Physical degradation of wheat straw by the in-vessel and windrow methods of mushroom compost production

Mushroom compost manufacturers in Ireland are moving away from the traditional outdoor phase I windrow method, favouring in-vessel production. Composters and growers have reported better quality compost with faster spawn run and higher yields produced by this process. In the present study, physical examination of samples highlighted differences when comparing the windrow and in-vessel methods of compost production. Observations using scanning electron microscopy suggest that the cuticle of wheat straw from in-vessel production is damaged during phase I, peeling away from the surface in fragments, and exposing the epidermis. Changes in silicon levels on the straw surface acted as a marker for cuticle damage when comparing both composting systems. Cuticle damage may be important during composting and afterwards, as substrate colonisation is faster, and consequently spawn run is shorter. The phase I compost microbial community is altered by the in-vessel technique, producing a predominantly thermophilic bacterial flora in contrast to the mesophilic and thermophilic bacteria and fungi found in windrow phase I compost. These differences may be significant in mushroom compost production.     

Investigating microbial activities in compost using mushroom (Agaricus bisporus) cultivation as an experimental system

Investigations into the dynamic nature of composting environments are necessary to understand and ultimately optimise the complex processes that occur. In this study, various parameters were measured to investigate physical, chemical and biological changes that occur in compost during the production of Agaricus bisporus. In addition to monitoring the compost samples during mushroom cultivation, uninoculated samples were maintained for comparative purposes. Principal components analysis of the variables measured showed a clear distinction between the thermophilic Phase I composts, uninoculated Phase II composts and mushroom inoculated composts. Leucine assimilation, a novel technique to composting environments, is presented as suitable method for assessing microbial activity in such systems. Strict agreement between leucine assimilation and fluorescein diacetate (FDA) hydrolysis, a rarely used technique in composting environments, was not observed, suggesting that neither should be used as a sole measure of microbial activity in compost. Association of FDA hydrolysis with the culturable heterotrophic count suggests that FDA hydrolysis may indicate bacterial as opposed to total microbial activity.     

Bioreclamation of chlorophenol-contaminated soil by composting

Summary Microbiological decontamination of technical chlorophenol-containing soil by composting was studied. In two 50 m³ windrows the concentration of chlorophenols went down from 212 mg kg^-1 to 30 mg kg^-1 in 4 summer months and after the second summer of composting it was only 15 mg kg^-1. All chlorophenol congeners present in the technical chlorophenol were degraded, but the main dimeric impurities, polychlorinated phenoxyphenols were recalcitrant. The contaminated soil was found to contain chlorophenol-degrading microbes, 5x10⁶ cfu g^-1 of dry windrow soil. Laboratory experiments with samples from the windrow compost showed that chlorophenols were truly degraded and that chlorophenol loss by evaporation was less than 1.5% under the circumstances studied. Laboratory experiments also showed that degradation of chlorophenols (120 mg kg^-1) was accelerated when sterilized contaminated soil was inoculated with Rhodococcus chlorophenolicus (mineralizer of several chlorophenols) or naturally occurring microbes of the field composts. Biomethylation of chlorophenols in the composts was insignificant compared to biodegradation.     

Effect of chitin waste-based composts produced by two-phase composting on two oomycete plant pathogens

Biphasic composts were prepared by first mixing peat moss and sawdust with a nitrogen-rich biomass such as chitinous waste or cow manure and composting them until termination of the thermophilic phase. These partially stabilized composts were then amended with shrimp waste inducing a second thermophilic phase. Filter-sterilized water extracts obtained from two mature biphasic composts (SP₂W₂+S and MPW+S) reduced the growth of two oomycete plant pathogens, Phytophthora fragariae var. rubi and Pythium ultimum. Both SP₂W₂+S and MPW+S composts significantly reduce the incidence of cucumber damping-off caused by Pythium ultimum as compared to a commercial brand of compost made from shrimp waste and peat moss. Hydrolysis products of chitin were unlikely to be responsible for growth inhibition since no oligomeric forms of chitin were detected in SP₂W₂+S. The shrimp waste amendment carried out after the first thermophilic phase modified the microbial populations of biphasic composts. Following the amendment, the proportion of branched-chain microbial fatty acids typical of Gram-positive bacteria increased considerably suggesting that this group of bacteria became more prevalent within the total microbial population. These data suggests that the two-phase composting process promotes the proliferation of Gram-positive bacteria antagonistic to oomycete plant pathogens.     

