Composting Toilets, a Decentralized Approach to Wastewater

Dennis M. Bushnell,  NASA Chief Scientist and futurist, closed the BlueTech Forum for Water 2016 in San Francisco on June 1 with a prediction that the future would see “extreme decentralization” of utilities. The nature of urbanization would change, with people no longer compelled to live in congested mega-cities. Food would be grown in deserts irrigated with seawater.

The conversation in my head when Dr. Bushnell discussed utility decentralization was, “who will manage the solids?” I leapt to the notion that in such systems the intention would be to render organics and nutrients suitable for on-site food production.  In that scenario, none of today’s issues with pathogens, odors or persistent pollutants are made easier by extreme decentralization, and perhaps they are even made more serious, particularly in tropical zones with serious pathogenic worm infestation. The amount of decentralization we already have in the U.S., with about a quarter of our residences on septic tanks, already begs the question of the fate of viruses, pharmaceuticals, surfactants, flame retardants, etc, in ground waters beneath on-lot leach fields.

The fellow sitting next to me whispered, “do you think he envisions a lot of Clivus Multrums?” I hadn’t thought of these composting toilets in a long time, and at that moment the thought made me uneasy. As Wikipedia explains in its article on Clivus Multrum: “In the 1970s, Abby Rockefeller, in the United States, read about the idea and wanted to buy a system, but was told they were not for sale due to lack of technical support. In 1973, Rockefeller founded Clivus Multrum, Inc. in Massachusetts under license from Lindström to market its composting toilet. The brand of Clivus Multrum composting toilets is marketed globally.”

If you have been around as long as I have been, you might recognize Abby Rockefeller as the author of SEWERS, SEWAGE TREATMENT, SLUDGE: DAMAGE WITHOUT END in which she rails against centralized sewerage systems and asserts “… spreading sewage sludge on land… must be banned.…”  Her interest in the Clivus Multrum option aligns with this opinion. If you don’t have central wastewater treatment, you need a lot of Clivus Multrum’s. We in the biosolids industry believed she was a supporter of anti-biosolids activists groups, and I remember EPA’s chief 503 author, Dr. Alan Rubin, saying something to the effect “even Abby Rockefeller has to comply with 503.”

I checked into today’s Clivus Multrum website and went to its Science and Technology page.  At the bottom is a recommendation that “for a fuller discussion of the environmental issues addressed with the Clivus Multrum” one source is: “Toxic Sludge is Good for You, John Stauber and Sheldon Rampton How the PR industry promotes the use of sludge.”  This publication is still sold by The Center for Media and Democracy’s PR Watch, but it seems the Center has been distracted from biosolids by the Koch Brothers, the American Legislative Exchange Council, fracking and such other small issues.

Importantly, the Clivus Multrum’s website provided a link to the National Sanitation Foundation and its certification for the composting toilet. This is  NSF/ANSI 41: Non-Liquid Systems,” a standard that certifies composting toilets and similar treatment systems that do not use a liquid saturated media as a primary means of storing or treating human excreta or human excreta mixed with other organic household materials.” In all of this, however, I did not see reference to 43 CFR Part 503.

You would think a certification of the Clivus Multrum from the NSF would have been the ticket to its widespread deployment, but it has not been.  The dry-composting toilet has had a complicated path over the years since Rockefeller gave it prominence. Despite the NSF’s certification, researchers have highlighted concerns. The sustainability web-based Appropedia summarized a view of  Composting Toilets: “The limited body of literature on [composting toilets], especially field versus laboratory studies, generally does not prove them reliable for decomposition or sanitation of fecal matter. Adequate temperatures are seldom, if ever, attained eliminating this reliable mechanism of pathogen destruction. Storage alone is unlikely to be a reliable pathogen destruction mechanism.”

