Biological treatment of the organic fibre from the autoclaving of municipal solid wastes : preliminary results

Commingled municipal solid waste (MSW) was autoclaved in the presence of saturated steam for 30 min at 145 °C and 600 kPa. The organic fibre fraction from the autoclaved resulting material was examined for biodegradability. Aerobic and anaerobic tests were carried out to characterise the fibre in terms of biodegradation potential, which was moderate (biogas production potential of 251 ± 22 l [biogas] kg⁻¹ [total solids (TS)] and dynamic respiration index (DRI) of 1575 ± 116 mg [O2] kg⁻¹ [TS] h⁻¹). Manual and chemical characterisations were also performed to organic fibre. Following this characterisation, a laboratory-scale thermophilic anaerobic digestion process and a pilot-scale composting process were carried out to determine the possibilities of these biological treatments. In the anaerobic digestion process the biogas yield values obtained were within 0.15-0.21 m³ [biogas] kg⁻¹ [volatile solids (VS)] with an organic loading rate (OLR) of 3 kg [VS] m⁻³ d⁻¹. However, it was difficult to reach the steady state in the anaerobic thermophilic process for the different organic loads tested. Further experiments are necessary to determine the optimal biogas production and performance under these conditions. The composting process performed correctly and the final material was stable (DRI of 504 ± 74 mg [O2] kg⁻¹ [TS] h⁻¹) and with good properties for its application to soil regarding heavy metal contents that corresponding to class B compost, with the exception of some metals that corresponded to class A

Estudi de les emissions gasoses del compostatge de fangs

En el tractament biològic de les aigües residuals urbanes es generen grans quantitats de fangs rics en matèria orgànica i determinats elements químics, composició que els fa un residu ideal per ser valoritzat mitjançant compostatge. Ara bé, les instal·lacions necessàries per realitzar aquest procés generen rebuig social, sovint vinculat a les males olors. Aquest article ha estudiat les emissions durant el procés de compostatge de dos tipus de fangs produïts en plantes depuradores. Els resultats obtinguts es poden utilitzar en diversos àmbits.En el tratamiento biológico de las aguas residuales urbanas se generan cantidades de lodos ricos en materia orgánica y determinados elementos q composición que los hace un residuo ideal para ser valorizado mediante com Ahora bien, las instalaciones necesarias para realizar este proceso generan social, a menudo vinculado a los malos olores. Este artículo ha estudi emisiones durante el proceso de compostaje de dos tipos de lodos produ plantas depuradoras. Los resultados obtenidos se pueden utilizar en ámbitos.Biological treatment of municipal waste water generates large amounts of slu rich in organic matter and certain chemicals. This composition rends sludge ideal waste to be valorised through composting. However, the compos facilities generate social rejection, often due to odour pollution. This article studied gaseous emissions during the composting process of two types of slu produced in wastewater treatment plants. The results obtained can be applie various fields

Gaseous emissions in municipal wastes composting : effect of the bulking agent

In this study, the emissions of volatile organic compounds (VOC), CH₄, N₂O and NH₃ during composting non-source selected MSW, source selected organic fraction of municipal solid wastes (OFMSW) with wood chips as bulking agent (OF_wood) and source selected OFMSW with polyethylene (PE) tube as bulking agent (OF_tube) and the effect of bulking agent on these emissions have been systematically studied. Emission factors are provided (in kg compound Mg⁻¹ dry matter): OF_tube (CH₄: 0.0185 ± 0.004; N₂O: 0.0211 ± 0.005; NH₃: 0.612 ± 0.269; VOC: 0.688 ± 0.082) and MSW (CH₄: 0.0549 ± 0.0171; N₂O: 0.032 ± 0.015; NH₃: 1.00 ± 0.20; VOC: 1.05 ± 0.18) present lower values than OF_wood (CH₄: 1.27 ± 0.09; N₂O: 0.021 ± 0.006; NH₃: 4.34 ± 2.79; VOC: 0.989 ± 0.249). A detailed composition of VOC is also presented. Terpenes were the main emitted VOC family in all the wastes studied. Higher emissions of alpha and beta pinene were found during OF_wood composting processes

A systematic study of the gaseous emissions from biosolids composting : raw sludge versus anaerobically digested sludge

