Urban Organic Waste Research Articles

From agricultural use of sewage sludge to nutrient extraction: A soil science outlook

The composition of municipal wastewater and sewage sludge reflects the use and proliferation of elements and contaminants within society. In Sweden, official statistics show that concentrations of toxic metals in municipal sewage sludge have steadily decreased, by up to 90 %, since the 1970s, due to environmental programmes and statutory limits on metals in sludge and soil. Results from long-term field experiments show that reduced metal pollution during repeated sewage sludge application has reversed negative trends in soil biology. Despite this Swedish success story, organic waste recycling from Swedish towns and cities to arable land is still limited to only about 20 % of the total amount produced. Resistance among industries and consumers to products grown on land treated with sewage sludge may not always be scientifically grounded; however, there are rational obstacles to application of sewage sludge to land based on its inherent properties rather than its content of pollutants. We argue that application of urban organic wastes to soil is an efficient form of recycling for small municipalities, but that organic waste treatment from large cities requires other solutions. The large volumes of sewage sludge collected in towns and cities are not equitably distributed back to arable land because of the following: (i) The high water and low nutrient content in sewage sludge make long-distance transportation too expensive; and (ii) the low plant availability of nutrients in sewage sludge results in small yield increases even after many years of repeated sludge addition. Therefore, nutrient extraction from urban wastes instead of direct organic waste recycling is a possible way forward. The trend for increased combustion of urban wastes will make ash a key waste type in future. Combustion not only concentrates the nutrients in the ash but also leads to metal enrichment; hence, direct application of the ash to land is most often not possible. However, inorganic fertiliser (e.g. mono-ammonium phosphate fertiliser, MAP) can be produced from metal-contaminated sewage sludge ash in a process whereby the metals are removed. We argue that the view on organic waste recycling needs to be diversified in order to improve the urban–rural nutrient cycle, since only recycling urban organic wastes directly is not a viable option to close the urban–rural nutrient cycle. Recovery and recycling of nutrients from organic wastes are a possible solution. When organic waste recycling is complemented by nutrient extraction, some nutrient loops within society can be closed, enabling more sustainable agricultural production in future.

Sustainable Solid Waste Management through Landscaped Landfills

Background/Objectives: The paper looks into an approach to develop landscape solution to landfill sites or an unused land which allows a sustainable disposal option of urban organic waste as well as a sustainable maintenance of land in urban areas. Methods/Statistical Analysis: The paper identifies landfills as specific examples of urban landscapes which can be transformed to landscaped landfills. Such a plan can be formulated only by knowing the quantity and quality of the waste generated the available resources and the environmental conditions of a particular region. This paper looks into an innovative approach where source separated biodegradable waste that is taken to a landfill could be a source for landscape development. Findings: As a result the paper describes a conceptual model for landscaped landfills where it considers two options; one is rehabilitating existing dump sites (due for a clean-up) and another for setting up new sites for disposal. For both these solutions the organic/biodegradable nature of the waste can provide nutrient for plant growth which is an essential element of landscape. However, for a continuous maintenance and management of such sites the model tries to integrate certain existing waste management techniques without overlooking the environmental risks associated. Further, the paper explains the cyclic process of landscaped landfills in three different phases which includes the dumping phase, degradation phase and the planting phase. The paper briefly outlinesthat the extent and intensity these phases are site specific and depends on the quantity and quality of the waste, plant growth period and climate. Application/Improvement: The model describes a strategy and methodology to convert landfills/open dumps or any vacant land into a fitting component of typical urban landscapes through enhancing its environmental significance and visual quality for sustainability.

