Permaculture’s principles are simple: take care of the earth, and the earth will take care of you. Practical Permaculture (Timber Press, 2015) by Jessi Bloom and Dave Boehnlein covers the basic principles of permaculture design and offers detailed information on wastewater recycling, composting, renewable energy systems, and much more.
The following excerpt from “Waste: Plugging Leaks in the System,” discusses how to design permaculture systems to recycle human waste, food and yard scraps, wastewater, and how to capture usable heat released from biodigestion.
You can purchase this book from the MOTHER EARTH NEWS store: Practical Permaculture.
In your permaculture design, you want to shoot for a near-zero-waste system. That doesn’t have to happen overnight, but it is definitely a primary goal. If the systems you design are wasteful, they will forever be reliant on large quantities of external inputs to keep them running. Most lawns are like this. Without chemical fertilizers, city water, and gasoline to run the mower, they would very quickly cease to look the way they do.
Many of the external resources we rely on every day are nonrenewable (at least in a human timescale). Once we use them, they’re gone. Relying heavily on these resources for day-to-day operations means we are more susceptible to market fluctuations and supply chains, and thus less resilient. In an emergency the lawn can just grow and become weedy, but what happens when we rely heavily on external inputs for our food, water, and heat?
This chapter focuses on where leaks often appear in systems and how we can minimize them, thus eliminating waste. The idea is to integrate those surpluses (another name for waste considered from a different perspective) back into our systems in some way. For instance, if we produce compost, apples that go bad can’t really go to waste. If we apply the principle of efficient energy planning and the concept of next highest use, we don’t really waste energy. Overall, the goal is to manage the inflows and outflows of our systems. We aren’t going to create completely closed-loop systems (where nothing enters or leaves), but we want to get a lot closer to that than where we are right now. Ultimately, we want to be very conscious of how the outflows of our systems can be used as inflows. Any outflows we do end up with should not harm the environment nor our neighbors.
Types of waste to address in your design include human waste, greywater, food and yard waste, and heat. We have already explored some ways to turn food and yard waste into compost in the earlier chapter on soil fertility. We’ll look more closely at the other topics here.
The topic of managing human waste, also known as humanure, is pretty much considered taboo in Western culture. You don’t talk about it in polite company. However, it is imperative that we begin to take responsibility for the humanure we produce. Unfortunately, the centralized systems upon which many of us rely and conventional home septic systems do not score that well on their ecological report card. In many parts of the world, waste collected by municipal sewer systems is dumped into the ocean or injected into the groundwater. Even the municipal systems that are ecologically kinder often have enormous energy inputs. The amount of fresh, clean water wasted by these systems is staggering. Consider, for example, that the Colorado River no longer reaches the Gulf of Mexico, thanks partly to all the flush toilets in huge desert metropolises like Las Vegas and Phoenix.
The good news is that there are some excellent ways to take responsibility for your own humanure instead of flushing it away where it both pollutes water and becomes someone else’s problem. In fact, with the right system, you can wrap this outflow right back into another part of your permaculture system in a way that’s neither gross nor unsanitary. Taking responsibility for your own humanure means managing it in a way that doesn’t risk anyone’s health or unintentionally cause pollution.
Before you get really excited and start ripping the toilet out of your bathroom, it is critical that you fully educate yourself on this topic. Laws and codes vary from location to location. Whether you choose to obey them or not, you should at least know what they are. Details of timing and temperature can vary from situation to situation. Do plenty of research before you try any of these options at home and start small. And realize that any humanure system requires a core personality trait: detail orientation. To safely operate any of these systems, you must pay close attention to the specifics of temperature, time, and cleanliness. If that doesn’t sound like you, everyone may be better off if you just keep flushing it.
In the meantime, there are intermediate options to help minimize negative impacts, such as flushing your toilet with greywater. You can even buy a toilet tank lid with a built-in sink that runs the greywater into the toilet tank.
When you are selecting a humanure management system, two extremely important factors will help to guide your decision: water table and culture.