Changes in physical,chemical and microbial parameters during the composting of municipal sewage sludge

Changes in physical, chemical and microbial parameters were investigated during the composting of municipal sewage sludge. Raw sewage sludge (30% dry matter) was mixed with compost from sewage sludge (85% dry matter) in 3:1 ratio (v/v). The mixture was divided into 4 windrows which were composted under the same conditions except the turning factor. The turning was every 7, 10, 15 days and according to the temperature which must be (55–65°C) for windrow 1 (W1), windrow 2 (W2), windrow 3 (W3) and windrow 4 (W4), respectively. Water was added to adjust the moisture content (40–60%). The composting process consisted of 2 periods; fermentation (12 weeks) and maturation (4 weeks). The results showed that the temperature reached the maximum after 12 weeks for W1 and 11 weeks for W2, W3 and W4 and then decreased. The final compost was nearly odourless and black, especially in case of W4. The general trend indicates a decrease in organic matter, organic carbon and nitrogen (N), whereas ash, potassium (K) and phosphorus (P) increased and consequently C/K and C/P ratios decreased. There was a slight increase in C/N ratio. The pH increased and then decreased to near neutrality at the end. The mesophilic bacteria increased during the fermentation period and decreased after that, whereas the thermophilic ones increased with increasing of temperature, decreased after 2 weeks and increased again during the fermentation period and then decreased. The mesophilic and thermophilic fungi were present during the first week and disappeared after that. The final compost was pathogens-free as indicated by the counts of coliforms and Salmonella.     

A review of composting as a management alternative for beef cattle feedlot manure in southern Alberta, Canada

Composting is gaining increased acceptance as a management alternative for the large volumes of manure produced by southern Alberta's beef cattle feedlots. Research on windrow composting of feedlot manure was initiated at the Lethbridge Research Centre of Agriculture and Agri-Food Canada in 1996. Early studies looked at physical and chemical changes during composting. Studies have also been conducted on greenhouse gas emissions during composting and the effect of composting on reduction of pathogens, parasites and weed seed viability. The quality of commercially-produced composts at southern Alberta feedlots has been examined as has the mineralization rates of soil-applied composts. This paper reviews results from our feedlot manure composting research program.     

Assessment of survival of Listeria monocytogenes,Salmonella Infantis and Enterococcus faecalis artificially inoculated into experimental waste or compost

Aims: To evaluate survival of pathogenic strains, Listeria monocytogenes and Salmonella Infantis and a sanitation indicator Enterococcus faecalis in composts at different stages of the composting process and during storage. Methods and Results: The studied pathogenic and indicator strains, originally isolated from compost, were inoculated into compost samples from the various stages of the composting process. During incubation, indigenous microflora diversity was monitored with DGGE analysis. After 90 days of incubation, strain survival was observed in compost sampled before the beginning of the cooling phase, and DGGE analysis demonstrated an increase of microbial diversity up to the cooling phase. However, inoculated strains were not detected in composts after 30, 60 or 90 days of incubation in compost sampled after the start of the cooling phase. Microbial diversity also became stable, and DGGE profiles reached a maximum number of bands at this stage. Conclusions: Strain survival was not observed in stabilized composts. The cooling phase seems to be the turning point for pathogen survival and at this stage the indigenous microflora appeared to play a significant role in suppression. Significance and Impact of the Study: The importance of indigenous microflora in the survival of pathogens in four different composts was demonstrated. Stabilized composts were recommended for spreading on land.     

Comparison of characterization and microbial communities in rice straw- and wheat straw-based compost for <Emphasis Type="Italic">Agaricus bisporus</Emphasis> production

Rice straw (RS) is an important raw material for the preparation of Agaricus bisporus compost in China. In this study, the characterization of composting process from RS and wheat straw (WS) was compared for mushroom production. The results showed that the temperature in RS compost increased rapidly compared with WS compost, and the carbon (C)/nitrogen (N) ratio decreased quickly. The microbial changes during the Phase I and Phase II composting process were monitored using denaturing gradient gel electrophoresis (DGGE) and phospholipid fatty acid (PLFA) analysis. Bacteria were the dominant species during the process of composting and the bacterial community structure dramatically changed during heap composting according to the DGGE results. The bacterial community diversity of RS compost was abundant compared with WS compost at stages 4–5, but no distinct difference was observed after the controlled tunnel Phase II process. The total amount of PLFAs of RS compost, as an indicator of microbial biomass, was higher than that of WS. Clustering by DGGE and principal component analysis of the PLFA compositions revealed that there were differences in both the microbial population and community structure between RS- and WS-based composts. Our data indicated that composting of RS resulted in improved degradation and assimilation of breakdown products by A. bisporus, and suggested that the RS compost was effective for sustaining A. bisporus mushroom growth as well as conventional WS compost.     

