Biuletyn producenta Pieczarek PIECZARKI 1/2017 S. 21-31
Is the production of compost and substrate a black box?
dr Nikodem Sakson, Poznań
To have high and stable yield of mushrooms one needs stable and high quality substrate used during the cultivation process. Analysing cultivations in mushroom farms, which had average yearly yield on a fresh market (in 2016) of 36 kg/m2, a question was asked, how can substrate, casing soil and mycelium influence the yield on sequential projections. In case of substrate, average yearly yield could be higher for around 2-3 kg/m2, if used materials didn’t depart form the expected standards of quality. Decrease in yield was sometimes significant, reaching up to 7 kg/m2. It is to be expected that this year (2017) there will be great differentiation in yield and lower average yield than in 2016.
In case of casing soil and mycelium from the group of intermediate spawns, close to U-1, differences in yield were minimal. Those materials rather influenced the assortment of fruiting bodies and the quality then the average yield. It means that – to have average yield on the level of 40 kg/m2 – one has to improve the stability of compost or (if the quality of substrate is far from standard) find the way of additional supplementation, which would improve the mass of mycelium in substrate between putting on the shelf to the end of the aeration.
This is the first reason, why in this article I would like to try to answer the question of sources of this variability, and also ask if there are some possibilities to improve quality and stability of substrate. Nowadays substrates with added to 1, 5% of protein feeding supplements allows to reach the maximum level of yield at 32-33 kg/m2. Without protein supplements the average yield would be lower at 2-3 kg. This means that in current production and growth systems we are able to deliver nutrients on a level of projected yield. Sporadically higher yield occur – reaching the level of even 40 kg/m2, but much lower yields also occur. Second reason for writing this article is the text by dr. K. Szudyga titled “The black box” that was published in “Pieczarka” Bulletin in issue 2/2017. The text was about production of compost and substrate.
The title alone gives an answer to the question – why the quality of compost and substrate in Poland is unstable. Their production is a proverbial black box. I am afraid that the meaning of the phrase “black box” would be unclear for the most of the readers that is why it needs some clarification. Searching on the Internet these words in Polish one can receive information, that this is a machine that registers flight’s details in planes, and recently in cars. But this doesn’t make it clearer. Only when searching for this phrase in English can we find an answer that can interest us. English Wikipedia writes: “In science, computing, and engineering, a black box is a device, system or object which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings.” This explains why the author of the article decided to use this phrase. We know what we put in (straw, chicken manure, gypsum, water, sometimes horse manure and urea) and we know what we get as a result (compost or substrate of specific features parameters), but we don’t know why this happens and how. In consequence to all these there is a tendency to assign a special role in compost yards to technological specialists, on whom the future of the whole market is supposedly dependent on. One can paraphrase a saying by Marek Ouden at this point, who stated that the production of materials for mushroom growth is more an art than science. This is why this author stresses the role of technology specialists in the process of production and the final result. It depends on their talent, experience, the sense of situation, involvement and on the fact whether they have an artistic flow on the given day or not. In this article one can find several information about achievements in the field of compost and substrate production, which are the basis of their technology of production nowadays. Descriptions of those achievements show, that the process of production is well documented scientifically and there is a problem in using this knowledge, and not in lack of it. It negates the dependence of character traits and involvement of technology specialists in compost yards, but doesn’t diminish their significance as people responsible for the process of production. Still the problem of black box is real, which can be exemplified by the fact that the basic process of producing compost is called alternately by two terms: “composting” and “fermentation”.
This shows significant chaos in the basic principles of knowledge about the process of compost production, because those terms and their way of working should negate each other. The term “composting” should be used only to describe the process of making compost (hot phase), always in oxygen conditions (availability of air). From the moment the mycelium is placed in the compost, we should use the word “substrate”, which contains mycelium and unused by it compost – organic matter, mineral compounds and microflora (mainly Scytalidium). Fermentation on the other hand is a process of achieving energy from dead organic matter by anaerobic microorganisms. It cannot be used to describe the process of production of compost. I too made the mistake of using this word in the past.
