Effect of volumetric water content on thermal properties of dairy cattle feces mixed with sawdust

This paper describes the thermal properties (effective thermal conductivity and thermal diffusivity) of an organic waste used to model the composting process in relation to volumetric water content at 20°C. The organic waste was a mixture of fresh dairy cattle feces and sawdust with a ratio of one-to-one on a dry weight basis. The thermal probe method was used to determine the effective thermal conductivity and diffusivity. The effective thermal conductivities were found to increase with volumetric water content, and ranged from 0.0500 to 0.202 W m⁻¹ K⁻¹ at volumetric water contents of 0% and 44.2%, respectively. The thermal diffusivity was not affected by the volumetric water content, and was found to have a mean value of 1.08 × 10⁻⁷ m² s⁻¹.     

Composting of pulp and paper mill fly ash with wastewater treatment sludge

Wastewater treatment sludge and power boiler fly ash were combined and composted in mixed and static windrows 50 m long, 4 m high and 6 m wide. Moisture content was maintained above 50%. The final compost had a pH of 8.5, contained high concentrations of specific nutrients, and an average C:N ratio of 43:1. All metal, PCB, chlorophenol and PAH concentrations were below levels stipulated by local regulations. Over the first 8 weeks of the composting period dioxin concentration decreased by 45% to 41 pg/g TEQ. Leachate tests indicated minimal (<0.1 mg/l Cu and Pb; <50 mg/l Na, P, and SO₄⁻²) leaching of contaminants from the composted material. Application of compost (8 cubic yards/acre) at a sod farm improved soil characteristics as measured by a number of parameters. The dioxin concentration in the final soil/compost mixture was 3 pg/g TEQ, allowing the soil/compost mixture to be classified as agricultural soil. It was concluded that composting produced an acceptable soil conditioner attractive for large volume users of inexpensive soil material (sod farms, golf courses, land reclamation sites).     

Nitrogen amendment of green waste impacts microbial community,enzyme secretion and potential for lignocellulose decomposition

Microorganisms involved in biomass deconstruction are an important resource for organic waste recycling and enzymes for lignocellulose bioconversion. The goals of this study were to examine the impact of nitrogen amendment on microbial community restructuring, secretion of xylanases and endoglucanases, and potential for biomass deconstruction. Communities were cultivated aerobically at 55 °C on green waste (GW) amended with varying levels of NH₄Cl. Bacterial and fungal communities were determined using 16S rRNA and ITS region gene sequencing and PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was applied to predict relative abundance of genes involved in lignocellulose hydrolysis. Nitrogen amendment significantly increased secretion of xylanases and endoglucanases, and microbial activity; enzyme activities and cumulative respiration were greatest when nitrogen level in GW was between 4.13–4.56 wt% (g/g), but decreased with higher nitrogen levels. The microbial community shifted to one with increasing potential to decompose complex polymers as nitrogen increased with peak potential occurring between 3.79–4.45 wt% (g/g) nitrogen amendment. The results will aid in informing the management of nitrogen level to foster microbial communities capable of secreting enzymes that hydrolyze recalcitrant polymers in lignocellulose and yield rapid decomposition of green waste.     

The air spora close to a compost facility in Northeast Oklahoma: Part I—spore trap sampling

A compost facility in northeast Oklahoma is located relatively close to a residential area and is the focus of complaints about smell and concerns about health effects. Several species of Aspergillus have been known to cause health problems, and at least one of these species is dominant in compost. The atmosphere surrounding the compost facility was monitored for 1 year using Burkard spore traps to determine if there was a significant difference in Penicillium/Aspergillus type spores concentration between a test and control site. Samplers were situated 710 m downwind for the test site and 6,085 m upwind at the control site. There was no significant difference in mean concentration of Penicillium/Aspergillus type spores between the two sites (t = 0.576 P > 0.05). The mean concentration of total spores was significantly higher at the upwind control site (t = −7.64, P < 0.01). Wind direction was examined to determine if the compost facility was a possible source for any spikes in concentration. No clear relationship was found between wind direction and mean Penicillium/Aspergillus concentration at the test site, but peak concentrations of Penicillium/Aspergillus seen at the test site were on days when it was downwind from the composting facility. However, these concentrations were no higher than those seen at the control site on other days. If the compost was releasing large amounts of Penicillium/Aspergillus type spores into the atmosphere they were generally diluted to background levels by the time they reached the test site.     

Bacterial community diversity assessment in municipal solid waste compost amended soil using DGGE and ARISA fingerprinting methods

Bacterial community structure and diversity of Tunisian agricultural soil treated with different amounts of municipal solid waste compost (MSWC) and other fertilizers were studied using DGGE and ARISA fingerprinting methods. Sequence analysis of dominant DGGE bands revealed the presence of three major clusters, Cytophaga/Flexibacter/Bacteroides (CFB) group, Proteobacteria and Acidobacteria group. Using ARISA profiles, dominant populations were assigned to low and high GC Gram positive bacteria, Cyanobacteria, Spirochetes and Cytophagales. The two methods revealed the absence of significant bacterial community shifts related to the different MSWC applications. Moreover, indigenous bacterial population of the used loam-clayey soil was observed to limit proliferation and survival of Proteobacteria, initially dominant in MSWC and farmyard manure. Effectiveness of the two methods for soil bacterial community studying was shown. While DGGE was more accurate for bacterial identification, ARISA was more practical for handling and rapid estimation of dominant bacteria.     

