Mushroom Production in the Circular Economy

Abstract

Global food production is unsustainable and relies on agricultural practices that are linear and create abundant waste. Mushrooms, especially oyster mushrooms from the genus Pleurotus, produce enzymes that can break down lignocellulose in these wastes and upcycle them into edible mushrooms. However, current research is insufficient. Most studies only report mushroom growth based on typical substrate recipes using local waste and weakly correlate their results to the essential nutrients of the substrates like cellulose, lignin, and nitrogen (mostly from protein). While this does demonstrate that mushroom production on waste is possible, it makes it difficult for small-scale mushroom producers to translate these results to a different context where that waste stream is not available. Additionally, most studies are conducted in a lab setting where some data (e.g. infection rate) is not considered relevant, although it is a critical element of commercial mushroom production. To close these gaps, this research took a two-step approach, focused on the common commercial grey oyster (Pleurotus ostreatus) and king oyster (Pleurotus eryngii) mushrooms. First, a literature analysis was conducted to generalize findings from relevant studies that investigated mushroom production on various waste streams. Biological efficiency and the essential nutrients in the substrate were standardized across all the studies if possible. Second, experimental research was performed at a small-scale commercial mushroom production company in Utrecht, The Netherlands. Here a variety of agricultural and urban waste stream were used to produce both species of mushrooms. Biological parameters of mushroom growth including infection rate, mycelial colonization time, fruiting time, and biological efficiency were then reported. The effects that the essential nutrients in the substrate have on these biological parameters (from literature and experiments) were analyzed using generalized linear mixed models. Overall, the amount of cellulose and lignin, but not nitrogen, in the substrate had the most effect on mushroom growth. More cellulose and less lignin apparently increased the biological efficiency of both mushroom species according to the literature analysis. However, in the experimental part of this research more cellulose increased infection rates for P. eryngii, possibly masking the effect of cellulose on mushroom growth, although it did appear that increased lignin decreased biological efficiency for this species. Experimentally, for P. ostreatus, cellulose had the opposite effect and decreased biological efficiency, possibly due to the strain that was used. Future research should focus on reducing infection rates and increasing the cellulose component of substrates to see if results from the literature can be replicated. Overall, this research adds to current evidence that these mushrooms can be effectively used to upcycle waste streams and close the loop in a circular economy.