6 thoughts on “Should we be using composting toilets? Should NYT’s “Toxic Waters” series on sewers, stormwater raise that question?

  1. When urine (urea) and proteins in sewage breaks down, you’ll get ammonia and depending on the pH, this ammonia is volatile and will escape from your composting tank. All these solutions seem logical, until you look at the entire element live cycles. Carbonaceous (fecal) waste should be converted into carbon dioxide and water, while nitrogenous waste should be converted into nitrogen gas and water. These are all very natural processes that can be maintained in a controlled environment.
    When all the cards are on the table, cities should have combined sewer collection systems without CSO’s and sewage treatment systems that not only can maintain the earlier mentioned biological processes, but also capable of handling large flow variations. All this is possible, provided we drop all the present traditional engineering approaches to collect and treat sewage, which presently only causes problems and hinders all innovation.

  2. Peter, thanks for weighing in. So you’re saying that composting toilets don’t work? I think they’re being sold. Should they not be sold?

    Under your system, how much larger would the sewage-treatment systems have to grow? How much would the expense grow?


  3. Robert,
    Composting toilets have their applications, especially in areas where you do not have utility services and you can get rid of the ammonia, thus mostly in remote areas. For cities I don’t think it is a solution, neither would be bringing back the night riders collecting urine and fecal waste for beneficial use.
    Your other question regarding size and cost mostly will depend on geological locations, basically mostly what the best solution is to collect the sewage and storm water, but as far as the sewage treatment, this does not require more space than conventional system and probably will cost less. And since their operation is very simple, they do not have to be centralized and they can be built underground.
    As far as cost goes for existing situations, this will depend on each location, but when a city already has a combined collection system, it will be much less expensive than building a separate collection system with all the new storm water treatment that will be required, although people now think that just building a holding tank for settling matter out of the storm water will be sufficient. This however is the same mistake that was made a century ago, when they thought that settling tanks (primary treatment) would be sufficient to prevent odor problems. Since it was not, it did require ‘secondary’ treatment and since now is realized that this too was not a solution, we are now talking about building ‘tertiary’ treatment.

  4. Peter, thanks for checking back and responding. I look forward to learning more about this.


  5. Peter, I’ve got to say piffle to your post. It does not sound like you’re talking about a composting toilet, but a holding tank, like one of those awful stinking port-a-cans.

    There are numerous possible treatment systems for human excrement and urine. They range from the elegant (e.g. John Todd’s aquatic systems) to quite simple (add sufficient dry matter to avoid free water (urine) and create the right ratio of Carbon:Nitrogen.

    For instance, where I used to live on Whidbey Island I created a system that (to simplify) consisted of urinating and defecating into a 55 gallon barrel and adding sufficient dry carbonaceous matter so there was no free water and the proper C:N ratio occurred. After a barrel was full, a small amount of compost from different portions of a compost pile was added to inoculate the barrel with a diversity of organisms from different stages of composting. The finished material from this process tested at 2 orders of magnitude below the Washington State standards (for Coliform) for finished material from composting toilets. Really, the Colifom levels were so low that they were within the range of error there not being any at all. And no flies, no smell whatsoever.

    Now, obviously this would not be a suitable system for mass deployment in an urban area. But the basic principles are the same. Its a question of designing a biological system that can be retrofitted to the particular situation. And by retrofit, I include social factors. For example check out Todd’s system for Fuzhou, China (from his website):

    “Fuzhou, a city of 6 million people, empties its commercial wastewater and sewage into 80 kilometers of canals that run throughout the city before emptying into a large river. The polluted canals are a health risk for the city’s inhabitants and threaten the livelihood of fishing communities downstream.
    A 600-meter canal named Baima, considered one of the worst in the city, had extreme problems with odor and floating solids created by the influx of 750,000 gallons per day of untreated domestic sewage. Rather than re-piping the polluted water to a remote wastewater treatment facility, the city government sought an affordable and low maintenance treatment system within the canal itself.
    In 2002, John Todd Ecological Design collaborated with Ocean Arks International to design a Restorer for their Chinese partners on the Baima canal using 12,000 plants composed of 20 native species. Built with a walkway down the center, the Restorer has met water quality goals and created a desired recreation area for the residents of the neighborhood.”

    Now, I can already hear protestations that such a system couldn’t be retrofitted into, say, New York City. Well, there’s a lot of derelict lots that could have greenhouses with these sorts of systems sized for individual neighborhoods or blocks. The invention popularized by Thomas Crapper can still be used, the only difference is that the water makes a detour on its way. And provides a neighborhood amenity. And lessens the load on the central plant.

    So, I think what’s needed more than anything is simply to recover the creativity that the modern western “sanitary” engineering discipline has lost.