Original Compost Research Articles

Biofuels from Pyrolysis of Third-Generation Biomass from Household and Garden Waste Composting Bin: Kinetics Analysis

The modern society produces large amounts of household waste with high organic matter content. The vermicomposting of household waste produces high-value humic substances and is a way to stabilize organic material for later use as raw material (3rd generation biomass) for bioenergy proposes. A 6-month matured compost, combining vegetable and fruit scraps from domestic trash and grass and shrub clippings from yard waste, was evaluated to assess its potential as a raw material in pyrolysis processes. The pyrolysis activation energy (Kissinger) of the composted material showed values in the range of 200–300 kJ/mol, thus confirming its suitability for pyrolysis processes with promising H2 yields. The treatment of the composted material with H2SO4 and NaOH solution (boiling; 1 mol/L) led to the production of solid residues that present higher pyrolysis activation energies, reaching 550 kJ/mol for the most resilient fraction, which makes them suitable to produce carbonaceous materials (biochar) that will have incorporated the inorganics existing in the original compost (ashes 37.6%). The high content of inorganics would play a chief role during pyrolysis since they act as gasification promoters.

THE ROLE OF SOIL MICROBIOCENOSIS IN THE COMPOSTING OF THE ORGANIC COMPONENT OF THE MUNICIPAL SOLID WASTE

In order to increase the efficiency of composting the organic component of solid municipal waste as a highly effective biotechnological method, and to compare the characteristics of the processes, it is suggested to use soil as an inoculum, as a microbiological additive - an extract from the soil. The original compost mixture is a multicomponent system, the decomposition and transformation of which depends on the functioning of a microorganisms complex, in particular, fungal and bacterial microflora. Since the main component of the organic fraction is cellulose, it is expedient, along with the definition of the total number of the microflora bacterial and fungal components, to determine the number of cellulose-decomposing microorganisms. An estimation of the change in the compost mixtures’ microbial population has been made, which shows that bacteria dominate over fungi in compost mixtures. A similar microbial complex is observed in soils. The article presents the results of the study of the soil microbiocenosis qualitative and quantitative composition in order to use it as an inoculum in the process of composting the organic part of solid municipal waste. The influence of microbiological additive on the process of the organic waste composting for acceleration in mesophilic and thermophilic temperature regimes with controlled parameters was studied. The results of the conducted studies allow us to conclude that the organic waste composting with the microbiological additive is appropriate, both in the case of thermophilic and in the case of mesophilic regimes. The period of the compost maturation with the use of a microbiological additive is 6 weeks. It was shown that the microbiological complex accelerates the process of composting the organic component of solid municipal waste by 3.3 times for the thermophilic regime and by 2.1 times for the mesophilic conditions of composting process, which testifies to the efficiency of its use in the operation of the solid municipal waste processing in order to improve the general level of environmental safety.

Invertebrates Associated With a Horizontal-Flow, Subsurface Constructed Wetland in a Northern Climate

Wetlands function as buffers between terrestrial and aquatic ecosystems, filtering pollutants generated by human activity. Constructed wetlands were developed to mimic the physical and biological filtering functions of natural systems for the treatment of human and animal waste under controlled conditions. Previous studies on the effect of constructed wetlands on native invertebrate populations have concentrated almost exclusively on mosquitoes. Here, we present the first study investigating the relationship between vegetation cover and aeration regime, and the diversity and abundance of nematodes and springtails (Collembola) in a constructed wetland designed to treat dairy farm wastewater in northwestern Vermont. We investigated four treatment cells differing in aeration regime and vegetation cover, but equally overlaid by a layer of compost to provide insulation. Analysis showed that nematodes were most abundant in the nonplanted and nonaerated cells, and that bacterivorous nematodes dominated the community in all cells. Springtails were found to be most numerous in the planted and nonaerated cells. We hypothesize that the vegetation provided differing environmental niches that supported a more diverse system of bacteria and fungi, as well as offering protection from predators and inclement weather. Nematodes were likely imported with the original compost material, while springtails migrated into the cells either via air, water, or direct locomotion.

