Co-production of Coprinus cinereus (Schaeff.) S. Gray. s. lato Mushrooms and Biogas from Palm Oil Wastes in Tanzania

Aims: The aim of this study was to investigate on the effect of: (a) mixed fractions of palm oil wastes on Coprinus cinereus edible and medicinal mushroom yield using solid state fermentation plastic bioreactor and (b) of spent mushrooms substrate (SMS) on the extent of methane yield in batch anaerobic bioreactors using cow dung manure as an inoculum. Only one research reported on pre-treatment of palm oil wastes and biogas production in Tanzania.

Study Design: Palm oil wastes were obtained from Bagamoyo district, Pwani Region, in Tanzania. Coprinus cinereus mushroom production was performed in solid state fermentation plastic bioreactor while biogas production was carried out in batch anaerobic bioreactors.

Place and Duration of Study: Department of Molecular Biology and Biotechnology, University of Dar es Salaam, between September 2012 and July 2013.

Methodology: Completely randomized design was used for this study where by nine different fractions of blended palm oil wastes were prepared, Spawn rate (mushroom seed of Coprinus cinereus) employed was 7% based on wet weight of the substrate (about 35 g per 500 g moist weight substrate), then placed in solid state fermentation plastic bioreactor and incubated in mushroom house. Time was recorded in days for the completion of growth of mycelium on substrates (/spawn running/vegetative growth), appearance of pinheads (pinning) and fruiting bodies (fructification). The data for the yield number, fresh weight of fruiting bodies and biological efficiency worked out against the dry weight of each substrate were also recorded. The substrates for biogas production used were biological treated palm oil wastes i.e. the spent mushroom substrates obtained after harvesting mushrooms and cow dung manure was as an inoculum. Anaerobic digestion of spent palm oil wastes mushroom substrates for biogas production was carried out in batch scale (500 ml E-Flask) under anaerobic condition at ambient temperature ranged from 28-30°C and at various mixing palm oil wastes composition fraction in triplicates. Determining both biogas volume and methane content monitored the performance of the anaerobic digestion process in the batch anaerobic bioreactors.

Results: Mushrooms grew well in different composition of palm oil wastes and days for completion of spawn running to fruiting body formation ranged from 13 to 23 days; the best substrate formulation was 98% EFB (Empty Fruit Bunches) +1% S (Sediment)+1% P (Pome) which had highest mushroom yield (189 g fresh mushrooms/kg moist substrate) and maximum biological efficiency (35%). When the Spent Mushroom Substrates (SMS) were employed in batch anaerobic bioreactors for biogas production. The best results 0.43 and 0.49 CH4 m3/kg Volatile Solids (VS) added was obtained from pretreated (SMS) 98% EFB+1% S+1% and 39% MF (Mesocarp Fibers)+39% EFB+ (20% PK (Palm Kernel )+ 1% P+1% S palm wastes substrates formulation, respectively. The highest methane yield were 1.3-1.4 fold higher compared to methane yields 0.33-0.34 CH4 m3/kg VS registered from corresponding non-pre-treated palm oil wastes substrates formulations, mean methane content of the biogas obtained from treated SMS was 82%, which was slightly higher than 79% recorded from untreated palm oil wastes substrates formulations.

Conclusion: In conclusion it is technically feasible to co-produce both food in the form of Coprinus cinereus edible and medicinal mushrooms and bio-energy in the form biogas rich methane from palm oil wastes while at the same time reducing environmental pollution.