Oxy-steam co-gasification of sewage sludge and woody biomass for bio-methane production: an experimental and numerical approach

Sewage sludge management is a current problem of extreme concern in Europe. Till now, the most frequent route for sludge management has been incineration or the reuse by shedding on agricultural land both directly or after composting. However, this last method is critically reconsidered lately owing to the increasing contamination of sewage sludge by chemicals, heavy metals, residual organic oils, etc.. In the present study, the performance of a steam-oxy gasification plant has been analyzed. The plant allows the thermo-chemical conversion of sewage sludge, together with woody biomass, into a gas mixture (syngas) composed by basic chemicals (synthetic hydrocarbons), suitable for subsequent industrial production of very high added-value products such as methane. In particular, a numerical model of methanation plant, composed by a downdraft gasifier, a syngas cleaning system and a Sabatier reactor, has been created within the commercial code Aspen-One and validated with the results obtained from a real scale air gasifier fed with sewage sludge and woody biomass. First results showed that the steam-oxy co-gasification process has a high energy conversion efficiency that reaches roughly 80% (i.e. produced syngas calorific value vs the dried feedstock calorific value) with an overall methane yield of about 20% (by mass) of the feedstock utilized.

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Co-Gasification of Sewage Sludge Mixed with Waste Wood in Different Proportions

Proceedings ◽

10.3390/proceedings2019038009 ◽

2019 ◽

Vol 38 (1) ◽

pp. 9

Author(s):

Alves ◽

Calado ◽

Panizio ◽

Santos ◽

Gonçalves ◽

...

Keyword(s):

Sewage Sludge ◽

Energy Conversion ◽

Conversion Efficiency ◽

Calorific Value ◽

Energy Conversion Efficiency ◽

Process Performance ◽

Waste Wood ◽

Downdraft Gasifier ◽

Product Gas ◽

Waste Mixture

co-gasification experiments with mixtures in various proportions of waste wood (WW) and sewage sludge (SS) were performed in a downdraft gasifier, in order to evaluate process performance and properties of gas and chars. Addition of SS improved the energy conversion efficiency and product gas yield, and minimised the formation of tars. Char production was greater, with formation of agglomerations inside the reactor. The optimal waste mixture contained 87.5 wt.% WW and 12.5 wt.% SS, generating a product gas yield of 2.9 m3/kg waste with a calorific value of 4.8 MJ/m3, and a tar production of 4.7 g/kg waste.

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Agricultural Use of Sewage Sludge as a Threat of Microplastic (MP) Spread in the Environment and the Role of Governance

Energies ◽

10.3390/en14196293 ◽

2021 ◽

Vol 14 (19) ◽

pp. 6293

Author(s):

Natalia Milojevic ◽

Agnieszka Cydzik-Kwiatkowska

Keyword(s):

Sewage Sludge ◽

Agricultural Land ◽

Wastewater Treatment Plants ◽

Soil Health ◽

The European Union ◽

High Concentration ◽

Management Options ◽

Sludge Management ◽

Global Trends ◽

The Impact

Sewage sludge from wastewater treatment plants is commonly used as a soil amendment on agricultural land. Unfortunately, more and more research indicates that large amounts of microplastic (MP) are re-introduced to soil with sludge. This study aims to present the impact MP has on soil ecosystems, global trends in agricultural sludge management resulting from a high concentration of micropollutants in sludge, and finally propose a high-level strategy for sustainable sludge management. This strategy is mostly dedicated to the European Union and involves multiple stakeholders and the links between each of them to achieve appropriate sludge management to avoid soil pollution with MP. Governance, Technology, Consumer Acceptance, and Economy and Commercial Viability is explored in depth. To the author’s knowledge, this is the first paper to discuss these topics in the context of a changing agricultural scene and identifies ways of which sewage sludge can limit MP pollution whilst still fitting into a circular economy. As total elimination of agriculturally used sludge is not a viable option, more stringent regulation on sludge quality before its use is necessary, especially on contaminant concentrations. This includes MPs limits, to improve sludge quality, in turn improving soil health. More alternative management options for sludge that does not meet land usage requirements are necessary and will be explored in this study. Overall, the combination of factors discussed will inevitably lead to more emphasis on sewage sludge management, therefore it can be expected that the information presented in this review will be of high demand and importance for sludge producers and serves as a comprehensive foundation for researchers to build off.