Short-term structure and functional changes in bacterial community composition following amendment with biosolids compost

Amendment of organic wastes and composts to soil is a common agricultural practice. The soil microbiota is responsible for the recycling and mineralization of these organic amendments and their activity affects soil structure and agricultural viability. In this study we assessed the short-term effects of compost amendment on bacterial community composition and activity in agricultural soil. Changes in biomass, respiration and enzymatic activity were correlated with bacterial community profiles, as determined by Denaturing Gradient Gel Electrophoresis (DGGE) of PCR-amplified 16S ribosomal RNA (rRNA) gene fragments and sequencing of relevant bands. Prior to wetting, the community profile of the compost amended soils was almost identical to that of the original compost, implying that the compost bacterial content was much higher than that of the soil. Nonetheless, wetting of compost-amended soils caused an immediate shift in the bacterial community profile resulting in a pattern similar to that of the original soil profile. Initially, in the first three days following wetting, the bacterial community profiles of the control and compost-amended soils were highly similar to each other. However, from day five to day 13, significant differences in the bacterial profiles developed between the control and compost-amended soils, indicating that the compost-related effect on the bacterial community is somewhat delayed. Compost-amended soils showed enhanced rates of nitrification, respiration, hydrolytic and metabolic activities relative to the control soils without compost. They were also characterized by proliferation of communities associated with the Bacteroidetes phylum, which may be explained by the involvement of this clade in the degradation of compost-derived complex organic substrates in the soil microcosms.

A novel composting process for plant wastes in Taiwan military barracks

Military barracks throughout Taiwan produce large quantities of organic wastes from gardening, such as leaves, grass and flowers. By manipulating and observing the related parameters of the windrow composting process, the study seeks to find an optimum treatment method for plant wastes. Mature compost was used in small amounts as a fermenting source for each experimental sample. Results show that unpleasant smells that other composting methods produce is significantly decreased with effective control of relationships between temperature, saturation and turnover frequency. Furthermore, the time required to complete composting is shortened to 2–3 months. The fertility of the products depends on the original compost materials and the composting method. Through windrow composting, composted matter can reach a fertility level between that of soil and manure. Additionally, this process greatly reduces waste management costs because it utilizes the barrack's undeveloped area. Experiments in the barracks show that advantages of windrow composting include low facility investment, high environmental-friendliness, easy operation and low failure rate. Thus, it is particularly suitable for military barracks, institutions or schools with large open areas, highly green environments and plenty of labor.

Identification of the infectious source of an unusual outbreak of histoplasmosis, in a hotel in Acapulco, state of Guerrero, Mexico

Three isolates of Histoplasma capsulatum were identified from mice lung, liver, and spleen inoculated with soil samples of the X hotel’s ornamental potted plants that had been fertilized with organic material known as compost. The presence of H. capsulatum in the original compost was detected using the dot-enzyme-linked immunosorbent assay. Nested-PCR, using a specific protein Hcp100 coding gene sequence, confirmed the fungal identification associated with an unusual histoplasmosis outbreak in Acapulco. Although, diversity between the H. capsulatum isolate from the hotel and some clinical isolates from Guerrero (positive controls) was observed using random amplification of polymorphic DNA based-PCR, sequence analyses of H-anti and ole fragment genes revealed a high homology (92–99%) between them.

Spectroscopic Analysis of Sequentially Extracted Humic Acid from Compost

Structural characterization of organic matter (OM) is crucial in assessing its role in soils and sediments. In this study, humic acids (HA) were sequentially extracted from a compost and characterized in terms of their molecular, chemical, and structural heterogeneity. HA was extracted in sequence a total of 28 times, using 0.1 mol L−1 Na4P2O7, and sequentially grouped into seven fractions. These fractions and the original compost were analyzed using UV–visible spectroscopy, 13C nuclear magnetic resonance spectroscopy (NMR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and an elemental analyzer. 13C‐NMR and DRIFTS data indicated significant structural variations among the extracted HA fractions and the original compost. These data corresponded to a decrease in the atomic C/H ratio and to an increase in the atomic C/O ratio among these sequentially extracted HA fractions, which together represented an increase in aliphaticity in conjunction with a decrease in polarity and aromaticity. E4/E6 ratios indicated an increase in molecular size with increasing number of extractions. The structural variability of HA may significantly affect the sorption of organic pollutants and the reduction and complexation of metals by organic matter. This paper was by special invitation as a contribution to a special issue of the journal entitled “Application of Spectroscopic Methods to Environmental Problems.” The special issue was organized by Professor Peter A. Tanner, Professor in the Department of Biology and Chemistry at City University of Hong Kong.

