Anaerobic Composting Review: Essential Guide

Ever stared at your kitchen scraps and wondered if there’s a better way than just tossing them in the trash? If composting sounds a little complicated, I get it. It can seem like a lot to learn at first. But what if I told you there’s a method that might be simpler, faster, and perfect for certain spaces? We’re going to break down anaerobic composting, step by step, so you can figure out if it’s the right fit for you.

Anaerobic Composting Review: Your Essential Beginner’s Guide

Hey there, it’s Troy D Harn from TopChooser! You know me – I love digging into home and garden projects and making them super easy for everyone. Today, we’re tackling a composting method that often gets a bit of a mixed reputation: anaerobic composting. If you’ve heard about it and felt a little lost, or if you’re just curious about different ways to turn waste into valuable garden food, you’re in the right place. We’ll explore what it is, how it works, and whether it’s the composting method for you.

What Exactly is Anaerobic Composting?

Let’s start with the basics. Composting is essentially nature’s way of recycling organic waste, like food scraps and yard trimmings, into a rich, soil-like material called compost. There are two main types: aerobic and anaerobic. Aerobic composting is the more common method. It relies on oxygen-loving (aerobic) microbes to break down organic matter. Think of it as composting with air.

Anaerobic composting, on the other hand, happens in the absence of oxygen. Instead of air-breathing microbes, it uses microbes that thrive without oxygen. These are often called anaerobic microbes. This difference in environment leads to some distinct characteristics and outcomes compared to its aerobic counterpart.

How Does Anaerobic Composting Work?

In anaerobic composting, organic materials are enclosed in a sealed container or pile, essentially cutting off the oxygen supply. Without oxygen, different types of bacteria and archaea take over. These microbes go through a process called anaerobic digestion.

This process involves several stages, including hydrolysis, acidogenesis, acetogenesis, and methanogenesis. Without getting too bogged down in the science, these stages break down complex organic compounds into simpler ones. The end result can be a nutrient-rich material, but it can also produce gases like methane, which is a potent greenhouse gas. This is one of the main reasons why anaerobic composting often gets a wary look from composters.

Anaerobic vs. Aerobic Composting: What’s the Difference?

This is where things get really interesting and help us understand why you might choose one over the other. The biggest difference, as we’ve touched on, is the presence or absence of oxygen.

Aerobic Composting:

• Requires Oxygen: Needs regular turning or aeration to let air in.
• Faster: Generally breaks down material more quickly if managed well.
• Less Odor: Produces a more earthy, pleasant smell.
• End Product: High-quality, stable compost.
• Microbes: Relies on aerobic bacteria.
• Ideal For: Gardeners with space and time for turning.

Anaerobic Composting:

• Oxygen-Free: Materials are kept sealed or compacted.
• Can Be Faster (for some): Certain types, like Bokashi, are very rapid.
• Potential Odor: Can produce sulfuric or sour smells if not managed carefully.
• End Product: Can be a fermented material requiring further breakdown or a different nutrient profile.
• Microbes: Relies on anaerobic bacteria and archaea.
• Ideal For: Small spaces, faster processing of food waste, or specific applications.

Think of aerobic composting like a well-ventilated campfire – it burns nicely and produces ash. Anaerobic composting is more like putting materials in an airtight container; the breakdown is different and can be smellier if you’re not careful.

Common Types of Anaerobic Composting Systems

While the concept is “no oxygen,” there are different ways to achieve this. Some are more popular and beginner-friendly than others.

1. Bokashi Composting

This is probably the most well-known and accessible form of anaerobic composting for home use. Bokashi isn’t technically composting in the traditional sense because it’s a fermentation process, but it’s often grouped with anaerobic methods. It uses a special Bokashi bran inoculated with Effective Microorganisms (EM) and requires an airtight bucket.

• How it works: You layer food scraps (including meat, dairy, and oils, which are tough for aerobic composting) with Bokashi bran in the airtight bucket. The microbes in the bran ferment the waste.
• What you get: After about two weeks, you have a fermented, pickled material. This isn’t finished compost yet; it needs to be buried in soil or added to a traditional compost pile to fully decompose.
• Pros: Very fast processing of food waste, can handle all types of food scraps, minimal odor during fermentation, reduces waste volume significantly, produces a liquid “tea” that can be diluted and used as fertilizer.
• Cons: Requires purchasing Bokashi bran and specialized buckets, the fermented product needs a second step (burying or adding to another compost system) to become usable as soil amendment.

If you’re looking for a system that quickly tackles kitchen waste, especially in an apartment or small space, Bokashi is a strong contender.

