By Mike Milne

The head or marine toilet, with a holding tank and pumpout system, is a convenience for boaters and an important piece of environmental protection equipment. But as most cruising boaters know, keeping it working well and avoiding clogs and odour is difficult — especially as hoses, seals and tanks age.

There’s an alternative with potential to keep both the marine environment and boaters’ living quarters in good odour: composting toilets. Already widely used in off-the-grid cabins, they are being increasingly adopted by West-coast salt-water boaters.

Properly installed and used, they can replace a head and holding tank system. (On inland waters, they may have to be used along with an existing holding tank to meet regulations, but more of that later.)

First, we have to be able to talk frankly about urine and feces (liquid and solid waste, pee and poo. . . take your pick). If you want to keep your sewage out of sight and out of mind — until it’s time for a pumpout or one of those inevitable onboard crises —stick with a head and holding tank. Regular chemical treatments, careful maintenance, and pumpouts should keep them working well. You may even be able to hire someone to handle that.

Composting toilets, on the other hand, are more of a do-it-yourself approach. They are self-contained units that handle liquid and sold waste separately and use low-power electric fans for constant ventilation to help eliminate odours. Brands most popular with boaters are Nature’s Head and Air Head, costing close to $1,500.

In practice, urine is diverted to a small holding tank, with a handle, that is normally removed for disposal, while feces (the greatest threat to human health and the environment) are deposited in the toilet’s main holding area. It contains sphagnum peat moss or coconut fibre (called coco coir). After each use, a handle is turned to mix the contents and promote composting. Users report no unpleasant odours.

Richard Brunt, operator of Victoria-based Composting Toilets Canada and distributor of Nature’s Head, says he’s been selling them for six years, mainly to boaters, all satisfied customers. Nature’s Head handles 40 to 60 “solid” uses before being emptied. What’s left in the tank, he says, is “gray matter that kind of smells like mushrooms.” Emptied into a garbage bag, it can be disposed with garbage or composted further at home and spread on flower gardens.

The toilets are approved by the U.S. Coast Guard as a Type III MSD or marine sanitation device. Canadian regulations are trickier, because the 2.5-gallon urine tank has to be emptied into a marina toilet or overboard. Even in salt water, no-discharge zones such as harbours, bays, anchorages or marine parks, don’t allow that. Canadian laws do allow vessels less than 400 gross tons to discharge treated sewage with fecal coliform counts of less than 14/100 ml — as close as one nautical mile from shore. Urine contains no fecal coliform and causes no harm in salt water.

Inland waters like the Great Lakes — where no discharges other than bilge and cleaning water are allowed — are another matter. Some boaters may be willing to skirt the law by emptying their urine tanks at their marinas. Do-it-yourself boaters whose craft already have holding tanks, says Brunt, can easily rig a hose from the composting toilet’s urine tank to their holding tank. That would meet no-discharge laws, vastly expand holding tank capacity, and make it easier to control tank odours.

On water as on land, do-it-yourself composting is not for everyone, but as an environment-friendly solution for sewage, it has great potential.

This article is featured in the Fall 2016 issue of Boats&Places.