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Economy, Ecology & Excrement: Why we installed a composting toilet!

by Michael Marcinek

Ecology, Excrement (sorry, I couldn’t resist this one), and Economy—the three E’s of why we decided to ditch our marine head with a holding tank and opt for a composting toilet.

If that second E is a bit too graphic for you, dear reader, my apologies! We can substitute another E—like ease (of use)—if that is more palatable, however, be forewarned, this post will discuss a very natural topic and we hope that it is not too crass.

*Btw, our posts may contain occasional affiliate links. It just means we might mention stuff we believe in and use, so if you try out something linked from our posts, we’d receive a small kickback but there’s no added cost to you. Note: We’re not sponsored by Air Head.


If you have read our previous posts, you will be aware of the fact that we are great admirers of Don Casey, author of the Complete Illustrated Sailboat Maintenance Manual and the universally-praised This Old Boat.

He has committed countless words to the page and web for the benefit of all boaters, and we are grateful for his commitment for sharing his experience and knowledge.

This Old Boat., 2nd ed., by Don Casey

In “The Straight Poop” from This Old Boat., 2nd ed., Casey argues that a well-equipped cruising boat generally doesn’t discharge enough waste overboard to make much of a difference from an environmental/ecological standpoint.

On the other hand, he isn’t shy about calling out how much sewage municipalities dump into our waterways every year, which makes Casey’s This Old Boat a thought-provoking read for boaters and environmentalists alike.

So how much sewage do municipalities dump into our waterways every year?

It is a staggering amount! You can read more about how and why that happens here.

According to American Rivers, “Each year, more than 860 billion gallons of this vile brew escapes sewer systems across the country. That’s enough to flood all of Pennsylvania ankle-deep. It’s enough for every American to take one bath each week for an entire year.”

Here’s a quick summary of Casey’s argument: he suggests that for a small cruising vessel, direct discharge is the safest way to handle waste. Holding tanks, he writes, not only stink, but storing sewage onboard is a health hazard.

In most cases, direct discharge for a small vessel pumps a relatively small amount of waste at a time (usually no more than a gallon per trip to the head), and certainly not enough to contribute significant pollution. Or as I jokingly say, “the ocean is vast, and a turd is but a drop.”

For a small sailboat in a remote anchorage (or a sparsely populated one), direct discharge is a reasonable solution, especially if said anchorage has a direct outlet to the ocean.

However, being East Coast sailors currently living in Florida, we can’t help but think about the great congregation of boats that happens every year as boats return from the Caribbean cruising season to wait out hurricane season.

Photo by Barna Bartis on Unsplash

Our little river—the Ortega River—is a great hurricane hole located 30 miles inland from the St. Johns inlet and as such, it doesn’t quite have the tidal outflow you might find further downstream. They call the Ortega River the “Miracle Mile” since there are 7 full-service marinas in a short stretch, and several thousand cruising boats wait out the season here every year. If we were all directly discharging, it would definitely make a significant impact on water quality, pollution, and would be an overall mess.

This makes me think of other hurricane hideouts up the coast: Brunswick, Beaufort, Charleston, New Bern, Beaufort again (spelled the same but different in pronunciation), Oriental, Wilmington, the rivers and estuaries of the Chesapeake.

How many boats? How many marinas, anchorages, mooring fields?

However, would the scale be anywhere close to what New York City discharges in a single heavy rainfall (reportedly about 20 billion gallons per year)? Not likely.

But would direct discharge by all these vessels cause significant enough damage to already struggling ecosystems? Absolutely!

From “When It Rains, It Pours Raw Sewage into New York City’s Waterways”:

Across about 60 percent of the Big Apple, storm runoff and sewage (i.e., what approximately 8.5 million New Yorkers flush down their toilets) stream through the same network of pipes on their way to the city’s 14 wastewater treatment plants. This combined sewer system works well enough on dry days, but when it rains a tenth of an inch per hour or more, the added volume quickly overwhelms the 150-year-old network. When this happens, “relief structures” allow a gruesome mixture of polluted urban runoff and raw sewage to bypass the water treatment plants and discharge directly into local waterways at up to 460 locations throughout the five boroughs. In the words of one New Yorker: blerg.

To be fair, I don’t think that Don Casey’s point is one of moral/ecological relativism. He is simply arguing that direct discharge from a small vessel—such as pumping a small quantity of waste per use for a cruising couple is far safer and cleaner (for the residents of the boat, and largely insignificant for the local reef) in comparison to the marine head with holding tank system. In a perfect world and under perfect circumstances, he is right.

