Editorial

4 pages, 460 KiB

Open AccessEditorial

Processes for Bioenergy and Resources Recovery from Biowaste

by Elsayed Elbeshbishy and Bipro Ranjan Dhar

Processes 2020, 8(8), 1005; https://doi.org/10.3390/pr8081005 - 18 Aug 2020

Cited by 2 | Viewed by 2077

The increasing quantity of biowaste generation and the requirements governing their ultimate disposal are of serious economic and environmental concern [...] Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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Research

Jump to: Editorial, Review

8 pages, 237 KiB

Open AccessCommunication

Sulfur, Phosphorus and Metals in the Stoichiometric Estimation of Biomethane and Biohydrogen Yields

by Yehor Pererva, Charles D. Miler and Ronald C. Sims

Processes 2020, 8(6), 714; https://doi.org/10.3390/pr8060714 - 20 Jun 2020

Cited by 4 | Viewed by 2658

Abstract

The estimation of biomethane or biohydrogen yield is used to evaluate energy recovery during the process of the anaerobic treatment of waste and wastewater. Mathematically calculated theoretical values can also be used in biomethane or biohydrogen potential tests as reference points to calculate [...] Read more.

The estimation of biomethane or biohydrogen yield is used to evaluate energy recovery during the process of the anaerobic treatment of waste and wastewater. Mathematically calculated theoretical values can also be used in biomethane or biohydrogen potential tests as reference points to calculate which fraction of substrate is decomposed, when the substrate degradation stopped and when the sample’s self-digestion begins. This study suggests expanded forms of equations for anaerobic processes leading to either biomethane or biohydrogen. The traditional equations describing the conversion of a substrate with known carbon, hydrogen, oxygen and nitrogen composition were expanded to account for the composition of sulfur (for biohydrogen yields) and phosphorus (both biohydrogen and biomethane yields). As an optional part, one metal cation was also incorporated into the chemical formula of the evaluated wastewater composition in case the compound of biodegradable interest exists as a salt. The equations derived here can be useful for researchers estimating energy recovery based on the elemental analysis of samples, such as algal biomass harvested during harmful algal blooms (HABs). Examples of biomethane and biohydrogen yield estimations from sulfur- and phosphorus-containing compounds are also provided. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

12 pages, 1926 KiB

Open AccessFeature PaperArticle

High-Solids Anaerobic Digestion Followed by Ultrasonication of Digestate and Wet-Type Anaerobic Digestion for Enhancing Methane Yield from OFMSW

by Bappi Chowdhury, Sarmad Bilal Magsi, Hok Nam Joey Ting and Bipro Ranjan Dhar

Processes 2020, 8(5), 555; https://doi.org/10.3390/pr8050555 - 09 May 2020

Cited by 11 | Viewed by 6235

Abstract

High-solids anaerobic digestion of organic fraction of municipal solid waste often shows inefficient biomethane recovery due to mass transfer limitations. Consequently, this study presents a two-stage anaerobic digestion process combining high-solids anaerobic digestion followed by ultrasonication of digestate and wet-type anaerobic digestion for [...] Read more.

High-solids anaerobic digestion of organic fraction of municipal solid waste often shows inefficient biomethane recovery due to mass transfer limitations. Consequently, this study presents a two-stage anaerobic digestion process combining high-solids anaerobic digestion followed by ultrasonication of digestate and wet-type anaerobic digestion for effective biomethane recovery from the organic fraction of municipal solid waste. The high-solids anaerobic digestion yielded methane production of 210 L CH₄/kg volatile solids (VS). The digestate from the high-solids anaerobic digestion process was ultrasonicated at three different specific energy inputs (1000, 2500, and 5000 kJ/kg total solids (TS)). The increases in the soluble chemical oxygen demand (SCOD) concentrations (8%–32%) and volatile solids (VS) removal efficiencies (3.5%–10%) at different specific energy inputs were linearly correlated (R² = 0.9356). Thus, ultrasonication led to the solubilization of particulate organics and released soluble organic matters. All ultrasonicated digestate samples showed significantly higher biomethane yields than that observed for the untreated digestate samples. The highest methane yield of 132 L CH₄/kg VS was observed for a specific energy input of 5000 kJ/kg TS, which was 1.94 times higher than the control (68 L CH₄/kg VS). Although specific energy inputs of 1000 kJ/kg TS and 2500 kJ/kg TS showed comparable methane yields (113–114 L CH₄/kg VS), they were ~1.67 times higher than the control. Overall, our results suggest that an integrated system of high-solids and wet-type anaerobic digestion with pre-ultrasonication of digestate has the potential to provide a technically viable solution to enhance biomethane recovery from the organic fraction of municipal solid waste. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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10 pages, 3570 KiB