Organic matter transformations and kinetics during sewage sludge composting in a two-stage system

The use of different proportions of rape straw and grass as amendments in the composting of dewatered sewage sludge from a municipal wastewater treatment plant was tested in a two-stage system (first stage, an aerated bioreactor and second stage, a periodically turned windrow). The composition of feedstock affected the temperature and organic matter degradation in the bioreactor and the formation of humic substances, especially humic acids (HA), during compost maturation in the windrow. The total HA content (the sum of labile and stable HA) increased according to first-order kinetics, whereas labile HA content was constant and did not exceed 12% of total HA. Δlog K of 1.0–1.1 indicated that HA was of R-type, indicating a low degree of humification. Temperature during composting was the main factor affecting polymerization of fulvic acids to HA and confirmed the value of the degree of polymerization, which increased only when thermophilic conditions were obtained.     

双孢蘑菇堆肥中真菌群落多样性分析

以农作物玉米秸和稻草、牛粪为原料,分别设计双孢蘑菇Agaricus bisporus堆肥配方并进行堆肥发酵,研究二者堆肥过程中真菌多样性。在建堆、一次发酵结束和二次发酵结束3个时期分别采集堆肥样品,提取总DNA,以真菌18S rDNA基因通用引物,进行PCR-DGGE扩增和序列分析。累计获得39条特异条带18S rDNA基因信息,分属于真菌14个属、藻类7个属和原生动物3个属。子囊菌是两种配方堆肥过程中的优势菌群,建堆时期的优势类群为Pichia和Wickerhamomyces,一次和二次发酵时期的优势类群为Chaetomium和Lecythophora。多样性指数分析显示,稻草配方微生物多样性大于玉米秸配方;主成分分析（PCA）显示,玉米秸配方一次发酵结束时期与稻草和玉米二次发酵结束时期聚为一类,说明玉米秸配方堆肥提前腐熟。     

Ash in composting of source-separated catering waste

Our earlier experiments in small composters (220 l) indicated the favourable effect of ash from co-incineration of sorted dry waste on the composting of catering waste. The aim of this new study was to clarify further, at a scale of 10 m3, the feasibility of using similar ash as an additive in composting. Source-separated catering waste was mixed with bulking agent (peat and wood chips) and fuel ash from a small (4 MW) district heating power plant. Three compost mixes (CM) were obtained: CM I with 0%, CM II with 10% and CM III with 20 wt.% of fuel ash. These three different mixes were composted in a 10-m3 drum composter as three parallel experiments for 2 weeks each, from January to April 2000. After drum composting, masses were placed according to mixing proportions in separate curing piles. The catering waste fed to the drum was cold, sometimes icy. Even then the temperature rapidly increased to over 50 degrees C. In CM III, the temperature rose as high as 80 degrees C, and after the first week of composting the temperature was about 20 degrees C higher in the CMs II and III than in the CM I. It also improved the oxygen concentrations at the feeding end of the drum and obviously prevented the formation of H2S. No odour problems arose during the composting. Addition of ash increased the heavy metal contents of the composting masses, but the compost was suitable for cultivation or green area construction. Ash clearly decreased the loss of total nitrogen in a time span of 2 years. The lower amounts of nitrogen mean that the amounts applied per hectare can be greater than for normal composts. Measured by mineralization, the breaking down of the organic matter was more rapid in the CM III than in the CM I. Humic acid increased steadily during first 12 months composting, from the initial 39 mg/g organic matter to 115 and 137 mg/g in CMs II and III. Measured by temperature, mineralization and humification the addition of ash appeared to boost the composting. Ash had also other beneficial effects on composting it improved the availability of oxygen in compost mass during the drum composting phase and reduced the formation of odorous gases, especially H2S.     