2. Pit Composting (Anaerobic Digestion Systems)

This is a more traditional, often larger-scale, anaerobic method. It involves burying organic waste in a pit. If the pit is sealed well, it can create anaerobic conditions.

• How it works: Organic materials are placed into a dug pit, and then covered with soil. The sealed nature of the pit limits oxygen.
• Pros: Can be done with minimal equipment if you have yard space, helps to decompose waste underground, away from pests.
• Cons: Much slower than aerobic composting (can take a year or more), produces methane (a greenhouse gas), the end product can be less stable and may retain pathogens if temperatures don’t get high enough, difficult to manage and monitor.

This method is less common for home gardeners due to its slow speed and potential environmental concerns regarding methane emissions. For most home users, Bokashi is a much more practical anaerobic approach.

3. Other Anaerobic Systems (e.g., Sealed Bins)

Some people might try to create anaerobic conditions in sealed bins or drums. The principle is the same: exclude oxygen. However, managing these systems without creating foul odors and ensuring a usable end product can be tricky. They often end up producing a mucky, unpleasant sludge rather than desirable compost.

Pros and Cons of Anaerobic Composting

Like any method, anaerobic composting has its ups and downs. It really comes down to what your priorities are.

Pros	Cons
Fast Processing of Food Scraps: Especially with Bokashi, it rapidly turns kitchen waste into a fermentable material.	Requires a Secondary Step (for Bokashi): The fermented material isn’t ready to use in the garden immediately; it needs to break down further.
Handles All Food Wastes: Can often process meat, dairy, and oily foods that aerobic systems struggle with.	Potential for Odor: Without careful management (especially in non-Bokashi systems), it can produce unpleasant smells, including sulfuric odors.
Volume Reduction: Fermentation can significantly reduce the volume of your food waste.	Methane Production: Anaerobic digestion naturally produces methane, a potent greenhouse gas. This is a significant environmental consideration.
Space Efficiency: Systems like Bokashi buckets are compact and suitable for small apartments or kitchens.	Nutrient Profile: The end product might have a different nutrient composition and stability compared to well-managed aerobic compost. It may also retain pathogens.
Less Work (No Turning): Doesn’t require the physical effort of turning a compost pile.	Requires Specific Products: Bokashi needs special bran and buckets, adding to the initial cost.

The key takeaway here is that anaerobic composting, particularly Bokashi, excels at the initial breakdown of food waste quickly and compactly. However, for creating ready-to-use garden compost, it often needs to be combined with another method.

Is Anaerobic Composting Right for You?

So, who should consider going anaerobic? Let’s break it down.

Consider Anaerobic Composting If:

• You have limited space: Living in an apartment, condo, or small home with no yard space. Bokashi buckets are perfect for kitchens.
• You want to process food waste quickly: You dislike seeing food scraps sit around and want a fast way to deal with them.
• You generate a lot of food waste: Especially if it includes meat, dairy, or oily items.
• You don’t have the time or physical ability to turn a compost pile: Anaerobic systems are typically “set it and forget it” for the initial fermentation stage.
• You don’t mind a two-step process: You understand that Bokashi fermentate needs further breakdown.

You Might Prefer Aerobic Composting If:

• You have yard space: You have room for a compost bin or pile.
• You want finished compost ready to use directly: You want to go from scraps to garden amendment in one system.
• You enjoy the gardening aspect: You don’t mind turning your compost and nurturing the process.
• You are concerned about methane emissions: Aerobic composting, especially when managed well, can reduce methane production compared to some anaerobic methods.
• You want to compost yard waste along with food scraps: Aerobic systems are generally better suited for large volumes of yard debris.

How to Get Started with Bokashi (The Most Beginner-Friendly Anaerobic Method)

If Bokashi sounds like a good fit, getting started is pretty straightforward. You’ll primarily need two things:

Essential Supplies:

• A Bokashi Bucket System: This is usually a set of two airtight buckets. One bucket has a spigot at the bottom to drain the liquid (“Bokashi tea”), and the lid seals tightly. The second bucket often acts as a holding container or a place to start the next batch. You can find these online or at some garden supply stores. For inspiration and reliable options, check out resources on composting systems from university extensions, like those found at Michigan State University Extension.
• Bokashi Bran (Inoculant): This is a rice bran or wheat bran that has been coated with a mixture of beneficial microbes (Effective Microorganisms or EM). You’ll need to purchase this, and it’s readily available online.