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Influence of Post- and Pre-Acid Treatment during Hydrothermal Carbonization of Sewage Sludge on P-Transformation and the Characteristics of Hydrochar

Processes ◽

10.3390/pr10010151 ◽

2022 ◽

Vol 10 (1) ◽

pp. 151

Author(s):

Vicky Shettigondahalli Ekanthalu ◽

Satyanarayana Narra ◽

Tommy Ender ◽

Edward Antwi ◽

Michael Nelles

Keyword(s):

Liquid Phase ◽

Sewage Sludge ◽

Agricultural Land ◽

Great Influence ◽

Calorific Value ◽

Hydrothermal Carbonization ◽

Proximate Analysis ◽

Process Conditions ◽

P Recovery ◽

P Leaching

Phosphorus (P) recovery from alternative P-rich residues is essential to meet the growing demands of food production globally. Despite sewage sludge being a potential source for P, its direct application on agricultural land is controversial because of the obvious concerns related to heavy metals and organic pollutants. Further, most of the available P recovery and sludge management technologies are cost-intensive as they require mandatory dewatering of sewage sludge. In this regard, hydrothermal carbonization (HTC) has gained great attention as a promising process to effectively treat the wet sewage sludge without it having to be dewatered, and it simultaneously enables the recovery of P. This study was conducted to analyse and compare the influence of acid (H2SO4) addition during and after HTC of sewage sludge on P leaching and the characteristics of hydrochar. The obtained results suggested that despite using the same amount of H2SO4, P leaching from solid to liquid phase was significantly higher when acid was used after the HTC of sewage sludge in comparison with acid utilization during the HTC process. After HTC, the reduction in acid-buffering capacity of sewage sludge and increase in solubility of phosphate precipitating metal ions had a greater influence on the mobilization of P from solid to liquid phase. In contrast, utilization of H2SO4 in different process conditions did not have a great influence on proximate analysis results and calorific value of consequently produced hydrochar.

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Sewage sludge management at the central wastewater treatment plant Ljubljana

The holistic approach to environment ◽

10.33765/thate.12.1.2 ◽

2021 ◽

Vol 12 (1) ◽

pp. 9-25

Author(s):

Vesna Mislej ◽

Viktor Grilc ◽

Barbara Novosel ◽

Ana Mladenovič ◽

Vesna Zalar Serjun

Keyword(s):

Sewage Sludge ◽

Agricultural Land ◽

Treatment Plant ◽

Holistic Approach ◽

Pilot Scale ◽

Waste To Energy ◽

Sludge Management ◽

Material Recovery ◽

Treated Sewage ◽

Sewage Sludge Management

The treated sewage sludge under consideration is a hygienized biodegradable waste in the form of pellets. It can be used as a fertilizer, but only for spreading on non-agricultural land. Regarding “waste to energy” philosophy, the specification of pellets as an alternative solid fuel according to EN 15359 resulted in “NCV4; Cl1; Hg3-4” class. The major problem regarding the final pellets utilization is the lack of facilities for energy and material recovery from this type of waste in Slovenia. According to the newest legislation regarding the waste management, a product status for residues generated in combustion and pyrolysis of pellets on a laboratory and semi-pilot scale was not achieved. The holistic approach to final pellets utilization was studied and regarding the full-scale level of self-sufficient sewage sludge management in Slovenia, some legislative provisions become significant obstacles.

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Influence of Valorization of Sewage Sludge on Energy Consumption in the Drying Process

Energies ◽

10.3390/en14154511 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4511

Author(s):

Ewa Siedlecka ◽

Jarosław Siedlecki

Keyword(s):

Energy Consumption ◽

Sewage Sludge ◽

Moisture Content ◽

Sewage Treatment Plant ◽

Treatment Plant ◽

Calorific Value ◽

High Energy ◽

Dry Matter Content ◽

Drying Process ◽

Digested Sewage Sludge

Valorization of digested sewage sludge generated in a medium-sized sewage treatment plant and the effect of valorization on energy consumption during sludge drying used for energy recovery are presented. Anaerobic digestion of sewage sludge reduces dry matter content compared to raw sludge. This lowers its calorific value leading to the lower interest of consumers in using it as fuel. The aim of the study was to valorize digested sewage sludge prior to drying with high-energy waste with low moisture content. The procedure led to the reduction in moisture content by about 50% in the substrate supplied for solidification and drying. The calorific value of digested sewage sludge increased by 50%–80%, and the energy consumption of the drying process decreased by about 50%. Physical and chemical properties of sewage sludge and moisture content of substrates and mixtures after valorization were determined. The heat of combustion of valorized sewage sludge mixtures, their elemental composition, and ash content is investigated. Their calorific value in the analytical and working states of 10% H2O was calculated. The highest calorific value was obtained for the mixture of sewage sludge valorized with waste plastics or combined with wood dust, averaging 23 MJ/kg. A mathematical approximation of sewage sludge valorization is presented.

