This study looked at the efficacy of treating straw for oyster mushroom cultivation with lime, fermentation, or wood ash instead of pasteurization. Three trials were done comparing mushroom yields between the four different treatment methods. Straw was treated and inoculated with six different strains of oyster mushrooms over 3 trial runs. For each treatment method 8 bags weighing 10 lbs was inoculated, incubated for 3 weeks, and then allowed to fruit for 2 months. Harvest weight was recorded over the 2-month period. All four treatment methods produced mushrooms, with lime producing 12% higher yield than pasteurization on average. The average biological efficiency overall was fermentation 18%, wood ash 20%, heat 29%, and lime 41%. A 36 page booklet on oyster mushroom production was created and distributed throughout new England. Presentations were given at NOFA summer Conference, Radical Mycology Convergence, Urban Farming Conference, and other events.
This grant was initiated to find a method other than pasteurization for treating straw in oyster mushroom cultivation. Finding an effective and alternative method to pasteurization will hopefully encourage more farmers to grow oyster mushrooms. The two people who conducted this study were Willie Crosby and Dylan Kessler. Willie owns Fungi Ally and teaches a mushroom cultivation course at Umass Amherst. Dylan was a co-owner of Fungi Ally and has been working with fungi for over 10 years. Our technical advisor is Rob Wick, who is a plant pathologist at Umass Amherst. Michael Crigler designed the booklet we published, and has worked with Fungi Ally to do all branding, labeling, and graphic design in the past. Our operation is now is a 2500 square foot warehouse. We produce about 200 pounds of oyster mushrooms a week and sell 150 ready to fruit bags a week. We market through 1 farmers market, local coops, and distributors. When the trials for this grant were conducted we did not have one location. We used a lab at Umass Amherst for growing spawn and a basic fruiting room in a tobacco barn for the fruiting.
The original plan of work described in the methods section was followed very closely.
- Six strains of oyster mushroom were used Wild Branch, Pearl, Yellow, Pink, 3015 and Elm A. Wild branch and Pearl were substituted for 3014 and Italian as the cultures were readily available.
- Straw was treated using four different methods Wood ash soak, lime soak, fermentation, and pasteurization. Once treated each strain was inoculated into eight total bags. Time of preparation for each treatment was recorded.
- The bag final weight was 10 pounds instead of 20 pounds and only 1 pound of spawn was used per bag. This change was made so the bags would fit on the shelves and all trials and outreach could be performed within the budget of the grant.
- All bags incubated for 3-4 weeks and then were moved into the grow room. Black tubing was used as the bag material, clear tubing would have been better to track colonization more accurately.
- Bags were maintained in the fruiting room for 8 weeks. The humidity was kept at an average of 87%, but temperature fluctuated greatly during the season. In late June through August grow room temperatures reached 90 degrees during the day.
- Biological efficiency was found for each trial and contamination rates were recorded. Photos were not taken during colonization as black bags were used rather than clear.
The method to prepare each of the four treatments was as follows.
1) Hot water pasteurization. A barrel was lifted off the ground with cinder blocks and filled half way with water. A turkey burner was placed underneath and the water was heated to 180 degrees. It took about 4 hours for the water to reach temperature. Straw stuffed in burlap sacks was then submerged into the water, the heat was cut and a top was placed on the barrel. After 2 hours the straw was lifted out of the barrel and allowed to drain and cool for 45 minutes.
2) Hydrated lime soak. Straw stuffed in burlap sacks was placed into a 55-gallon barrel. One gallon of hydrated lime with magnesium content below 10% was placed into a 5-gallon bucket. The lime was mixed with water in the 5-gallon bucket as the 55-gallon barrel was filled. The lime solution was gradually added to the barrel as it filled. A pH of about 12-13 was achieved through this ratio of water to lime. A concrete block was placed on top to keep the straw submerged. The straw was left for 16 hours submerged and then lifted out of the water and allowed to drain for 20 minutes.
3) Straw stuffed in burlap sacks was placed in a 55-gallon barrel. The barrel was then filled with water. Concrete blocks were placed on top of the straw to keep it submerged for 5-7 days. The spring treatment took 7 days while the summer and fall treatment only took 5 days until they were ready. A strong fermentation smell was the determining factor. Straw was the lifted out of the barrel and allowed to drain for 20 minutes
4) Wood ash soak. Straw stuffed in burlap sacks was placed in a 55-gallon barrel. Four gallons of wood ash was mixed with water in an 18 gallon bin. As the Barrel filled the wood ash solution was added until it was thoroughly mixed in. This achieved a pH of about 11. It was not possible for us to get a pH reading of 12 or 13 using wood ash. A concrete block was placed on top to keep the straw submerged. The straw was left for 16 hours submerged and then lifted out of the water and allowed to drain for 20 minutes.
For the first trial the timeline is below
- February 26th begin first generation of grain spawn
- March 5th grain was expanded into 2nd
- April 2nd straw was chopped
- April 8th fermentation process was started
- April 14th Lime and wood ash soak were started
- April 15th Pasteurization treatment was conducted and inoculation of Pearl and Wild Branch completed.
