(339f) Improving the Quality of Spent Mushroom Substrate (SMS) As Feedstock for Biorefineries

In the current ecological climate there is a strong push to find a renewable energy resource to reduce the usage of fossil fuels which are depleting and are causing greenhouse gas emissions. Biorenewable materials, particularly lignocellulosic biomass, have received increased attention recently as the only carbon-containing resources to produce renewable energy, particularly liquid transportation fuels.  Many biomass resources that have been explored in the past include wood chips, tree bark, corn stover, switch grass, bagasse, and other organic wastes. Some of these sources are byproducts of commercial agriculture and some provide opportunities for biomass to energy agribusiness, where the crop is grown just for energy harvesting. At Villanova University, we are interested in research on biomass to energy conversions because the school is situated in the proximity of some major agricultural areas in the Mid-Atlantic region, like Lancaster County in Pennsylvania, which produces numerous biorenewable materials that can be used for energy production.  Another important region near Villanova University is Chester County, which is known to be “the mushroom growing capital of the world”. Currently, Chester County accounts for around 37% of mushroom production in the U.S.

Mushroom growing produces a large amount of waste product called spent mushroom substrate (SMS). After the mushroom fungi grow and fruit the nutrients in the substrate are no longer favorable for mushroom growth and the substrate is considered waste. SMS poses a unique opportunity as a renewable energy resource since it is available in very large amounts, especially in Chester County and the surrounding areas in Pennsylvania. SMS is typically land applied in nearby agricultural fields or sold as compost. These avenues provide little benefit to the mushroom growing companies and are unsustainable due to the methane released through the decomposition of the substrate.

As is, SMS is not the most ideal feedstock for biorefining due to its high moisture and ash/inorganic materials content. Our research is to explore how to improve the quality of SMS to make it an ideal feedstock for biorefining by using torrefaction as a pretreatment method.  Torrefaction is the process by which a biomass source is heated in the absence of oxygen to between 200 and 300°C for residence times ranging from 15 to 60 minutes. In this process the biomass will lose 30% of its mass, but only lose 10% of its initial energy which results in significant energy densification. This energy densification is important for biomass feedstocks which may require transportation from the source to further processing facilities. Additionally, torrefaction helps to make biomass properties uniform which enables processing facilities to expend less energy adjusting to various feedstock properties. One of the crucial steps in the conversion of biomass to energy is making sure that the biomass characteristics are within optimal specifications for pyrolysis and further thermal degradation.

To be reported are the results of the torrefaction of SMS at various process temperatures and lengths of processing time. Properties being evaluated are heating values, ash content, and elemental chemical composition. These properties will be analyzed to determine the effects that torrefaction and cleaning by mechanical separation have on the quality of the SMS. Results from fast pyrolysis of torrefied/cleaned SMS compared to untreated SMS by using pyro-GC/MS will be reported as well.  Finally, assessment on the sustainability of the torrefaction and cleaning by mechanical separation process for improving the quality of SMS will be presented.