Coal fly ash and lime addition enhances the rate and efficiency of decomposition of food waste during composting

To evaluate the use of coal fly ash (CFA) on the decomposition efficiency of food waste, synthetic food waste was mixed with lime at 1.5% and 3% (equivalent to 0.94% and 1.88% CaCO₃, respectively), CFA at 5%, 10% and 15% with lime so as to achieve CaCO₃ equivalent of 1.88% and composted for 42 days in a thermophilic 20 l composter with two replicates each. Alkaline materials at 1.88% CaCO₃ equivalent successfully buffered the pH during the composting and enhanced the decomposition efficiency. When these buffering was achieved with CFA + lime, the composting period could be shortened to ∼28 days compared with ∼42 days in 3% lime. Organic decomposition in terms of CO₂ loss, carbon turnover and nitrogen transformation were significantly higher for treatments with 1.88% CaCO₃ equivalent. Nutrient transformations and compost maturity parameters indicated that addition of CFA (5–10%) with lime at 1.88% CaCO₃ equivalent enhances the decomposition efficiency and shortens the composting period by 35%.     

Sample storage for soil enzyme activity and bacterial community profiles

Storage of samples is often an unavoidable step in environmental data collection, since available analytical capacity seldom permits immediate processing of large sample sets needed for representative data. In microbiological soil studies, sample pretreatments may have a strong influence on measurement results, and thus careful consideration is required in the selection of storage conditions. The aim of this study was to investigate the suitability of prolonged (up to 16 weeks) frozen or air-dried storage for divergent soil materials. The samples selected to this study were mineral soil (clay loam) from an agricultural field, humus from a pine forest and compost from a municipal sewage sludge composting field. The measured microbiological parameters included functional profiling with ten different hydrolysing enzyme activities determined by artificial fluorogenic substrates, and structural profiling with bacterial 16S rDNA community fingerprints by amplicon length heterogeneity analysis (LH-PCR). Storage of samples affected the observed fluorescence intensity of the enzyme assay's fluorophor standards dissolved in soil suspension. The impact was highly dependent on the soil matrix and storage method, making it important to use separate standardisation for each combination of matrix type, storage method and time. Freezing proved to be a better storage method than air-drying for all the matrices and enzyme activities studied. The effect of freezing on the enzyme activities was small (< 20%) in clay loam and forest humus and moderate (generally 20-30%) in compost. The most dramatic decreases (> 50%) in activity were observed in compost after air-drying. The bacterial LH-PCR community fingerprints were unaffected by frozen storage in all matrices. The effect of storage treatments was tested using a new statistical method based on showing similarity rather than difference of results.     

Organic matter fractions by SP-MAS C NMR and microbial communities involved in the suppression of Fusarium wilt in organic growth media

Fusarium wilt is an economically important disease in carnation and tomato plants. The use of suppressive plant growth media has become an alternative method for plant disease control due to the lack of effective chemical control measures. Plant disease suppressiveness is sustained only in plant growth media with an adequate organic matter (OM) composition. Carbohydrate polymers are the most important sources of carbon nutrient for microbial community in these media, mainly consisting of cellulose and hemicellulose. This determines microbial activity, biomass and selects microbial communities in plant growth media, which are reported factors associated with Fusarium wilt suppressiveness.This work determined OM carbon functional groups using Single Pulse Magic Angle Spinning ¹³C-Nuclear Magnetic Resonance (SP-MAS ¹³C-NMR) in three plant growth media with different suppressiveness levels to Fusarium wilt in two crops, carnation and tomato. We propose that the critical role of OM to sustain naturally occurring suppressiveness in those media is not related with cellulose reserve. This could be explained because cellulose protected by lignin encrustation is not available to microbial degradation, meaning that cellulose availability is critical to sustenance of microorganism-mediated biological control. However, the hemicellulose relative abundance (peak 175 ppm) was associated to Fusarium wilt suppression level in plant growth media studied.Carbon source availability in OM was related to microbial biomass and econutritional group population densities involved in biocontrol. For these composts, Bacillus spp., oligotrophic and cellulolytic actinomycetes, and oligotrophic actinomycetes/oligotrophic bacteria and cellulolytic actinomycetes/cellulolytic bacteria ratios were indicated as microbial populations potentially involved in suppression.     

鸡粪堆肥的酶活特性研究

目的研究以鸡粪和菌糠为主体物料在高温堆肥发酵过程中纤维素酶、木聚糖酶、淀粉酶以及蛋白酶酶活性的变化。方法通过测定各酶活动态变化,了解各酶在鸡粪堆肥中的变化规律。其中纤维素酶和淀粉酶采用DNS比色法,木聚糖酶活采用还原糖法,蛋白酶活采用福林法进行测定。结果随温度不断变化和酶本身的性质以及物料的作用机制机制不同,酶活动态变化表现出一定的差异性。物料发酵温度在0～3 d时迅速上升,在3～18 d持续高温期,15 d之后下降趋于恒定。各酶活变化基本上符合先上升至峰值再下降,最后保持恒定的规律。其中各酶发生高效反应的时间具有不一致性,纤维素酶活在第18天时达到峰值,淀粉酶活在第9天时达到峰值,木聚糖酶在第12天时达到峰值,而蛋白酶活在第3天时即达到峰值。结论酶对物料腐熟具有重要用,本研究结果为堆肥腐熟提供参考指标,对优化堆肥工艺具有重要意义。