Applying spent coffee grounds directly to urban agriculture soils greatly reduces plant growth

There are frequent anecdotal recommendations for the use of locally produced spent coffee grounds in urban agriculture and gardens, either through direct soil application or after composting with other urban organic wastes. This study investigates the scientific basis for direct application of spent coffee grounds (SCG) and the influence of different: (i) plant pH and nitrogen preferences, (ii) soil types, and (iii) application rates. We specifically consider impacts upon plant growth, soil hydrology and nitrogen transformation processes.We grew five horticultural plants (broccoli, leek, radish, viola and sunflower) in sandy, sandy clay loam and loam soils, with and without SCG and fertilizer amendments. The same horticultural plants were grown in the field with 0, 2.5, 5, 10 and 25% SCG amendment rates. Plant biomass growth was related to soil pH, soil moisture, nitrogen concentration and net mineralization, as was weed growth after harvesting.All horticultural plants grew poorly in response to SCG, regardless of soil type and fertiliser addition. Increasing SCG amendment significantly increased soil water holding capacity, but also decreased horticultural plant growth and subsequent weed growth. There was evidence of nitrate immobilization with SCG amendment. Growth suppression was not explained by soil pH change, or nitrogen availability, so is more likely due to phytotoxic effects.Fresh SCG should not be used as a soil amendment in ‘closed loop’ urban food production systems without consideration of potential growth suppression. Further research is required to determine the optimal composting conditions for SCG and blends with other organic wastes.

Co-digestion of food and garden waste with mixed sludge from wastewater treatment in continuously stirred tank reactors

Co-digestions of urban organic waste were conducted to investigate the effect of the mixing ratio between sludge, food waste, grass clippings and green waste at different hydraulic retention times (HRTs). Compared to the digestion of 100% sludge, the methane yield increased by 48% and 35%, when co-digesting sludge with food waste, grass clippings and garden waste with a corresponding %VS of 10:67.5:15.75:6.75 (R1) and 10:45:31.5:13.5 (R2), respectively. The methane yield remained constant at around 425 and 385NmL CH4/g VS in R1 and R2, respectively, when the reactors were operated at HRTs of 15, 20 and 30days. However, the methane yield dropped significantly to 356 (R1) and 315 (R2) NmL CH4/g VS when reducing the HRT to 10days, indicating that the process was stressed. Since the methane production rate improved significantly with decreasing HRT, the trade-off between yield and productivity was obtained at 15days HRT.

Design and Economic Evaluation of a Prototype Biogas Plant Fed by Restaurant Food Waste

Food waste and other biodegradable matter in the municipal solid waste stream are a source of environmental and public health concern in cities of developing countries. Anaerobic digestion applied to urban solid organic waste treatment is an option to address those issues and to produce biogas, a renewable energy source. This paper presents the design and economic evaluation of a prototype biogas plant fed by food waste from a restaurant in Mexico City. On average, the restaurant produces 40.5 kg/day of food waste with 23.0% total solids (TS) and 94.2% total volatile solids (TVS). With this amount of food waste, around 69.2 L/day of feeding substrate with 12.7% TVS are produced. Considering an operating temperature of 20°C, total anaerobic digester volume required was calculated at 6.0 m 3 . Plant design comprises a continuous stirred tank reactor (1 m 3 ) coupled with a conventional digester (5 m 3 ). Organic loading rate and hydraulic retention time were 1.9 kg-TVS/(m 3 ∙day) and 86 days, respectively. The plant is expected to produce 6.1 m 3 /day of biogas for use as a cooking fuel at the same restaurant, leading to LP gas savings of 692 kg/year. Plant investment cost was estimated at MXN 129,000 (~9,550 USD). Economic evaluation showed that the biogas plant profitability is highly dependent on LP gas price and its annual growth rate. The prototype biogas plant described here is a step forward in the conception of a biogas facility suitable for cities in developing countries to collaborate in solving their environmental, public health, and energy concerns.