Evaluation of mixture effects in a crude extract of compost using the CALUX bioassay and HPLC fractionation

Potential synergistic interactions between polycyclic aromatic hydrocarbons in a household sewage sludge compost extract were investigated using the Dioxin-Responsive Chemical-Activated Luciferase gene eXpression (DR-CALUX) assay and reverse-phase high-performance liquid chromatography (RP-HPLC) fractionation. The biological activity of the crude extract was measured in vitro using the CALUX assay. The CALUX activity of the extract was as potent as 360-pg CALUX-TEQ (2,3,7,8-TCDD equivalent value) per g sample, this was 70 times above the WHO-TEQ value which was derived from chemical analyses of dioxins/furans and dioxin-like PCBs of the mixture. The CALUX activity pattern of the crude extract and the retention times of 26 polycyclic aromatic compounds (PACs), as determined by RP-HPLC on an octadecylsilica column, suggested that the dioxin-like compounds with the log K OW ( n-octanol/water partition coefficient) values corresponding to 6.0–7.0 contributed highly to the whole activity. The CALUX activity of the crude extract was three times the sum of the CALUX activities of the RP-HPLC separated fractions. Mixture effects were assessed by co-exposure of each HPLC fraction and 2,3,7,8-TCDD to the cells. The four concentration levels of added 2,3,7,8-TCDD corresponded to the TEQ value in the original compost sample. The experimental CALUX activity was higher than the predicted CALUX activity for some fractions. It was demonstrated that some compounds in the compost sample interacted synergistically with 2,3,7,8-TCDD in terms of dioxin-like activity. This finding points out the necessity for detailed investigation of synergistic effects in environmental samples.

Similarity of bacterial communities in sawdust- and straw-amended cow manure composts

We analyzed bacterial communities in two cow manure composts derived from the same feed manure and composted in the same location, but composted with different carbon amendments, and in peat-based potting mixes amended with these composts. Bacterial communities were characterized by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of extracted DNAs, and population fingerprints generated for each sample were compared. Sequence analyses of dominant DGGE bands revealed that members of the phylum Bacteroidetes were the most dominant bacteria detected in this study (19 of 31 clones). These analyses demonstrate that bacterial community profiles of individual composts were highly similar, as were profiles of compost-amended potting mixes. However, potting mix profiles differed substantially from the original compost profiles and from that of the peat base. These data indicate that highly similar bacterial populations were active in the two composts, and suggest that the effects of the initial carbon amendment on the mature compost bacterial communities were minor, while factors such as the feed manure and composting location may have been more influential.

Changes in microbial and soil properties following compost treatment of degraded temperate forest soils

The long-term effect of compost treatment on soil microbial respiration, microbial biomass carbon (C mic) and biomass nitrogen (N mic), soil organic carbon (SOC), and soil total nitrogen (STN) was studied in six degraded forests, Lower Saxony, Germany. The study was conducted in mature beech ( Fagus sylvatica L.), pine ( Pinus sylvestris L.) and spruce ( Picea abies Karst.) forests on silty soils at Solling and on sandy soils at Unterlüß. Mature compost from separately collected organic household waste was applied for soil amelioration at an amount of 6.3 kg m −2 on the soil surface. After 2 years, soil samples were taken from the control and compost plots and were separated into >2 and <2 mm fractions of the O-horizon and into mineral soil intervals from 0–5, 5–10, and 10–20 cm depths. The original compost had a pH of 7.5, high inorganic salt content, low organic C content, narrow C-to-N ratio, and low microbial activity and biomass. Compost significantly reduced the microbial respiration per mass unit in the O-horizons >2 mm by 17% and in the O-horizons <2 mm by 25%. C mic and N mic decreased significantly by 22 and 23% in the O-horizons <2 mm and by 35 and 28% in the O-horizons >2 mm, respectively. Our estimates suggest that the reduction in microbial respiration and biomass in the O-horizons resulted partly from the mixture of compost and the O-horizons. The average loss of 1.2 kg m −2 organic matter may have also contributed to the reduction in microbial biomass and respiration in the O-horizons of the compost plots. However, it is not clear whether the decomposition of the original organic matter in the O-horizons was increased by the compost application. In the mineral soils, the compost treatment caused significant increases in microbial respiration, C mic and N mic by 14–21% at 0–5 cm and by 14–23% at 10–20 cm depth. Although not significant, a similar trend was found for the 5–10 cm depth. Increased release of nutrients and dissolved organic matter (DOM) could have promoted microbial growth and activity in the mineral soils. The significant increase in STN and the narrowing C-to-N ratio indicate that the investigated forest soils were not N-saturated. This field study suggests that superficial application of compost from separately collected organic household waste increase microbial activity and biomass in the mineral soil by release of nutrients from the O-horizon to the mineral soil.