Volatile organic compound (VOC) and ammonia, that contribute to odor pollution, and methane and nitrous oxide, with an important greenhouse effect, are compounds present in gaseous emission from waste treatment installations, including composting plants. In this work, gaseous emissions from the composting of raw (RS) and anaerobically digested sludge (ADS) have been investigated and compared at pilot scale aiming to provide emission factors and to identify the different VOC families present. CH₄ and N₂O emissions were higher in ADS composting (0.73 and 0.55 kg Mg⁻¹ sludge, respectively) than in RS composting (0.01 kg Mg⁻¹ sludge for both CH₄ and N₂O). NH₃ and VOCs emitted were higher during the RS composting process (19.37 and 0.21 kg Mg⁻¹ sludge, respectively) than in ADS composting (0.16 and 0.04 kg Mg⁻¹ sludge). Significant differences were found in the VOC compositions emitted in ADS and RS composting, being more diverse in RS than ADS composting

A systematic study of the gaseous emissions from biosolids composting : raw sludge versus anaerobically digested sludge

Volatile organic compound (VOC) and ammonia, that contribute to odor pollution, and methane and nitrous oxide, with an important greenhouse effect, are compounds present in gaseous emission from waste treatment installations, including composting plants. In this work, gaseous emissions from the composting of raw (RS) and anaerobically digested sludge (ADS) have been investigated and compared at pilot scale aiming to provide emission factors and to identify the different VOC families present. CH₄ and N₂O emissions were higher in ADS composting (0.73 and 0.55 kg Mg⁻¹ sludge, respectively) than in RS composting (0.01 kg Mg⁻¹ sludge for both CH₄ and N₂O). NH₃ and VOCs emitted were higher during the RS composting process (19.37 and 0.21 kg Mg⁻¹ sludge, respectively) than in ADS composting (0.16 and 0.04 kg Mg⁻¹ sludge). Significant differences were found in the VOC compositions emitted in ADS and RS composting, being more diverse in RS than ADS composting

VOC emissions from the composting of the organic fraction of municipal solid waste using standard and advanced aeration strategies

Background: the emission of volatile organic compounds (VOC) during the composting process is mainly responsible for the odors generated in these types of waste treatment plants. In this work, VOC emissions from the source-separated organic fraction of municipal solid waste (OFMSW) composting process have been investigated in 50 L pilot reactors operating under different aeration control strategies during the active decomposition stage. - Results: the VOC emissions from traditional aeration control options such as oxygen feedback control or cyclic on-off aeration have been compared with VOC emissions under an oxygen uptake rate (OUR) control strategy. Total VOC emission (mg C m⁻³) and VOC composition (%) have been determined during the first active decomposition stage of composting. Study of VOC composition indicated a high presence of terpenes. Carcinogenic compounds, such as furans, have occasionally been found at very low concentration. Results indicate some differences in VOC composition according to the aeration strategy used. - Conclusions: the evolution of total VOC emissions was relatively similar, being high in the first days of the process. However, the results obtained show some differences in VOC composition depending on the aeration strategy used. The OUR controller provided a more steady emissions profile, which will help the performance of further gas treatment operations, specially biological systems

Gaseous emissions during the solid state fermentation of different wastes for enzyme production at pilot scale

The emissions of volatile organic compounds (VOC), CH₄, N₂O and NH₃ during the solid state fermentation process of some selected wastes to obtain different enzymes have been determined at pilot scale. Orange peel + compost (OP), hair wastes + raw sludge (HW) and winterization residue + raw sludge (WR) have been processed in duplicate in 50 L reactors to provide emission factors and to identify the different VOC families present in exhaust gaseous emissions. Ammonia emission from HW fermentation (3.2 ± 0.5 kg Mg⁻¹ dry matter) and VOC emission during OP processes (18 ± 6 kg Mg⁻¹ dry matter) should be considered in an industrial application of these processes. Terpenes have been the most emitted VOC family during all the processes although the emission of sulphide molecules during HW SSF is notable. The most emitted compound was dimethyl disulfide in HW and WR processes, and limonene in the SSF of OP

Co-composting: An Opportunity to Produce Compost with Designated Tailor-Made Properties

