A study was conducted to determine the feasiblility of using 100 percent waste stream substrates for commercial edible mushroom production. The target species was Pleurotus ostreatus, the common tree oyster. Biological efficiency of four different waste substrate mixtures was compared to that of the commercial standard substrate mixture consisting, by dry weight, of 80 percent oak fuel pellets, 18 percent wheat bran and 2 percent gypsum. The four waste substrates were spent coffee grounds, cacao shells, soy “dust and husks”, and malthouse “fines and beards”. The four formulations were created by using these substrates in place of the bran as the enriching agent and combining them with mixed species sawdust from a local sawmill. The sawdust replaced the fuel pellets as the carbon and lignin source in the study. The substrates were innoculated and fruited out and the spent substrate was composted. The compost was sampled and tested for nutrient values and cation exchange capacity. The powerpoint presentation attached below describes in great detail the entire study and includes graphic information. We would advise the reviewers to use the power point to get greater detail than has been provided in the text below.
WHY IS THIS STUDY VALUABLE?
- Thousands of pounds of waste stream products are discarded into landfills every day in every city in the world.
- Many of these products may be suitable as substrates for growing edible and medicinal mushrooms.
- This study will determine the feasibility of using these substrates in commercial mushroom production.
OBJECTIVES OF THE STUDY:
- To develop substrate formulations that utilize readily available waste stream products for growing edible mushrooms.
- To compare the yields of waste stream substrates to that of the “industry standard” commercial substrate formulation
- To compost spent mushroom bags for use as a nutrient rich fertilizer, thus closing the loop.
The Industry Standard Formulation (20 % enriched):
- 40 lbs of compressed hardwood fuel pellets (the lignin source)
- 8 lbs of Bran (the Nitrogen source)
- 1.5 lbs of Gypsum (provides sulfur, which fungi require for growth)
- 7 gallons of water (hydrate to carrying capacity)
Waste Substrate Formulations (20 % enriched):
- Mixed species sawdust was used in all WS recipes as a lignin source
- Recipe one uses spent coffee grounds in place of bran.
- Recipe two uses soy dust and husks in place of bran.
- Recipe three uses cacao shells in place of bran.
- Recipe four uses fines and beards in place of bran.
- All recipes are enriched to approximately twenty percent by weight.
- Harvest period- 90 days for all substrate formulations.
- Hydrated bag weight- 5 pounds for all substrate formulations.
- Sterilization- active steam for 8 hours for all substrate formulations.
- Spawn Rate- 250 ml spawn per bag for all substrate formulations.
Results: Standard Mix
- Harvest Period- May 30th to Aug 30th (90 Days)
- Average weight harvested per bag- 2.15 pounds
- Biological Efficiency (wet weight)- 43%
- Biological Efficiency (dry weight)- 107%
Results: Coffee Grounds
- Harvest Period- May 31st to August 31st (90 Days)
- Average weight harvested per bag- .81 pounds
- Biological Effeciency (wet weight)- 16.2 %
- Biological Efficiency (dry weight, estimated) 40.5 %
Results: Soy Dust and Husk
- Harvest Period- August 7th to November 7th (90 Days)
- Average weight harvested per bag- .89 pounds
- Biological Effeciency (wet weight)- 17.8 %
- Biological Efficiency (dry weight, estimated)- 44.5 %
Results: Fines and Beards
- Crop Failure- No results
Final thoughts: Although the commercial substrate mixture outperformed all of the waste stream substrates, we believe that this is due to the quality of the sawdust, not the enriching agents. Mixed sawdust likely contains a percentage of softwood or rot resistant species and this would have an impact on overall productivity. This combined with the the cost analysis data presented in the powerpoint demonstrates that waste substrates, although less productive, are still a viable option in commercial mushroom production.
Educational & Outreach Activities
A free seminar was given on Monday, March 1st, 2015 from 5-7 pm at Villagers in Asheville North Carolina. The seminar explained in detail the nature of the research grant, experimental design, results, and conclusions. We provided printed information containing formulations using waste stream substrates that were proven effective in the production of one species of edible mushroom, Pleurotus ostreatus. Approximately 40 individuals attended the seminar, including many mushroom growers.
A post card advertising the free seminar was distributed to the community at large with a focus on individuals involved in commercial mushroom production.
A brocure, From Waste Stream to Protein, was published and distributed to individuals that attended the free seminar.
A digital version of the powerpoint presentation shown at the seminar was published at www.shroomcentral.com. The digital version is also attached here.
This research study determined which waste stream products were viable substitutes for commercial substrates. We accomplished this goal by demonstating statistically, the productivity of three different enriching agents versus the standard commercial mix. We believe that the data generated by this study will be useful to future growers that may wish to use waste subsrates in place of standard commercial substrates.
We have contributed to the overall knowledge in the ever expanding field of mushroom cultivation and mushroom science. Growing mushrooms can be a challenge due to the unpredictibility of working with fungi. Our research will help future growers to better understand and predict the implications and outcomes of using waste stream substrates as a substitute for commercial substrate mixes.
We recommend that other growers expand on the data generated by this reseach grant, including:
1. Using different mushroom species
2. Varying the amount of waste substrate
3. Varying the amount of the initial spawn rate
4. Mixing waste substrate enriching agents together