The Multifunctional Environmental Energy Tower: Carbon Footprint and Land Use Analysis of an Integrated Renewable Energy Plant

The Multifunctional Environmental Energy Tower (MEET) is a single, vertical, stand-alone renewable energy plant designed to decrease the primary energy consumption from fossil fuels, to reduce greenhouse gas emissions, to maximize the energy production from renewable sources available in place and to minimize land use. A feasibility case study was performed for the city of Rome, Italy. Several technologies are exploited and integrated in a single system, including a photovoltaic plant, a geothermal plant and a biomass digester for urban organic waste and sewage sludge. In the proposed configuration, the MEET could cover more than 11% of the electric power demand and up to 3% of the space heating demand of the surrounding urban area. An LCA analysis evaluates the environmental impact in a cradle-to-grave approach for two impact categories: global warming (carbon footprint) and land use (land occupation and land transformation). The functional unit is a mix of electric (49.1%) and thermal (50.9%) energy (kWhmix). The carbon footprint is 48.70 g CO2eq/kWhmix; the land transformation is 4.058 m2/GWhmix; and the land occupation is 969.3 m2y/GWhmix. With respect to other energy production technologies, the carbon footprint is lower and similar to the best-performing ones (e.g., co-generation from wood chips); both of the land use indicators are considerably smaller than the least-impacting technologies. A systematic study was finally performed, and possible optimizations of the original design are proposed. Thanks to the modular design, the conceptual idea can be easily applied to other urban and non-urban scenarios.

Analysis of hydrogen production by anaerobic fermentation from urban organic waste

The production of hydrogen by anaerobic fermentation of urban organic waste from fruits and vegetables was studied. Ten tests were carried out under an incomplete factorial experiment design with four factors and three levels. The factors were: acidification pH, acidification time, operational pH, and organic load. The response variables were: maximum hydrogen content (%) and maximum hydrogen production (L/day). The results were fitted to a quadratic polynomial model. In the case of the maximum hydrogen content, an R2 and an R2adjusted of 0.9987 and 0.988 were obtained, respectively. For the maximum production, an R2 and an R2adjusted of 0.9815 and 0.833 were obtained, respectively. Three mathematical techniques were used to obtain the maximum values in the response variables. Fuzzy logic showed the best fit between the experimental values and estimated values. In addition, it predicts a maximum hydrogen content of 58.5% and a maximum production of 63.4 L/day.

The combination of compost addition and arbuscular mycorrhizal inoculation produced positive and synergistic effects on the phytomanagement of a semiarid mine tailing

A field experiment was carried out to assess the effectiveness of combining mycorrhizal inoculation with a native AM fungus (Glomus sp.) and the addition of an urban organic waste compost (OWC) applied at two rates (0.5 and 2.0% (w:w)), with regard to promoting the establishment of Anthyllis cytisoides L. seedlings in a heavy metal polluted mine tailing, as well as stimulating soil microbial functions. The results showed that the combined use of the highest dose of OWC and AM inoculation significantly increased shoot biomass – by 64% – compared to the control value. However, the separate use of each treatment had no effect on the shoot biomass of this shrub species. At the 2% rate, OWC enhanced root colonisation by the introduced fungus as well as soil nutrient content and soil dehydrogenase and ß-glucosidase activities. The combined treatment increased the uptake of Zn and Mn in shoots, although only Zn reached excessive or potentially toxic levels. This study demonstrates that the combination of organic amendment and an AM fungus is a suitable tool for the phytomanagement of degraded mine tailings, although its effectiveness is dependent on the dose of the amendment.

Exploring the immediate and long-term impact on bacterial communities in soil amended with animal and urban organic waste fertilizers using pyrosequencing and screening for horizontal transfer of antibiotic resistance.

