Hey there, DIYers and garden enthusiasts! Troy D Harn here from TopChooser. Are you looking to give your garden a boost with nutrient-rich compost but feel overwhelmed by the options? Composting can seem a little daunting, but I’m here to make it super simple. Today, we’re diving into anaerobic composting. It might sound fancy, but it’s a straightforward way to break down organic waste right in your backyard. Stick with me, and I’ll guide you step-by-step to creating fantastic compost, no green thumb required!

Anaerobic Composting Tips: Your Essential Beginner’s Guide

Composting is a fantastic way to reduce waste and create a superfood for your garden. While many people are familiar with the common “hot” or aerobic composting, there’s another method that’s gaining attention: anaerobic composting. This guide is designed to break down everything you need to know about anaerobic composting, making it an easy and accessible option for beginners.

We’ll cover what it is, how it works, what you can and can’t compost, the best containers to use, and some practical tips to help you succeed. By the end, you’ll be ready to start your own anaerobic compost bin and see the amazing benefits it brings to your soil.

What is Anaerobic Composting?

Simply put, anaerobic composting is a decomposition process that happens in the absence of oxygen. Unlike aerobic composting, which relies on oxygen-loving microbes to break down organic matter, anaerobic decomposition involves bacteria that thrive in oxygen-poor environments. This method typically results in a faster composting process, especially in contained systems.

Think of it like this: aerobic composting is like a well-ventilated campfire where everything burns quickly. Anaerobic composting is more like a slow, smoldering fire in a sealed container. Both break things down, but the process and the end product can differ.

How Does Anaerobic Composting Work?

The magic happens thanks to anaerobic bacteria and archaea. These microorganisms don’t need oxygen and produce different byproducts as they break down organic material. The process generally moves through several stages:

• Hydrolysis: Large organic molecules like carbohydrates and fats are broken down into smaller, soluble molecules.
• Acidogenesis: These smaller molecules are converted into volatile fatty acids, ammonia, carbon dioxide, and hydrogen sulfide. This stage can sometimes lead to an unpleasant odor if not managed correctly.
• Acetogenesis: Volatile fatty acids are further broken down into acetic acid, formic acid, carbon dioxide, and hydrogen.
• Methanogenesis: Finally, methane-producing bacteria convert these compounds into methane and carbon dioxide. This stage results in the final compost product.

Because oxygen is limited, the decomposition process is slower in terms of oxygen consumption but can be quite efficient in breaking down materials. Moisture and temperature play crucial roles in how effectively these microbes do their work.

Pros and Cons of Anaerobic Composting

Like any composting method, anaerobic composting has its advantages and disadvantages. Understanding these will help you decide if it’s the right choice for your needs.

Advantages:

• Faster Decomposition: In certain setups, anaerobic composting can break down organic materials more quickly than traditional aerobic methods.
• Less Turning Required: Many anaerobic systems are sealed, meaning you don’t need to frequently turn or aerate the pile, saving you time and effort.
• Reduced Odor (with proper management): While an initial unpleasant smell can occur, a well-managed anaerobic system can become relatively odorless.
• Can Handle More Diverse Waste: Some anaerobic systems can break down materials that might be slower to decompose aerobically, like certain types of food scraps.
• Can Produce Biogas: In more advanced setups (like anaerobic digesters), methane gas can be captured and used as an energy source. This is beyond typical home composting but worth noting.

Disadvantages:

• Potential for Odor: If not managed properly, the intermediate stages can produce strong, unpleasant odors. This is a significant concern for backyard composting.
• Requires Specific Conditions: Anaerobic decomposition needs precise moisture and temperature levels to be effective and avoid problematic byproducts.
• Slower Final Curing: While the initial breakdown can be fast, the final curing of the compost might take longer to become fully stable and nutrient-rich.
• Pathogen Concerns: If temperatures don’t reach high levels (which can be harder to achieve consistently in a simple anaerobic system compared to hot aerobic composting), there’s a greater risk of pathogens surviving. This makes it less ideal for composting diseased plants or meat/dairy if not carefully managed.
• Less “Finished” Compost: The resulting compost can sometimes be less crumbly and darker than aerobic compost, often described as a “muck” or “slurry” if too wet.

What Can You Compost Anaerobically?

The good news is that many common household organic wastes can be composted anaerobically. You’ll generally want to avoid materials that are difficult to break down or could cause issues.

