Handbook” paint bucket method to avoid problems when the electricity would go out for a week and none of the flush toilets worked, and I used the same system for three years in my apartment in Los Angeles at the Urban Eco-village, planting trees with my “wastes” so they wouldn't be wasted”. I've since used my own sh*t, and that of my two children when they were in diapers, to start and continue to produce methane in home built biodigesters on our porch in Germany and in New York. I've taken 100 liter tanks and filled them with sh*t on my porch and run air through them and watched as algae grew and completely removed all smell and danger in a matter of weeks.

Basically sh*t doesn't scare me. It is the least threatening output of the human condition, much more tractable than the chemicals we use routinely to spray our food and the produce of our gardens before we eat them and turn them into sh*t. And I would argue that sh*t is much less of a problem than food waste as an engineering problem although that too has a simple solution. And both are really trivial compared to the “grey water problem” – that grey area in waste treatment where you have to deal with the awful effects of chemical soaps – basically salts and fats and perfumes and antibacterial toxic inhibitors – on waterways. Yet that too can be simply, if more expensively solved, using the “living machines” or “eco-machines” a la John Todd that I spoke of earlier (basically constructed wetlands and tanks with lots of plants, algae, fish and snails, wonderful snails). The right quantity and diversity of life forms in the right formations can take care of everything organic we throw at it. It is the inorganic material – the poisons we put in our environment – that is the only real threat.


The two Puxin 4m3 toilet waste digesters and one 10m3 food waste digester built by Solar Cities Solutions at an elementary school in Niteroi, Brazil.  For maximum efficiency the two systems should be connected but concerns about safety of the toilet digesters require that we keep them separate until we can prove zero pathogenicity.

Meanwhile, in Brazil, as “foreign experts” riding in on our decidedly white horses to save the day in our bid to “help the poor” in the favelas, we are arguing endlessly about how we are going to “deal with” the “sanitation problem”. As if it hadn't already been solved. And while we Norte Americanos try to call our engineering acumen into play, negotiating with agencies and drawing up plans and planning public relations bonanzas to level up our projects once we have our “first successful demonstration”, the Central Americans, Mexicans in particular, are quietly going about their business in how to treat the result of us “doing our business” (sh*tting), creating business empires at the same time as they save lives in communities.

The two toilet waste treatment digester tanks before infill. The first tank, on the left acts as a settling chamber and primary digester. The supernatant flows into the second tank where internal surface area further cures the liquid, which then flows back out to a constructed wetland that Solar Cities Solutions team member Marcello Ambrosia is building proposed by team member Yair Teller in discussions with Executive Director Gail Richardson and Creative Director T.H. Culhane and funded by the Insinkerator corporation.

Around the world many companies are beginning to understand sh*t and providing effective low cost solutions to what was once a scourge of humanity.  One huge Mexican company in particular – Rotoplas - has already installed more than 200,000 “Bano Dignos” in Latin America with the support of the Mexican and Brazilian governments, completely eliminating the threat of human waste from each household by working incrementally, household by household. They will soon be up to half a million installations. Eschewing the idea of large treatment plants for economic, topographic, logistical and social reasons, they simply provide to families a complete home scaled system called the “Bano Digno” or “dignified toilet”. It consists of a rain water collection tank, a manual pump, a fiberglass molded outhouse with flush toilet and gravity feed water storage container and a small biodigester system that in turn consists of a 1300 liter plastic rotomolded anaerobic chamber, a contained wicking bed (gravel filled plastic chamber of about 400 liters) and a sludge collection tank of a couple hundred liters that enables “self-cleaning” of the digestor and yearly home processing with lime powder to provide good soil for growing plants.














Each part of the system is modular and can be installed all at once or iteratively, depending on the circumstances and need. The systems scale up for larger families and institutions and can be installed in a day. 600 liter systems are available for families of up to 5 people, 1300 liter systems for families up to 10 people, 3000 liter systems for community centers with up to 20 people, and 7000 liter systems for schools and institutions with up to 60 people.  Multiple systems can be concatenated for larger institutions.  While the complete systems may be  too expensive for most poor families to afford as an initial capital outlay, the governments of Mexico and Brazil and other countries subsidize most of the cost as part of their role in supplying social welfare infrastructure and microloan programs are being considered.