We investigated immediate and long-term effects on bacterial populations of soil amended with cattle manure, sewage sludge or municipal solid waste compost in an ongoing agricultural field trial. Soils were sampled in weeks 0, 3, 9 and 29 after fertilizer application. Pseudomonas isolates were enumerated, and the impact on soil bacterial community structure was investigated using 16S rRNA amplicon pyrosequencing. Bacterial community structure at phylum level remained mostly unaffected. Actinobacteria, Proteobacteria and Chloroflexi were the most prevalent phyla significantly responding to sampling time. Seasonal changes seemed to prevail with decreasing bacterial richness in week 9 followed by a significant increase in week 29 (springtime). The Pseudomonas population richness seemed temporarily affected by fertilizer treatments, especially in sludge- and compost-amended soils. To explain these changes, prevalence of antibiotic- and mercury-resistant pseudomonads was investigated. Fertilizer amendment had a transient impact on the resistance profile of the soil community; abundance of resistant isolates decreased with time after fertilizer application, but persistent strains appeared multiresistant, also in unfertilized soil. Finally, the ability of a P. putida strain to take up resistance genes from indigenous soil bacteria by horizontal gene transfer was present only in week 0, indicating a temporary increase in prevalence of transferable antibiotic resistance genes.

Extraction of soluble substances from organic solid municipal waste to increase methane production

This work deals with the analysis of the methane production from Mexico City’s urban organic wastes after separating soluble from suspended substances. Water was used to extract soluble substances under three different water to waste ratios and after three extraction procedures. Methane production was measured at 35°C during 21days using a commercial methane potential testing device. Results indicate that volatile solids extraction increases with dilution rate to a maximum of 40% at 20°C and to 43% at 93°C. The extracts methane production increases with the dilution rate as a result of enhanced dissolved solids extraction. The combined (extract and bagasse) methane production reached, in 6days, 66% of the total methane produced in 21days. The highest methane production rates were measured during the first six days.

Sustainable Urban Horticulture of Sweet Pepper via Vermicomposting in Summer Season

The need for extend the urban horticulture to cover the food security demands, to mitigate CO2 emissions and avoid the extreme heat waves drive this study to investigate the ability of using soilless culture systems, vermicomposting technology and net cover in producing vegetables in urban area in summer season. The aim of this study was to determine the effect of different vermicompost rates mixed with the standard substrate peat moss: perlite (perlite: peat moss: vermicompost (45:45:10) (Mix.10%), perlite: peat moss: vermicompost (40:40:20) (Mix.20%), perlite: peat moss: vermicompost (35:35:30) (Mix.30%) and perlite: peat moss (50:50 V/V) (Control) under three microclimate conditions (plants covered with black net, white net and without cover) on vegetative growth and yield of sweet pepper (Capsicum annuum L. cv. Reda) grown in pots culture during summer seasons of 2012 and 2013 at the Central Laboratory for Agricultural Climate, Agricultural Research Center, Dokki, Giza Governorate.
 Physical and chemical properties of substrates, vegetative growth and yield characteristics, agrometerological data and mineral contents were determined. The obtained data indicated that vermicomposting could contribute in mitigate CO2 emission, save the essential nutrients and energy via recycling the urban organic wastes to vermicompost. The physical and chemical properties were affected by vermicompost. The best vegetative growth and yield of sweet pepper were given by (Mix.20%) vermicompost mixture followed by (Mix.10%) and (Mix.30%) vermicompost mixture. There were also significant differences between cover net treatments in affecting vegetative growth and yield of pepper, the white net was superior for producing pepper during the summer season; while the black net gave the lowest plant growth and yield. The best treatment was (Mix.20%) vermicompost mixture with white net cover, while the lowest vegetative growth and yield were obtained by (Control) vermicompost mixture with black cover net during the two tested seasons. These results suggested that vermicomposting and green roof can be used in urban area for producing food instead of incineration the urban organic wastes or imported food from rural area and using white cover net to improve the pepper growth and productivity during summer season.