Carbohydrates as Chemical Constituents of Biowaste Composts and their Humic and Fulvic Acids

he decomposition of organic matter of source-separated biowaste during composting was followed during 18 months. Compost samples were fractionated into three parts: (i) hot water soluble extract (HWE) (ii) bitumen fraction and (iii) humic substances (humic acids (HA) and fulvic acids (FA)). Original compost samples and the HA and FA fractions were hydrolyzed with sulfuric acid for hexoses and pentoses. Quantitative spectrophotometric and qualitative GC/MS analyses of monosaccharides as trimethylsilyl ethers of the corresponding alditols were carried out.During composting, the amount of HA in the organic matter of the compost increased, the amounts of HWE and bitumen decreased and the amount of the FA fraction changed only a little. Carbohydrates were found to be important constituents of biowaste composts and their HA and FA fractions. Elemental analysis (C, N and H) of compost and HA samples showed an increase in the C:H ratio and in unsaturation of compounds during composting. The decrease in the C:N ratio was marginal.The amounts of hexoses and pentoses in original compost samples and the HA and FA fractions decreased during composting. The sugar alcohols erythritol, xylitol, L-arabitol, ribitol, L-rhamnitol, L-fucitol, D-mannitol, D-glucitol and galactitol were identified in both the HA and FA fractions. 2-Deoxy-D-erythro-pentitol was identified in one HA fraction and inositol in two FA fractions. An analysis of gas chromatographic data for relative abundances showed that, in every sample except one and in every stage of composting D-glucitol was the main sugar alcohol. In general, the relative amount of D-glucitol decreased during composting, while the relative amounts of all other sugar alcohols increased.As chemical indicators of compost maturity, carbohydrates would appear to be a important group of compounds. Most informative as a general indicator would be the ratio of the amount of HA to the amount of organic matter in the total compost samples.According to our studies, the carbohydrates in composts are covalently bound to the structures of FA and HA. Carbohydrate determination clearly deserves more attention in the structural elucidation of FA and HA.

Leaching From Land Disposed Municipal Compost: 4. Heavy Metals

The leachates from 17 lysimeters containing composts of varying origin, age (3 and 12 months), and packing depths (15-50 cm) were monitored for a 2.5-year period. This paper reports on the results on heavy metals. The initial leachate concentrations exceeded the drinking water standards for all heavy metals studied (Cd, Ni, Co, Zn, Cu, Pb, Cr), but after one and half year of leaching (c.450 mm leachate) only Ni exceeded the standard. Ni was identified as the most serious heavy metal pollutant but was considered less critical than nitrogen compounds and organic matter previously reported in the leachate, The heavy metal leaching is only moderately affected by compost origin, compost age and packing depth. The first year of leaching released between 0.1% (Pb, Cr) and 1.9% (Ni) of the original compost heavy metal content.

Leaching from land disposed municipal compost: 4. Heavy metals

The leachates from 17 lysimeters containing composts of varying origin, age (3 and 12 months), and packing depths (15–50 cm) were monitored for a 2.5-year period. This paper reports on the results on heavy metals. The initial leachate concentrations exceeded the drinking water standards for all heavy metals studied (Cd, Ni, Co, Zn, Cu, Pb, Cr), but after one and half year of leaching (c.450 mm leachate) only Ni exceeded the standard. Ni was identified as the most serious heavy metal pollutant but was considered less critical than nitrogen compounds and organic matter previously reported in the leachate. The heavy metal leaching is only moderately affected by compost origin, compost age and packing depth. The first year of leaching released between 0.1% (Pb, Cr) and 1.9% (Ni) of the original compost heavy metal content.