Open AccessArticle

Methane Emission Reduction Enhanced by Hydrophobic Biochar-Modified Soil Cover

by Beibei Wu, Beidou Xi, Xiaosong He, Xiaojie Sun, Qian Li, Quanyi Ouche, Hongxia Zhang and Chennan Xue

Processes 2020, 8(2), 162; https://doi.org/10.3390/pr8020162 - 01 Feb 2020

Cited by 17 | Viewed by 3552

Abstract

The microbial oxidation of CH₄ in biochar-modified soil cover is considered a potent option for the mitigation of emissions from old landfills or sites containing wastes full of low CH₄ generation rates. The mechanism of methane oxidizing bacteria (MOB) can be [...] Read more.

The microbial oxidation of CH₄ in biochar-modified soil cover is considered a potent option for the mitigation of emissions from old landfills or sites containing wastes full of low CH₄ generation rates. The mechanism of methane oxidizing bacteria (MOB) can be enhanced by amending the landfill cover soil with biochar, which is recalcitrant to biological degradation and can adsorb CH₄ while facilitating the growth and activity of MOB within its porous structure. However, the increase in the permeability coefficient and water content of the cover due to the addition of biochar also affects the methane removal efficiency. A hydrophobic biochar modified by KH-570 was employed to reduce the water content and to promote the diffusion and oxidation of CH₄ in the cover. Several series of small-scale column tests were conducted to quantify the CH₄ oxidation properties of the landfill cover soil amended with biochar and hydrophobic biochar under different levels of exposed CH₄ concentrations (5% and 15%), heights (10–66 cm), and temperatures (15–40 °C). After 30 days of domestication, the removal rate of the hydrophobic biochar-modified soil cover reached 98.8%. The water holding capacity of the cover and the CH₄ oxidation efficiency under different moisture contents were investigated in different columns. The hydrophobic biochar-modified soil cover has a weak water holding capacity, low saturated water content, and optimal CH₄ oxidation efficiency at this time. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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11 pages, 3170 KiB

Open AccessArticle

Characteristics of Low-Temperature Polyvinyl Chloride Carbonization by Catalytic CuAl Layered Double Hydroxide

by Erwei Pang, Weijun Liu, Shuhua Zhang, Nengshuo Fu and Zhongxun Tian

Processes 2020, 8(1), 120; https://doi.org/10.3390/pr8010120 - 17 Jan 2020

Cited by 3 | Viewed by 4133

Abstract

A good way to make carbon materials was presented in low-temperature polyvinyl chloride (PVC) carbonization by catalysis. The process of low-temperature PVC carbonization by CuAl-layered double hydroxide (CuAl-LDH) was investigated by thermogravimetric analysis (TGA) and tubular furnace. The results show that CuAl-LDH accounting [...] Read more.

A good way to make carbon materials was presented in low-temperature polyvinyl chloride (PVC) carbonization by catalysis. The process of low-temperature PVC carbonization by CuAl-layered double hydroxide (CuAl-LDH) was investigated by thermogravimetric analysis (TGA) and tubular furnace. The results show that CuAl-LDH accounting for 5% of PVC mass enabled acceleration of the dehydrochlorination in PVC as soon as possible and maximized the yield of the PVC carbonized product. The vacuum with 0.08 MPa, 20 °C/min heating rate and 90 min carbonized maintenance time were optimal for PVC carbonization. Moreover, the best morphology and yield of the carbonized product was provided at a carbonization temperature of 300 °C. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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14 pages, 1390 KiB

Open AccessArticle

Analyses for Synthesis Gas from Municipal Solid Waste Gasification under Medium Temperatures

by Qinyang Gu, Wei Wu, Baosheng Jin and Zheng Zhou

Processes 2020, 8(1), 84; https://doi.org/10.3390/pr8010084 - 08 Jan 2020

Cited by 12 | Viewed by 5856

Abstract

Municipal solid waste (MSW) gasification could be a novel method that shows the various advantages over traditional MSW treatments in China. Other research concluded that MSW gasification was operating by the assistant heat, and the gasification may occur under medium temperature. So, this [...] Read more.