Good to Compost:

• Fruit and Vegetable Scraps: Peels, cores, rinds, wilted greens, etc.
• Coffee Grounds and Tea Bags: Yes, even those little paper tea bags can go in!
• Eggshells: Crushed for easier breakdown.
• Grass Clippings (in moderation): Too many can create dense, slimy layers.
• Leaves and Yard Waste: Small twigs, fallen leaves.
• Shredded Paper and Cardboard: Non-glossy only, and torn or shredded.
• Manure (from herbivores): Like chicken, cow, horse, or rabbit manure. Avoid pet waste from carnivores.

What to Avoid:

• Meat, Fish, and Bones: These can attract pests and create strong odors.
• Dairy Products: Similar to meat, these can attract pests and smell bad.
• Oily or Greasy Foods: These slow down decomposition and can cause odors.
• Diseased Plants: Unless your system is guaranteed to reach high temperatures, it’s safer to avoid these to prevent spreading disease.
• Weeds with Seeds: Again, if temperatures aren’t high enough, seeds can survive and sprout in your garden.
• Pet Waste (from dogs and cats): Can contain harmful pathogens.
• Treated Wood and Sawdust: Chemicals can leach into your compost.
• Coal or Charcoal Ash: Can contain harmful substances.

Choosing an Anaerobic Composting System

For simple backyard composting, a sealed bin is key to creating the anaerobic environment. You don’t need fancy equipment; a repurposed container can work wonders.

Popular Options:

1. Sealed Plastic Bins: These are widely available and work well. Look for bins with tight-fitting lids. Many commercial compost bins are designed to be relatively enclosed.
2. Garbage Cans with Lids: An old metal or plastic garbage can with a secured lid can be an excellent DIY anaerobic compost bin. Ensure the lid fits snugly. You might even drill a few holes in the bottom for drainage, but keep the top sealed.
3. Tumblers (Sealed Variants): Some compost tumblers are designed to be relatively airtight. While tumblers are often associated with aerobic composting due to their ability to mix, a tightly sealed tumbler can also facilitate anaerobic decomposition, especially if not turned frequently.
4. DIY Sealed Bins: Get creative! Large plastic storage totes with a secure lid, or even a wooden bin lined with thick plastic and a well-fitting cover, can work.

Key Features to Look For:

• Airtight Lid: This is the most crucial element for creating an anaerobic environment.
• Durability: The container should be able to withstand being outdoors and holding compost materials.
• Size: Choose a size that fits your space and the amount of organic waste you generate. A bin around 50-100 gallons (about 200-400 liters) is a good starting point for most households.
• Drainage (Optional but Recommended): While the system is anaerobic, having a way for excess liquid (leachate) to drain from the bottom can prevent the compost from becoming too waterlogged, which can worsen odors. However, if you’re aiming for a truly sealed system, you’ll need to manage moisture carefully.

If you’re going the DIY route with a garbage can or tote, make sure the lid seals well. You can use bungee cords or even WEATHERSTRIPPING to improve the seal if needed. For a bit of airflow control, you can consider adding a single, small vent covered with fine screening, but the primary goal is minimal oxygen ingress.

Getting Started: Step-by-Step Anaerobic Composting

Ready to get your hands dirty? Here’s a simple, step-by-step guide to setting up your anaerobic compost bin.

Step 1: Choose and Prepare Your Bin

Select a suitable container based on the options above. If you’re using a repurposed item like a garbage can, ensure it’s clean. If there are holes in the bottom, you might want to cover them with mesh or screen to prevent pests but allow some liquid drainage. If your lid isn’t perfectly tight, consider adding weather stripping or a bungee cord to secure it.

Step 2: Gather Your Materials

Start collecting your kitchen scraps (fruits, veggies, coffee grounds) and yard waste (leaves, grass clippings). It’s a good idea to have a mix of “greens” (nitrogen-rich materials like food scraps and grass clippings) and “browns” (carbon-rich materials like shredded paper, cardboard, and dry leaves).

Step 3: Layer Your Bin

Begin by putting a layer of “browns” at the bottom. This helps with drainage and aeration as you start. Then, add your kitchen scraps and other materials. Aim for a good mix of greens and browns – a common guideline is about 2-3 parts browns to 1 part greens. This ratio helps manage moisture and odor.

Tip: Chop or shred larger items before adding them. This increases the surface area, allowing microorganisms to work faster.