An investigation of the biodiversity of thermophilic and thermotolerant fungal species in composts using culture-based and molecular techniques

In this study, the biodiversity of thermophilous fungi in two different commercial composts was investigated using culture-based methods, denaturing gradient gel electrophoresis (DGGE) and tag-encoded pyrosequencing. 454 pyrosequencing of the internal transcribed spacer (ITS) region recovered a total of 175 OTUs between the two composts. The Ascomycota was the dominant phylum in both composts (90 % of all sequences recovered) with the thermophilic-rich orders Sordariales and Eurotiales being the most numerous. Molecular studies demonstrated the frequent presence of several thermophilic (Scytalidium thermophilum, Myriococcum thermophilum) and thermotolerant (Pseudallescheria boydii, Corynascus verrucosus and Coprinopsis sp.) fungi in the composts, despite the absence of these species from the culture-based analysis. Conversely, Aspergillus fumigatus and Mycocladus corymbifer, which were the dominant species in cultivation analyses, had very low representation in molecular studies. The results show that the previous picture of the dominant thermophilous fungi in compost communities derived from culture-based analysis has been biased, and that composting environments represent a potentially rich resource of novel fungi.     

Evaluation of composting as a strategy for managing organic wastes from a municipal market in Nicaragua

A pilot-scale study was undertaken to evaluate alternatives to the solid waste management of a Central American municipal market located in Estelí, Nicaragua. The municipal solid waste from the local market is the second largest contributor to the municipal solid waste (MSW) stream. Waste from the market without any previous sorting or treatment is open dumped. The options evaluated in this study were windrow composting, windrow composting with yard waste, bokashi and vermicompost. Significant differences between the properties of composts produced were found; however, all of them reduce the initial waste volume and are potential useful agronomic products for a survival agrarian milieu.     

Humic substances change during the co-composting process of municipal solid wastes and sewage sludge

The change of the degree of stability of compost during the composting process was a kind of guideline for our study. This stability was estimated by monitoring the chemical fractionation (extraction of humic and fulvic acids, and humin) during two cycles of composting. Change of humin (H), humic-like acid carbon (CHA) and fulvic-like acid carbon (CFA) fractions during the composting process of municipal solid wastes were investigated using two windrows W1 (100% of municipal solid wastes) and W2 (60% of municipal solid wastes and 40% of dried sewage sludge). Humin and fulvic acid fractions in the two windrows decreased since the start of composting process and tend to stabilize. At the end of composting process, humic acid fraction is more important in the windrow without sludge (W1) than the one with sludge (W2). The humification indexes used in this study showed that the humic-like acid carbon fraction production takes place largely during the phase of temperature increase (thermophilic phase), and it appeared very active in the windrow W2. At the end of composting process, the E₄/E₆ ratio value indicated that the compost of W1 is more mature than the compost of W2. The humification ratio (HR) allowed a correct estimation of compost organic matter stabilization level.     

Changes in Bacterial and Fungal Communities across Compost Recipes,Preparation Methods,and Composting Times

Compost production is a critical component of organic waste handling, and compost applications to soil are increasingly important to crop production. However, we know surprisingly little about the microbial communities involved in the composting process and the factors shaping compost microbial dynamics. Here, we used high-throughput sequencing approaches to assess the diversity and composition of both bacterial and fungal communities in compost produced at a commercial-scale. Bacterial and fungal communities responded to both compost recipe and composting method. Specifically, bacterial communities in manure and hay recipes contained greater relative abundances of Firmicutes than hardwood recipes with hay recipes containing relatively more Actinobacteria and Gemmatimonadetes. In contrast, hardwood recipes contained a large relative abundance of Acidobacteria and Chloroflexi. Fungal communities of compost from a mixture of dairy manure and silage-based bedding were distinguished by a greater relative abundance of Pezizomycetes and Microascales. Hay recipes uniquely contained abundant Epicoccum, Thermomyces, Eurotium, Arthrobotrys, and Myriococcum. Hardwood recipes contained relatively abundant Sordariomycetes. Holding recipe constant, there were significantly different bacterial and fungal communities when the composting process was managed by windrow, aerated static pile, or vermicompost. Temporal dynamics of the composting process followed known patterns of degradative succession in herbivore manure. The initial community was dominated by Phycomycetes, followed by Ascomycota and finally Basidiomycota. Zygomycota were associated more with manure-silage and hay than hardwood composts. Most commercial composters focus on the thermophilic phase as an economic means to insure sanitation of compost from pathogens. However, the community succeeding the thermophilic phase begs further investigation to determine how the microbial dynamics observed here can be best managed to generate compost with the desired properties.     

