Organic Fraction Of Urban Wastes Research Articles

Microbiome dynamics and phaC synthase genes selected in a pilot plant producing polyhydroxyalkanoate from the organic fraction of urban waste

This study analyses the bacterial population dynamics of a mixed microbial community (MMC) selected in a pilot plant producing polyhydroxyalkanoate (PHA) from the fermentation of the organic fraction of urban waste (OFMSW) and sewage sludge (SS). 16S rRNA gene high-throughput sequencing revealed the occurrence of a variety of PHA accumulating bacteria that ensured a stable PHA production in an open system operating with real substrates and without temperature control. The Volatile Fatty Acids (VFA) changes in the feed and the temperature variation affected the dynamics of the PHA-accumulating bacteria over the plant operation. Remarkably, the higher PHA content was associated to a MMC largely comprising of Hydrogenophaga species during the operation at higher working temperature. The involvement of a heterogeneous PHA-accumulating MMC was associated with a high phaC synthase genes biodiversity confirming the occurrence of a functional redundancy.

Elucidation of reaction pathways of nitrogenous species by hydrothermal liquefaction process of model compounds

The reaction pathway of nitrogen containing compounds under hydrothermal liquefaction (HTL) conditions was investigated by using amino acids as protein model compounds. The effect of organic acids and alkaline catalysts was also investigated by determining the structure and the partition of nitrogen containing species between the resulting solid, aqueous and bio-oil phases.Representative results showed that operating in a water-acetic acid (95/5% v/v) binary solvent system resulted in a dramatic improvement in carbon recovery in the oil phase due to the transformation of water soluble hydrophilic products into oil soluble derivatives by acylation of the amino moiety.The conclusions of this study provide a useful tool to improve the HTL process applied to nitrogen rich biomass, such as the organic fraction of urban waste, sewage sludge, and aquatic biomass (microalgae).

Choice of pyrolysis parameters for urban wastes affects soil enzymes and plant germination in a Mediterranean soil

The production of organic waste has steadily increased in recent years, with subsequent impact on the environment. The European Union committed to diminish the volume of biodegradable municipal waste disposed of in landfills by 2016–2020. The synthesis of biochar from urban waste and its application to improve soil quality can constitute a novel route for valorization. The aim of this paper was to study the effect of three biochars originated from pyrolysis of the organic fraction of urban waste at two different temperatures (300°C and 500°C) and two residence times (1h and 5h) on the biochemical properties of an agricultural soil. Soil was amended with biochars at a rate of 8% and incubated for 74days. A phytotoxicity assay, using garden cress as the test species, was conducted. CO2 emissions, microbial biomass C and the enzymes dehydrogenase, phosphomonoesterase and β-glucosidase were measured in tested soils. Biochars prepared at 300°C resulted in lower germination index values, which could partly be ascribed to a higher bioavailability of heavy metals and higher soluble organic matter, while the biochar prepared as 500°C exhibited a phytostimulant effect. Biochars produced at 300°C (B300-1h, B300-5h) augmented soil CO2 emissions while there was no effect on microbial respiration in the soil amended with the biochar prepared at 500°C. Pyrolysis temperature and, for some enzymes, residence time, controlled soil enzymatic activity.

Hydrochars from Biosolids and Urban Wastes as Substitute Materials for Peat

AbstractPeat is the most widely used substrate component and extensively used in greenhouse cultivation, landfill cover soils, urban parks and gardens, urban agriculture or green roofs, due to its excellent combination of physicochemical properties. The production of hydrochar by hydrothermal carbonization (a process at lower temperatures than pyrolysis and using wet conditions) could industrially reproduce the initial conditions of biomass humification and lead to materials with similar properties to those of peat. The objective of this work was to compare peat (PT, Control), a hydrochar prepared from biosolids (HSL), a hydrochar prepared from the organic fraction of urban wastes (HUW) and two mixtures (PT + HSL and PT + HUW) at a 50% volume rate for their potential use as substrates with multiple applications. Ryegrass was established at a rate of 40 g seeds cm−2 in the potting mixtures. Hydrophysical and biochemical properties (microbial biomass and the enzymes dehydrogenase, β‐glucosidase and phosphomonoesterase) were analyzed for PT, HSL, HUV and their combination (PT + HSL and PT + HUW). Treatments with biosolids hydrochar increased ryegrass production by 184% (HSL) and by 216% (PT + HSL) dry weight compared to the control (peat). Biochemical properties depended strongly on hydrochar type, while the hydrophysical properties of the hydrochars were similar to those of peat. Overall, our results found hydrochar–peat mixtures (PT + HSL and PT + HUW) to be suitable for the preparation of growing media. Copyright © 2017 John Wiley & Sons, Ltd.

