Nowadays, more and more people and companies are starting to grow diverse types of mushrooms all across the world. Statistics say that global production has increased to about 27 billion kg in 2012. Along with the steadily growing industry comes the increased volume of spent mushroom substrate. The production of mushrooms always results in significant residual material after harvest. The term “spent mushroom compost” (SMC) is mainly used by Europeans, while “spent mushroom substrate” (SMS) by Americans. SMS/SMC is made from various agricultural materials like hay, gypsum, wheat-straw horse manure, sawdust, cocoa shells. Commonly, each cultivation cycle lasts for about 5 to 6 months and the spent substrate is usually disposed although it still has some available nutrients. Usually, before removing it from the mushroom house, the person in charge “pasteurizes” it with steam to kill any pathogens that might be found in the substrate. All in all, mostly all seeds, insects and agents that may cause mushroom disease are killed.
The abundance of spent substrate and the lack of waste management supervision has led the world in the search of new alternative ways of recycling and reusing.
Bioremediation represents the use of living organisms such as bacteria and fungi in the removal and neutralization of different air, soil, water contaminants. The mushroom enzyme system has compounds like laccase, lignin peroxidase and manganese-dependent peroxidase which are responsible for catalyzing the metabolization of many structures like Polycyclic Aromatic Hydrocarbons and Phenols. SMS adsorbs the organic and inorganic pollutants and the microbes that inhabit the substrate have the ability to break down organic xenobiotic compounds. They also have strong pollutant catabolizing capabilities.
Mushrooms are generally cultivated using organic substrates and therefore scientists have searched different methods of using the spent substrate for growing different plants. Spent substrate of Agaricus bisporus has been used for asparagus, beetroot, onion, potato, radish and many more plants and has proved itself to have nutritional qualities.
In India, SMS has been used with success as “manure”. It’s converted to a liquid fertilizer and used on the soil. Also, the spent substrate of Pleurotus has been evaluated as a potential biofertilizer.
Biogas for heating or cooking
SMS is an ideal material for the production of marsh gas. It holds many nutrient substances that provide the basis for long-term propagation of bacteria that produces methane. Studies have showed that 3 to 5 kg of SMS can produce 6-10 m3 of biogas, enough for the daily use of a family.
Scientists in Japan have developed a liquid plant hormone by using spent mushroom substrate. This was used on cucumbers, tomatoes, soybeans to promote their growth and increase the overall production.
Food for animals
Mushroom substrate holds different ingredients that are usually present in animal diets. They contain cereal straws and multiple grains that provide nutritional value. Lentinula edodes spent substrate is used in ruminants for digestion and Ganoderma balabacense to aid milk production.
Agaricus bisporus, Pleurotus and Lentinula edodes are candidates to produce biogas, biofuel and alternative fuel. The substrate from mushrooms holds an optimum C/N ratio and therefore it improves the susceptibility to digestion of anaerobic fermenters. The low lignin content hand in hand with high nitrogen and ash content make the spent mushroom substrate more easily digested and therefore not working with it is less complicated.
Years of research have concluded that spent mushroom substrate is no longer a waste product that should be thrown away but a renewable source with numerous uses. Moreover, its utilization will not be limited to a few applications, SMS will be seen as a constant challenge for famers, scientists and entrepreneurs who will brainstorm more and more strategies for its roles.
A report by Malina Puia
Danny Lee Rinker “Spent Mushroom Substrate Uses”, 2017
Peter Oei et al., “The alternative uses of spent mushroom compost”, 2007
“Recycling of Spent Mushroom Substrate to use as Organic Manure” book
J. Maher, “The Use of Spent Mushroom Substrate (SMS) as anOrganic Manure and Plant Substrate Component”, 1994
Chia-Wey Phan, VikinesvarySabaratnam, “Potential uses of spent mushroom substrate and its associatedlignocellulosic enzymes”, 2012