In this situation it is worth it to ask a question whether mentioned black box is a fact or a myth. The fact, that no system of controlling of technology of production of compost and substrate was developed based on the scientific knowledge about composting process with Agaricus, doesn’t allow us, in my opinion, to say that this process is a black box. To sum up – the main reason of changing quality of compost and substrate (apart from mistakes and technological failures) is lack of means to assess what and how much of it we use at the beginning and what – after mixing the materials – we should get as a result and what kind of characteristics should the substrate have. The technology itself allows achieving temporarily or sporadically high quality compost and substrate for mushrooms production, which means there are possibilities of improvement of their stability and quality.
Scientific knowledge gives us information: what should we put in (what materials to use), how does the process of production of compost and its colonization proceed, and what should we get out of it, or what kind of substrate we are expecting end eventually, how to enrich it, to achieve expected yield.
What don’t we know? What in reality we are putting in and what we get as a result, what is the yielding potential of the substrate offered for sale and how can we enrich the compost and substrate. It is a result of lack of information about what kind of characteristics can we measure and how to correct the process of production based on a system of control of materials, compost in sequential phases, and substrate.
In this situation it is worth to answer the question what conditions have to be fulfilled, for the composting process to undergo correctly and what kind of expectations from the compost and substrate can we have, taking into consideration the expected level of yield. The last question is “why”?
The main reason that is stopping the development of technology and minimalizing changing quality is a lack of connection between used technology and the nutrient needs of mushrooms. Division of the process of production of compost from the cultivation of mushrooms only deepens the divide. In companies, where such connection exists, there is a lack of tools for interpretation of characteristics of compost in comparison to achieved yield.
Introduction into the control system of new methods of analysing the characteristics of compost (NIR – spectroscopy with short range infrared) didn’t change the situation. Polish compost yards, which use this analytical system, do not produce substrate of better quality and stability.
What is next?
Improvement of production of compost and substrate should be based on scientific knowledge about the nutrition of Agaricus, and also on methods of analysis based on NIR adopted (and further developed) from feed industry, taking into consideration nutritional needs of mushrooms. Following factors should be considered:
- Planes are the natural habitat of Agaricus. Places where grass dominates undergo decomposition after dying, mineralization and humification (composting). This means that Agaricus, as a saprobiont is best adjusted to use dead organic waste originating from grass.
- What is it feeding on? Mushrooms feed during the enzymatic decomposition process (biodegradation, bioconversion and biosynthesis) of dead cell membranes (CWC) containing hemicellulose, cellulose, lignin, pectin, cut in, wax and silicon) and dead content of insides of cells (CC) containing soluble proteins, fats, non-protein nitrogen, amides, organic acids, soluble sugars, starch, pectin, mineral contents, glucosides, alkaloids and tannin) of grass and dead microorganisms and dissolved in water basic sugars and mineral content, that are delivered by decomposition of biomass, that are released in mineralization process by microorganisms that are in the vicinity. The basic mechanism of decomposition of cellular membranes and insides of the cells (cytoplasm) is external enzymatic decomposition. Its main function is to get glucose (mainly cellulose and hemicellulose), which is used to get energy necessary for sustaining life functions, It is al used as a building material, by transforming it into polysaccharide chitin (glucose + nitrogen, mainly dissolved in water NH4+, a result of ammonification process), used in development of mycelium and later of a fruiting body. In mushroom cultivation lignin is used very rarely. It is a part of substrates construction, which gives it a structure. If quick decomposition of lignin occurred, the substrate wouldn’t have the structure needed for the yield that would allow for gas exchange and water volume. Agaricus doesn’t have the ability to use the amino acids directly. It synthesises its own amino acids and other contents of cytoplasm by itself. The feeding process can be disrupted by contents called inhibitors of Agaricus enzymes. But this is a different issue.
- What is a level of yield of mushrooms dependent on?