Whether you are in an area with a high water table or one that is quite deep will determine what options are most appropriate. For instance, an outhouse where you dig a hole in the ground, fill it up with your humanure, then cover it and move on is not appropriate in an area with a high water table, where it may pollute your groundwater (as an aging septic system might also do in this case). Conversely, if your water table is quite deep, this system can work great as it leaves behind big, spongy plugs of composted material that surrounding plants can tap into while allowing you to avoid actually handling the humanure in any way.
Waterless composting toilet systems
Waterless options are the best for water conservation. In these types of systems, each time you make a deposit you must throw some carbonaceous material such as sawdust or wood chips down the hole to maintain a good carbon-to-nitrogen ratio and keep down smells and flies (just like a cat burying its poop in kitty litter). Throwing a handful of red wiggler worms down there can help, too. The worms will stay away from the hot center of the pile and stay close to the outside, and will help to move material around in the pile so it gets more evenly composted. It is also advisable to use a device called a urine excluder in these systems. That basically routes your urine to another location so it doesn’t mix with the humanure and cause bad smells, as the urine is what really gets stinky.
Several models of prefabricated composting toilets are available, with brand names like Clivus Multrum and Sun-Mar. In many places throughout the United States, the building code makes allowances for such systems.
If you want to make your own composting toilet, a two-chambered model is an excellent design. The throne is elevated with a concrete, ferrocement, or stone vault below. The vault is divided in two to accommodate two deposit holes in the top, and each side has a generous access port at ground level. You use one side to do your business until it’s full and then switch to the other side. By the time the second side is full, the first side should be mostly composted. You can remove the material, turning it in the process, and put it into a designated area (protected from both animals and rain) to finish composting. For a bigger group of people, there’s no problem with creating a three- or four-chambered system.
A ventilation pipe with a chimney can take the fumes out above the height where people generally spend time. Installing a sheet metal sheath below each throne that extends down lower than the vent pipe will prevent fumes from rising back up through the throne. In fact, if this is done well, the person sitting on the throne will often be able to feel air being pulled down the hole; it’s then moved out via convection through the vent pipe, resulting in a stink-free experience.
Another waterless option is a bucket system managed just like the two-chambered system. All you need is a 5-gallon bucket with a toilet seat fitted to the top. You do your business in the bucket, add your carbonaceous material, and every few days empty the bucket into a designated humanure composting area. You let it compost for several months, turning it occasionally. The advantage of this system is that it doesn’t require major construction, but it does require more maintenance-intensive management.
So what do you do with the humanure from a composting toilet? It’s critical to research temperature and timing for your climate and conditions to make sure you compost it long enough to kill pathogens. It may even be advisable to solarize the humanure at some point under glass. Just in case a pathogen manages to survive, you should avoid using the humanure on crops where it may be in direct contact with your food (for example, root vegetables, lettuces, asparagus). Humanure is great for mulching tree crops, ornamentals, and other nonedible crops.
Sometimes a flush-compatible system is more appropriate than a waterless one. The effluent that comes from a toilet is commonly referred to as blackwater. Although these systems all have the disadvantage of using water, the wastefulness of this practice can be drastically reduced by finding ways to derive value from the blackwater that is produced.
Engineered wetlands are a great way to manage blackwater by using a biological resource. An engineer will need to help with the design, but in a nutshell, when you flush, your effluent goes into an aboveground series of wetland “cells” that you’ve created. Much like in a septic system, the blackwater moves through these cells and bacteria breaks down the organic material. Unlike in a septic system, you can fill the cells with nonwoody wetland or prairie plants to absorb those nutrients. The water that comes out the end of a well-designed engineered wetland will generally be cleaner in most respects than what comes out of a municipal wastewater treatment system. This water should be routinely tested, but it can be used in your landscape for irrigation. Obviously, these systems can be somewhat costly as well, but a single system can handle multiple households, so cost can be shared among neighbors.