DÉCHET URBAIN-AGRICULTURE-ENVIRONNEMENT (DUAE): USING WASTE AS A RESOURCE FOR AGRICULTURE

Increasing agricultural production sustainably implies the use of organic fertilizer. Urban wastes in developing countries are rich in recyclable organic matter and they increase as urbanization increases. A recent project carried out in Dakar analyzed the potential contribution of urban organic waste (OW) to urban horticultural production. A research project was conducted in order to 1) carry out farm surveys to understand local fertilization practices; 2) identify and characterize locally available organic wastes chemically; and 3) carry out experiments with these wastes in greenhouses and farms to evaluate their agronomic potentialities and their implementation in local farmers' practices. Horse and poultry manure are the main OW used by farmers around Dakar; however, these may become less available and/or more expensive in the future. The OW obtained after sifting through other sources of urban wastes (i.e., compost) could provide an alternative and unlimited source of organic matter. However, chemical analyses of this compost show that organic matter and nitrogen levels are weak compared to manure. Experiments were therefore conducted in greenhouses with the two representative soils of the region, a sandy-clay soil (Deck) and a sandy soil (Dior): these showed no significant effect of compost on the early growth of tomatoes compared to treatment without compost, but rather a light-positive effect at the end of the tomato-growth cycle, consistent with the analytical properties of the product. The fertilizing value of this compost is low and will require the addition of other fertilizing inputs. On-farm tests have been carried out on tomato in the same soils, where the agronomic values of treatments combining compost, manure and other local organic inputs are compared. The initial results are now under study (available December 2010).

Characterization of activated carbon produced from urban organic waste

The difficulties to decompose organic waste can be handled naturally by pyrolisis so it can decomposes quickly that produces charcoal as the product. This study aims to investigate the characteristics of activated carbon from urban organic waste. Charcoal results of pyrolysis of organic waste activated with KOH 1.0 M at a temperature of 700 and 800 o C for 60 to 120 minutes. Characteristics of activated carbon were identified by Furrier Transform Infra Red (FTIR), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). However, their quality is determined yield, moisture content, ash, fly substances, fixed carbon, and the power of adsorption of iodine and benzene. The identified functional groups on activated carbon, such as OH (3448,5-3436,9 cm -1 ), and C=O (1639,4 cm -1 ). In general, the degree and distance between the layers of active carbon crystallites produced activation in all treatments showed no significant difference. The pattern of activated carbon surface topography structure shows that the greater the pore formation in accordance with the temperature increase the more activation time needed. The yield of activated carbon obtained ranged from 72.04 to 82.75%. The results of characterization properties of activated carbon was obtained from 1.11 to 5.41% water, 13.68 to 17.27% substance fly, 20.36 to 26.59% ash, and 56.14 to 62.31% of fixed carbon . Absorption of activated carbon was good enough at 800 o C and 120 minutes of activation time, that was equal to 409.52 mg/g of iodine and 14.03% of benzene. Activated carbon produced has less good quality, because only the water content and flying substances that meet the standards. Doi : 10.12777/ijse.5.2.89-94 [ How to cite this article : Haji, A.G., Pari, G., Nazar, M., and Habibati. (2013). Characterization of activated carbon produced from urban organic waste . International Journal of Science and Engineering , 5(2),89-94. Doi: 10.12777/ijse.5.2.89-94 ]

English

Ornamental industry demanding large amounts of container substrate which is giving opportunity to recycle agricultural and urban organic waste materials. The study presents the physical and physicochemical characterisation of hazelnut husk substrates supplemented with biosolid in different proportions (0, 25, 50 and 75%), comparing to the standard peat substrate. In addition, plants were planted into 10 L pots filled with the prepared substrates and cultivated in a glasshouse. On the basis of the research results, it was concluded that physical and physico-chemical properties of hazelnut husk substrates were in the range of optimum, except for the higher dose of biosolid (75%). Furthermore, it was also observed that biosolid mixture with hazelnut husk can be used in the cultivation of ornamental palm tree. The main factor affecting plant growth was higher substrate nitrogen value in higher dose of biosolid application, which is positively correlated with leaf N and plant dry weight. Based on substrate characteristics and plant growth, hazelnut husk and municipal biosolid can be recycle in the ornamental industry as a container substrate.

