Production of oyster mushroom (Pleurotus ostreatus) on sawdust supplemented with anaerobic digestate

Anaerobic digestion of organic waste results in production of biogas and a nutrient-rich digestate that has an established use as fertilizer in plant production. This study evaluated use of anaerobic digestate based on a high concentration of organic household waste as a fertilizer in sawdust-based production of oyster mushrooms (Pleurotus ostreatus). Inclusion of 0.5 L of anaerobic digestate (AD) per kg sawdust gave similar productivity in terms of biological efficiency (79.5 +/- 5.4 %), and protein concentration (24.7 +/- 2.4 % of dry weight (dw)) as standard mushroom substrate (78.1 +/- 5.3 %, and 21.9 +/- 3.0 % of dw, respectively). However, mushroom growth was impaired at the highest concentration of anaerobic digestate tested, 1 L digestate per kg dw sawdust. Comparison of the AD-fertilized substrate with a mushroom substrate with standard components (sawdust, wheat bran, calcium sulfate) and with similar C/N-ratio revealed some differences in elemental composition of the fruiting bodies, with an major increase in sodium concentration for the AD-fertilized substrate compared with the standard substrate (413.3 +/- 28.9 and 226.7 +/- 30.6 mg kg(-1) dw, respectively). This difference can be explained by high sodium concentration in the anaerobic digestate, most likely due to inclusion of food scraps from households and restaurants in the biodigester feedstock. Screening of both substrates for a total of 133 micro -pollutants revealed that total sum of micropollutants was significantly higher in the AD-fertilized substrate (258 +/- 12 ng/g dw substrate) than in the standard substrate (191 +/- 35 ng/g dw substrate). Nitrogen losses during preparation of the AD-fertilized substrate were negligible.