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19 pages, 4050 KiB

Open AccessArticle

Co-Ensiling of Wheat Straw as an Alternative Pre-Treatment to Chemical, Hydrothermal and Mechanical Methods for Methane Production

by Mads Ujarak Sieborg, Brian Dahl Jønson, Søren Ugilt Larsen, Ali Heidarzadeh Vazifehkhoran and Jin Mi Triolo

Energies 2020, 13(16), 4047; https://doi.org/10.3390/en13164047 - 05 Aug 2020

Cited by 16 | Viewed by 2329

Abstract

Wheat straw without pre-treatment is only converted to methane to a low degree during anaerobic digestion for fuel production due to its low hydrolysis. Current pre-treatment technologies are challenged by high expenses to energy or chemical agents. We examined the low-tech co-ensiling pre-treatment [...] Read more.

Wheat straw without pre-treatment is only converted to methane to a low degree during anaerobic digestion for fuel production due to its low hydrolysis. Current pre-treatment technologies are challenged by high expenses to energy or chemical agents. We examined the low-tech co-ensiling pre-treatment as an alternative pre-treatment of wheat straw, and compared the results with hydrothermal, chemical and mechanical pre-treatment methods. The effects of co-ensiling duration and the mixing ratio between straw and sugar beet root on the methane yields, surface morphology and chemical composition were examined. It was found that co-ensiling could improve production of methane by 34.7%, while a combined hydrothermal and chemical pre-treatment could increase the production of methane by 25.4%. The study demonstrated that the effect of co-ensiling could overlap with hydrothermal and chemical pre-treatment by having similar effects to increase lignocellulosic hydrolysis and improve methane production. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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12 pages, 478 KiB

Open AccessArticle

Agricultural Biogas—An Important Element in the Circular and Low-Carbon Development in Poland

by Arkadiusz Piwowar

Energies 2020, 13(7), 1733; https://doi.org/10.3390/en13071733 - 05 Apr 2020

Cited by 23 | Viewed by 3957

Abstract

The agricultural sector can play an important role in the transformation of the energy economy in Poland. Special attention in this paper has been paid to the development of the agricultural biogas market in Poland. The considerations mainly concern organizational and economic aspects. [...] Read more.

The agricultural sector can play an important role in the transformation of the energy economy in Poland. Special attention in this paper has been paid to the development of the agricultural biogas market in Poland. The considerations mainly concern organizational and economic aspects. Agricultural biogas plant represents the circular cycle of matter and energy. It enables the establishment of low-carbon, resource-efficient links between the agriculture and energy sectors. This is an important element of the circular economy, where waste from agricultural production and the agri-food industry, coming from renewable resources, is transformed into goods with a higher added value. The social and economic needs of the present generation and future generations are considered. The paper presented the characteristics of the Polish market, i.e., the number of entities, the number and location of plants, as well as the production volumes. Analyses were performed in the area of raw materials used to produce agricultural biogas. The analyses were carried out between 2011 and 2018. According to analyses, the potential of the agricultural biogas market in Poland is currently being used to a small extent. It is necessary not only to provide institutional support but also to increase the awareness of farmers and managers in agri-food companies of the possibility of using production waste for energy purposes. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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15 pages, 881 KiB

Open AccessArticle

Ammonium Sulphate from a Bio-Refinery System as a Fertilizer—Agronomic and Economic Effectiveness on the Farm Scale

by Magdalena Szymańska, Tomasz Sosulski, Ewa Szara, Adam Wąs, Piotr Sulewski, Gijs W.P. van Pruissen and René L. Cornelissen

Energies 2019, 12(24), 4721; https://doi.org/10.3390/en12244721 - 11 Dec 2019

Cited by 18 | Viewed by 5025

Abstract

This paper presents the results of a pot experiment aimed at the assessment of the agronomic and economic effectiveness of ammonium sulphate from an agro bio-refinery (Bio-AS). The Bio-AS was obtained by means of the ammonia stripping process from effluent after struvite precipitation [...] Read more.

This paper presents the results of a pot experiment aimed at the assessment of the agronomic and economic effectiveness of ammonium sulphate from an agro bio-refinery (Bio-AS). The Bio-AS was obtained by means of the ammonia stripping process from effluent after struvite precipitation from a liquid fraction of digestate. The agronomic effectiveness of Bio-AS in a pot experiment with maize and grass in two different soils, silty loam (SL) and loamy sand (LS), was investigated. The fertilising effect of Bio-AS was compared to commercial ammonium sulphate fertilizer (Com-AS) and control treatment (without fertilisation). The crop yields were found to depend on both soil type and nitrogen treatment. Crop yields produced under Bio-AS and Com-AS exceeded those under control treatments, respectively for SL and LS soils, by 88% and 125% for maize and 73% and 94% for grass. Crop yields under Bio-AS were similar to those under the Com-AS treatment. The fertilizer use of Bio-AS affected the chemical composition of plants and soil properties similarly as Com-AS. This suggests that Bio-AS from a bio-refinery can replace industrial ammonium sulphate, resulting in both economic and environmental benefits. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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13 pages, 1071 KiB

Open AccessArticle

Application of Response Surface Analysis to Evaluate the Effect of Concentrations of Ammonia and Propionic Acid on Acetate-Utilizing Methanogenesis

by Seung Gu Shin, Joonyeob Lee, Trong Hoan Do, Su In Kim and Seokhwan Hwang

Energies 2019, 12(17), 3394; https://doi.org/10.3390/en12173394 - 03 Sep 2019

Cited by 5 | Viewed by 2216

Abstract

Ammonia and propionate are known inhibitors of anaerobic methanogenesis at higher concentrations, and are likely to coexist in digesters treating high-strength wastewater. Therefore, this study was conducted to assess the effects of ammonia and propionate on acetate-utilizing methanogenesis when they coexist. Response surface [...] Read more.

