What Is The Role Of Composting Human Waste In Permaculture?

“I’m thinking about using human waste in my compost to improve soil fertility. My family and I are relatively new to permaculture, and we live on a decent-sized plot just outside of Cardiff in Wales. I’ve read a little about using humanure (human manure), but I’m uncertain about the safety and practicality of it, especially around food crops. Can we safely use composted human waste in our garden, and if so, what do we need to consider before getting started?” Cheers, James, Cardiff, UK.

Understanding the Role of Human Waste in Permaculture

James, it’s great that you’re open to exploring different aspects of permaculture. Composting human waste, often referred to as humanure, is a topic that might raise a few eyebrows, but it’s a smart and sustainable way to close the nutrient loop on your property. In permaculture, we’re all about working with nature rather than against it, and properly composted humanure can be a valuable resource, boosting soil fertility and reducing waste.

However, like any composting technique, there are critical aspects to get right to ensure safety and effectiveness, especially when we’re talking about potentially pathogenic materials. Let’s go through what you need to know to make humanure composting both safe and beneficial for your garden.

Why Consider Composting Human Waste?

To put it simply, all living things, including us humans, return nutrients to the earth when they break down. Human waste is no exception. Our waste is rich in nitrogen, phosphorus, and organic matter—elements that are key to healthy soil and vigorous plant growth. Unlike animal manure, which is commonly composted and used in gardens, human waste tends to get flushed down the toilet, treated in wastewater facilities, or worse—ends up in water bodies, causing pollution.

Through humanure composting, you’re recycling these nutrients instead of sending them away as waste. Not only does this create a closed-loop nutrient cycle, but it also lessens your environmental footprint. Plus, it’s free fertilizer, and who doesn’t like free?

The Science Behind Humanure Composting

Composting is all about creating the right environment for microbes to break down organic material into humus. For humanure, the key is achieving a thermophilic (heat-loving) composting process. This process not only breaks down the waste but also kills harmful pathogens, making the compost safe to use.

Temperature Matters

The bulk of the decomposition happens when the compost pile heats up. In successful humanure composting, the pile should reach a temperature of at least 55°C (131°F) consistently for several days to kill off pathogens. Larger piles generally retain heat better, so aim for a compost bin that’s at least a cubic meter in size. This might require collecting waste for a while before composting.

Carbon-to-Nitrogen Ratio

Human waste is high in nitrogen, so you’ll need to balance it with carbon-rich materials, like straw, sawdust, or leaves. Aim for about a 30:1 carbon-to-nitrogen ratio in your pile. This ratio helps maintain the right conditions for decomposition and minimizes any odors.

Steps for Safe Humanure Composting

1. Choose the Right Toilet

To get started with humanure composting, you’ll need a composting toilet or a humanure system rather than a flush toilet. A simple composting toilet can be nothing more than a bucket with a seat and a cover material like sawdust, but more advanced systems exist if you’re willing to invest. Whichever you choose, make sure it separates liquids from solids to prevent odor and manage moisture levels.

2. Use Cover Materials

Each time your toilet is used, cover the waste completely with carbon-rich materials like sawdust, straw, or dry leaves. This not only absorbs moisture but also helps with odor control and adds carbon to balance the nitrogen-rich waste.

3. Rotate Your Compost Piles

Set up at least two composting bins or piles so that while one is actively being filled, the other is resting and composting. Allow the pile to rest for at least a year after the last addition of waste to ensure full decomposition and pathogen destruction.

4. Monitor Temperature

Use a compost thermometer to monitor the pile’s internal temperature. You’re aiming for that magic 55°C to kill pathogens. If the pile isn’t heating up adequately, you may need to add more green material (for nitrogen) or moisture, or turn the pile for better aeration. However, avoid turning it too often; frequent turning can disrupt the heat cycles necessary for pathogen kill-off.

5. Use It Wisely

Once your humanure compost is fully matured and crumbly (and devoid of any unpleasant smells), it’s ready for use. While it’s technically safe after following proper composting steps, many folks still opt to use it on fruit trees, shrubs, and ornamental plants rather than directly on vegetable gardens. It’s a belt-and-suspenders approach to food safety.

Challenges and Solutions in Humanure Composting

Like any natural process, composting human waste comes with its fair share of challenges. But don’t worry, James; there are solutions to each one!

Odor Control

Worried about the smell? Proper cover materials—like sawdust, leaves, or even shredded newspaper—are your best friends here. They not only help balance the moisture but also keep the odors in check. If your pile still smells, it might be too wet or lacking in carbon-rich materials. Add some dry carbon, like straw or dry leaves, and give it some air by turning it gently.

Managing Moisture

Getting the moisture level right can also be tricky. Too wet, and the pile goes anaerobic (where it smells bad and doesn’t break down well). Too dry, and the composting process slows down. Ideally, your pile should feel like a wrung-out sponge—not too wet, not too dry. If it’s too dry, sprinkle some water on the pile as you add more waste and cover material.

Pathogen Concerns

Heat kills most pathogens, but if you’re unsure, longer composting times (two years) can add an extra level of safety. Or, to play it even safer, use the compost only on non-edible plants, as mentioned earlier. The bottom line is, as long as you’re diligent about maintaining the heat and giving it ample time, the compost will be safe.

Skeptical Neighbors or Family Members

Not everyone will be on board with composting human waste, especially if they haven’t seen it done before. This is where a little education and some careful demonstration of the facts can help ease concerns. Share how it reduces waste, conserves water, and closes the nutrient loop. Plus, show them the fruits—literally—of your labor when your garden beds teem with abundance!

Alternatives and Variations

If humanure composting seems too daunting or if you’re not ready to handle it all on your own, there are alternatives that still align with permaculture principles:

• Dry Toilets: These systems keep urine and feces separate, which can simplify the process and reduce odor. The urine can be diluted and used as a nitrogen-rich fertilizer.
• Vermicomposting Toilets: Worms are added to the compost pile or directly into specialized toilets. These worms help break down the waste quicker and leave behind high-quality vermicast, a super fertile material for the garden.
• Compost Partners: If you’re not comfortable managing humanure on your property, consider forming partnerships with a local farm or community garden that might be better equipped to handle it.

Regulations and Legal Considerations

James, before diving headfirst into human waste composting, it’s worth checking local regulations in Wales or specifically in Cardiff. Rules vary widely about what’s allowable, especially concerning waste management. Some areas have strict guidelines, while others are more lenient as long as you handle things properly. It’s always better to be safe than sorry, so ensure you have a green light before proceeding.

Is Humanure Right For You?

Composting human waste is rewarding but requires a commitment to the process. If you want to be as sustainable as possible and don’t mind putting in some work, then humanure composting could be a game-changer for your permaculture garden.

On the other hand, if it sounds too high-maintenance, or if you’re worried about potential mistakes, consider starting small and see how it goes. You might start with a dry toilet and evolve into full-scale humanure composting later on.

Final Thoughts…

James, thank you for your thoughtful question! I know composting human waste might seem a bit out of the ordinary, but it’s actually a beautifully natural way to enrich your permaculture garden while doing your part to reduce waste. The key is treating the process carefully—consistent temperature, balanced materials, and giving it all ample time.

If you decide to go for it, take those first steps I’ve outlined, and before long, you’ll have nutrient-rich compost helping your garden thrive. Good luck, and enjoy the journey!