Compost producer's workshop provides international viewpoint.

The 3rd Compost Workshop held in Helvoirt, Netherlands, was hosted in May by PPO Paddestoelen, Christiaens Group, C-Point and AdVisie. Chair Robert van Loo from PPO opened the workshop and outlined the research organization he directs. Research conducted there covers basic compost science, spawn breeding, virus research and alternative to chemicals for pest control. The goals of the workshop were outlined as:

* Sharing information among researchers and commercial composters

* Interactive discussions on all aspects of composting

* Define knowledge gaps for research opportunities

* Discuss the differences and or similarities in Phase I through Phase III systems

The first speaker, Gerben Straasma, discussed the various alternative uses for compost ingredients that contain lignocellulose and cellulose. The variety of potentially more profitable uses of straw and straw-bedded horse manure is amazingly broad. General agriculture feeding materials, paper-pulp uses, potential fuel sources and even building materials are all developing uses for traditional bulk ingredients. For example, in Germany, 60,000 hectares of wheat were planted just for production of ethanol fuels. Growers should be concerned because of the potential value of straw and what that would do to the supply and cost of making compost. Some important points of the degradation of lignin and cellulose by microbes and mushrooms were also reviewed.

I was the next speaker, charged with a discussion of quality and characteristics of bulk ingredients for mushroom composting and nutrition. A brief description of the different straw and grasses used and their chemical and physical characteristics were presented. The importance of Phase I chemical reactions on the chemical constituents in straw and hay were related back to mushroom nutrition. Examples of other possible ingredients used or tested were presented. The research conducted at Penn State on Kenaf Core, a by-product of a hemp plant used in fiber production, served as an example of the importance of Pentosans, an important carbohydrate found in corn cobs, sought out by chemical companies, but important for mushroom nutrition. A farm using straight dairy manure (no straw) to grow mushrooms suggested materials that cows cannot digest are the type of lignin-nitrogen compounds that the mushroom can use.

Jan Gielen, from C Point, gave a very descriptive talk on important parameters for the environment to maintain optimum compost conditions and mushroom quality. He described the drying processes where heat release helps production and moisture release helps mushroom quality. Critical control of heat, moisture and carbon dioxide (HMC) measuring systems were important for all tunnels and monitoring these variables can be related back to efficiency and quality of the compost.

A discussion session followed on the quality to production chain, methods and criteria to assess and control raw materials and compost quality. It was the group's consensus that feedback from the compost and grower customers was the most important criteria. Input criteria include people, goody water, structure, lab data, sensory and sampling techniques, to name a few. Output includes lab results, temperature, oxygen, moisture and discussions with internal customers and many other subjective and objective observations. Feedback on compost would include growers results, mushroom quality and shelf life, shrink, advice to growers and again most importantly the feedback from customers.

Con Hermans of AdVisie discussed a very difficult topic, "Troubleshooting a Compost Yard." To find a mistake one has to work systematically, be critical, compare and make connections. He suggested there were three types of mistakes made on compost yards: conscious, unexpected and unconscious. Details in the construction and maintenance of tunnel operations are critical for preventing or correcting problems. Infections can occur inside or between tunnels, from the Phase II to Phase III tunnel; in the Phase III tunnel, or anytime that the compost is exposed. Growers must use feedback, checklists, graphics and, most important, control urges to make changes or try new procedures.

The "Law of Limiting Factors" was the theme of Gerben Straatsma's next presentation. When mushroom yield is limited by the lack of a particular nutrient and that nutrient is then provided, another nutrient becomes the limiting factor or the "weakest link" in the total yield. Analysis of the compost throughout the cropping cycle and of the mushroom fruit bodies during the different breaks suggested that phosphorous and magnesium may be limiting factors in mushroom yield. However, he was quick to note that this data has to be carefully interpreted because of the many variables in sampling and analysis that can occur. He also suggested that water is probably a more important limiting factor in mushroom yield and quality.

Jos Buth of C Point gave an overview of Phase III compost, covering both the benefits and pitfalls of these systems. The obvious benefits include a reduced volume of compost to handle, more growing cycles for production rooms each year, more homogeneity of the compost, less energy required and more efficiency from the composts and farms. Limitations are the need for very selective compost, very strict hygiene requirements and depending on cooling capacity, possible limitation for the use of supplementation. He described the key points for construction of the tunnels and loading and emptying hallways. These points include an over-pressurized air handling system with efficient filtration. Fan capacity is also a critical component and under sizing the fan can cause major cultural problems.

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The last discussion session was on avian influenza virus and its impact on poultry manure supplies around the world. Breakout groups discussed their previous experiences and also what they either have tried or would try to reduce or eliminate poultry manure from a formula. Compost with synthetic nitrogen, ammonium sulfate, ammonium nitrate and or urea has been tried or used at some farms around the world. Other "organic" sources of nitrogen were considered as alternatives, however cost and availability was the major concern. It was pointed out that if all producers were simultaneously hit by a shortage of poultry manure, cost would not be a concern to compost producers, but would impact customers and may create difficult times for growers. Other feedlot manures could be used; some European composters have already successfully used pig manure in a formula. It was mentioned that maybe the ISMS could play a role in disseminating information and or alternative formulations to growers worldwide. Research facilities around the world could concentrate on this problem, but the question of who would provide funds would need to be addressed.

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There was plenty of time for informal discussions between suppliers, growers and researchers, which helps all to prioritize the challenges of the mushroom community. It was interesting to see the difference in topics from the workshop I attended four years ago, when odors were a major issue and this workshop, where it was mentioned but not considered a challenge anymore. It seemed that the consensus of the workshop attendees was that this type of meeting is important, but a broader scope may bring different visions for it.

The workshop was well organized and run, thanks to Els Josten, who was ever present and efficient in getting things done. All agreed that many thanks should be given to the organizers who had the foresight to put together the program and provide a venue for the productive discussion it stimulated.

David M. Beyer

Associate Professor Penn State

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