- May 11th all bags were moved into the fruiting room.
- June 15th all bags were moved out of the room.
For the Second trial the timeline is below
- March 22nd first generation of grain was started for Yellow and Pink oyster
- April 23rd second generation of grain was expanded
- May 17th straw was chopped
- May 17th fermentation process was started
- May 20th wood ash and lime soak were started
- May 21st pasteurization was conducted and all bags were inoculated
- June 16th bags for trial two were moved into the fruiting room
- July 20th bags were removed from the grow room
For the third trial the timeline is below
- End of May first generation of 3015 and Elm A were started
- Middle of June 2nd generation of grain was expanded
- July 9th straw was chopped
- July 10th fermentation process was started
- July 14th wood ash and lime soak were started
- July 15th Pasteurization was conducted and all bags were inoculated
- August 3rd all bags moved into the grow room
- September 10th all bags were removed from the grow room
There are three major factors that may have influenced the yields of these trials. Average B.E.
Spawn was produced in a laboratory that was not customized for the production of mushroom mycelium. There may have been contamination in the grain spawn that would not have allowed for maximum yields. If repeating this study spawn would be grown in a lab designed for growing mushroom mycelium.
2) Fruiting parameters
Fruiting was done in a simple structure created in a tobacco barn. The humidity was controlled by daily watering and a humidistat hooked up to a commercial humidifier. The humidity was typically held in an appropriate range. Temperature was not modified at all. The temperature was typically 5 degrees F cooler than outdoor temperature, which meant in the summer grow room temperatures fluctuated between 75-95 degrees F. This is extremely hot for most mushrooms to fruit in and was likely part of the reason for poor yields of the yellow oyster.
3) Contamination was not worked into the biological efficiency numbers. Some trials had higher levels of contamination than others. Because black bags were used contamination could not be detected and recorded until bags were composted. The number of completely contaminated bags was much higher for the fermentation and wood ash treatments compared to lime and pasteurization.
- All four treatments will fruit mushrooms.
- The average biological efficiency (BE) overall was fermentation 18%, wood ash 20%, heat 29%, and lime 41%. A break even point for many growers is 100%, by working with one technique and one or two strains it is possible to refine and improve BE.
- It is much faster and less intensive to use lime treatment compared to heat. The lime preparation took on average 10 minutes. While the heat took about 30 minutes to set up plus on and off monitoring for about 6 hours.
- Fruiting temperature had a large impact on yields. The second and third trials were difficult to get consistent and abundant pin set because of high temperatures. The pink strain did fine in the summer time because it fruits at high temperature. Fruiting rooms should be arranged to maintain temperatures below 70 degrees.
- Rotating strains to allow fruiting at different temperatures is a lot of work and planning. It is easier, and more productive to perfect methods using 1 or 2 strains and stick with those.
- Lime is the most profitable treatment method to use. It takes less input about $2 in lime compared to $10 for propane and less time. For our trial yields increased by 12% on average compared to pasteurization.
Education & Outreach Activities and Participation Summary
fungially_oyster_booklet_finalWillie Crosby spoke at two conferences about this research, the 2015 NOFA summer conference and the Radical Mycology Convergence in October 2016. These talks were well attended by about 30 people each. Willie also taught oyster mushroom cultivation and presented this research at 3 different two-day mushroom cultivation courses. These courses were offered in New York, Massachusetts, and Kentucky. Willie presented at Shiitakepalooza in April of 2016 on oyster mushroom cultivation on straw.
Another aspect of outreach for this grant was the completion of a 36-page booklet on oyster mushroom cultivation. 250 copies of this booklet were printed and distributed to farmers and mushroom growers. The booklet was shared with Fungi Ally’s 750-person newsletter, the Commercial Mushroom Growers Network, the Mushroom Listserv, and the Mushroom Growers Newsletter. This booklet is available for free through the Internet at fungially.com and was promoted through the Fungi Ally Facebook page.
Yes, we answered the question we wanted to at the beginning of this study. For commercial mushroom farming lime treatment can be used instead of pasteurization. At home any of these four treatments can be used. We will continue using the lime method for demonstration and small-scale applications. This method is also very effective for growing mushrooms while inter-cropping with vegetables. As our mushroom production business has grown we do not use this method any longer. We are now producing about 250 pounds of mushrooms a week and were able to invest the time and money into a more productive system. We no longer use straw, instead we use higher nutrient substrate which can give a higher yield. This required us to build an aseptic lab and devise a system for steam treating the substrate. If we were growing 75 pounds or less a week we would still use the straw and lime method. Next steps could be
- Introduce more farmers to oyster mushroom cultivation
- Develop and teach a simple system for vegetable farmers to grow and offer mushrooms to their existing customers.
- Work on mushroom intercropping systems
- Incorporate local agricultural waste products like coffee grounds or brewers grain into oyster mushroom cultivation.