Municipal solid waste (MSW) gasification could be a novel method that shows the various advantages over traditional MSW treatments in China. Other research concluded that MSW gasification was operating by the assistant heat, and the gasification may occur under medium temperature. So, this study is aimed to investigate MSW gasification and pyrolysis behavior and analyze the syngas evolution and reaction mechanism. The MSW samples were collected in daily life and the experiments were carried out in a fixed tubular reactor below 650 °C. The effects of medium temperature and oxygen content on syngas quality were elucidated in depth. The results have shown that temperature can promote the syngas quality in the range of 550–650 °C, because the increasing temperature strengthens the reaction rate. The oxygen content should be controlled in a certain range, or oxidation reactions will be more prominent during gasification. The optimal gasification condition in this study was obtained at 650 °C and an oxygen concentration of 1.25%, the combustible gas yield and the lower heating value (LHV) of syngas of this condition were 0.296 L/g and 10.98 kJ/L, respectively. This study provides insights for MSW gasification under medium temperature, and a practical gasification system can be designed under a certain condition. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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17 pages, 4342 KiB

Open AccessArticle

Synergistic Effect on the Non-Oxygenated Fraction of Bio-Oil in Thermal Co-Pyrolysis of Biomass and Polypropylene at Low Heating Rate

by Dijan Supramono, Adithya Fernando Sitorus and Mohammad Nasikin

Processes 2020, 8(1), 57; https://doi.org/10.3390/pr8010057 - 02 Jan 2020

Cited by 8 | Viewed by 2730

Abstract

Biomass pyrolysis and polypropylene (PP) pyrolysis in a stirred tank reactor exhibited different heat transfer phenomena whereby heat transfer in biomass pyrolysis was driven predominantly by heat radiation and PP pyrolysis by heat convection. Therefore, co-pyrolysis could exhibit be expected to display various [...] Read more.

Biomass pyrolysis and polypropylene (PP) pyrolysis in a stirred tank reactor exhibited different heat transfer phenomena whereby heat transfer in biomass pyrolysis was driven predominantly by heat radiation and PP pyrolysis by heat convection. Therefore, co-pyrolysis could exhibit be expected to display various heat transfer phenomena depending on the feed composition. The objective of the present work was to determine how heat transfer, which was affected by feed composition, affected the yield and composition of the non-polar fraction. Analysis of heat transfer phenomena was based on the existence of two regimes in the previous research in which in regime 1 (the range of PP composition in the feeds is 0–40%), mass ejection from biomass particles occurred without biomass particle swelling, while in regime 2 (the range of PP composition in the feeds is 40–100%), mass ejection was preceded by biomass particle swelling. The co-pyrolysis was carried out in a stirred tank reactor with heating rate of 5 °C/min until 500 °C and using N₂ gas as carrier gas. Temperature measurement was applied to pyrolysis fluid at the lower part of the reactor and small biomass spheres of 6 mm diameter to simulate heat transfer to biomass particles. The results indicate that in regime 1 convective and radiative heat transfers sparingly occurred and synergistic effect on the yield of non-oxygenated phase increased with increasing convective heat transfer at increasing %PP in feed. On the other hand, in regime 2, convective heat transfer was predominant with decreasing synergistic effect at increasing %PP in feed. The optimum PP composition in feed to reach maximum synergistic effect was 50%. Non-oxygenated phase portion in the reactor leading to the wax formation acted as donor of methyl and hydrogen radicals in the removal of oxygen to improve synergistic effect. Non-oxygenated fraction of bio-oil contained mostly methyl comprising about 53% by mole fraction, while commercial diesel contained mostly methylene comprising about 59% by mole fraction Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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15 pages, 6602 KiB

Open AccessArticle

CFD Study of Gas Holdup and Frictional Pressure Drop of Vertical Riser Inside IC Reactor

by Sheng Wang, He Dong, Zhongfeng Geng and Xiuqin Dong

Processes 2019, 7(12), 936; https://doi.org/10.3390/pr7120936 - 09 Dec 2019

Cited by 3 | Viewed by 3046

Abstract

The internal circulation system in Internal Circulation (IC) reactor plays an important role in increasing volumetric loading rate and promoting the mixing between sludge and wastewater. In order to design the internal circulation system, the flow behaviors of gas-liquid inside vertical riser should [...] Read more.