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Theoretical and Experimental Analysis on Co-Gasification of Sewage Sludge with Energetic Crops

Energies ◽

10.3390/en12091750 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1750 ◽

Cited By ~ 3

Author(s):

Stanislaw Szwaja ◽

Anna Poskart ◽

Monika Zajemska ◽

Magdalena Szwaja

Keyword(s):

Sewage Sludge ◽

Thermal Processing ◽

Mineral Content ◽

Combustion Engine ◽

Waste Water Treatment ◽

Preliminary Investigation ◽

Calorific Value ◽

High Energy ◽

Zone Model ◽

Gasification Process

As known, dried sewage sludge, is a by-product produced from waste water treatment, contains significant amounts of organic content, and makes up to 60% with overall calorific value from 9 to 12 MJ/kg. Hence, it can be considered as material for thermal processing focusing on heat and power production. Among thermal conversion technologies, gasification is seen as the effective one because it can be easily combined with heat and power cogeneration units. On the other hand, due to high mineral content (40–50%) in the sludge, it is difficult to be gasified and obtain syngas with calorific value satisfactory enough for fueling the internal combustion engine. The dried sludge can be subjected to be gasified at temperature above 850 °C. However, large amounts of mineral content do not provide favorable conditions to obtain this required temperature. Thus, it is proposed to enrich the sewage sludge with biomass characterized with significantly higher calorific value. In the article, co-gasification of sewage sludge and Virginia Mallow—energetic crops was investigated. Results from experimental and numerical investigation have been presented. The dried sewage sludge enriched with Virginia Mallow at a mass ratio of 0/100%, 50/50% and 100/0% in tests and in the range from 0 to 100% for theoretical analysis was applied in order to achieve effective gasification process. As observed, lignocellulosic biomass like Virginia Mallow contains low amounts of mineral content below 2%, which makes it appropriate for thermal processing. It contributes to more stable and efficient gasification process. Additionally, Virginia Mallow caused that the process temperature possible to achieve, was 950 °C. Thus, sewage sludge was mixed with this high-energy component in order to improve the gasification parameters and obtain syngas with higher calorific value. A zero-dimensional, two-zone model was developed with aid of the POLIMI kinetics mechanism developed by CRECK Modeling Group to simulate gasification of low calorific substances enriched with high calorific biomass. Obtained results showed that sewage sludge can be completely gasified at presence of Virginia Mallow. Syngas calorific value of approximately 5 MJ/Nm3 was produced from this gasification process. The maximal percentage of Virginia Mallow in the mixture with the sewage sludge was set at 50% due to economic aspects of the technology. It was found, that satisfactory conditions for effective gasification were achieved at this 50/50% percentage of sewage sludge and Virginia Mallow. Potential intensity of gasification was predicted from this 0-D 2-zones model, which calculates area of reduction zone to area of combustion zone. This reduction-to-combustion area ratio for the sewage sludge-Virginia Mallow mixture was estimated at value of 2. Finally, the model was successfully verified with results from tests, hence it was proposed as a tool for preliminary investigation on poor fuels gasification.

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Pine Wood and Sewage Sludge Torrefaction Process for Production Renewable Solid Biofuels and Biochar as Carbon Carrier for Fertilizers

Energies ◽

10.3390/en14238176 ◽

2021 ◽

Vol 14 (23) ◽

pp. 8176

Author(s):

Piotr Piersa ◽

Szymon Szufa ◽

Justyna Czerwińska ◽

Hilal Ünyay ◽

Łukasz Adrian ◽

...

Keyword(s):

Sewage Sludge ◽

Flow Reactor ◽

Sewage Treatment Plant ◽

Treatment Plant ◽

Woody Biomass ◽

Chemical Conversion ◽

Biofuel Production ◽

Optimum Process ◽

Pine Wood ◽

Solid Biofuel

This work presents the results of research on the thermo-chemical conversion of woody biomass–pine wood coming from lodzkie voivodship forests and sewage sludge from the Group Sewage Treatment Plant of the Łódź Urban Agglomeration. Laboratory scale analyses of the carbonization process were carried out, initially using the TGA technique (to assess activation energy (EA)), followed by a flow reactor operating at temperature levels of 280–525 °C. Both the parameters of carbonized solid biofuel and biochar as a carrier for fertilizer (proximate and ultimate analysis) and the quality of the torgas (VOC) were analyzed. Analysis of the pine wood and sewage sludge torrefaction process shows clearly that the optimum process temperature would be around 325–350 °C from a mass loss ratio and economical perspective. This paper shows clearly that woody biomass, such as pine wood and sewage sludge, is a very interesting material both for biofuel production and in further processing for biochar production, used not only as an energy carrier but also as a new type of carbon source in fertilizer mixtures.