Since my wife and I are working aboard as we sail, it’s likely we would be in locations where we couldn’t legally direct discharge overboard (and probably shouldn’t anyway, even if it were legal).

Here’s another point: if you are not in a place where it is legal to discharge, you are simply delaying the inevitable. Meaning, you are storing your waste in a holding tank that you would normally flush down a toilet. You pump out the tank via a hose, and this waste is then added to the sewage treatment process for local municipalities.

Sewer photo by Jake Nackos on Unsplash
Photo by Jake Nackos on Unsplash

What does the sewage treatment process involve? How much water does it waste? Is the sewage system a CSO (combined sewer overflow systems)?

Essentially, storing your waste in a holding tank to later pump out at a marina or fuel dock still contributes to the local sewage system. This also means that the waste you pump out today has an equal risk of ending up downstream as it does being processed at the local treatment plant—a prospect that my wife and I are not very comfortable with.

We also plan to travel in some pretty remote areas of the world, so in those cases, discharging small quantities might be fine, but we would prefer to leave as small of a footprint as possible. Will the municipalities we provision in also have the means to deal with our waste?

We definitely wanted an option C not mentioned in Don Casey’s article, and thankfully there is one—enter the composting head.

Airhead install


What makes a compost head an attractive option for a cruising couple? Is it safe and easy to use? I mean, you haven’t cured the storage problem that Don Casey mentions about marine head systems since you have a bin for #2’s, right?

These are some of the questions that we had, so let’s go over what we have learned, including some tips we have already picked up along the way.

So why is a compost head a great option for a cruising sailboat?

Simple! Holding tanks are gross! Fact! Every time you use the bathroom you are pumping the contents from the bowl into a tank. Consider that many production sailboats have their holding tanks set directly under a berth! Nothing says a great night’s sleep in a beautiful location like sleeping over 10 gallons of human effluence, right?

On our boat, Hope, we were “lucky” in that our holding tank was in our port settee—our luck eventually ran out, however, when our 18-gallon tank ruptured and emptied its contents into a well-constructed fiberglass and marine plywood bowl, YIKES! Not to mention the stories by cruisers about their holding tanks going awry and sometimes during a passage.

Let’s consider the simple fact that marine head systems have a limited life span. Seawater, chemicals—and even our waste— attacks all of the components of the system (pumps, hoses, and tanks), so failure is inevitable.

When the system finally fails, you will find yourself considering what items you have onboard that you can effectively use to remove the contents of that tank out of your bilge/berth/ settee. For us, it was a mixing cup, small siphon pump, an old sponge, and a 2.5 gallon bucket.

Everyone who has owned a boat for long enough has a story about ladling crap out of some area of their boat. Nothing says fun to me like sopping up a brew of raw sewage and mineral crystals! Yep, all that seawater and urine make you feel like you are mining a diamond vein.

This isn’t just gross, it is utterly unnecessary.

Myths about sewage

Don Casey is 100% right: storing sewage on a boat is disgusting and a health hazard. To us, the easiest way to solve the problem is to not make sewage to begin with. I know what you are thinking, how does one NOT make sewage? Isn’t sewage just human waste, right?

That is what we previously thought too. The reality is whenever we go #2, we pass with our feces microbes and bacteria that normally would have broken down our waste into a biological and ecologically safe compound.

I always presumed that modern sewage solutions and treatment were a necessary evil of safely disposing our waste to prevent the spread of disease and other microbial nastiness. On the contrary! Mixing then storing urine and feces together IS the problem that our sewage containment and treatment is attempting to solve. Treating wastewater is a global problem and one that sucks up a significant amount of energy and water resources.

Wastewater is roughly composed of 99% water and 1% suspended, colloidal and dissolved solids (UN-Water, 2015a). Although the exact composition of wastewater obviously varies between different sources and over time, water remains, by far, its principal constitute. Wastewater management generally receives little social and political attention in comparison to water supply challenges, especially in the context of water scarcity. Yet, the two are intrinsically related – neglecting wastewater can have highly detrimental impacts on the sustainability of water supplies, human health, the economy and the environment.

The United Nations world water development report 2017: wastewater: the untapped resource; 
facts and figures

Basically, if we keep the liquids out of the solids, nature would handle the rest.

Here is the other thing, when properly operating, a compost head does not really emit any odor except for a slight smell that can be described as “damp earth.” In comparison, our old marine head system always had an odor which permeated the cabin. It wasn’t until we removed the tank and all of the lines that I really noticed just how prevalent the odor was.

Are composting heads simple to use?

