The Mushroom Farming Industry: Transforming Environmental Risks into Positive Environmental and Economic Outcomes

By Max Laufer
September 5th, 2017

A little known fact about Pennsylvania is that it is the single largest source of edible mushrooms in the United States.1 The vast majority of mushroom production in Pennsylvania is concentrated in the 759 square mile 1 Chester County in the southeast of the state. Chester County alone has over 60 mushroom farms 2 harvesting over 400 million pounds of mushrooms per year, nearly 50% of the entire U.S. supply.3 Mushroom production is Pennsylvania’s second largest industry in its agricultural sector 3 and shows no signs of slowing down as demand for mushrooms in the U.S. continues to increase.4

Mushroom production has substantially less negative environmental impact than other agricultural industries and, as such, receives little to no criticism from the concerned public. In Chester County, PA, however, mushroom farming happens on a larger scale than anywhere else in the country and thus its aggregate negative environmental impact is greater than one might expect. Therefore, it is important to analyze the impact that exists and devise approaches toward decreasing it. This report will first look at the practice of mushroom farming and the ways it can affect the environment. Secondly, the report will propose specific solutions for mitigating the environmental impacts, while also considering the economic demands of the agricultural industry.

Mitigating Environmental Risks: At what Economic Cost?

Typical discourse about mitigating the environmental impacts of farming centers on minimizing both economic and environmental risk. Much discussion, for instance, has taken place about the imposing of certain economic sanctions on corporations that engage in practices that result in a substantial amount of carbon emissions. These discussions occur on the basis of environmentalists’ hopes for decreasing the frequency of use of said practices. Traditional discourse about the balancing of economic and environmental success, however, is not necessarily applicable to the mushroom industry. In fact, one’s environmental concerns need not be compromised in ensuring a balance of positive environmental and economic outcomes,. What is fascinating about the mushroom farming industry is that its harmful environmental impact actually holds the potential to be transformed into both positive environmental and economic outcomes.

Environmental Risks of Mushroom Farming

Environmental concerns over mushroom farming are almost entirely centered around the refining and disposing of its by-products. This potential environmental harm manifests itself in a couple of ways. The process of growing mushrooms entails the fungal bodies converting compost into nutrients. Carbon from said compost undergoes a conversion process initiated by the mushrooms into useable carbohydrates.5 Such a process results in a by-product known as “spent compost.”5 Spent compost is not intrinsically harmful to the environment (and, in fact, can be highly useful: a concept that will be expounded upon later). There are two aspects of spent compost that have the potential to affect environmental harm, each multifaceted in and of themselves. The first concern is that mushrooms are often commercially grown in recycled organic matter containing pesticides. The problem with this is not related to the pesticides themselves, per se, but rather with the methods of disposal of spent compost containing said pesticides. Or, perhaps, the fact that it is disposed of at all. When spent compost containing pesticides is disposed of instead of being reused for other purposes (a concept that will also be explained later in greater detail), it can pose a significant environmental threat. This threat primarily manifests itself in the form of runoff.5 Runoff from disposed spent mushroom compost can contaminate local water supplies and natural, water-based ecosystems.5

Aside from the issue of pesticide pollution, spent compost also potentially harbors harmful viruses and diseases. These diseases pose risks parallel to those caused by pesticides. They have the potential to contaminate water supplies and disrupt ecosystems. The risk of spent mushroom compost containing diseases can be easily decreased through a pasteurization process.6 Pasteurizing mushroom compost also maximizes its potential for reutilization,6 which one might predict would decrease the tendency of mushroom farmers to dispose of it in the first place.

The disposal of spent mushroom compost can pose numerous environmental risks. It does not, however, have to be disposed of. In fact, it can also be reused in several ways. Spent compost has water-retaining properties as well as the potential to retain nitrate levels of its water due to the presence of high amounts of carbon.5 As such, spent compost has the potential to be highly useful as an addition to soil for commercial farming. Further, there is also promising research that shows the efficacy of spent mushroom compost for increasing the quality of turfgrass. According to a study conducted by the Department of Plant Science at Penn State, spent mushroom compost “can improve the structure of clay soils, reduce surface crusting and compaction, promote drainage, increase microbial activity, and provide nutrients to turfgrasses.”7 Spent compost also has the potential to be reused for further mushroom harvesting. According to research also done at Penn State, “phosphorous availability may be a limiting factor” in terms of the reusability of supposedly spent compost.5 Their research has shown, however, that phosphorous availability can be increased in the substrate “by controlling the ionic activity of calcium and potassium.”5 Through this process, there lies a potential for spent mushroom compost to not actually be as “spent” as previously thought in regards to its ability to be reused for its original purpose.