Co-composting of oil exhausted olive-cake, poultry manure and industrial residues of agro-food activity for soil amendment

The co-composting of exhausted olive-cake with poultry manure and sesame shells was investigated. These organic solid wastes were watered by the confectionary wastewater which is characterized by its high content of residual sugars raising its COD. Four aerated windrows were performed to establish the effects of confectionary by-products on the compost process. Different mixtures of the agro-industrial wastes were used. During the composting process, physico-chemical parameters (temperature, moisture, pH, electrical conductivity, total carbon and total nitrogen) were studied. The stability of the biological system was noticed after 70 days. The final products were characterized by their relatively high organic matter content, and low C/N ratio of 14-17. The humidification of the windrows with the wastewater seemed to have accelerated the composting process in comparison to a windrow humidified with water. In addition, the organic matter degradation was enhanced to reach 55-70%. The application of the obtained composts to soil appeared to significantly improve the soil fertility. Indeed, field experiments showed an increase in potato yield; the production was 30.5-37.5 tons ha(-1), compared to 30.5 tons ha(-1) with farm manure.     

Composting of straw in small units

Summary Straw could be composted satisfactorily in 4 to 5 months in small concrete cells holding 30 lb. material (dry basis), providing the straw was thoroughly moistened and sufficient easily available nitrogeneous material added to give an initial carbon/nitrogen ratio of 40. During the composting process about half the dry matter was lost. Results were similar to those obtained using large cells holding 1500 lb. straw. Wire units holding 100 lb. straw were unsatisfactory. Changes in dry matter, carbon/nitrogen ratio, temperature, soluble inorganic nitrogen, and pH of composts prepared with various accelerators are reported.     

Analysis of thermophilic fungal populations during phase II of composting for the cultivation of Agaricus subrufescens

The composition and genetic diversity of fungal populations during phase II of compost production for the cultivation of Agaricus subrufescens was determined using culture-dependent and -independent methods on days 3, 6, 10, 12, and 14 of phase II composting. The isolates were morphologically characterized and subsequently analyzed using repetitive extragenic palindromic sequences (rep-PCR), and the intergenic region was sequenced to genetically identify the isolates. Changes on in the filamentous fungi population were analyzed using denaturing gradient gel electrophoresis (DGGE), and the resulting bands were sequenced. The population did not significantly change from day 3 to 10 (2.55 x 10⁵ –6 x 10⁵ CFU g^?1), and maximum counts on day 14 of phase II composting (6.92 log CFU g^?1). In the morphological characterization, Scytalidium thermophilum, Thermomyces lanuginosus, and Thermomyces ibadanensis were the most abundant identified species. The 26 most abundant isolates identified by morphological analysis were characterized using rep-PCR. A significant amount of genetic diversity was detected among the isolates of all three studied species. Based on the DGGE analysis, the diversity of the fungi was reduced during phase II composting, and S. thermophilum was the predominant species identified throughout the entire process. Thus, this study presents the first report of the involvement of T. ibadanensis in the production of compost for Agaricus mushroom cultivation.     

Characters of aerated compost tea from immature compost that limit colonization of bean leaflets by Botrytis cinerea

Aims: The aim was to produce and characterize an aerated compost tea (ACT) that suppressed growth of the plant pathogen Botrytis cinerea. Methods and Results: Three different open‐windrow composts were sampled weekly from the early secondary mesophilic stage until maturity. Each 10 kg of compost sample was extracted in 30 l of aerated water for 24, 48 or 72 h. Relative to water, all batches of ACT applied to detached bean leaflets reduced lesion development following single‐point inoculations of B. cinerea. There was a significant linear, inverse relationship between the internal windrow temperature of compost (≤51°C) used to prepare ACT and the extent of lesion development. Bacterial diversity in ACTs from one windrow was highest using compost sampled at 48°C. The compost weight‐to‐water volume ratios of 1 : 3, 1 : 10 or 1 : 30, using compost sampled from a fourth windrow at 50°C, also produced ACTs that reduced the growth of B. cinerea on bean leaflets. The ‘1 : 3’ ACT, and to a lesser degree the same ACT filtered to remove micro‐organisms, inhibited the germination of B. cinerea conidia. Conclusions: ACT produced using the methods reported here suppressed the growth of B. cinerea on bean leaflets, with an abundant and diverse microbial community likely to contribute to pathogen suppression. Significance and Impact of the Study: This is the first report of the use of immature compost to produce a pathogen‐suppressive ACT, suggesting that compost stage is an important production variable.     

Do earthworms affect dynamics of functional response and genetic structure of microbial community in a lab-scale composting system?

Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH(4)(+)-N and ash content) showed similar evolution in both systems except a higher NH(4)(+)-N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.