Using the composting head is quite simple, as a matter of fact, it isn’t really that different than a standard home toilet except for the fact that it uses no water and has a trap door instead of a flushing mechanism. Men will have to get used to sitting down to pee, but, for the sake of keeping the head clean, many men are already accustomed to doing that while underway.

As for a women’s perspective, Esther says,

Early on, we resolved a problem of some urine leaking into the solids tank (we go into this later in the post). Well, I was unknowingly contributing to that problem at first, but I realized that sitting a little more forward on the seat for #1s helped solved that issue. I was nervous about trying the composting toilet, but now, I can honestly say that I wish we’d switched earlier, especially in light of what we know now about the environmental impacts and annoyance of conventional marine heads. Overall, for anyone considering a composting toilet, I’d say it’s easy to use, surprisingly not stinky at all, and it’s reassuring to know we’ll never have to deal with the risk and maintenance of flushing toilets again. We’ve been gradually adopting more sustainable practices and swapping out products onboard like toilet paper for options with less of a waste footprint, so we feel great about this swap to a composting head too.

Operating a compost head does require a little bit of planning. By that I mean you need to rehydrate your composting medium in advance before emptying the solids tank, otherwise it’s not ready for use.

We use Plantonix Coco Coir, a material made from organic coconut husks. This requires us to add water to a block of condensed dried coir which needs to be broken apart which can be a little tedious (takes roughly 30 minutes to break apart a coir brick, but only once every 3-4 weeks).

Rehydrating coir
Michael breaking up some recently hydrated coco-coir. Looks like he is having fun!

Our biggest learning curve was finding the right balance of water to re-hydrate the coco-coir blocks with, and we’ve found that between a 1/2 a cup to a full cup of water allows for us to break apart the medium effectively (we are currently experimenting with a way to make this process easier and will update with our findings).

At first, we also discovered that we had some urine leaking into the solids tank, a problem that we solved with a little bit of caulk along the urine-diverting tray in the seat and by adding a shim to tilt the entire head slightly forward to help gravity do it’s work.

Maintaining the compost toilet vs. marine head

We have found that we get about three weeks of full-time usage before we need to refresh the solids bin, a very simple process thanks to the design of the Air Head which can be taken apart and brought out into the cockpit in less then a minute. To do so requires that you twist off the vent hose, loosen two toggle bolts to remove the urine tank, and two toggle bolts to remove the solids tank.

Once in the cockpit, there are four toggle bolts that need to be loosened to remove the seat section from the tank. The compost material from the solids bin can then be easily emptied into a bag for disposal, cleaned, and refilled with coir. The entire process takes us 20-30 minutes. The liquids tank we empty about every 1-2 days, which takes a few minutes.

In comparison, using our old marine head full-time meant pumping out every week and a half to two weeks. That entailed a more time-consuming and smelly process of getting the boat to a pump-out station or reserving a pump-out cart at our marina (which wasn’t always available).

Also, in an absolute worst-case scenario, if a marine head fails, you’re likely dealing with a more complex (and messy) system, whereas a composting head is much simpler (and won’t explode). Failure is far less likely with a compost head, if not impossible.

Even if you were to run out of coco-coir, you can easily substitute just about any other medium (i.e. in a pinch, you could temporarily use peat moss, potting soil, maybe kitty litter) that can cover your solids until you can get more coir although you might have a bit of extra cleaning to do. Bonus if the substitute medium can help dissipate moisture.

It should also be noted that the material in the solids container of composting heads are considered a “Class B Biosolid.” This means they can be disposed of in the trash bin just as one disposes of diapers. While it is called a composting toilet, at the end of 3-4 weeks for us, the composting process is far from complete.

If you or someone you know has a compost pile, the process can be completed there and will take several more months, but it will completely break down into a safe organic material. That said, during the 3-4 week window that you are using the same batch of medium, natural composting processes are fully at work so the material you are keeping onboard is quite safe.


For us, we knew we would eventually install an Air Head or the Nature’s Head composting toilet. In the end, the choice was made for us when a neighbor was selling a never-installed Air Head at a very discounted price!

We really scored since the Air Head’s dimensions fit the best in our space. The unit is offered with many different options—a straight back model, a hull shaped model, marine head size as well as a traditional “home” sized seat. We have the hull shaped model with the larger “home” style seat. The Air Head also allows for some additional options to tailor it to your space.

Let’s break down some numbers for the install cost.