Another option is a biodigester, or biogas digester, a device that accepts the effluent that comes from your flush toilet and digests it anaerobically in a large tank. During this process, methane is released and captured. This methane can be used as a fuel. The remaining material that comes out of the biodigester, referred to as digestate, can be composted and then serves as an excellent, pathogen-free fertilizer for crops. Anaerobic digestion can actually be used for animal manures and organic waste as well as humanure. The city of Lloydminster, Alberta, Canada, has a municipal system for collecting waste and converting it via biodigestion to electricity, fertilizer, and other uses.
If you choose to use one of these types of systems to manage blackwater, you need to be aware that many household cleaning products contain toxins such as bleach that will actually kill off the microorganisms that are supposed to be processing the waste. The best solution is to find nontoxic alternatives, like hydrogen peroxide, vinegar, and baking soda, for cleaning toilets.
Urine is an interesting human by-product. Unless a person is sick, it generally leaves the body without pathogens. Mixing it with our humanure or blackwater can cause problems and result in the waste of a very useful substance. Urine is high in nitrogen. The nitrogen in urine happens to come in a form that is quite bioavailable to plants. That means your urine is one of the best nitrogen fertilizers available for use in your garden! According to a study from the University of Kuopio in Finland, one person’s urine can supply the nutrients to grow more than 150 cabbages per year. From a design perspective, consider managing urine separately from humanure.
Pathogenic risks of using urine in the garden are minimal. If you are sick or live in the ultratropics, you may want to do more research. Otherwise, for most of us salmonella is the one thing to think about, but it generally dies shortly after excretion. To avoid any danger of salmonella poisoning, you may choose not to harvest urine-fertilized crops for a few days after your last application. You can also ferment your urine for six months before using it. This will cause it to stink, so there is a trade-off. This may be something to consider if you’re collecting urine from other people.
When your urine is ready to use, there are several ways you can go:
- You can dilute it and apply it directly to your garden in areas with good drainage. Use cold water and dilute eight parts water to one part urine. If applying your fresh urine daily, spread it around so that no single area gets overloaded with salts. This will also help to avoid odors.
- You can apply your urine to a compost pile and use it to help speed the composting process. If you do this, make sure you make a carbon-rich compost mix to accommodate the extra nitrogen you will be adding.
- You can integrate your urine into a greywater irrigation system.
Greywater refers to the water that comes from sources not containing human waste. This includes kitchen sinks (in most places), bathroom sinks, dishwashers, clothes washing machines, and showers. In places where water conservation is a high priority, this greywater can be used to help irrigate a productive landscape, minimizing the use of clean tap water for that purpose. Think of using greywater in the landscape as the next highest use for it after it has been used to scrub vegetables or wash clothes.
For any greywater system, two cardinal rules should never be broken:
No surface greywater
Although greywater can be applied to the soil surface, it should not stay there. If the system you’ve created involves pools, puddles, aqueducts, or ponds of greywater, it’s time to rethink the design. All of these can go septic, and animals of all types can become vectors after they interact with the greywater, then interact with you.
No greywater storage
Storing your greywater in a big tank until you’re ready to use it will result in it going septic. This means it will stink and possibly contain harmful pathogens. Avoid systems where greywater is held in storage for more than twenty-four hours. Beyond that, greywater should be treated as blackwater.
In addition, if you are going to reuse greywater you need to avoid using household cleaning products that contain toxins that will come out in the greywater.
A couple of greywater systems that work really well are dishpan to yard, and branched drain system to mulch basins.
Dishpan to yard is just as simple as it sounds. You can wash your dishes in a dishpan and then dump the water at the base of a fruit tree. You can also disconnect the p-trap in your bathroom sink and collect the greywater in a plastic bucket, emptying it every day. (If you do this, make sure to plug the pipe going to the sewer so gases don’t come back into your home.) Assuming your soil percolates, the water you dump on the surface should soak in in just a few minutes. A huge benefit of this system is that it costs less than five dollars to implement.
A branched drain system to mulch basins is the Cadillac of greywater systems. Art Ludwig (a.k.a. the Greywater Guru) of Oasis Design produces a plumbing part called a flow splitter that looks much like a T-fitting. If placed dead level in the landscape, the flow splitter takes the water entering it and divides it in two. With three flow splitters, you end up with four pipes each carrying a quarter of the total load.