The internal circulation system in Internal Circulation (IC) reactor plays an important role in increasing volumetric loading rate and promoting the mixing between sludge and wastewater. In order to design the internal circulation system, the flow behaviors of gas-liquid inside vertical riser should be studied in detail. In the present study, the Multiple Flow Regimes model is adopted to capture the phase interface for different flow conditions. The flow patterns, internal circulation flow rate, gas holdup, and frictional pressure drop of vertical riser are investigated. The results show that the bubble flow inside a vertical riser is in a stable flow condition. There exists a maximum value for internal circulation flow rate with the increasing superficial gas velocity. The parameters of Martinelli models for gas holdup and frictional pressure drop are improved based on Computational Fluid Dynamics (CFD) results. The deviations between the calculated gas holdup and frictional pressure drop by improved model and experimental value are reduced to 14% and 13.2%, respectively. The improved gas holdup and frictional pressure drop model can be used for the optimal design of internal circulation system. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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11 pages, 9779 KiB

Open AccessArticle

CFD Simulation on Hydrodynamic Behaviors of Anaerobic Granule Swarms

by Xiuqin Dong, Sheng Wang and Zhongfeng Geng

Processes 2019, 7(12), 880; https://doi.org/10.3390/pr7120880 - 26 Nov 2019

Cited by 2 | Viewed by 2456

Abstract

An internal circulation (IC) anaerobic reactor is widely used in the treatment of municipal and industrial wastewater with high volumetric loading rates. The performance of an IC reactor is closely related with hydrodynamic behaviors of anaerobic granules. Typically, anaerobic granules work in swarms [...] Read more.

An internal circulation (IC) anaerobic reactor is widely used in the treatment of municipal and industrial wastewater with high volumetric loading rates. The performance of an IC reactor is closely related with hydrodynamic behaviors of anaerobic granules. Typically, anaerobic granules work in swarms and the settling behavior of a granule is disturbed by other granules. However, the research on anaerobic granule swarms is insufficient. In this work, Computational Fluid Dynamics (CFD) method was employed to study the hydrodynamic behaviors of anaerobic granule swarms with various voidages. The simulated results showed that the average velocity inside granules increased significantly as the voidage of granule swarm decreased and as the Reynolds number increased. The maximum shear stress on the granule’s surface increased with decreasing voidage and increasing Reynolds number. Based on the hydrodynamic behaviors of anaerobic granule swarms, an improved model of drag force coefficient for granule swarms was developed. The predicted expanded height, using the improved model, gives better consistency with experimental results. The improved model can embed in CFD code to improve the precision of the description of the IC reactor model and provide valuable information for designing and operating an IC reactor. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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20 pages, 1972 KiB

Open AccessFeature PaperArticle

Effect of Hydrothermal Pretreatment on Volatile Fatty Acids Production from Source-Separated Organics

by Farokh laqa Kakar, Ehssan Hosseini Koupaie, Hisham Hafez and Elsayed Elbeshbishy

Processes 2019, 7(9), 576; https://doi.org/10.3390/pr7090576 - 01 Sep 2019

Cited by 7 | Viewed by 4177

Abstract

The current study investigates the effect of hydrothermal pretreatment (HTP) on acidification of source-separated organics (SSO) in terms of volatile fatty acids (VFAs) production and solubilization. Temperature and retention time for HTP of SSO ranged from 150 to 240 °C and 5 to [...] Read more.

The current study investigates the effect of hydrothermal pretreatment (HTP) on acidification of source-separated organics (SSO) in terms of volatile fatty acids (VFAs) production and solubilization. Temperature and retention time for HTP of SSO ranged from 150 to 240 °C and 5 to 30 min, respectively. The soluble substance after hydrothermal pretreatment initially increased, reaching its peak at 210 °C and then declined gradually. The highest overall chemical oxygen demand (COD) solubilization of 63% was observed at “210 °C-20 min” compared to 17% for raw SSO. The highest VFAs yield of 1536 mg VFAs/g VSS added was observed at “210 °C-20 min” compared to 768 mg VFAs/g VSS for raw SSO. Intensification of hydrothermal pretreatment temperature beyond 210 °C resulted in the mineralization of the organics and adversely affected the process. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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12 pages, 1247 KiB

Open AccessArticle

Enhanced Anaerobic Mixed Culture Fermentation with Anion-Exchange Resin for Caproate Production

by Jiangnan Yu, Jialin Liao, Zhenxing Huang, Peng Wu, Mingxing Zhao, Chunmei Liu and Wenquan Ruan

Processes 2019, 7(7), 404; https://doi.org/10.3390/pr7070404 - 01 Jul 2019

Cited by 9 | Viewed by 3278

Abstract

The bioproduction of caproate from organic waste by anaerobic mixed culture is a very attractive technology for upgrading low-grade biomass to a high-value resource. However, the caproate production process is markedly restricted by the feedback inhibition of caproate. In this study, four types [...] Read more.

