Feeling overwhelmed by food scraps and yard waste? Wish you could turn that mess into garden gold without all the fuss? You’re in the right place! Many folks think composting is tricky, but it doesn’t have to be.
This guide is your friendly walkthrough. We’ll break down anaerobic composting, showing you how surprisingly simple it can be to get started. No fancy lingo, just clear steps to make your compost pile work for you.
Let’s dig in and discover how easy it is to create nutrient-rich soil right at home!
Anaerobic Composting Review: Your Essential Guide
Hey there, I’m Troy D Harn from TopChooser, your go-to for making home projects, gardening, and yes, even composting, a breeze. We’ve all got waste, and the idea of turning it into something amazing for our gardens is super appealing. But sometimes, the usual composting methods can seem like a lot of work. You know, lots of turning, checking temperatures, and worrying about smells.
Well, what if I told you there’s a way to compost that’s a bit different, and for some situations, might be even easier? We’re talking about anaerobic composting. Now, the word “anaerobic” might sound a bit science-y, but stick with me! It just means “without air.” This method has its own way of breaking down your organic materials, and today, we’re going to review it thoroughly, focusing on what beginners like us need to know.
We’ll cover what it is, how it works, the good stuff (pros) and the not-so-good stuff (cons), and most importantly, how you can actually do it at home. By the end of this, you’ll know if anaerobic composting is the right choice for your composting journey. Ready to turn that kitchen and yard waste into black gold? Let’s get started!
What Exactly is Anaerobic Composting?
So, what’s “anaerobic composting” all about? Think of it as composting that happens in an environment with very little or no oxygen. Most composting we hear about is “aerobic,” which means it needs air to work. Aerobic composting relies on tiny living things called microbes that need oxygen to do their job, breaking down your waste into compost.
Anaerobic composting, on the other hand, uses different microbes that thrive in oxygen-free conditions. These microbes work a bit differently and can break down organic matter too, but the process and the end product can be different from aerobic composting. It’s not the “hot” composting method; it’s more of a “cold” or “slow” breakdown process.
This method is often seen in larger-scale operations like anaerobic digesters, which can even capture methane gas for energy. But it can also be done on a smaller, home scale, often in sealed bins or piles.
How Does Anaerobic Composting Work?
The core idea behind anaerobic composting is creating a sealed environment where oxygen can’t get in. When organic materials like food scraps, leaves, and grass clippings are placed in such an environment, the microbes that don’t need oxygen take over. These are often bacteria like Clostridium. They start to break down the organic matter.
This process generally happens in stages. Initially, mesophilic bacteria (which like moderate temperatures) will start the decomposition. As the material breaks down and potentially generates some heat (though usually not as much as hot aerobic composting), thermophilic bacteria might kick in briefly, or the process continues with other anaerobic microbes. The breakdown is slower, and without oxygen, the byproducts are different. Instead of mostly carbon dioxide and water, you also get gases like methane and ammonia. This is why managing odors can be a key consideration with anaerobic setups.
The goal is to get the organic matter broken down into a stable, nutrient-rich material that can be used in gardens. However, it’s crucial to manage the process to avoid creating a smelly, unusable mess.
Is Anaerobic Composting Right for You? Pros and Cons
Like any method, anaerobic composting has its ups and downs. Before you dive in, let’s weigh the benefits against the challenges. This will help you decide if it fits your lifestyle and composting goals.
The Good Stuff: Pros of Anaerobic Composting
Here are some of the reasons why people might choose anaerobic composting:
- Less Outdoor Work: Often, anaerobic composting requires less turning and managing of the pile. If you’re busy or don’t have the physical capacity for turning a hot compost pile regularly, this can be a big plus.
- Sealed Systems Can Reduce Pests: Many anaerobic composting systems use bins or containers that are sealed or mostly sealed. This can help to keep out rodents and other pests that might be attracted to an open compost pile.
- Can Handle Certain Wastes: Some anaerobic systems are designed to handle a wider range of food waste, including meat and dairy, which are often avoided in traditional aerobic composting due to odor and pest issues. However, this still needs careful management.
- Potentially Faster for Certain Materials (in specialized systems): While generally slower, highly controlled anaerobic digesters can break down materials quickly. For home users, this usually translates to a less labor-intensive process rather than speed.
- Odor Control (if managed correctly): While an improperly managed anaerobic pile can smell bad, a well-functioning, sealed system can actually contain odors better than an open aerobic pile.
The Not-So-Good Stuff: Cons of Anaerobic Composting
Now, let’s look at the challenges:
- Slower Decomposition: Generally, anaerobic composting breaks down organic matter more slowly than hot aerobic composting. You won’t get finished compost in a few weeks.