Step 4: Maintain Moisture Levels

Anaerobic decomposition thrives in a moist environment, like a wrung-out sponge – not soaking wet and not dry. If your compost mix seems too dry, add a little water. If it looks too wet and slimy, add more dry “browns” (like shredded cardboard or dry leaves).

Check occasionally: While you don’t need to turn, you should periodically check the moisture. You can do this by poking a stick down into the pile or by feeling the material.

Step 5: Add Materials Regularly

Continue adding your kitchen scraps and yard waste as you generate them. Try to bury fresh food scraps under a layer of “browns” to help minimize odors and deter pests. This layering also helps keep the compost moist and balances the carbon-to-nitrogen ratio.

Step 6: Monitor and Manage Odor

The most common issue with anaerobic composting is odor. If you notice a strong ammonia or rotten egg smell, it usually means the pile is too wet or has too much nitrogen (“greens”).

• Too Wet: Add more dry carbon materials (browns) like shredded paper, cardboard, or dry leaves.
• Too Many Greens: Add more carbon materials (browns) to balance the nitrogen.
• Pests: Ensure fresh food scraps are buried under a layer of browns, and that the lid is sealed tightly.

Step 7: Harvesting Your Compost

The time it takes for compost to be ready can vary greatly, from a few weeks to several months, depending on the materials, temperature, and moisture. You’ll know it’s ready when it turns dark, crumbly, and smells earthy and pleasant. If it still smells sour or has recognizable food scraps, it needs more time to cure.

To harvest, you can either empty the entire bin if it’s small, or dig out the finished compost from the bottom if your bin allows. You might need to let it cure for a couple more weeks in a pile to fully stabilize before using it in your garden.

Tips for Success with Anaerobic Composting

Here are some extra tips to make your anaerobic composting journey smooth and successful:

• Chop It Up: Smaller pieces decompose much faster. Spend a few minutes chopping up larger kitchen scraps or shredding cardboard.
• Balance Greens and Browns: This is crucial. Too many greens lead to wetness and odor. Too many browns make the process slow. A good mix is key.
• Bury Food Scraps: Always cover fresh food scraps with a layer of browns. This is the #1 tip for odor and pest control.
• Moisture, Not Soggy: Aim for the consistency of a wrung-out sponge. If you can squeeze water out easily, it’s too wet. If it crumbles apart dryly, it’s too dry.
• Location Matters: Place your bin in a location that gets some sun to help with warmth, but not so much that it dries out too quickly. Avoid areas prone to waterlogging.
• Be Patient: Composting takes time. Don’t get discouraged if it doesn’t seem to be breaking down as fast as you’d hoped.
• Consider Leachate: If your bin collects liquid (leachate), it can be a very potent fertilizer. Dilute it with water (about 10:1 water to leachate) before using it on your plants.

Anaerobic vs. Aerobic Composting: A Quick Comparison

It’s helpful to understand how anaerobic composting differs from the more common aerobic method. This table breaks down the key distinctions:

Feature	Anaerobic Composting	Aerobic Composting
Oxygen Requirement	Requires little to no oxygen	Requires plenty of oxygen
Microbes Involved	Anaerobic bacteria and archaea	Aerobic bacteria, fungi, and actinomycetes
Process Speed	Can be faster initially, but final curing might take longer. Can be very fast in high-tech digesters.	Generally slower initial breakdown, but can cure faster if properly aerated and heated.
Odor Potential	Higher risk of unpleasant odors if not managed well.	Less risk of odor if properly managed; smells earthy when healthy.
Turning/Aeration	Little to no turning required.	Requires regular turning and aeration.
Temperature	Can be cooler, potentially hosting fewer pathogens if low temps are maintained.	Can reach high temperatures (130-160°F / 54-71°C) to kill pathogens and weed seeds when managed as “hot composting.”
End Product	Dark, sometimes more acidic, organic material.	Dark, crumbly, nutrient-rich, “earthy” smelling compost.
Ease for Beginners	Simplified if using a sealed bin and managing moisture/greens.	Requires more active management (turning) to be efficient.

For most home gardeners just looking to reduce waste and enrich their soil without a lot of fuss, a well-managed anaerobic system in a sealed bin is often easier due to the lack of turning. However, the key is proper management to avoid those dreaded odors and ensure a safe end product.

What About Different Types of Anaerobic Systems?