Industrial and urban organic wastes increase soil microbial activity and biomass

Microbial processes have been used as indicators of soil quality, due to the high sensitivity to small changes in management to evaluate, e.g., the impact of applying organic residues to the soil. In an experiment in a completely randomized factorial design 6 x 13 + 4, (pot without soil and residue or absolute control) the effect of following organic wastes was evaluated: pulp mill sludge, petrochemical complex sludge, municipal sewage sludge, dairy factory sewage sludge, waste from pulp industry and control (soil without organic waste) after 2, 4, 6, 12, 14, 20, 28, 36, 44, 60, 74, 86, and 98 days of incubation on some soil microbial properties, with four replications. The soil microbial activity was highly sensitive to the carbon/nitrogen ratio of the organic wastes. The amount of mineralized carbon was proportional to the quantity of soil-applied carbon. The average carbon dioxide emanating from the soil with pulp mill sludge, corresponding to soil basal respiration, was 0.141 mg C-CO2 100 g-1 soil h-1. This value is 6.4 times higher than in the control, resulting in a significant increase in the metabolic quotient from 0.005 in the control to 0.025 mg C-CO2 g-1 Cmic h-1 in the soil with pulp mill sludge. The metabolic quotient in the other treatments did not differ from the control (p < 0.01), demonstrating that these organic wastes cause no disturbance in the microbial community.

Application of a real-time qPCR method to measure the methanogen concentration during anaerobic digestion as an indicator of biogas production capacity

Biogas is an energy source that is produced via the anaerobic digestion of various organic materials, including waste-water sludge and organic urban wastes. Among the microorganisms involved in digestion, methanogens are the major microbiological group responsible for methane production. To study the microbiological equilibrium in an anaerobic reactor, we detected the methanogen concentration during wet digestion processes fed with pre-treated urban organic waste and waste-water sludge. Two different pre-treatments were used in successive experimental digestions: pressure-extrusion and turbo-mixing. Chemical parameters were collected to describe the process and its production. The method used is based on real-time quantitative PCR (RT-qPCR) with the functional gene mcrA as target. First, we evaluated the validity of the analyses. Next, we applied this method to 50 digestate samples and then we performed a statistical analysis. A positive and significant correlation between the biogas production rate and methanogen abundance was observed (r = 0.579, p < 0.001). This correlation holds both when considering all of the collected data and when the two data sets are separated. The pressure-extrusion pre-treatment allowed to obtain the higher methane amount and also the higher methanogen presence (F = 41.190, p < 0.01). Moreover a higher mean methanogen concentration was observed for production rate above than of 0.6 m3 biogas/kg TVS (F = 7.053; p < 0.05). The applied method is suitable to describe microbiome into the anaerobic reactor, moreover methanogen concentration may have potential for use as a digestion optimisation tool.

Microbial remediation of pollution in tropical coastal environments

The impact of waste on the coastal environment from urban sources and the agriculture, manufacturing and aquaculture industries can be mitigated by the use of appropriate microbes either individually or in consortia with plants. Aquaculture—coastal land-based and estuarine or bay cage aquaculture—and urban sewage and industrial organic wastes are particularly amenable to microbial technologies. Several criteria must be applied to ensure success. Appropriate species for microbial technology, i.e. microbes that are natural to, or integrate easily into, the natural ecological communities and provide the desired beneficial actions, have to be selected and produced at a cost that is acceptable to the end users. The microbes have to be added at a high enough population density to compete with the natural flora in the treatment sites. Bacteria that carry genes for antibiotic resistance and disease virulence must not be used in sites where they could affect not only human, but also fish and shrimp health; safety checks must be made during selection and production processes. Microbial technologies are now being used widely in the field of aquaculture, where an obvious cost-benefit is seen at harvest. Microbial technologies can lower energy and other costs of treating of urban and industrial wastes and assist in meeting regulatory targets for effluent quality.