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PROSPECTS OF OBTAINING ALTERNATIVE FUEL FROM VARIOUS BIOMASS AND WASTE SPECIES IN AZERBAIJAN

Alternative Energy and Ecology (ISJAEE) ◽

10.15518/isjaee.2019.01-03.025-041 ◽

2019 ◽

pp. 25-41

Author(s):

O. M. Salamov ◽

F. F. Aliyev

Keyword(s):

Power Plants ◽

Energy Intensity ◽

Oil And Gas ◽

Renewable Energy Sources ◽

Calorific Value ◽

High Energy ◽

Energy Sector ◽

Energy Sources ◽

Mineral Fertilizers ◽

Gaseous Fuels

The paper discusses the possibility of obtaining liquid and gaseous fuels from different types of biomass (BM) and combustible solid waste (CSW) of various origins. The available world reserves of traditional types of fuel are analyzed and a number of environmental shortcomings that created during their use are indicated. The tables present the data on the conditional calorific value (CCV) of the main traditional and alternative types of solid, liquid and gaseous fuels which compared with CCV of various types of BM and CSW. Possible methods for utilization of BM and CSW are analyzed, as well as the methods for converting them into alternative types of fuel, especially into combustible gases.Reliable information is given on the available oil and gas reserves in Azerbaijan. As a result of the research, it was revealed that the currently available oil reserves of Azerbaijan can completely dry out after 33.5 years, and gas reserves–after 117 years, without taking into account the growth rates of the exported part of these fuels to European countries. In order to fix this situation, first of all it is necessary to use as much as possible alternative and renewable energy sources, especially wind power plants (WPP) and solar photovoltaic energy sources (SFES) in the energy sector of the republic. Azerbaijan has large reserves of solar and wind energy. In addition, all regions of the country have large reserves of BM, and in the big cities, especially in industrial ones, there are CSW from which through pyrolysis and gasification is possible to obtain a high-quality combustible gas mixture, comprising: H2 + CO + CH4, with the least amount of harmful waste. The remains of the reaction of thermochemical decomposition of BM and CSW to combustible gases can also be used as mineral fertilizers in agriculture. The available and projected resources of Azerbaijan for the BM and the CSW are given, as well as their assumed energy intensity in the energy sector of the republic.Given the high energy intensity of the pyrolysis and gasification of the BM and CSW, at the present time for carrying out these reactions, the high-temperature solar installations with limited power are used as energy sources, and further preference is given to the use of WPP and SFES on industrial scale.

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VALUE INCREASING OF REJECT COAL WITH BIOMASS ADDING AS BIO-COAL BRIQUETTE

INDONESIAN JOURNAL OF URBAN AND ENVIRONMENTAL TECHNOLOGY ◽

10.25105/urbanenvirotech.v3i2.5110 ◽

2020 ◽

Vol 3 (2) ◽

pp. 123

Author(s):

Dyah Marganingrum ◽

Lenny Marilyn Estiaty

Keyword(s):

Alternative Energy ◽

Ignition Time ◽

Bottom Ash ◽

Calorific Value ◽

Added Value ◽

Physical Test ◽

Chemical Test ◽

Agglomeration Process ◽

Strategic Solution ◽

Index Value

Aim: This paper aims to explain the added value increasing method of reject coal which has not utilized by the company. Methodology and Results: The method to increase added value in this study used the agglomeration process of briquettes form that changing composition by adding biomass. The biomass functions to minimize bottom ash produced from burning briquettes so that the briquettes burn entirely. Stages processes in this study consist of characterization, briquetting, physical test, and chemical test. Based on the analysis, reject coal still has a high calorific value of 5,929 cal/gr. Shapes and sizes that were not following needs of coal market or consumer due to reject coal to be a waste. Briquettes have been successfully produced and meet specification requirements based on applicable regulations in Indonesia. Besides physical properties, the briquette meet density requirements which are greater than or equal to 1 gr/cm3 and shatter index value is less than 0.5%. The gas emission test shows below threshold, which is CO 0-30 ppm, H2S 0-3.6 ppm, and NOx is not detected. After evaluation, it showed that by adding 30% biomass, ignition time could be decreased and remaining unburned briquettes or bottom ash was reduced as much as 68.68%. Conclusion, significance and impact study: The bio-coal briquettes is a strategic solution to environmental problems and alternative energy sources that are environmentally friendly, because CO and H2S emissions are still below the threshold, even for NOx not detected. Making Bio-coal briquettes as a solution to the utilization of reject coal mining waste to be used as an alternative energy source has been successfully carried out.

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