While our focus today is on simple backyard bins, it’s worth mentioning that anaerobic digestion (AD) is a more advanced technology used on a larger scale. These systems are specifically designed to capture biogas (methane) produced during decomposition.

Anaerobic Digesters: These are engineered systems that control conditions very precisely to maximize biogas production and produce a nutrient-rich digestate (the leftover material, similar to compost). They are used in places like wastewater treatment plants, farms, and even some research facilities. You can find smaller, DIY biogas digester kits, but they require more technical knowledge and careful handling of methane gas.

For the average homeowner, a simple sealed bin that relies on anaerobic processes is the most practical and accessible approach. The goal isn’t biogas capture, but efficient decomposition in a low-oxygen environment.

Using Your Finished Anaerobic Compost

Once your compost is ready, it’s time to reap the rewards! Your nutrient-rich compost is a fantastic soil amendment. Here’s how you can use it:

• Soil Amendment: Mix compost into your garden beds before planting. It improves soil structure, water retention, and drainage. This is especially beneficial for clay soils that get compacted or sandy soils that lose nutrients easily. For more on soil amendments, check out resources from university extension offices, like Michigan State University Extension, which often have great local advice.
• Mulch: Apply a layer of compost around plants to suppress weeds, retain soil moisture, and slowly release nutrients.
• Top Dressing: Spread a thin layer of compost around established plants during the growing season as a nutrient boost.
• Potting Mix: If your compost has fully cured and has a good texture, you can mix it with other ingredients like perlite or coir to create your own potting mix for containers.

Remember, if your compost smells a bit “off” or is still quite wet, it might not be fully cured. It’s best to let it air out for a week or two in a separate small pile or bin before using it directly around plants. This allows it to stabilize further and lose any lingering sour smells.

Conclusion

So there you have it! Anaerobic composting, while it sounds technical, can be a very straightforward and effective way to turn your kitchen scraps and yard waste into valuable compost for your garden. By understanding how it works, what to put in your bin, and how to manage moisture and materials, you can set up a system that requires minimal effort but delivers fantastic results.

Remember to choose a good, sealed container, aim for that “wrung-out sponge” moisture level, balance your greens and browns, and always bury those food scraps. Don’t be afraid to experiment a little; composting is a natural process, and even if you encounter a minor hiccup like an odor, you’ll learn how to adjust and get back on track.

Give anaerobic composting a try. You’ll be reducing landfill waste, enriching your soil naturally, and saving money on garden supplies. Happy composting!

Frequently Asked Questions about Anaerobic Composting

Here are some common questions beginners have about anaerobic composting.

What’s the biggest mistake beginners make with anaerobic composting?

The most common mistake is not managing moisture and the green/brown balance. Too much food scraps (greens) and not enough carbon-rich materials (browns) will make the bin too wet and smelly. Always bury food scraps and add brown material.

Will my anaerobic compost bin smell bad?

It can, especially if it’s too wet or unbalanced. However, a well-managed anaerobic bin, where food scraps are buried and there’s a good mix of greens and browns, should develop an earthy, slightly sour smell rather than a foul one. If it smells like rotten eggs or strong ammonia, it needs more browns and better moisture control.

How long does it take for anaerobic compost to be ready?

This varies a lot. It can range from as little as 4-8 weeks for a fast anaerobic system (like a dedicated digester) to several months for a simple backyard bin. Factors like material size, moisture, temperature, and the mix of ingredients all play a role. The key is to wait until it looks and smells like finished compost.

Can I compost meat and dairy in an anaerobic bin?

It’s generally not recommended for simple backyard systems. While anaerobic bacteria can break them down, they are very prone to attracting pests and creating strong odors. For safer composting of these items, a hot aerobic composting method or a specialized enclosed system designed for them would be better.

What is leachate and what do I do with it?

Leachate is the liquid that drains from the bottom of a compost bin. In anaerobic systems, it can be quite potent. If you collect it, dilute it with water (about 10 parts water to 1 part leachate) and use it as a liquid fertilizer for your plants. It’s packed with nutrients!

How do I know if it’s truly anaerobic?

The primary indicator is the lack of regular turning and the way materials break down. Truly anaerobic systems aim to exclude air as much as possible, unlike aerobic systems where turning introduces air. If your bin has a tight-fitting lid and you’re not actively aerating it, it’s likely operating anaerobically.