Effects of fertilization with urban and agricultural organic wastes in a field trial – Waste imprint on soil microbial activity

In the past decades a significant change in composition of urban organic waste products has occurred in many first world countries, due to cleaner technologies as well as outsourcing of heavy industries. However, the societal perception of organic urban waste has become increasingly negative, leading to widespread advocacy of incineration. Therefore we established the ‘CRUCIAL’ long-term field trial in 2003, with the rationale that by approaching the known limits for a number of heavy metals below which no profound disturbance should be observed on key soil ecological functions, it should be possible to discern if some of the many unknown components in the composite urban waste as well as agriculturally based fertilizers have measurable impacts. The following treatments were established: human urine, sewage sludge (normal N-level and accelerated level aiming at three times normal N-level), degassed and subsequently composted organic municipal waste (normal and accelerated level), deep litter, cattle slurry, cattle manure (accelerated level), NPK fertilizer, unfertilized but with clover undersown and an unfertilized control. After 4 years the soil organic matter (SOM) C content, basal CO2 respiration and soil microbial biomass (SMB) C was significantly affected by treatments. All soils having received organic fertilizer had higher SMB C than those with no added fertilizer (unfertilized and unfertilized with clover undersown) and inorganic fertilizer. The treatment effect on qCO2 (CO2/SMB C) was not significant, but the unfertilized treatments showed the highest values. Treatments with accelerated levels of composted household waste and sewage sludge had the highest number of colony forming heterotrophic bacteria. Sole carbon source utilization in EcoPlates indicated a very robust microbial community in the treatments. Cumulative input of heavy metals was less than that required for reaching the heavy metal ecotoxicological limits, even after accelerated loading with sewage sludge corresponding to approximately 55 years of normal application. This could indicate that it is possible use organic urban waste for an extended period on a given site, without compromising soil functioning as long as ecotoxicological guidelines for heavy metal content are observed.

Effects of fertilization with urban and agricultural organic wastes in a field trial – Prokaryotic diversity investigated by pyrosequencing

The impact of different fertilizer treatments on prokaryotic diversity in a Danish urban waste field trial was investigated using tag-encoded amplicon pyrosequencing. The field trial was established in 2003 to investigate the application of urban organic waste as fertilizer in agriculture and to identify the effects on soil quality. The fertilizers (e.g. composted organic household waste, sewage sludge and human urine) contain a large amount of nutrients but possibly also undesirable toxic compounds that may influence the bacterial flora in the soil. A 561bp fragment of the 16S rRNA gene flanking the V4, V5 and V6 regions, was amplified from each soil sample, tagged and sequenced using pyrosequencing. The major classified bacterial phyla and proteobacterial classes for all treatments were Actinobacteria, Acidobacteria and Betaproteobacteria, while the Crenarchaeota was the most frequent phylum of Archaea. No major changes in the community composition due to different fertilizer treatments were found, demonstrating a high robustness of the soil microbiota. However, some differences were observed e.g. Cyanobacteria were most frequent in the unfertilized soil, in comparison to the soils treated with nitrogen containing fertilizers and Firmicutes had higher occurrence in the soil with the composted household waste compared to all other treatments. Additionally, we used quantitative PCR (qPCR) to quantify specific bacterial groups, and used these numbers to convert the relative abundances of all bacteria obtained by pyrosequencing, to the actual numbers present in one gram of soil. All treatments resulted in a total number of bacteria between 1.99×109 and 4.11×109 gram−1 soil.

Root growth promotion by humic acids from composted and non-composted urban organic wastes

Background and aims Besides general effect of organic residues on soil quality and plant crop, hormonal direct effect on plant growth by extracted humic acids of organic materials is interesting and profitable theme. In the present work, we studied on direct interaction between humic acid and root growth, depending on different origin of organic materials.