- Potential for Foul Odors: If not managed properly, anaerobic decomposition can produce strong, unpleasant smells (like rotten eggs due to hydrogen sulfide). This is because the breakdown process releases different gases.
- Pathogen Concerns: Anaerobic composting, especially at lower temperatures, may not kill weed seeds or pathogens as effectively as hot aerobic composting. This means the finished compost needs careful handling or may not be suitable for all uses. For instance, the US Environmental Protection Agency (EPA) recommends composting temperatures reach 131°F to 170°F (55°C to 77°C) for pathogen destruction in aerobic systems. Anaerobic systems typically don’t reliably reach these temperatures.
- Specific Equipment Might Be Needed: While you can make a basic anaerobic pile, more efficient or odor-controlled systems often involve specific bins or setups that might require a purchase.
- Can Produce Methane: Anaerobic decomposition generates methane, a potent greenhouse gas. While at home scale this impact is minimal, it’s something to be aware of in larger contexts.
So, as you can see, it’s a trade-off. Less work, potentially fewer pests, but a slower process and a need for careful management to avoid smells and ensure safety.
Methods of Anaerobic Composting for Home Use
When we talk about anaerobic composting at home, it usually falls into a couple of categories. These aren’t industrial-scale digesters, but rather ways to create that low-oxygen environment in your backyard or kitchen nook.
1. The Sealed Bin Method (often called Bokashi)
This is perhaps the most popular and accessible form of home anaerobic composting. Bokashi is actually a Japanese word meaning “fermented organic matter.” It’s not traditional decomposition but rather a pickling or fermentation process using a special inoculated bran or other medium.
How it works:
- You feed your kitchen scraps (including meat, dairy, and cooked foods – which is a big advantage!) into a special airtight Bokashi bin.
- With each addition of food scraps, you sprinkle a layer of Bokashi bran (which contains beneficial microbes like Lactobacillus and yeast).
- The bin is sealed tightly to keep oxygen out.
- The microbes in the bran ferment the food waste, preventing foul odors and breaking it down without much rotting.
- You’ll regularly drain a liquid by-product from the bin. This liquid is nutrient-rich and can be diluted and used as fertilizer.
- After about 2-3 weeks, the material inside the bin is no longer recognizable kitchen scraps but rather a pickled, fermented mass.
- Crucially, this fermented material is NOT finished compost. It needs to be buried in soil (in your garden beds, a compost pile, or a large pot) to fully decompose. This final decomposition step is usually aerobic and happens relatively quickly because the material has already been pre-digested by the fermentation.
Pros of Bokashi:
- Can handle almost all food scraps, including meat, dairy, and oily foods.
- Reduces waste volume significantly.
- Produces a nutrient-rich liquid fertilizer.
- Minimizes odor during the fermentation stage.
- Kills most pathogens due to the acidic fermentation process.
Cons of Bokashi:
- Requires purchasing Bokashi bran and specialized bins.
- The fermented material needs a secondary decomposition step in soil or compost.
- The fermented material is acidic and can harm plants if not buried properly.
2. The Trench or Burial Method
This is a simpler, no-bin approach. It’s essentially burying your organic waste directly into your garden soil.
How it works:
- Dig a hole or trench in your garden bed, at least 12-18 inches deep. The depth is important to keep oxygen out and deter pests.
- Add your kitchen scraps and garden waste to the hole/trench. Try to mix in some soil or “browns” like dry leaves or shredded paper as you go, although strict carbon-to-nitrogen ratios aren’t as critical here as in aerobic composting.
- Cover the waste completely with at least 6-8 inches of soil. Ensure no scraps are exposed.
- Repeat the process in a different spot in your garden when you have more waste to add, or layer them if in a large trench.
- Allow several weeks to months for the material to decompose in place before planting directly over it (unless you are burying it where you plan to plant in the distant future).
Pros of Trench Composting:
- Extremely simple, requires no special equipment.
- Helps improve soil structure and fertility directly where the waste decomposes.
- Minimal odor if buried deep enough.
- Helps deter pests effectively.
Cons of Trench Composting:
- Slower decomposition as it relies on ambient soil microbes.
- You can’t access the compost for immediate use elsewhere; it decomposes in situ.
- Difficult to manage if you have heavy clay or very compacted soil.
- Not suitable for large volumes of waste if you only have a small garden space.
3. Simple Sealed Pile (less common and trickier for beginners)
This involves creating a pile of organic material and then sealing it off from the air with a tarp or plastic sheeting, and perhaps burying it slightly. The idea is to encourage anaerobic decomposition within the pile itself.