AbstractCo-composting is a technique that allows the aerobic degradation of organic waste mixtures, primarily aiming at obtaining compost that can be used as fertiliser or soil amendment. As compared to the typical composting activity, the main difference is not merely the use of more than one feedstock to start and sustain the biodegradation process, but also the possibility of combining various kinds of waste to obtain 'tailored' products with designed properties, or to reclaim and valorise natural resources, such as degraded soils or polluted soils and sediments. Set up of appropriate co-composting protocols can be a way to optimise the management of waste produced by different sectors of agriculture and industry and also from human settlements. Different formulations can not only optimise the biodegradation process through the adjustment of nutrient ratios, but also lead to the formation of products with innovative properties. Moreover, co-composting can be a technique of choice for the reclamation of soils degraded by intensive agriculture or contaminated soils and sediments. In fact, an appropriate mix of organic waste and soils can restore the soil structure and induce fertility in nutrient-depleted soils, and also remediate polluted soils and sediments through degradation of organic pollutants and stabilisation of heavy metals. While the selection of different mixes of organic waste may lead to the design of composts with specific properties and the potential valorisation of selected waste materials, there are still several factors that hamper the development of co-composting platforms, mainly insufficient knowledge of some chemical and microbiological processes, but also some legislative aspects. This chapter illustrates the progress achieved in co-composting technology worldwide, some key legislative aspects related to the co-composting process, the main scientific and technical aspects that deserve research attention to further develop co-composting technology, and successful applications of co-composting for the reclamation of soils and sediments, allowing their use for cultivation or as growing media in plant nurseries. A specific case study of the production of fertile plant-growing media from sediment co-composting with green waste is also illustrated

Estudi de les emissions gasoses en processos biològics de valorització material de residus sòlids. Caracterització de l’emissió de compostos orgànics volàtils

