Should a Compost Pile Be Covered for Optimal Composting

Covering a compost pile can be a game-changer for optimal composting. By keeping pests out and maintaining moisture, a covered compost pile can turn your kitchen scraps into nutrient-rich soil in as little as 2-3 weeks.

A covered compost pile can help retain heat, with temperatures reaching up to 160°F, ideal for killing off pathogens and weed seeds. This is especially important for composting meat, dairy, and oils, which can attract pests and create odors.

Covering the pile also helps to prevent moisture loss, keeping the composting process efficient and reducing the risk of mold and anaerobic conditions.

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Compost piles can be covered with various types of materials, each with its own advantages and disadvantages. Impermeable covers are becoming less common, but they still provide a waterproof barrier. Fleece covers, on the other hand, allow rainfall to pass through via capillary action within the fabric.

There are four common types of compost covers: impermeable, fleece, microporous, and biolayer. The impermeable and fleece covers are less common due to their physical properties. The biolayer cover, however, provides excellent insulation and allows air to flow through, making it ideal for cold weather conditions.

Here are some key differences between the cover types, as shown in Table 1:

These costs highlight the significant difference in cost between microporous and biolayer covers, with biolayer being the more cost-effective option.

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Micro-Porous covers allow movement of air while forming a waterproof barrier. They're often made with an expanded polytetrafluoroethylene (ePTFE) membrane sandwiched between durable polyester fabric layers for stability.

The pore size of micro-porous covers is typically between 0.02 and 40 microns, which prevents rain from entering the pile. This allows regulatory agencies to manage runoff as stormwater rather than leachate.

Some air and gases can travel through the membrane from high pressure to low, including water vapor. But most of the moisture rising from the compost pile condenses on the cool underside of the fabric cover.

Micro-porous systems most often use positive single direction aeration with on-off timer or temperature controls. The CFM/CY of material is typically quite low because of the fabric impermeability.

Micro-porous covers are considerably more expensive than other cover types because of the fabric production costs and semi-frequent replacement cycle. They need to be replaced every 6-8 years.

Micro-porous covers contain per- and polyfluoroalkyl substances (PFAS), which exist in the production, use, and disposal of PTFE-based covers.

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Fabric covers are a type of compost cover that allows movement of air while forming a waterproof barrier. They're often made with an expanded polytetrafluoroethylene (ePTFE) membrane sandwiched between durable polyester fabric layers for stability.

Some fabric covers have pore sizes between 0.02 and 40 microns, which prevents rain from entering the pile and allows regulatory agencies to manage runoff as stormwater rather than leachate. This is a crucial aspect of fabric covers, as it helps prevent contamination of the compost.

Fleece covers, on the other hand, shed rainfall via capillary action within the fabric, which is generally 1/16” thick non-woven polyester. This makes them lightweight and easy to use, often for passively aerated piles or turned windrows during rainy weather.

Micro-porous covers are considerably more expensive than other cover types because of the fabric production costs and semi-frequent replacement cycle. This can be a significant factor to consider when choosing a compost cover.

In large installations, fabric covers require machines for moving them on and off the piles, such as sidewinders, straddle winders, winches, or tractor-pulled winders. This adds an extra layer of complexity to the composting process.

Fabric covers contain per- and polyfluoroalkyl substances (PFAS), which exist in the production, use, and disposal of PTFE-based covers. This is a concern, as PFAS are persistent harmful chemicals that are becoming increasingly regulated.

Covering your compost pile can help regulate moisture levels, reduce odors, and maintain a healthy environment for microorganisms.

If you live in an area with prolonged sub-freezing temperatures, it's best to avoid using fabric covers like fleece, microporous, or impermeable covers, as they provide little insulation value and can lead to issues like pathogen survival and ice formation.

However, biolayer covers are a different story. They provide excellent insulation, allowing for airflow and easy removal, even in cold weather. This makes them a great option for large commercial composting facilities.

In fact, biolayer covers are not only effective but also cost-efficient, with a lower capital expense and operating expense compared to other cover types. Here's a comparison of the typical costs:

By choosing the right cover for your compost pile, you can create a healthy environment for microorganisms to thrive and reduce odors and other issues.

Controlling pests is crucial for maintaining a healthy compost bin. A securely fitting lid is your first line of defense against rats, mice, opossums, raccoons, and other pest animals.

Allowing some animals to enjoy a meal from your compost may not seem like a big deal, but it can lead to frequent visits from pests. With a consistent food supply like compost provides, those pest animals won't just be occasional visitors.

Keeping pests far away from your home is a good idea, especially if your compost bin is set up in close proximity to your living space. As the saying goes, "If you give a mouse a cookie, he's going to want a glass of milk."

Once your compost has finished its decomposition process, it's essential to put the lid on the container and leave it shut. Without a cover, your compost will continue breaking down past its completion point, losing potency and becoming less effective.

Managing Moisture is a crucial aspect of composting, and it's essential to have a lid on your compost bin to regulate the moisture level of your materials. Without a lid, the moisture level will fluctuate with the weather, making it challenging to manage.

Too much moisture can slow down the decomposition process, while too little moisture can cause microbes to slow down. This can be a real problem if you're trying to get your compost done quickly.

Propping up the lid when materials get too wet allows sunshine to dry things out, which is a great way to adjust the hydration level. This is especially important if you don't have a lid, as every time it rains, your compost ingredients will get soaked.

Even if your compost bin is located under an awning or in a shed, the process of adding compost ingredients will still result in fluctuating hydration levels. Without a lid, your moisture management options will be limited.

If you don't have a lid, you'll face the challenge of drying your compost out over and over again, which can be frustrating and time-consuming. This is why it's essential to have a lid on your compost bin to manage moisture effectively.