The yield of mushrooms in the first and second flushes depends on the mass of mycelium in the substrate and casing soil, in the third and sequential flushes – it depends on availability of nutrients released by microorganism that are in the substrate, mainly Scytalidium.
- What process do we use for compost production and what is the connection with the way the mushrooms behave? Composting process is the base, and in mushroom production we use a part of it called mineralization process, which is decomposition of complex dead organic matter by enzymes of microorganisms into simpler inorganic (biodegradation) and organic (bioconversion) compounds and non-enzymatic decomposition of organic matter in Mallards’ process (caramelization). The basis for composting of dead organic matter is its content, which provides the 30 to 1 carbon to nitrogen ratio (the composting process starts which much higher ratio of C to N, 17-30 : 1) and water and phosphorus to carbon ratio as 100 : 1 in condition of availability of oxygen. The source of nitrogen is uric acid from chicken manure and horse urine (when using horse manure). During the production of compost to grow mushrooms we use the first phase of composting process, called the hot phase, during which biodegradation of straw takes place, which means its opening (biodegradation of wax) and defibration (biodegradation of pectin). For the digestibility of cellular membranes to be higher, higher access to the insides of cells, increased water volume of compost and the process of ammonification are needed. Those processes are done by mesophilic microorganism. Further increase of temperature is done by thermophilic organisms, which further the process of straw’s biodegradation. After reaching the temperature of above 75oC non-enzymatic process of transformation of sugars and proteins in high temperatures begin (caramelization), which delivers nutrients to the developing microflora in the process of maturing and sanitization (pasteurization). Elimination of adverse for the process microorganisms during the so called “cold composting” phase (mineralization of compost by mushrooms) also takes place. This stage can be described as preparation of nutritional base for microorganism multiplied during the maturing process and releasing of ammonia (volatile nitrogen). However ammonia is the source of loss of nitrogen during the composting process. This is why it is so important to aerate the prisms, when the release of ammonia is too high. Loss of nitrogen can also happen when there are anaerobic zones in the compost. Then the process of denitrification starts, meaning transformation of nitrates into gas forms of nitrogen. Another undesirable process is the loss of carbon in the process of too intense mineralization (it is caused by the mineralization process taking too long or by maintaining too high temperatures of compost for too long). Composting process is exothermically, in which polysaccharides are transformed into energy, and at the same time there is a decrease of their amount, so they are not available for microflora during the maturity process and for mushrooms during the phase of compost’s hypertrophy. Observations indicate that there is a necessity of adjusting the high temperatures phase to the hardness of the straw. During the same schemata of production we can achieve very different results. The differences occur especially in the amount of nutrients for mushrooms in the compost. Compost made of soft straw can be very easily made with too much decrease of carbon, cellulose and hemicellulose content. After thermophilic microorganisms use easily accessed sugars and nitrogen, the temperature lowers, thermophilic microorganisms die (phase II). The result is a biomass, contents of which are partaking in the maturity process of dead cells of microorganism and not mineralized organic matter. The progress of biochemical processes that take place in the compost is well known. Sown mycelium, after colonization of the compost (eliminating adverse microorganisms and unnecessary for its development, leaving only Scytalidium) will use the nutrients by enzymatic digestion and builds mycelium in the biosynthesis process. Cellulose leftover after the shock is still digested, mainly by Scytalidium. Simple sugars and mineral content that were dissolved in water are used by mushrooms, mainly in the third and sequential flushes.
In case of mushroom cultivation the humification process starts after introduction of substrate into soil after hypertrophy. It take place by decomposition of not mineralized straw of the harder to dissolve polysaccharides, mainly lignin, by soil organisms and its transformation into caries that is enriched by mineral contents that were made in the process of mineralization.