Step-by-Step Bokashi Process:

1. Add Food Scraps: Chop larger scraps into smaller pieces. This helps with faster fermentation. Add your food waste to the Bokashi bucket. Remember, Bokashi can handle most food scraps, including meat, dairy, and oils.
2. Add Bokashi Bran: Sprinkle a tablespoon or two of Bokashi bran evenly over the food scraps. The general ratio is about 1-2 tablespoons of bran per inch of food waste.
3. Compact Scraps: Press down firmly on the food scraps to remove as much air as possible. This is crucial for creating anaerobic conditions.
4. Seal the Bucket: Close the lid tightly to ensure an airtight seal.
5. Repeat: Continue adding layers of food scraps, bran, and compacting until the bucket is full.
6. Fermentation Period: Once the bucket is full, seal it tightly and let it sit in a temperature-stable place (like under your sink or in a pantry) for about two weeks. During this time, the waste will ferment.
7. Drain the “Tea”: Every couple of days, drain any liquid that collects at the bottom using the spigot. This liquid is nutrient-rich “Bokashi tea.” Dilute it with water (about 100:1 ratio – 1 part tea to 100 parts water) to use as a liquid fertilizer for plants.
8. Bury the Fermented Product: After the two-week fermentation, you’ll have a pickled material. It will smell tangy or like pickles. This is NOT finished compost. You need to bury this fermented waste in your garden soil, a larger compost bin, or a planter box. It will continue to break down and enrich the soil over the next 2-4 weeks.

It sounds like a lot, but once you do it a few times, it becomes a simple routine. The key is to keep it enclosed and let those microbes do their work!

What About the Odor?

This is a big concern for many people considering anaerobic composting. Traditional methods of anaerobic decomposition, particularly in large piles or pits without proper management, can indeed produce foul, sulfuric odors. This is because certain types of anaerobic bacteria produce hydrogen sulfide gas.

However, Bokashi is specifically designed to minimize these odors. The Effective Microorganisms in the Bokashi bran help to promote a clean fermentation process. While it will smell “fermented” or “pickled,” it shouldn’t smell rotten or putrid. If your Bokashi bucket starts to smell truly awful, it’s usually a sign that there wasn’t enough bran added, the seal wasn’t airtight, or the fermented material was left sitting too long before being buried.

Properly managed Bokashi should have a mild, tangy, or yeasty smell, no worse than a jar of sauerkraut. This makes it ideal for indoor use.

Environmental Considerations: Methane

One of the most significant drawbacks of anaerobic decomposition is its natural production of methane (CH4). Methane is a greenhouse gas that has a much stronger warming effect on the atmosphere than carbon dioxide (CO2) over shorter timescales. Aerobic decomposition, when managed well with plenty of oxygen, produces primarily CO2 and water.

Bokashi systems, because they are closed systems and the material is then buried, have a more complex environmental footprint. While the initial fermentation produces methane, the subsequent decomposition in the soil, especially if the soil is aerated, can lead to further breakdown of methane or its conversion to CO2. Studies are ongoing, but the general consensus is that while Bokashi does produce methane during fermentation, its overall impact compared to landfilling food waste is still beneficial due to reduced landfill methane and nutrient recapture.

However, if your primary composting goal is to minimize greenhouse gas emissions, a well-managed aerobic compost pile is often considered a more environmentally neutral option.

Can You Combine Anaerobic and Aerobic Composting?

Absolutely! This is where things get really powerful for home composting beginners.

A very effective strategy is to use Bokashi for the initial, fast fermentation of your kitchen scraps. Once you have your fermented Bokashi product, you can then add it to your traditional aerobic compost bin or pile. Why is this great?

• Speeds up Aerobic Composting: Adding pre-fermented material to an aerobic pile gives those “good” microbes a head start. The hard-to-break-down materials have already been partially processed.
• Adds Nutrients: The fermented Bokashi material is rich in nutrients.
• Less Work Overall: You avoid the need to turn a dedicated aerobic bin for your food waste, and the aerobic system handles the final breakdown into usable compost.

This hybrid approach leverages the speed and convenience of Bokashi for food waste with the established, effective nature of aerobic composting for the final product. It’s a fantastic way to manage kitchen scraps efficiently, especially in urban or suburban settings.

Troubleshooting Common Issues

Even with simple systems, you might run into a snag. Here are a few common issues:

Issue: My Bokashi bucket smells really bad (rotten eggs, sulfuric).

Cause: Primarily lack of oxygen during fermentation, or not enough Bokashi bran. If the lid isn’t sealing or you didn’t press down scraps, air can get in and cause foul decomposition. Too much moisture can also be an issue if you’re not draining the liquid.

Solution: Ensure the lid is airtight. Press down on scraps firmly each time. Add a little extra Bokashi bran. Drain the liquid regularly. If it’s really bad, you might need to discard the batch and start over