One important scientific study suggested that better than dry composting is worm composting.  This article is Vermicomposting toilets, an alternative to latrine style microbial composting toilets, prove far superior in mass reduction, pathogen destruction, compost quality, and operational cost. A web-search uncovered the project of Clint Elston, of Afton, Minnesota, an inventor who designed a self-contained home sewage treatment system using worms, according to a local newspaper article. On his website, he writes “Next, I have learned to successfully convert the composted blackwater, or RESOURCE, into a liquid agricultural fertilizer for non-edible agriculture.”  From there he goes on major political rants.  Mr. Elston has a GoFundMe campaign that has raise $275 of the $1,000,000 he needs to implement his project.  Beyond that high hurdle, it’s hard to see how NSF/ANSI standard 41 applies to his self-contained home vermicompost toilet.

In actual operation, the effectiveness of dry composting toilets to stabilize and sanitize human excreta has been called into question.  Some report that indicator organisms are often not effectively reduced: Survival of Fecal Coliforms in Dry-Composting Toilets. And other researchers suggest that indicator organisms do not adequately measure disinfection in composting toilets -- Microbiological assessments of compost toilets: In situ measurements and laboratory studies on the survival of fecal microbial indicators using sentinel chambers.  Others have looked at indicators of viral pathogens and they, too, express concern that the technology is not robust and that reduction of viruses is highly variable: A fate model of pathogenic viruses in a composting toilet based on coliphage inactivation.

Composting toilets may have a special niche for remote park facilities and small communities.  One special niche is parks far beyond the reach of utility services. Here the public health issue is whether the solids are sufficiently stable, sanitized and appropriate for spreading in a public access area (Composting toilets a misnomer: Excessive ammonia from urine inhibits microbial activity yet is insufficient in sanitizing the end-product).  When dry toilet systems were used in a Swedish Eco-Village, with residents presumably motivated to be environmental stewards, the researchers ( Experiences with dry sanitation and greywater treatment in the ecovillage Toarp, Sweden) minced no words: “Composting toilets were implemented without sufficient knowledge and usage directions, resulting in partly disastrous operational results. In consequence, the majority of the ecovillage's composting toilets are now replaced by water toilets.”

Perhaps this technology has a niche in undeveloped rural communities. But, maybe not.  In one study, analysts pointed specifically to lack of understanding of the nature and risks of handling the solids as the factor that brings down the concept. The authors report in Ensuring Sustainability of Non-Networked Sanitation Technologies: An Approach to Standardization: “A main drawback was insufficient quality of the byproducts from on-site treatment, making recycling in agriculture a hygienic and environmental risk. Further, no technology was sufficiently mature (requiring e.g. to shift wastes by hand).”

The concern for distributed treatment systems is not just one of direct human health, but to a range of contaminants carried in sewage. Surfactants, pharmaceuticals and other potential endocrine-disrupting or bio-accumulative compounds, the origin of which are commodities used by homeowners, are at issue regardless of whether toilets are connected to sewer collectors, septic tanks or compost toilets / greywater treatment systems.  Environmental scientists have documented that in traditional septic tanks and leach field systems, septage retains many compounds (Occurrence and Fate of Organic Contaminants during Onsite Wastewater Treatment).  For soluble constituents, the leaching fields do not fully remove them, and the compounds of concern are in the ground water plumes emanating from the on-lot fields.

The issue of quality in decentralized treatment is solvable. A comparison of decentralized treatment has shown that advanced systems with aerobic treatment and ultrafiltration can successfully produce re-usable water, Evaluation of On-Site Wastewater Treatment Technology to Remove Estrogens, Nonylphenols, and Estrogenic Activity from Wastewater.  Yet even in those systems that claim low yield of solids, residuals disposal is not recommended for on-site fertilization of soil.  The “brine” from water re-use systems is often landfilled or trucked to POTWs.  The circle is not yet fully closed in these systems.

The issues raised by biosolids are not ones of centralized versus decentralized systems. Regardless of the side you take on the debate, we need good science, innovative technologies, responsible professional management and reduced use of persistent organic compounds. The quality of what you get out is only as good as the effort you put in, and that is the Central Dilemma of Biosolids.