The Flush Stops Here

One of the most vexing problems in designing for sustainability is what to do with human biological waste. We invariably take for granted the simple magic that sweeps the waste away from our homes and into sewage treatment devices. In most cases, the massive community processors and individual septic systems will not function after Peak Oil, which begs an important question: what do we do then?

Untreated human waste harbors harmful bacteria and other organisms that can be threats to human health. If not dealt with appropriately, bacteria like E. coli can contaminate our drinking water, crops, or animals.

The simplest method of human waste disposal is to bury it. That’s the technique used exclusively for millennia can used by the traditional outhouse. Of course, anyone who has used an outhouse knows that the smell of decomposing waste is potent and unpleasant (to say the least) and few relish the though of using one on a daily basis. An alternative is to dig a new latrine every few days, which not only involves tiring work, but will cause you to run out of real estate very quickly.

In addition, buried waste decomposes very slowly and you could be leaving an unpleasant surprise for the next poor soul (perhaps yourself!) who chooses a digging spot unwisely even years down the line.

Septic systems (pdf) consist of a large tank to separate solids, liquids, and oils. The solids and oils settle to the bottom and top of the tank, respectively, while the liquid flows into the leach field to be treated and filtered by agents in the soil.

Septic systems rely on large volumes of water to flush waste products into digesters. These digesters make use of anaerobic bacteria, which emit foul-smelling odors. Septic systems require regular maintenance, including professional inspections, pumping of the solid products, and repairs to the plumbing. If a failure occurs, the entire system could require replacement -– a task so onerous it should not be considered possible post-Peak Oil. Even pumping the tank after Peak Oil (a required periodic task with septic tanks) is wrought with problems.

There is a surprisingly elegant solution to this problem, known as the composting toilet. Organic gardeners should be familiar with the idea of composting waste, whether using a compost pile, methane digester, or vermiculture (worms). The exact same principles apply with human waste –- if given the proper environment and nutrition, microbes will decompose waste into a non-toxic nutrient-rich fertilizer, which you need to remove only about once per year.

A composting toilet collects waste in a bin and agitates the bin’s contents periodically. Gas products from the decomposition process are vented to the outdoors, sometimes with the help of a fan. In some designs, liquid products are piped into the soil (similar to a septic leach field), although the low volume of effluent compared to a septic system makes such composting toilets much safer and more manageable.

There are many different configurations for composting toilets. They can use rotating bins (batch) or continuously move material through a single bin; they can be self-contained or have the digester placed remotely; they can be electrically powered, manual, or passive. All types have benefits and drawbacks –- your particular needs will dictate which type you purchase or construct.

As mentioned at oikos, current regulations in most states in the U.S. regarding the solid product from composting toilets require either removal by a licensed hauler or burial. While disease is not a concern with properly built and operated composters, even after Peak Oil dispenses with the regulations I would recommend not spreading the humus product on vegetable crops. Since there is always the chance of incomplete digestion of the waste, a better plan would be to use the humus around your trees or ornamentals (similar to the recommendations for grey water).

Composting toilets have another extreme advantage over modern systems –- water efficiency. Most composting toilets don’t use any water at all! Envirolet estimates a savings of 30,000 liters per year for a family of four. For a Peak Oil homestead, that savings is invaluable.

Depending on your desired design and skill, you could build a composting toilet for less than $200 in materials. Commercial manufacturers range in price from $400 (example only – the company appears out-of-commission) to $2000 to $3000.

In my opinion, human waste disposal should be one of the very first things you focus on when building your homestead. Keeping your living area healthy trumps electricity, an irrigation system, a heating system, or even permanent shelter. If you have the ability to deal with waste at the outset, you have a smaller chance of running into problems as your development progresses. The rest of the infrastructure can come later.