Application of physical analytical methods in production of compost and substrate
Using analytical methods using NIR (close infrared spectroscopy)
For quick analysis of compost, also phase III compost and chicken manure and straw, one can purchase in Poland laboratory equipment offered by Mc Substradd. It contains analyser with according programming and data base. Measurement method is indirect and needs calibration, which means determining connection between the spectrum and compost. Producer offers such calibration, but it is necessary to adjust the readings to the conditions of specific compost yard. Buying such equipment doesn’t mean getting rid of a laboratory that is working with previously used wet methods, because there is a necessity of doing measurements supporting the calibration. NIR doesn’t denote the micro- and macro elements. The main advantage, because of which it is used nowadays, is simplicity and quickness of the analysis process. To get correct results a representative sample of analysed material is needed. Because of possibility of doing a lot of analyses in a short period of time it is possible to characterise compost in more precise way. However those are still the results after getting a sample, and not done in real time. Similar solutions are offered in Poland by Nuscana Biotechnika Laboratoryjna. This company offers, apart from NIR, calibration to specific needs of compost producers. The advantage is that the tests and calibrations are made in Poland, and the calibrations are free. Making the tests with classical methods is the only cost here. Calibrations curves are created by using the laboratory tests and spectrum of samples, and are then installed into the NIR. Those calibrations can be widened and improved upon by adding additional points. One can add new characteristics to existing methods. Companies that have their own laboratory are equipped by Nuscana with programs for calibration. They offer training courses too.
Following parameters of compost and correlations between them can be used (from McSubstradd):
- raw proteins,
General proteins, raw proteins – whole amount of nitrogen based nutrients, which means proper proteins, complex proteins and non-protein nitrogen compounds (NPN), which have nitrogen in their content.
- general volatile nitrogen (TVN)
- ADF cellulose
- NDF hemicellulose
- ADL lignin
The following words from the website characterize the way to understand the meaning of tested parameters in compost production: “By the last three parameters we can characterize the content of carbohydrates in compost, one of the main sources of nutrition for mycelium. Composting as a process is based on decomposition of carbohydrates and making them with organic nitrogen available for mycelium. Analysing this is a step forward.” It is hard to agree with the statement that Agaricus is directly using organic nitrogen. Scientific knowledge doesn’t confirm that.
In chicken manure one can measure humidity, ash, nitrogen and ammonia.
NIR allows measuring its structure, water volume, and nutritional level.
There is no information on possibilities of measuring the content of liquid manure.
Process of production of compost and substrate and a range of analysis done on it
Here is a proposal for analysis program during the process of production of compost and substrate:
- Analysis of raw materials;
- Chicken manure: humidity, ash, nitrogen and ammonia, NSP (biomass), NDF (hemicellulose), ADF (cellulose) and NPN (non-protein nitrogen);
- Straw: structure, water volume, and nutritional level and pectin and waxes;
- Liquid manure: nitrogen content, pH, RD;
Another open issue is the question if raw materials have contents that disrupt the composting process, and if yes what are they and how to measure them?
- Phase I compost;
- determining the recipe according to previous analysis; Determining the C: N recipe taking into consideration the losses that are the result of release of ammonia. This is, at this moment, the hardest element of the technology. Determining and achieving the right ratio of C : N is the basic condition of achieving stable compost. Type and state of chicken manure, besides the correct weight of the raw materials, is the biggest challenge. The ratio of carbon to phosphorus (C: P) has to be controlled also, using wet analysis.
- mixing the materials.
After mixing the materials: humidity, NSP (biomass) and NPN (non-protein nitrogen), C: P, C: N (according to previously determined standard);
- mesophilic phase – opening and defibration of straw, building in water, beginning of nitrification process in aeration conditions;
The level of content of wax and pectin should be an indication of the level of opening of straw.
- biochemical thermophilic phase with aeration, multiplication of thermophilic microorganisms and caramelization process;
Measuring NFC (non-structural sugars) and NPN (non-protein nitrogen), apart from standard measurements for compost;
- Phase II compost
The goal of this phase of compost production is maximal accumulation of biomass from dead microorganisms, hemicellulose, and cellulose and non-protein nitrogen. Their level indicates nutritional potential that are assimilated by mycelium during the enzymatic distribution. After the end of pasteurisation, maturing and cooling of compost standard analysis should be made, the same as in phase 1 compost and also: NSP (biomass), NPN (non-protein nitrogen), NDF (hemicellulose), ADF (cellulose) and NFC (non-structural sugars can indicate the possibility of growth of green mould).