 The Rotoplas Bano Digno Biodigestores are already sold in Rio De Janeiro at Leroy Martin and other chain hardware stores all over Brazil so there is no technological or logistical hurdle involved in eliminating current scourge caused by improperly treated human wastes.  The issue now is purely financial and this is where governmental, non-governmental and other organizations can focus. 





The Rotoplas Bano Digno biodigestor  intervention is so simple and elegant and readily available that for dignity focused projects like the one that the Brazilian NGO Catalytic Communities is creating with favela community leaders  in Muzema it would make the most sense to immediately become part of the program the Rotoplas company already has with the Brazilian government to install hundreds of thousands of household digesters at a subsidized cost and work from there. Can we do this? Si, se puede!



Anybody who doubts the potential of home scale biodigesters to rapidly enter the market and positively impact sustainable development also severely underestimates the power and magic of Mexico. This will be the real revenge of Montezuma, when his people end dysentery. cholera and other waterborne diseases all while also giving clean reliable fuel and fertilizer to make deserts bloom once those features are added to the existing solution set. 






I have now had the pleasure of working with the good folks at Rotoplas to help improve the home scale biodigesters they manufacture and deploy by adding two dimensions to their project – 1) to slightly modify the existing systems so the methane they naturally produce can be captured and utilized (for example, to cook and boil water, and improve the temperature of the digester so it can process more effectively, insuring that disease does not spread if it is present) and 2) to radically increase the amount of useful methane they produce through the addition of ground up food waste, spoiled fruits and vegetables, flowers and other energy rich organic residuals (thereby increasing the utility of the above). A third improvement is the use of solar heated or gas heated water (post consumer use in showers) to further raise the effective temperature of the digestor to get maximum output. But regardless of whether we add heat or other organic wastes to the system and thereby enable people to have clean, smoke free biogas or just leave them the way they are to more slowly treat the human wastes alone, the simplicity of the system makes a mockery of many of the brow furrowing long winded discussions going on in the north about how to solve sanitation problems in the south. As the Emerson Electronics slogan goes, “consider it solved”.





And of course, adding solutions like the Emerson/Insinkerator food-grinders (or local equivalent) to the Rotoplas Bano Digno solution really does add dimensions that can really radically improve their efficiency. High calorie organic residuals are a huge benefit to biodigestion processes while being a bane to society when simply discarded.



I will continue to argue (and here I depart from many of my fellow northern specialists) that food wastes actually are more of a burden to society than toilet wastes.

Looked at from one perspective (a non fecophobic perspective) toilet wastes ARE food wastes – food wastes that have been “pre-digested” because they have been digested by us. In this sense toilet wastes are already broken down by the appropriate microbes using our stomachs and intestines as the anaerobic reactors for partial hydrolytic, acidogenic, acetogenic and methanogenic processes. This is why you can use your own sh*t to start an effective biogas system (I used my babies' diaper wastes). We are biogas systems. We are anaerobic digesters. Yup, the proof that we are, in fact, biogas yielding biodigesters is that we fart. Our flatulance (another subject consider risibly taboo in polite discussion) is the indication that much of the energy found in our food does not make it to our cells. We release it into the air every day (I know, I know, ladies, you never pass gass, but we men do right?).

When you look at human beings as a tubular plug flow biodigester you see why our fear of sh*t is so unfounded – we've already started the process of transubstantiation of food back into soil. All our sh*t needs is more processing time in the airless phase and then a bit of time being exposed to aerobic bacteria, insects and worms and plants for finishing. To have allowed sh*t to have become a major health hazard (which only happens anyway when a few people with unbalanced internal and external ecosystems allow the invasion and growth of pathogens and then discharge them directly into drinking water supplies or onto vegetables – most people's sh*t is actually pathogen free!) is unconscionable. Treated at its origin through simple systems like the Rotoplas Bano Digno what was stupidly seen as the scourge of mankind can readily be turned into its greatest promise.

On the other hand I argue that food waste, which still contains an enormous amount of high calorie photsynthetic energy, is a far more formidable threat as it is dealt with by modern society (based on northern models of waste disposal). Because food waste is so energetic it attracts every member of the biosphere that needs that energy. Where toilet wastes can hardly support more than a handful of specialized detritivores like the aforementioned dung beetles and fish and pigs, there are legions of organisms, from bacteria to insects to higher birds and mammals that literally jump at the chance to dine at the banquet of our high calorie organic wastes.