The bioproduction of caproate from organic waste by anaerobic mixed culture is a very attractive technology for upgrading low-grade biomass to a high-value resource. However, the caproate production process is markedly restricted by the feedback inhibition of caproate. In this study, four types of anion-exchange resin were investigated for their enhancing capability in caproate fermentation of anaerobic mixed culture. The strong base anion-exchange resin D201 showed the highest adsorption capacity (62 mg/g), selectivity (7.50), and desorption efficiency (88.2%) for caproate among the test resins. Subsequently, the optimal desorption temperature and NaOH concentration of eluent for D201 were determined. The adsorption and desorption efficiency of D201 remained stable during eight rounds of the adsorption–desorption cycle, indicating a satisfactory reusability of D201. Finally, performances of caproate fermentation with and without resin adsorption for carboxylate were evaluated. The results demonstrated that the final concentration of caproate was improved from 12.43 ± 0.29 g/L (without adsorption) to 17.30 ± 0.13 g/L (with adsorption) and the maximum caproate production rate was improved from 0.60 ± 0.01 g/L/d to 2.03 ± 0.02 g/L/d. In the group with adsorption, the cumulative caproate production was increased to 29.10 ± 0.33 g/L broth, which was 134% higher than that of the control group. Therefore, this study provides effective approaches to enhance caproate production. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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9 pages, 3468 KiB

Open AccessArticle

Enhanced Anaerobic Performances of Kitchen Wastes in a Semi-Continuous Reactor by EDTA Improving the Water-Soluble Fraction of Fe

by Yali Liu, Xiaorong Kang and Han Cheng

Processes 2019, 7(6), 351; https://doi.org/10.3390/pr7060351 - 08 Jun 2019

Cited by 4 | Viewed by 2435

Abstract

The addition of Fe²⁺ is considered an effective method for increasing methane production, but the added Fe²⁺ may not be absorbed by anaerobic microorganisms due to complex chemical reactions. In this study, ethylenediaminetetraacetic acid (EDTA) was used as a ligand of [...] Read more.

The addition of Fe²⁺ is considered an effective method for increasing methane production, but the added Fe²⁺ may not be absorbed by anaerobic microorganisms due to complex chemical reactions. In this study, ethylenediaminetetraacetic acid (EDTA) was used as a ligand of Fe²⁺ (EDTA-Fe) to promote the dissolution of Fe, and the anaerobic performances of kitchen wastes (KWs) in a semi-continuous reactor were studied. The results indicated that the biogas yields and methane contents were enhanced to 594–613 mL·g⁻¹VS_add·d⁻¹ and 63.6–64.4% at an organic loading rate (OLR) of 2.5 gVS_add·L⁻¹·d⁻¹ due to EDTA-Fe addition. Simultaneously, the EDTA-Fe was more effective than Fe²⁺ in preventing the acidification of KWs with a high OLR (5.0 gVS_add·L⁻¹·d⁻¹). In addition, the sequential extraction results showed that the water-soluble fraction of Fe in the R3 (EDTA-Fe addition) was 1.49-fold of that in the R2 with Fe²⁺ addition. The contents of coenzymes F420 and F430 were also improved 1.09 and 1.11 times, respectively. Mechanism analysis confirmed that the EDTA enhanced methane production and operational stability by promoting the dissolution of Fe and maintaining a high content of water-soluble Fe. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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Review

Jump to: Editorial, Research

19 pages, 610 KiB

Open AccessReview

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

by Anthony Anukam, Ali Mohammadi, Muhammad Naqvi and Karin Granström

Processes 2019, 7(8), 504; https://doi.org/10.3390/pr7080504 - 02 Aug 2019

Cited by 217 | Viewed by 17061

Abstract

The anaerobic digestion technology has been in existence for centuries and its underlying theory established for decades. It is considered a useful technology for the generation of renewable energy, and provides means to alleviate problems associated with low access to energy. However, a [...] Read more.

The anaerobic digestion technology has been in existence for centuries and its underlying theory established for decades. It is considered a useful technology for the generation of renewable energy, and provides means to alleviate problems associated with low access to energy. However, a great deal of current research is targeted towards the optimization of this technology under diverse digestion process conditions. This review presents an in-depth analysis of the chemistry of anaerobic digestion and discusses how process chemistry can be used to optimize system performance through identification of methods that can accelerate syntrophic interactions of different microorganisms for improved methanogenic reactions. Recent advances in addition to old research are discussed in order to offer a general but comprehensive synopsis of accumulated knowledge in the theory of anaerobic digestion, as well as an overview of previous research and future directions and opportunities of the AD technology. Achieving a sustainable energy system requires comprehensive reforms in not just economic, social and policy aspects, but also in all technical aspects, which represents one of the most crucial future investments for anaerobic digestion systems. Full article

(This article belongs to the Special Issue Processes for Bioenergy and Resources Recovery from Biowaste)

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