Emily Johnson
Mushroom compost, also known as spent mushroom substrate (SMS), has a distinctive smell that can be described as sharp, tarry, or similar to diesel fuel and fresh manure. This odour is caused by the presence of alcohol and anaerobic bacteria, which can produce toxic levels of alcohol if concentrations reach 1 ppm. The smell is typically stronger when the compost is bagged or in large amounts, and it tends to dissipate over time, especially after mulching. While mushroom compost is marketed as a gardening product, it is not considered real compost and is steam-pasteurized to kill beneficial microbes before being inoculated with the desired species of mushroom.
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What You'll Learn
- Mushroom compost is not real compost
- It's called mushroom compost as a marketing ploy to help dispose of it
- It's made from a combination of wheat straw, dried blood, gypsum, lime, and more
- It's bagged and palletized, pushing out oxygen and causing anaerobiosis
- The lack of oxygen causes microorganisms to emit ions, creating a tar-like smell
Mushroom compost is not real compost
Mushroom compost, also known as mushroom soil, is not real compost. It is a by-product of mushroom farming—the growth medium of mushrooms is removed after the mushrooms are harvested. The more accurate name for it is spent mushroom substrate (SMS). The term "mushroom compost" is used as a marketing tactic to facilitate its disposal.
SMS is made from a combination of wheat straw, dried blood, gypsum, lime or crushed limestone, poultry litter, cow or horse manure, hay, corn cobs, cottonseed hulls, cocoa bean hulls, clay, peat moss, and other materials depending on availability. The material is partially composted for a few weeks and then steam-pasteurized (sterilized) to kill off all beneficial microbes. This process also kills weed seeds and any other harmful agents, such as disease pathogens. The substrate is then inoculated with the desired species of mushroom. Additionally, the substrate is often loaded with table salt to ensure only the selected mushroom species will grow.
Mushroom compost has a distinct smell, described as sharp, or similar to tar, vinegar, sour milk, vomit, or rotting meat. These odours indicate the presence of alcohol, which is toxic to plant roots even in very low concentrations. Mushroom compost is alkaline and has high salt levels due to the addition of table salt during the production process. These salt levels can kill germinating seeds, harm young seedlings, and damage salt-sensitive plants, such as azaleas, rhododendrons, and camellias. Therefore, it should be used with caution and is not suitable as the sole growth medium.
Despite not being real compost, mushroom compost has several benefits in gardening. It is a good soil amendment, retaining water well and preventing soil compaction. It can be used as a mulch to suppress weeds and as a light top-dressing layer for lawns. Mushroom compost also enriches the soil and boosts plant growth by supplying nutrients. It is particularly beneficial for plants that tolerate higher salt content and require additional calcium, such as tomatoes.
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It's called mushroom compost as a marketing ploy to help dispose of it
Mushroom compost, also known as spent mushroom substrate (SMS), has an unpleasant smell due to the presence of alcohol, which is toxic to plant roots even in low concentrations. The odour has been described as similar to vinegar, sour milk, vomit, rotting meat, ammonia, or rotten eggs. This odour is likely a byproduct of the composting process, specifically the anaerobic conditions that occur when bagged, which can cause the emission of sulphide ions, resulting in a diesel fuel-like odour.
While mushroom compost is marketed as a beneficial gardening product, it is important to note that it is not true compost. The name "mushroom compost" is a marketing strategy to facilitate the disposal of spent mushroom substrate. SMS is composed of wheat straw, dried blood, gypsum, lime or crushed limestone, poultry litter, cow or horse manure, bedding, hay, corn cobs, cottonseed hulls, and other materials, depending on regional availability. The material is partially composted, pasteurized to sterilize it, and then inoculated with the desired mushroom species.
The distinctive smell of mushroom compost is not harmful and will dissipate over time, especially after mulching. However, it is essential to understand the risks associated with using SMS in gardening. The presence of alcohol indicates potential toxicity, and the high salt content can be detrimental to plants, especially in clay soils where it can contribute to hardpan formation. Proper usage and regional variations play a significant role in the quality and safety of SMS, with reports ranging from beneficial to toxic outcomes.
When using mushroom compost, it is recommended to mix it with other materials such as peat or coconut coir, sand, and vermiculite to dilute any potentially harmful substances. Additionally, it is crucial to avoid direct application to crops intended for consumption within a short period. While the odour and appearance of mushroom compost may be off-putting, it can be safely used in gardening when combined with other materials and applied appropriately.
In conclusion, the marketing of SMS as "mushroom compost" has provided a convenient disposal solution for mushroom farmers. However, gardeners must be aware of the potential risks associated with this product and take the necessary precautions to ensure safe and effective use in their gardens.
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It's made from a combination of wheat straw, dried blood, gypsum, lime, and more
Mushroom compost is made from a variety of organic materials, including wheat straw, dried blood, gypsum, and lime, among other ingredients. This mixture provides the ideal environment for mushrooms to grow and also contributes to the distinct aroma associated with mushroom compost.
Wheat straw, a major component, offers a carbon-rich source of nutrition and helps with aeration and drainage, preventing waterlogging. Dried blood is an excellent source of nitrogen, which promotes healthy mushroom growth. Gypsum, or calcium sulfate, helps to maintain the pH balance of the compost, ensuring it remains in the optimal range for mushroom cultivation. Lime, or calcium hydroxide, also plays a role in pH regulation and can help neutralize acidic compounds.