- Substrate (phase III)
The effect of this phase is achieving the maximum transfer of nutrients that are assimilated by mushrooms into the mycelium. After the compost hypertrophy – the analysis spectrum the same as for phase II compost, measurement of mycelium’s mass by marking organic nitrogen as indirect indication (mycelium+ Scytalidium), and NSP (biomass), NPN (non-protein nitrogen), NDF (hemicellulose), ADF (cellulose) and NFC (non-structural sugars), which will show the potential of yield of the third flush that is in the compost, nutrients for Scytalidium.
The basics of controlling the process of production of compost and substrate
Production of substrate of stable quality allowing for the yield to achieve the level of 40 kg/m2 is possible by doing the following tasks in order:
- Rating the state of raw materials,
- Working out the recipe,
- Mixing the materials,
- Executing the biodegradation of straw with mesophilic and thermophilic microorganisms,
- Executing caramelization process of mixture of materials in Mallard’s process,
- Rating the production process of phase I substrate and deciding whether to use supplement of nutrient, up to the accepted standard,
- Executing pasteurization and conditioning,
- Rating the production process of phase II substrate deciding whether to use supplement of nutrient, up to the accepted standard,
- Sowing of mycelium and executing substrate’s hypertrophy,
- Rating the process of hypertrophy and substrate and deciding whether to use supplement of nutrient up to the accepted standard, or passing recommendations to mushroom growers about eventual supplementation program.
The key is determining the C: N ratio at the start, rating the level of straws defibration and the release of carbohydrates and the level of transformation of organic matter into useful microflora and straw for the mushrooms’ enzymatic decomposition.
The implementation process needs time and a lot of intellectual and organizational work in compost yard, and also cooperation with clients.
It can be divided into the following phases:
- Implementation of measuring procedures and verification of company’s standards (calibration) and accepting different concept of rating of compost and substrate;
- Building company’s own data base integrating achieved results and information about the way substrate behaves when clients get it, and also abilities for analysis of received information and abilities to draw conclusions to use it in potential changes in technology;
- Controlling the production phases based on the results of analysis and observation;
- Deciding whether to use supplements and feeding supplements or not, at what scale and doing trial tests before integrating them into production of compost and substrate.
What are the main reasons for changes in the quality of substrate nowadays?
- Uncontrolled process of straw’s decomposition after mixing the materials. The yield is much lower, if the level of opening of straw is smaller. The indication of this state is higher amount of waxes, mainly pectin. It results in a smaller content of sugars available in the maturing phase in the caramelization phase and lower availability of hemicellulose and cellulose to microorganisms during the maturity phase. As an effect the availability of biomass form mushrooms is lower.
- Too low availability of non-protein nitrogen during the whole process of compost production. It is a result of high differences of amino acids in chicken manure, and that it is evaporating easily in the process of ammonification. Scarcity of non-protein nitrogen restricts the creation of biomass in phase II and limits the possibility of using the glucose obtained in the process of enzymatic digestion by Agaricus, and as a result it limits its ability to create chitin and proteins.
- High loss of carbon in crumbly straw by using the same technological cycles. This is probably the main reason of decrease of yield level in the second flush.
Expected level of abundance of substrate allowing for a yield of 40kg/m2 in three flushes on fresh market can be achieved by its production in compost yards or by supplementing on mushroom farm. Right now demand for this kind of product is not high, because not many producers of mushrooms can achieve such yield. What is left in this situation is to find such supplements and feeding supplements, which would meet those expectations, independently of the quality of the produced substrate. Can those expectations be met? I think so. The basis of those feeding supplements should be cellulose supplements enriched in micro- and macro elements without causing thermal effect. It would allow using them in high dosages, so it would be always possible to achieve expected yield. First tests show that those assumptions are correct.