Hydrogen sulphide gas production from spent mushroom compost under field and laboratory conditions

Hydrogen sulphide (H2S) gas production was monitored during the disturbance of four heaps of
Spent Mushroom Compost (SMC) that were stored for up to 12 months either outdoors or under
cover (indoors). QRAE (www.raesystems.eu) and ITX (www.indsci.com) gas monitors with data
logging facilities were used to measure the 10-second average concentration of H2S released into
the air above the heaps of SMC as they were being disturbed. The highest concentrations of up
to 2083 ppm were detected for the outdoor stored material in comparison to concentrations of up
to 687 ppm detected for indoor stored material. Outdoor stored SMC had higher moisture
contents (66-72%) compared to indoor stored material (53-65%). Laboratory studies were
conducted to study the effects of moisture content (69 – 85%) and temperature (35ºC or 45ºC) on
H2S production from fresh un-steamed and steamed samples of SMC. The H2S gas concentration
in the head space of the incubation vessels was measured every 24 hours for 3 days. Un-steamed
SMC produced higher levels of H2S than steamed SMC and in general the higher the moisture
content the higher the H2S concentration. Higher concentrations of H2S were also produced with
the higher incubation temperature of 45 ºC. These results suggest that the high levels of H2S
detected during disturbance of stored SMC are heavily influenced by moisture content. The
higher rates of H2S production at 45 ºC also suggest that thermophilic microorganisms are
involved in the process. Health and Safety aspects of H2S production from stored SMC are
discussed