How it works:
- Gather a good amount of organic materials (greens and browns).
- Pile them up.
- Cover the entire pile securely with a heavy-duty tarp or plastic sheeting, ensuring there are no gaps. You might weigh down the edges with rocks or soil.
- Leave it undisturbed.
Pros:
- No special bins needed.
- Can take a variety of materials.
Cons:
- High risk of becoming a smelly, anaerobic mess if not built and managed correctly.
- Difficult to monitor and control.
- Decomposition can be very slow and unpredictable.
- Potential for anaerobic pathogens to survive.
- This method is generally not recommended for beginners due to the high risk of odors and incomplete decomposition.
For most beginners looking for an anaerobic approach, Bokashi is the most practical and effective option, followed by the simple trench method.
What Can You Compost Anaerobically?
The “what” of anaerobic composting, especially with Bokashi, is a bit more forgiving than traditional aerobic composting.
Generally Acceptable Materials (Especially for Bokashi):
- Fruit and vegetable scraps
- Meat, fish, and bones (small pieces)
- Dairy products (cheese, yogurt, milk)
- Cooked leftovers
- Oils and fats (in small quantities, Bokashi can handle them)
- Bread and grains
- Coffee grounds and tea bags
- Eggshells
- Yard waste (small amounts, like grass clippings or plant trimmings)
Materials to Use Sparingly or Avoid:
- Large bones or whole meat cuts: While Bokashi can handle them, smaller pieces will break down more effectively and faster.
- Excessive amounts of liquid: Too much liquid, especially from very wet food scraps, can create a sludge that hinders fermentation.
- Paper and cardboard: While some Bokashi systems might allow small amounts, excessive use can make the fermented material too wet and hinder the microbe action. It’s better to compost these aerobically or in a separate system.
- Diseased plants: While Bokashi can kill many pathogens through acidification, it’s still best practice to avoid composting diseased plants to prevent any potential spread when the fermented material is buried.
- Pet waste (dog, cat): These contain pathogens that are not reliably killed by Bokashi fermentation and pose a significant health risk.
- Woody materials: Too much of this will slow down the fermentation process significantly.
The key with Bokashi is that it ferments rather than decomposes, so it can handle a broader range of food waste. However, remember that the end product is not finished compost and needs that final burial step.
The Anaerobic Composting Process: Step-by-Step (Focusing on Bokashi)
Let’s walk through how to get started with Bokashi, the most common home anaerobic composting method. It’s less about pile-turning and more about layering and sealing.
What You’ll Need:
- A Bokashi bin system (usually comes with two buckets with airtight lids and a spigot, plus a tamper).
- Bokashi bran (inoculated with effective microorganisms).
- Your kitchen scraps (food waste).
Step-by-Step Guide:
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Prepare Your Bin:
Ensure your Bokashi bin is clean. Some systems have a filter or draining mechanism at the bottom that you might want to check or clean.
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Add Your First Layer of Scraps:
Start adding your food scraps to the Bokashi bin. Chop larger items into smaller pieces (about 1-2 inches) to speed up the fermentation process.
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Sprinkle the Bokashi Bran:
Once you have a layer of scraps (about an inch or two deep), generously sprinkle a thin layer of Bokashi bran over them. The amount recommended per sprinkle usually comes with the bran packaging, but a good rule of thumb is about 1-2 tablespoons per inch of scraps.
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Compact the Scraps:
Use the tamper (or another tool) to press down on the scraps. This helps to remove air pockets and ensure the scraps are in good contact with the bran.
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Seal the Lid Tightly:
Place the airtight lid back on the Bokashi bin. The goal is to keep as much oxygen out as possible.
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Repeat the Process:
Continue adding food scraps, sprinkling bran, and compacting for each new layer of waste. Aim to add scraps daily or as you generate them.
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Drain the “Tea”:
Every 1-3 days (or when you see liquid accumulating), open the spigot at the bottom of the bin to drain the fermented liquid, often called “Bokashi tea.” Be prepared; it might be a bit cloudy and have a slightly vinegary or fermented smell, but it shouldn’t be foul. Dilute this liquid with water (typically 1:100 ratio for houseplants, 1:50 for outdoor gardens) and use it as a potent liquid fertilizer. If you don’t drain it, the liquid can create an anaerobic breakdown that smells bad.
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Complete the Fermentation:
Once the bin is full, seal it tightly and let it sit for about 2 weeks (this is the fermentation period). It’s best to do this in a moderate
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