Each of these pipes should end at a basin you’ve dug into the ground in a spot with good drainage, ample distance from the water table, and perennials nearby that you want to irrigate. The basin should be about 16 inches deep (actual size will vary depending on your percolation rate and volume of greywater produced). Each of these basins should be filled with mulch. Choose something like coarse wood chips that won’t readily float. When the greywater flows through the system, one quarter of the total volume should end up flowing into each mulch basin. It will quickly sink below the mulch so we don’t violate our first cardinal rule. The greywater is cleaned in this system by bacterial action in the mulch basin. The nutrients released will benefit nearby plants along with the water itself.
If code requires it, you can use some sort of infiltration technology to transition between the pipes and the mulch basins, although it is easier to just have the greywater daylight for a brief moment before it sinks into the basin. Occasionally, it will be necessary to remove the mulch material and replace it as it begins to break down. The material removed is an excellent product to use for mulching other nearby trees.
For places with very cold climates, special considerations may be needed for winter months. As a first step, it is possible to install a valve that provides a choice to either send greywater to the branched drain system or to the conventional sewer or septic system. That way you can always reroute the water in the winter or in case you need to work on the system.
Food and Yard Waste
The earlier chapter on soil fertility has already explored many ways to cycle food and yard waste back into your system. Here we will mention just one more great way to use woody debris from pruning, plant removals, and other general gardening tasks. Hügelkultur, roughly meaning mound culture in German, refers to a method of mounding coarse organic material in layers and covering it with soil to create a bed for growing crops. This method can be applied at many scales.
Creating a hügelkultur bed is a simple process of layering organic material of different coarseness, starting with larger woody material like logs and twigs, and then layering finer material on top. The finer layer could be manure, compost, or other organic matter, then finally topsoil. You can plant directly into the soil and mulch with wood chips or straw. As the plants grow, they draw moisture and nutrients from the layers of organic material slowly breaking down inside the mound.
Heat is an often overlooked waste product. Most biological processes generate heat. Any process involving burning involves heat. The sun produces heat. If heat is in short supply all or part of the year where you are, it’s important to look at ways to capture heat that’s trying to escape your systems.
Heat generated by animals and compost piles can be captured by greenhouses, hot beds, or even by housing arrangements that place human living quarters above animal stalls (remember that heat rises). Unless you regularly take cold showers, the greywater that goes down your shower drain will take heat with it. Drainline heat exchangers can capture some of that heat and put it back into your hot water tank. The take-home message here is to think creatively and recognize heat at a resource.
Many opportunities exist for us to make use of the leaks in other people’s systems. In many places, especially in the developed world, it is easy to tap into the waste stream to gain access to things you can use to boost fertility and functionality on your property. In urban areas this waste stream is especially huge. Before you buy new things, make sure you first see if you can salvage something that already exists. This can mean trading a crate of apples for wood chips from your local arborist. It can also mean getting grass clippings from neighbors who don’t use chemicals on their lawn to use as mulch in your gardens.
We definitely want to use these resources, but at the same time it is important not to become reliant upon them. If permaculture design takes off in a big way (and we think it will), many of these “waste resources” may become hot commodities. There may be competition for that 5-gallon bucket of coffee grounds you pick up from your local coffee shop every week.
Imagine a day when the waste stream is significantly smaller because it is no longer cost effective to move things around the globe with ease. Imagine that the waste products you rely upon dry up because the processes that produced them become unfeasible or unprofitable. And remember the transitional ethic. Use these wastes as a way to set yourself up for greater resilience in the future but don’t become reliant upon them for your everyday life. That means not relying on external sources for your soil fertility but moving toward generating the fertility your property needs on-site (or locally) whenever possible. The same goes for energy, water, food, and shelter systems as well.
Taken from Practical Permaculture for Home Landscapes, Your Community, and the Whole Earth © Copyright 2015 by Jessi Bloom and Dave Boehnlein. Illustrations by Paul Kearsley. Published by Timber Press, Portland, OR. Used by permission of the publisher. All rights reserved.