If spent mushroom compost is not truly spent, however, then why is it so often disposed of? The answer appears to be simpler than one might assume. There is not widespread knowledge of the potential reusability of spent compost. According to the same research implicated earlier, mushroom farmers “must try to educate not only the community but also all possible users about the value of post mushroom substrate.”5 Ultimately, the problem appears not to be that the spent compost itself lacks uses, rather that its uses are not at all adequately considered. More widespread reuse of spent compost would not only be positive for the environment by reducing rates of environmentally harmful disposal, but it could also benefit the mushroom industry in a very positive way. In addition to producing and selling mushrooms, the mushroom industry now also has a farming substrate with remarkable potential for use in various industries. Ignoring the fact that reusing the spent compost would substantially mitigate the environmental risks associated with it, spent compost also poses a fascinating economic opportunity for the mushroom industry. The mushroom industry has the potential to repurpose its by-products for commercial sale while simultaneously mitigating the environmental risks associated with said by-product’s disposal. Investing in consumer education could prove to hold substantial economic benefits for the mushroom industry and environmental benefits for Chester County and other areas where the industry flourishes.

It is apparent that spent mushroom compost can be reused for a variety of purposes. Further, however, it is also important to note that disposal is not necessarily a terrible option if creating demand for spent mushroom compost fails. In order to minimize the environmental harm of the disposal process, though, two steps would have to be taken. The first and most obvious step would be to eliminate the use of growing substrate containing pesticides. Doing this would result in a rather innocuous by-product rather than one that poses risk of runoff. In fact, spent mushroom compost itself appears to pose no environmental risk if it does not contain pesticides (and if it has undergone a process about to be elaborated on). According to research at Penn State, the spent compost simply “decomposes to an unobjectionable soil.”5

The second step that would have to be taken to reduce environmental harm resulting from spent mushroom compost disposal would be to put in place a pasteurization process. This process involves heating the substrate to a temperature high enough to eliminate harmful bacteria and diseases.6 The primary reason why the pasteurization process is not widespread despite its apparent efficacy in minimizing environmental risks is, simply put, the cost associated with it.6 The process is not legally required and thus little incentive exists for commercial mushroom farmers to implement it.

Two potential solutions to this quandary exist: the first is for environmental regulatory agencies to legally require a pasteurization process. This, however, would likely have a negative economic impact. It would increase the costs associated with mushroom farming, potentially making the endeavor less profitable and/or driving up the price of mushrooms. Given that mushroom farming plays an integral role in the economy of Chester County, such policies might appear untenable to those fiscally-minded. Another solution, and one with less potential economic impact, would be establishing tax incentives for implementing a pasteurization process. Such a tax incentive would inevitably shift some amount of a tax burden onto taxpayers or on other industries to compensate, though it would have benefits that would not exist if a legal requirement for pasteurization was put into place. It would give mushroom farmers more ownership over their process, while still increasing pasteurization rates in the industry. Increasing pasteurization rates, of course, is highly important in regards to controlling the spread of disease resulting from disposal of spent compost. While it is unclear exactly what the economic impacts of the aforementioned policy recommendations would be, they are certainly steps worth taking if environmental risk is wished to be minimized. Economic risks from the aforementioned policies, however, would not have to be assumed if demand for spent compost meets the supply. This would, of course, be the optimal solution to the problem. What is clear, however, is that there are ways to mitigate environmental risk even if the demand never meets the supply. As such, the aforementioned policies are important considerations.

It is remarkable how much potential exists for the process of mushroom farming to be refined and realigned with common environmental goals while also providing new possible economic opportunities. By using organic material containing less pesticides, implementing a pasteurization process for spent compost, and encouraging more widespread reuse of spent compost, environmental risks can be nearly completely mitigated. Economic benefits may lie in the potential for repurposing spent compost for commercial sale. The primary barrier to overcome to realize this potential is the lack of industry knowledge about the reusability of spent compost. If such a barrier cannot be crossed, however, policy changes exist that hold the potential to still substantially mitigate environmental harm. Disposing of spent compost has little environmental risk if the mushroom industry operates under regulations either requiring or incentivizing pasteurization and lower pesticide use.


About the Author:

Max Laufer is a rising sophomore at Haverford College. Max was one of the co-founders of the Ideas for Action 14-18 program at Wharton. Max is passionate about problem solving and how young people can affect positive environmental change.



  1. The One Tiny Region That Produces Nearly Half of U.S. Mushrooms – Modern Farmer. (2014). Modern Farmer. Retrieved 13 April 2017, from
  2. Facts About Chester County | Chester County, PA – Official Website. (2017). org. Retrieved 13 April 2017, from
  3. NSTATE, w. (2017). Economy of Pennsylvania including Pennsylvania Agriculture and Manufacturing from NETSTATE.COM. com. Retrieved 13 April 2017, from
  4. Mitchell, D. (2015). Mushroom demand grows across board | The Packer. Retrieved 13 April 2017, from
  5. Impact of the Mushroom Industry on the Environment (Mushrooms). (2017). Mushrooms (Penn State Extension). Retrieved 19 August 2017, from
  6. (2017). Pasteurization of Mushroom Substrate and other Solids. Retrieved 19 August 2017, from
  7. Using Spent Mushroom Substrate (mushroom soil) as a Soil Amendment to Improve Turf (Center for Turfgrass Science). (2017). Center for Turfgrass Science (Penn State University). Retrieved 19 August 2017, from

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s