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry

Dissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical–chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban wastes (DOM-P) has been analysed by FT-IR, CPMAS 13C NMR spectroscopy and 1H T 1 NMR relaxometry with fast field cycling (FFC) setup. While the first two spectroscopic techniques revealed the chemical changes of dissolved organic matter after adsorption either on kaolinite (DOM-K) or montmorillonite (DOM-S), the latter permitted the evaluation of the conformational variations as assessed by longitudinal relaxation time ( T 1) distribution at the fixed magnetic field of 500 mT. Alterations of T 1 distributions from DOM-P to DOM-K and DOM-S were attributed to a decreasing molecular complexity following DOM-P adsorption on the clay minerals. This study applied for the first time solid state 1H T 1 NMR relaxometry to dissolved organic matter from compost obtained from the organic fraction of urban wastes and revealed that this technique is very promising for studying environmentally relevant natural organic systems.

SOIL AND PLANT NITROGEN DYNAMICS OF A TOMATO CROP UNDER DIFFERENT FERTILIZATION STRATEGIES

A field experiment was conducted in 2007 to investigate the effects of the N fertilizer source on the soil and plant N dynamics of a tomato crop grown in a sandy loam soil. The fertilization treatments were: mineral N-fertilization applied by fertigation (TM); organic N-fertilization (TO) with compost obtained from the organic fraction of urban waste (OFUW); and a combined treatment (TC) with half organic and half mineral N. Compost was incorporated in November 2006. Plants were drip irrigated with well water. The nitrate concentrations in the irrigation solutions were determined on a weekly basis. Soil samples were taken before planting and at harvest from depths of up to 90 cm in order to determine moisture and N-NO 3 levels. The estimated amounts of total N-NO 3 - available in the different treatments, including the initial content in the 0-90 cm soil layer, were 560 (TC), 570 (TO) and 610 (TM) kg N ha -1 . The N contents of plants sampled on three occasions during the growing period and those of marketable fruits were also analyzed. Total marketable yield was determined at the end of the harvest period. The EU-Rotate_N model was used to predict the effects of the applied treatments. The model was calibrated using data from a previous experiment. No differences between treatments were observed with respect to yield or N content in marketable fruits. The amount of N left in the field at the end of the cropping period was significantly lower in TO than in TC and TM. Simulated plant growth, marketable yield and N uptake were similar to observed data. N leaching predicted by the model for the TM treatment was 50% higher than in the TC and TO treatments. However, an underestimation of residual N contents was found in all treatments. It was concluded that tomato fertilization with compost obtained from the OFUW could offer a suitable strategy for reducing N leaching without affecting yield when there is sufficient mineral N available throughout the growing period. The EU-Rotate_N model may be a valuable tool for evaluating N fertilizer practices for tomato crops.

Soil microbial activity after restoration of a semiarid soil by organic amendments

Unsuitable agricultural practices together with adverse environmental conditions have led to degradation of soil in many Mediterranean areas. One method for recovering degraded soils in semiarid regions, is to add organic matter in order to improve soil characteristics, thereby enhancing biogeochemical nutrient cycles. In this study, the effect of adding the organic fraction of urban wastes (both fresh and composted) on different carbon fractions and on microbiological and biochemical parameters (microbial biomass C, basal respiration and different enzymatic activities) of a degraded soil of SE Spain has been assessed in a 2 year experiment. Three months after the addition of the organic material, spontaneous plant growth occurred and the plant cover lasted until the end of the experiment. Organic soil amendment initially increased the levels of soil organic matter, microbial biomass, basal respiration and some enzyme activities related to the C and N cycles These values decreased but always remained higher than those of the unamended soil. The results indicate that the addition of urban organic waste is beneficial for recovering degraded soils, the microbial activity of which clearly increases with amendment. The incorporation of compost seemed to have a greater positive effect on the soil characteristics studied than the incorporation of fresh organic matter.