The combination of these ingredients creates a nutrient-rich, slightly alkaline environment that is ideal for mushrooms. The straw and gypsum contribute to the aeration and structure of the compost, allowing oxygen to reach the mushrooms and facilitating drainage. This prevents the buildup of anaerobic bacteria, which could otherwise create unpleasant odors.
Additionally, the composting process involves the breakdown of organic matter by microorganisms, which can produce volatile organic compounds (VOCs). These VOCs contribute to the distinctive earthy, musty aroma associated with mushroom compost. The smell is a natural byproduct of the decomposition and microbial activity occurring within the compost.
The unique blend of ingredients in mushroom compost provides the mushrooms with the nutrients they need to thrive while also creating an environment that fosters the decomposition process. This decomposition process is what gives mushroom compost its characteristic smell, a natural and expected aspect of mushroom cultivation.
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It's bagged and palletized, pushing out oxygen and causing anaerobiosis
Mushroom compost, or spent mushroom substrate (SMS), is known to have an unpleasant smell. This odour has been described as similar to tar, diesel fuel, manure, vinegar, sour milk, vomit, and rotting meat. While the smell is off-putting, it does not indicate that the compost is unsafe for use in gardens. In fact, SMS can be beneficial for soil due to its high organic content.
The smell of mushroom compost is a result of the product being bagged and palletized. When this happens, oxygen is pushed out of the bags, and the composting process is halted, resulting in a condition known as anaerobiosis. This means that there is a lack of oxygen, which causes beneficial microorganisms in the compost to emit sulfide ions, creating the distinctive odour.
The odour of mushroom compost is not permanent and will dissipate over time. Once the compost is exposed to oxygen again, the composting process will resume, and the smell will gradually fade. This can be accelerated by mixing the compost with other substances, such as peat or coconut coir, sand, and vermiculite.
It is important to note that while mushroom compost is generally safe for gardening use, it should not be used on crops intended for consumption within a short period. Additionally, the presence of a strong tar-like odour could indicate the presence of creosote, a potentially harmful substance. Therefore, it is advisable to source mushroom compost from reputable suppliers and follow recommended safety guidelines.
To summarize, the bagged and palletized nature of mushroom compost contributes to the development of its distinctive odour by creating an anaerobic environment. However, this smell is not indicative of unsafe or toxic compost, and proper ventilation can help alleviate the odour.
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The lack of oxygen causes microorganisms to emit ions, creating a tar-like smell
Mushroom compost, also known as spent mushroom substrate (SMS), is made from a combination of wheat straw, dried blood, gypsum, lime or crushed limestone, poultry litter, cow or horse manure, and bedding. This mixture is partially composted and then steam-treated to kill off any microbes. The distinctive tar-like odour that sometimes accompanies mushroom compost is caused by a lack of oxygen during the composting process.
When mushroom compost is bagged and palletized, most of the oxygen is pushed out of the bags, halting the composting process. This condition, known as anaerobiosis, leads to an interesting phenomenon. The beneficial microorganisms present in the compost, deprived of oxygen, begin to emit sulfide ions, resulting in a pungent smell reminiscent of diesel fuel and fresh manure.
This odour, while unpleasant, is not an indication of toxicity or any harmful substances. In fact, it's quite the opposite. The presence of these microorganisms and the subsequent odour indicate that the compost is rich in organic material and is efficiently breaking down the contents. This process is entirely natural and safe, and the smell will dissipate once the compost is exposed to oxygen again and the composting process continues.
It is worth noting that while the tar-like smell is often associated with the lack of oxygen during bagging, other factors can contribute to odour development. For example, if the compost is stored in a dense pile that isn't regularly flipped or rotated, it can create an environment with limited oxygen, leading to similar odour issues. Additionally, some people have described the smell of mushroom compost as sharp, which may be attributed to anaerobic composting bacteria.
To summarise, the lack of oxygen during the composting process of mushroom compost causes beneficial microorganisms to emit sulfide ions, resulting in a tar-like odour. However, this odour is not harmful and will fade once the compost is exposed to oxygen.
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Frequently asked questions
Mushroom compost, or spent mushroom substrate (SMS), is made from a combination of wheat straw, dried blood, gypsum, lime or crushed limestone, poultry litter, cow or horse manure, and bedding. The smell is caused by the lack of oxygen during the composting process, which creates a condition called anaerobiosis. This leads to the growth of anaerobic bacteria and the emission of sulfide ions, resulting in an unpleasant odor.
Mushroom compost can have a variety of odors, including vinegar, sour milk, vomit, rotting meat, ammonia, or rotten eggs. Some people have also described the smell as "'sharp" or similar to tar, diesel fuel, or fresh manure.
The smell of mushroom compost is typically not dangerous. The strong odor is often due to the presence of anaerobic bacteria and sulfide ions, which are not harmful. However, if the compost contains alcohol, it can be toxic to plant roots, even in low concentrations.
The smell of mushroom compost should dissipate over time, especially after it has been spread out and exposed to oxygen. Mixing the compost with other materials, such as peat or sand, can also help mask the odor and improve its quality. Additionally, the smell is likely to fade once it is incorporated into the garden bed and diluted with other soil or mulch.