One could very convincingly argue that the entire (and scandalous) loss of life from the “black death” or “bubonic plague” owes its tragic dimensions to the improper disposal of food wastes. Rats, originally forest rodents, invaded European cities like Remy in Ratatouille, looking for food waste. They carried with them the fleas that carried the microbe Yersinia pestis that caused the horrible plague. Had northerners simply composted the food waste, or used it in biodigesters (as myancestors, the Assyrians, did in the fertile crescent as long ago as1000 BC), there would have been nothing for the rats to eat, hence no urban rat population and hence no plague.

Similarly, all of the problems with cockroaches (another forest species that has made its way into the urban jungle to feast on our organic garbage) could be eliminated when food wastes are transformed in controlled conditions (sealed tanks or open compost facilities) into biogas and liquid or solid fertilizer. Then we wouldn't keep poisoning ourselves with foul smelling and toxic insecticides like the ones that were routinely sprayed in my apartment building when I was a child in New York. The same is true of flies. The same is true of ALL so called “vermin”. Stray dogs and cats, possums, racoons, avian flu bearing pigeons and other birds – none of them would last in the built environment long if we didn't stupidly generate food waste and leave it in bags and trash cans and dumpsters for “disposal” by the garbage industry. Home and community scale biodigesters would completely eliminate the threat they create – a threat much graver than toilet waste, which is not only of much lesser volume (each of us generates much less toilet waste on a per gram basis than food waste) but of little or no interest to such a wide variety of potential pests.

Another problem with food waste that we don't have with toilet waste is that food waste is generally transported to landfill or incineration (both significant causes of greenhouse gases) in plastic bags. One could argue that the real reason for the despoilation of our oceans and the mortality of marine life by plastic bags (now accumulating in the plastic vortex in the pacific ocean) and the real reason for the constant flooding of our streets and back ups of our sewage systems such as I experienced in Nigeria, spreading disease and carnage in cities around the world, is the build up of plastic bags that were thrown into the streets because they contained smelly food waste.

When food waste is put through a food waste grinder in the kitchen sink, or into compost bins or biodigesters, the number of plastic bags thrown away drops so dramatically that it no longer becomes a threat. Toilet wastes are much easier to manage in this sense than food wastes. Only in the slums of Nairobi has the author witnessed sh*t disposed of in plastic bags (the famous “flying bag of sh*t” in Mukuru and Kibera are the subject of much discussion because the city has provided no adequate sewage solution. Biodigesters will eliminate that practice if we move fast enough and get our priorities straight).

So on the whole I maintain that cleaning up food waste is a much higher priority than treating toilet wastes as it generates many more problems. Nature has been converting the predigested solids and liquids from animal asses back into soil since time began. The real issue with sanitation is simply keeping the sh*t out of the water supply, nothing more. And in impoverished areas this can be most easily achieved, in my opinion, using household and community scale digesters using the Rotoplas model developed in the south for handling the problems facing the south. When combined with food grinders, warm water feeding and gas collection improvements, the Rotoplas Bano Digno program can also tackle energy poverty and deforestation (along with the consequent erosion and flooding it causes) and prevent deaths and illnesses due to indoor air pollution. Further combined with vertical farming techniques and aeroponics, hydroponics and aquaponics, the proper home and community transformation of human and animal and food wastes can also provide food security and enhance health and nutrition on the input (feeding) side of the equation as well as the output (toilet and trash can) side.

Once we have these systems in place, we can move on to tackle the more intransigent grey water problem, which requires more surface area, exploring the use of gardens filled with plants and living machines to get rid of the smelly, toxic situation created by our irresponsible use of sodium laureth sulphate, phosphates, salts and other chemicals used in our synthetic soaps and detergents. These are substances that inhibit biodiversity and appropriate rapid recycling of resources, either by killing life forms or by causing huge unbalanced population explosions of species we consider pests. But that topic is for another day. For now let us celebrate the simplicity with which biological processes in the tropical and subtropical regions of the world can be harnessed household by household to clean up all of our organic wastes and put them back into service again. In the south, where small scale systems can best make use of the existing ecology of transformation, we can do this. But I wouldn't necessarily trust most northerners to understand this. Most of us northerners, fecophobic, even biophobic, and steeped in super-sized solutions and chemical warfare, simply don't understand sh*t. And that may have been the problem all along...
Still, sh*t happens.  And we can deal with it.