Biogas production from Latvian forest mushrooms

Abstract

In Latvia, edible mushrooms are widely used as a means of nutrition. For this purpose, both picked in the forests and specially grown are used. Several countries have special mushroom farms, where they are grown on a large scale. Researchers in several countries have found that a mixture of mushroom residues, straw and manure used for mushroom production can be used well for biogas production. Digestate from biogas plants can also be used as a substrate for a new mushroom crop. The aim of this study was to find out whether and how much methane can be obtained from several mushrooms commonly found in Latvian forests. Lactarias rufus, Lactarias forminosus, Amanita mappa, Amanita muscaria, Boletus elegans, Russula paludosa, Russula foetens and Russula xerampelina were fermented in the laboratory bioreactors under anaerobic conditions. The mushrooms were crushed and stuffed in fourteen bioreactors. Anaerobic fermentation took place at 38 C. In order to find out how much gas could still be obtained from the inoculum, it was fermented in two bioreactors. After 21 days of fermentation, the highest methane yield of 0.433 L·gDOM was obtained from russula paludosa. The study shows that mushrooms are a good raw material for biogas production and there is no need to fear that if they end up in household waste used for biogas production, even Amanita mappa, yield could not be reduced. Latvian mushroom growers can also safely add their mushroom residues to other raw materials and use them in biogas plants.