Frankford and Boat Projects (2013-09-09)

N 44° 11.906' W 077° 35.475'

We arrived at Frankford, Trent-Severn Lock 6, yesterday at about 1600.  We had planned on stopping enroute for another night at anchor, but the winds yesterday on the Bay of Quinte were strong and from the north, limiting the number of anchorages available.  Instead we decided to push through to Trenton, and to Lock 6, where we will be leaving the boat for a few days while we head back to Ottawa.


One of the nice things about travel downtime is that it gives me a chance to get some work done on the projects on the boat project list.  Today I spent most of the day finishing up the build of our composting toilet.  In this post I'll give some background on composting toilets.  Tomorrow I'll do a post detailing the project of the composting toilet I built.

Before I talk about composting toilets on cruising boats, I think it's important to understand the 'why' of composting toilets in general.  There's a lot of good information on the Internet about the subject, but one of the best is Joe Jenkins' "The Humanure Handbook".  If you dig about the website you'll find a link to read the book online for free, but you can also buy it to help support the author's work in promoting humanure sanitation.

There's a lot of good information in The Humanure Handbook, much of it eye opening.  It seems incredible that we as a society think it's normal to spend millions of dollars to purify water, only to defecate in it and flush it away to repeat the cycle all over again.  Joe Jenkins also makes a good point about the breaking of the nutrient cycle by not recycling our humanure (a nice word for the brown business :-)).  I'll leave it to everyone to make their own decisions about the value of either of those two points.

While all of this is good, for a cruising boat waste management is a lot more up close and personal than it is when you're living in a house.  Typical marine toilets work in a similar fashion to the more stationary variant.  You do your business and then flush it away.  Unfortunately, 'away' isn't all that far on a boat, as the contents of the 'business' ends up in a 'black water' holding tank.  A holding tank has limited storage, and regardless of how well it's all sealed up and ventilated, the contents in storage give off a definite and identifiable aroma.  If it isn't the holding tank creating an odour, it is the hoses between the toilet and the holding tank, or the fittings, or any of a number of different odoriferous escape points.

The bottom line is that standard marine head systems on a boat stink.  That isn't the end of it though.  Because there's a finite amount of space in a holding tank, you have to have it pumped out regularly, which usually costs from ten to twenty dollars each time, and pity the person that forgets and has an overflow...

The reason for the stink is quite simple.  The environment inside a holding tank is ideal for the flourishing of anaerobic bacteria.  Anaerobic bacteria create a number of foul smelling gases during the process of consuming the products inside the holding tank.

There is another type of bacteria that can perform the same function, without any of the bad smelling bi-products, called aerobic bacteria.  While anaerobic bacteria die off in an oxygen rich environment, aerobic bacteria thrive in it.  This simple fact is the whole basis of composting toilets.

I won't spend any more time with the theory of all of this.  To understand more about this process and how it works, I urge you to read The Humanure Handbook.

So for the cruising boater, replacing a traditional marine toilet with a composting toilet brings three tangible benefits.  The first is the elimination of the 'head smell' aboard the boat.  The second benefit is the recovery of all of the space that was previously taken up by the components of the marine toilet system.  Finally it removes the requirement to find locations to do a pump out, with it's attendant expense.  As for this final point, users of a composting toilet still have to deal with disposal of the waste, but because of the way that composting toilets work it isn't as unpleasant a task as a pump out.  The waste can be stored safely and spill free on the boat until you get to a location that you can dispose of it in a shore side toilet.

There are a number of commercially available composting toilets for both fixed location and marine applications.  The three main manufacturers of marine composting toilets are Nature's Head, Air Head, and, my personal favourite, the C-Head.  While these are all great devices, the biggest problem with them is the cost.  To buy one of these you'll spend anywhere from $500 for the C-Head, to close to $1000 for the others.  Being the cheap bugger that I am, it was an easy decision to instead build my own.

All three of these composting toilets use a process called 'Urine Diversion', where the urine is separated from the solid waste and stored separately.  This helps the aerobic process in the solid waste storage container, which also means the best thing; no smell.

I could have made my own urine diverter, but you can buy one from a company called Ecovita.

Stay tuned for the part two post, where I'll detail the composting toilet that I built.