El creixement econòmic mundial viscut durant la segona meitat del segle XX, ha provocat un gran increment en la generació de residus. És per això que les darreres polítiques europees defineixen l’objectiu de tractar un mínim del 50% dels residus municipals mitjançant el reciclatge abans de l’any 2020. En el cas dels residus orgànics biodegradables, aquest reciclatge o valorització s’aconsegueix principalment mitjançant processos biològics com el compostatge i la digestió anaeròbia. L’actual escenari europeu pel que fa a instal·lacions de valorització de residus orgànics i l’aparició d’aquestes noves polítiques, fan pensar en una futura proliferació d’instal·lacions, entre les quals hi haurà una gran quantitat de plantes de compostatge, que permetin assolir l’objectiu fixat. Davant aquesta futura proliferació d’instal·lacions de compostatge (i de tractament de residus en general) caldrà tenir en compte els impactes ambientals associats al propi procés, entre els quals destaquen les emissions gasoses derivades de la degradació biològica de la matèria orgànica. Entre els compostos gasosos presents en aquestes emissions cal destacar el metà, l’amoníac, l’òxid nitrós i els compostos orgànics volàtils (COV). D’aquests compostos, el metà i l’òxid nitrós són considerats gasos d’efecte hivernacle, mentre que l’amoníac i els COV són els principals causants de les males olors associades a aquestes instal·lacions de tractament. El Grup de Recerca en Compostatge (GICOM), en el que s’ha desenvolupat aquesta tesi, té una àmplia experiència en l’estudi del compostatge, ja sigui a nivell del propi procés, del seu control o de les seves emissions a escala industrial. Tanmateix, en els darrers anys s’ha iniciat una nova línia de recerca dins el grup per explorar el potencial de la fermentació en estat sòlid (SSF) com una altra via de valorització material de residus, habitualment industrials, amb l’objectiu d’obtenir productes de valor afegit (enzims, biopesticides, biosurfactants, etc.) a partir de residus. Així doncs, en aquesta tesi s’ha volgut aprofitar l’àmplia experiència en compostatge del grup de recerca per tal d’aprofundir en el coneixement de les emissions gasoses derivades dels processos biològics de valorització material de residus sòlids orgànics, determinant els factors d’emissió per COV, CH4, N2O, NH3 i caracteritzant, per identificació i quantificació, els COV emesos durant el tractament de diferents residus a escala pilot. Per assolir aquest objectiu genèric, s’ha posat en marxa un mètode d’identificació i quantificació dels COV mitjançant la cromatografia de gasos acoblada a l’espectrometria de masses i s’han estudiat les emissions de COV d’un procés de compostatge convencional sota diferents estratègies d’aeració del procés. D’aquesta manera es defineixen dos aspectes metodològics que permetran continuar la recerca d’aquesta tesi, l’estratègia de procés, per una banda, i la metodologia de presa de mostra i anàlisi dels gasos per l’altra. A partir d’aquesta base metodològica es procedeix a analitzar, quantitativament i qualitativa, les emissions derivades del procés de compostatge de residus d’origen urbà com poden ser els fangs d’EDAR, frescos i digerits, o bé la Fracció Orgànica dels Residus Municipals (FORM). En aquest darrer cas, comparant el desenvolupament del procés de compostatge de la FORM separada selectivament i dels Residus Sòlids Urbans no separats selectivament amb les emissions que se’n deriven, així com determinant la contribució de la fusta utilitzada com a agent estructurant a les emissions del procés. Finalment, s’han estudiat també les emissions associades a la valorització material de residus més específics com són la pela de taronja, el residu de pèl i el residu de winterització amb l’objectiu de produir diferents enzims a través de la SSF.World economic growth during the second half of the XX century has caused a great increase in waste generation. This fact has been reflected in European policies which define the objective of recycling, at least, 50% of municipal waste before 2020. In the case of biodegradable organic wastes, this purpose can be achieved mainly through biological treatments such as composting and anaerobic digestion. In order to achieve the proposed target, the current European scenario in terms of organic waste valorisation facilities and the emergence of these new policies, suggest a future proliferation of biological treatment facilities, among which there will be a lot of composting plants. Given this upcoming proliferation of composting facilities (and waste treatment plants in general), the environmental impacts associated with the composting process must be taken into account, paying special attention to gaseous emissions resulting from biological degradation of organic matter. The main contaminants in these emissions are methane, ammonia, nitrous oxide and volatile organic compounds (VOC). Methane and nitrous oxide are considered greenhouse gases, while ammonia and VOC are the main cause of odours associated with these treatment facilities. The Composting Research Group (GICOM), where this thesis has been developed, has a wide research experience in composting, either studying the biological process itself, process control or process gaseous emissions at full scale. Besides, in recent years GICOM has started a new research line exploring the potentiality of solid state fermentation (SSF) as another way to valorise organic wastes, commonly from industrial processes, with the aim of obtaining value-­‐added products (enzymes, biopesticides, biosurfactants, etc.). In this thesis the research experience of the group has been used to analyse in depth the gaseous emissions from biological valorisation processes of solid organic wastes, determining emission factors for VOC, CH4, N2O, NH3 and characterizing, by identification and quantification, VOC emissions during the treatment of different wastes at pilot scale. To achieve this overall objective, a methodology to identify and quantify VOC by gas chromatography coupled to mass spectrometry has been set-­‐up. Also, VOC emissions during a conventional composting process under different aeration strategies have been studied. Thus, two methodological issues essential for the development of this thesis have been defined on one hand, the process strategy and on the other hand, the gaseous emission sampling methodology and analysis. From this methodological basis, gaseous emissions from the composting process of urban wastes, such as WWTP sludge, either raw or digested, and also de Organic Fraction of Municipal Solid Wastes (OFMSW) have been analysed, quantitatively and qualitatively. The OFMSW composting process and its emissions have been compared to non-­‐source selected Municipal Solid Wastes (MSW). Also, the contribution of wood chips (used as bulking agent) to the composting process emissions has been determined. Finally, the emissions associated to the material valorisation of specific wastes such as orange peel, hair wastes and residue of winterization in order to produce various enzymes through SSF, have also been studied. In addition to the scientific interest of this thesis, which is reflected by the papers published in high impact journals in the field of Environmental Engineering, it increases the research group know-­‐how on the treatment of different wastes at pilot scale. The definition of a methodology for gaseous emissions determination that can be implemented in future experiments performed in the GICOM pilot plant is also relevant. This methodology will allow the quantification of CH4, N2O and NH3, the qualitatively determination of VOC emissions and the quantification of the most commonly found compounds. This last point will permit to include data on the emissions of the material valorisation processes carried out in the research group pilot plant, reporting valuable information on the environmental impact of the process also useful in the design of the required emissions equipment