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Composting can continue year-round, even in cold weather, with the right cover. In areas where winters get chilly, compost piles can freeze through, halting microbial activity until temperatures rise in the spring.

Fleece, microporous, and impermeable covers provide little insulation value, leading to issues like low surface temperatures, ice formation, and inhibited airflow. This can cause pathogen survival and regrowth, making removal of the cover challenging.

A biolayer cover, however, provides excellent insulation, allowing airflow and easy removal, even in sub-freezing conditions. This type of cover is also more cost-effective, with a lower capital and operational cost compared to other cover types.

Table 1 compares the typical capital and operational costs of different cover types. Here's a breakdown of the costs:

By using a biolayer cover, you can keep your compost pile warm and active, even in the dead of winter. This means you can continue to compost year-round, without worrying about freezing temperatures.

Biolayer covers are a simple yet effective solution for managing compost. They're made from a layer of relatively stable, pathogen-free organic materials, such as post-PFRP compost or unscreened compost.

This layer acts as both an insulation barrier for pathogen destruction and a modest surface biofilter. Biolayer covers need to be at least 6 inches deep to function, but they're often required to be 12 inches in very cold climates.

The scrubbing effect of biolayer covers can vary depending on surface temperature and moisture, reducing VOCs by anywhere from 10% to 70%. This makes them a valuable tool for managing odors and VOCs.

In a commercial composting facility, the biolayer material is typically found or produced on site at no additional cost. This can be a significant cost savings compared to other cover types.

Here's a comparison of the typical capital and operational costs of different cover types:

Air flow is not noticeably restricted with biolayer covers, unlike some other cover types. This means operators can continue to achieve PFRP without worrying about increased fan power requirements.

Covering your compost pile can significantly speed up the process, making your compost ready to use in weeks or months, rather than taking months to complete.

A covered container tends to hold more heat, which encourages microbes to break down your compost materials more quickly.

Heat is a crucial factor in the composting process, and a covered container helps retain it, allowing the microbes to work efficiently.

By using a covered bin, you can expect to see your compost pile break down faster, making it ready to use sooner.

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Compost operations can be significantly improved with the right cover. A biolayer cover, made from materials like post Process to Further Reduce Pathogens (PFRP) compost, can act as an insulation layer for pathogen destruction and a surface biofilter, reducing VOCs by 10-70%.

Biolayer covers need to be at least 6 inches deep to function, but can be 12 inches deep in very cold climates. They can be produced on site at no additional cost, and can even be mixed into the compost at the end of primary composting, saving operational costs.

Biolayer covers are a game-changer for compost operations, especially in cold weather. They provide excellent insulation, enabling operators to continue achieving PFRP even in sub-freezing temperatures.

In fact, biolayer covers can maintain air flow rates, whereas fleece, microporous, and impermeable covers can severely inhibit airflow due to ice formation. This is a major advantage, as it ensures that the composting process can continue uninterrupted.

Biolayer covers are also incredibly cost-effective, with a cover cost of $0 per square foot, compared to microporous covers which cost $19 per square foot. This is a significant difference, especially for large commercial composting facilities.

The biolayer material can be found or produced on site at no additional cost, making it a free resource for operators. Additionally, the biolayer cover can be mixed into the compost at the end of primary composting, eliminating the need for removal and disposal.

Table 1 provides a comparison of typical capital and operational costs for different cover types. Here's a summary of the costs:

Overall, biolayer covers offer a cost-effective and efficient solution for compost operations, especially in cold weather conditions.

Covered containers are a game-changer for composting. They hold more heat, which encourages microbes to work more quickly, saving you weeks or months of waiting for your compost to be ready.

A covered container can make a big difference in the speed of your composting process. This means you'll get to see the rewards of your work that much faster.

Using a covered bin can also help keep pests and odors at bay, making the composting process more enjoyable.

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Biolayer covers, which add another foot to an eight- or nine-foot pile height, create only a small amount of pressure drop.

Fleece covers behave similarly, with some pressure drop but much less than microporous fabrics.

Typically, blowers are connected to multiple aeration floors with a manifold, allowing for efficient distribution of airflow.

Only one pile needs high aeration rates at any given time, making it unnecessary to oversize blowers.

Figures 8 and 9 show the typical difference between inadequate and adequate blowers, assuming biolayer covers.

In cold weather, fabric covers like fleece, microporous, and impermeable provide very little insulation value, leading to issues like pathogen survival and regrowth.

Low temperatures on the pile surface can enable pathogen survival and potential regrowth.

Ice formation along the inside of the cover can cause it to 'stick' to the pile, making removal very challenging.

Severely inhibited airflow rates can occur due to ice formation.

Most operators choose to avoid using fabric covers during sub-freezing winter conditions.

The biolayer cover provides excellent insulation, enabling the operator to continue achieving PFRP, even in cold weather.

Ice may form on the biolayer cover, but air is still able to flow through, and it can be easily broken apart when unloading a zone.

Table 1 compares the capital and operational costs of different cover types used for large commercial composting facilities.

Covering a compost pile may seem like a good idea, but it's not always the best solution. The primary roles of covers for large ASP systems are surface insulation and mitigation of VOC and odor emissions.

Optimizing the composting process is the first step to reducing odor and VOC generation. ECS believes that by optimizing the process, we can greatly reduce the need for covers altogether.

High aeration rates are crucial for successful composting. For low pH feedstocks like food waste, an initial short period of very high aeration allows mesophilic bacteria to stabilize the pH of the material.

Microporous fabric covers can actually impede adequate aeration, causing more problems than they solve. They are also expensive to purchase and deploy.

A biolayer cover made from compost on site is a better option. It allows high aeration rates, has significant odor scrubbing capabilities, and is more cost-effective than other types of covers.