The Air Head currently sells for $1,029 (note: all $$ amounts are USD) and must be ordered directly through their website. This includes everything you need to install the toilet except for the deck level vent and any additional hose you may need. The kit comes with 5 feet of hose, however, we ended up needing 14 feet since we replaced our old pump out deck fill with our vent. The additional hose cost us $45 purchased at a local hardware store. We purchased a Vetus 3″ Mushroom Vent, which was $80 from the Nature’s Head store and a Whitecap Teak winch pad ($19 on Amazon) which we used to elevate the vent from the deck. This is optional, but we think it looks damn good!

Airhead Vent

For us, all in, the full cost to install was $1173, which is not cheap by any stretch of the imagination. But is it necessarily more to install another holding tank though?

In our case, our marine head system was getting old (our boat was built in 1994) and needed an upgrade, so let’s take a look at what it would have cost us to replace everything onboard one to one:

For the sake of consideration, a generic 18-gallon Dometic holding tank will set you back $386 (list $669) at Defender Marine. This price can significantly increase if a custom size, shape, or fit are needed. We definitely would have needed a custom tank on our Island Packet 35.

A simple manual Raritan PHII, a great budget marine head, and the exact model we removed will set you back $449 ($725 list). Meanwhile, electric flush and other more “robust” installs can easily top $1000. A new macerator ($189-$300 or more) plus hoses and fittings will easily match the $1173 install cost that we spent on the Air Head, so the cost to install is essentially the same.

Of course, as all things go, there are maintenance and use costs which need to be considered.

To keep our Air Head working properly, we need to empty the “solids” tank on a monthly basis (really about every three weeks for full-time liveaboard usage). Like we mentioned, we order Plantonix Coco-coir from Amazon which costs $25 for a pack of 5. We can stock up with nearly a year’s supply for roughly $75. Plantonix will even send the bricks unwrapped (NO PLASTIC!) with their no-nonsense packing options! Besides emptying the “liquid” and “solids” tanks, the Air Head requires no additional maintenance!

On the other hand, the rebuild kit for marine heads like the Raritan PHII would typically set us back $63-75 per year, as long as nothing else broke. Holding tanks need to be pumped out (vs. direct discharge) if you are in U.S. waters, and some locations charge between $5-10 per pump out which we would need to do every 2 weeks at minimum.

On a mooring, a visit from the local pump out barge (often referred to as the “poo-poo canoe”) can cost even more than that. Between maintenance and pump-outs, the cost to operate a standard marine head will end up costing more than operating a composting head year over year. And really, a composting head is really simple—no pumps, handles, sewage hose, or tanks to break fail or clog. This also means less things that can break which in turn means less spent on parts and time to repair.

So far, we think that swapping our old head out and replacing it with a composting head has been a vast improvement to our life onboard. It definitely required a little bit of adjustment the first few weeks, but we are definitely seeing the benefits of the change and wish we could’ve done it sooner.

We really believe that composting heads are not just for life onboard, but they should be considered a practical means of handling our personal waste for all types of dwellings both on and off grid!

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azsailor August 28, 2020 - 10:47 pm

I think your philosophy will change once you head south. Try to find coco-noir in Zihuatenejo or anywhere. Note: you missed the pun, “Every time you use the bathroom you are pumping the contents from the bowl into a tank.” Should be bowels not bowl. I like what you’re doing. I like your DIY dodger/bimini: info was good to know.

Wayfinders Now August 29, 2020 - 12:53 am

Great suggestion! We may have to edit the post to include your pun, if we do, we’ll be sure to give you credit!

As for our philosophy’s potential for change, well, we embrace it. If the compost head route doesn’t work out, we’ll try something else and be sure to admit what went wrong and report it here. So far it has been a great solution, and thankfully coco-coir, while not entirely ubiquitous, has some practical applications in agriculture so some form of it is likely to be found at most of our larger ports of call. Maybe not in Zihuatanejo, we may just have to stock up a bit further down the line in Acapulco.

Coco-coir bricks are pretty compact(8″ x 4″ x 2.5″) as well and can be tucked away in the dead storage areas at the bottom of our settees or deep in the galley cupboards that other provisions cannot fit in. Considering a single brick gives us a medium base that reasonably lasts 3 weeks, bulk provisioning coco-coir to last us several years shouldn’t be too difficult in our estimation. Honestly, the space that previously housed our holding tank could easily hold a 3 year supply of coir bricks, but, it would be foolish for us to simply fill that void with coir bricks when it can more practically store tools, spares, food as well. We’ll see how it goes, that is a part of the adventure.

Thanks again for your comment, and thanks for spending time reading our ideas and letting us know your own!

crushed0ranges November 24, 2020 - 1:15 am

Hi there! Thanks for the thorough post! What do you do to empty the liquids tank when you’re in a “no dumping zone”?


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