I am still preparing the "how do we currently measure sustainability" article, and I thought I should include this first. Here are 8 conditions to sustainable infrastructure, presented as a work in progress.
To be sustainable, a system must avoid failure. Failure to a higher system means that as a subsystem, it failed to do its necessary function. Some aspects to plumbing may change (like toilets that don't use water) but the function of providing transportation for water will be necessary. If our system dictates fresh water in the home, that system will almost certainly involve pipes. I'm not going to discuss water infrastructure in the example, I will limit the discussion to 'sustainable plumbing in the home'.
Systems can fail in a myriad of interesting and painful ways. To avoid failures we need to figure out "How" to avoid the failures. We know that when something fails, it wasn't Sustainable. Are we smart enough to figure out if something is not sustainable before it fails? Apparently not so far. I have checked hundreds of groups. Nobody knows what "sustainable" really IS. Our collective knowledge seems limited to knowing "failure = bad" and "sustainable = no failure". That tells us nothing for planning, measurement or evaluation.
How do we have sustainable agriculture? The answers are there, but we don't know how effective, scalable, and adoptable they are. We know that mulching and not using oil as fertilizer is important, but we don't know how long we can keep any particular path going without a means of measurement.
In the open system that is Earth, we may not ever be able to figure that out. Smaller closed systems are measurable, they get faster feedback, and many other advantages. I propose that we make small communities designed to be sustainable - In A Measurable Way. Those measurements will allow people outside the communities to choose sustainable living or adapt aspects of the smaller communities into larger ones.
So, in the interests of sustainable infrastructure in general and sustainable plumbing as a specific example, here are a few requirements of a Sustainability Metric e.g. knowing if something is sustainable.
1. Building materials should be made from renewable or recyclable resources.
2. The installation and repair should be performed with renewable or recyclable resources.
3. The infrastructure used to build the materials, installation parts and performance should all be renewable or recyclable.
Renewable materials are classified as being made available through natural cycles, like wood, mud, possibly clay. Renewable resources each have a different time delay to replenish the resouce. Typical farmed pine is on a 24-25 year cycle, tropical forests are on a 300 year cycle. (David Holmgren, 2003) Using recyclable resources boils down to "if we can make it, we can unmake it and remake it." Some plumbing glue for example, is not renewable unless someone can make the raw materials necessary, in this case oil. Most of the plumbing glues are oil based, and no oil means no plumbing glue. Most insulation, binding and wrapping is oil based.
So with the current plumbing, we may just run out of parts or glue some day. PVC pipes are also made from oil. Many of these parts cannot be recycled, since the polymers break down and become brittle (they become not plastic after a few cycles, or in UV light, or other conditions).
Recycling is a way of renewing a resource, but in the case of some (there are over 20,000 kinds) plastics the heat to reshape them damages the bonds. Most plastics have a lifetime, and the lifetime varies, often cut shorter through recycling. This does not mean recycling won't work, it means there will be losses going through the cycles. The ability to recover the losses alters the long term renewability.
Steel can be recycled very well, but it also rusts during its life cycle. This leads us into the next segment. Energy in and energy out. We can recover iron from rust, and turn it back into steel with a lot of energy (also requires some rare metals in the process). The amount of energy needed vastly exceeds any sort of reasonable amount. Not to mention the collection of the rust and removing extra particles, etc. There may be some other chemical to add that rips away the oxygen from the iron, but is the production of that other chemical renewable and energy efficient? Usually no. Cheaper yes, renewable, no. Almost all industrial processes involve entropy. Taking something from a high energy state, and putting it into a low energy state. We just gather the stuff in the higher state from nature, and then use and refine it at our leisure.
4. All processes must involve a reproducible amount of energy without undue strain.
5. All processes must be reversible with a reproducible amount of energy.
We can turn rust back into steel, but the electrolysis necessary would be extremely intense. We only perform electrolysis on rare occasions, contributing an electron directly to each atom is extremely expensive. In order to reverse the chemical processes, we would often be required to perform electrolysis. The Hall-Heroult process is one example of electrolysis still used in industry. Aluminum requires 3 electrons for each atom, and consumes 15KWh per Kg of aluminum produced.
Far more commercially viable is using chemicals in a higher energy state (like natural gas or oil) and moving them to a lower energy state. The methane reforming method of producing hydrogen is approximately half the price ($2 per liter) of the electrolysis of water to produce hydrogen ($2 per liter). In order for a society to be sustainable, it must either create (or recreate) the higher energy state chemicals, or not rely on these practices. The reliance on open systems to create higher energy states (like peat moss in swamps creating coal, plankton buried to create oil, etc) generally dictates their exploitation, and that exploitation occurs faster than their production. The production of methane from decomposing matter creates a high energy state material as for producing hydrogen, but it is produced from a higher energy state material than itself. The creation of higher energy state materials is linked to available energy, in this case sunlight used to grow plants and produce cellulose. This is another topic I will write more about later.
6 Each component must be able to be recycled or reused in some fashion.
This is an extension of 4 and 5, claiming that not only does every process need to function in fully closed loops, but each part must function in a closed loop as well. If the pipes are sustainable, the glue and binding needs to be as well for the whole system to be sustainable.
7 Every component needs replacement parts, or a sustainable alternative.
This is basic "no single point of failure." You could have the most efficient, most recyclable plumbing system on the planet, but if you can't replace a single part when you need to, the whole thing is broken. If there are no spare parts, it must never fail.
8 Components must be able to be produced with available resources.
The definition of "available" really depends on the system involved. Assuming that we are dealing with a global economy to create plumbing, the resources of the Earth can be used. I have read, but not confirmed, there is not enough of the element nickel on the Earth to create stainless steel sinks for everyone in China and India. Recycling steel for plumbing is easier than recycling steel for plastic, but the limits of steel available prevent wide scale adoption. If only a smaller segment of the population has stainless steel, that might be a sustainable system. If global adoption is not permitted, then a different global solution must be found. (The simple answer is: don't make sinks. People don't need to live like middle class America.)
This isn't a complete list, but there seems to be a shortage of these low level mechanical lists. An alternative style would be the Living Systems Sustainability, which I will probably create after I have written about Living Systems more.