Ammonia and propionate are known inhibitors of anaerobic methanogenesis at higher concentrations, and are likely to coexist in digesters treating high-strength wastewater. Therefore, this study was conducted to assess the effects of ammonia and propionate on acetate-utilizing methanogenesis when they coexist. Response surface analysis with face-centered central composite design was used to explore the total ammonia nitrogen (TAN) level of 2–5 g/L and the propionate level of 2–8 g/L in acetate-fed batch incubation. Two models were successfully derived to estimate the lag period and the methane yield in response to the concentrations of the two chemicals. The lag period was affected by both inhibitors, with clues obtained of a synergistic effect at a higher concentration rage ([TAN] > 3.5 g/L and [propionate] > 5 g/L). The methane yield was also affected by the two inhibitors; between the two, it was more significantly dependent on the TAN concentration than on the propionate concentration. Real-time PCR showed that Methanosarcinaceae was the major methanogen group in this system. The results of this study improve our understanding of the inhibition of biogas reactors. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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21 pages, 2867 KiB

Open AccessArticle

Effects of Two-Stage Operation on Stability and Efficiency in Co-Digestion of Food Waste and Waste Activated Sludge

by Xinyuan Liu, Ruying Li and Min Ji

Energies 2019, 12(14), 2748; https://doi.org/10.3390/en12142748 - 18 Jul 2019

Cited by 19 | Viewed by 3911

Abstract

The two-stage anaerobic digestion (AD) technology attracts increasing attention due to its ability to collect both hydrogen and methane. A two-stage AD system feeding with food waste and waste activated sludge was investigated in order to achieve higher energy yield and organics removal. [...] Read more.

The two-stage anaerobic digestion (AD) technology attracts increasing attention due to its ability to collect both hydrogen and methane. A two-stage AD system feeding with food waste and waste activated sludge was investigated in order to achieve higher energy yield and organics removal. The two-stage process consists of a thermophilic H₂-reactor and a mesophilic CH₄-reactor, achieved the highest hydrogen and methane yields of 76.8 mL/g-VS and 147.6 mL/g-VS at hydraulic retention times (HRTs) of 0.8 d and 6 d, respectively. The co-digestion process in this study required much less external alkalinity to maintain the pH values than sole food waste digestion in the literature. Compared with the single-stage mesophilic methane AD process, the two-stage AD system had better performance on operation stability, biogas and energy yields, organics removal and chemical oxygen demand (COD) conversion at high organic loading rates (OLRs). According to the TA-cloning analysis, the dominant bacteria in H₂-reactor was closely related to Clostridium sp. strain Z6 and species Thermoanaerobacterium thermosaccharolyticum. The dominant methanogens in two-stage and single-stage CH₄-reactor were recognized as acetotrophic methanogens and hydrogenotrophic methanogens, respectively. The presence of the genus Nitrososphaera in the two CH₄-reactors might contribute to the low NH₄⁺-N concentration in digestate and low CO₂ content in biogas. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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13 pages, 1437 KiB

Open AccessArticle

Sequential Production of Lignin, Fatty Acid Methyl Esters and Biogas from Spent Coffee Grounds via an Integrated Physicochemical and Biological Process

by Minjeong Lee, Minseok Yang, Sangki Choi, Jingyeong Shin, Chanhyuk Park, Si-Kyung Cho and Young Mo Kim

Energies 2019, 12(12), 2360; https://doi.org/10.3390/en12122360 - 19 Jun 2019

Cited by 22 | Viewed by 3850

Abstract

Spent coffee grounds (SCG) are one of the lignocellulosic biomasses that have gained much attention due to their high potential both in valorization and biomethane production. Previous studies have reported single processes that extract either fatty acids/lignin or biogas. In this study, an [...] Read more.

Spent coffee grounds (SCG) are one of the lignocellulosic biomasses that have gained much attention due to their high potential both in valorization and biomethane production. Previous studies have reported single processes that extract either fatty acids/lignin or biogas. In this study, an integrated physicochemical and biological process was investigated, which sequentially recovers lignin, fatty acid methyl esters (FAME) and biogas from the residue of SCG. The determination of optimal conditions for sequential separation was based on central composite design (CCD) and response surface methodology (RSM). Independent variables adopted in this study were reaction temperature (86.1–203.9 °C), concentration of sulfuric acid (0.0–6.4%v/v) and methanol to SCG ratio (1.3–4.7 mL/g). Under determined optimal conditions of 161.0 °C, 3.6% and 4.7 mL/g, lignin and FAME yields were estimated to be 55.5% and 62.4%, respectively. FAME extracted from SCG consisted of 41.7% C16 and 48.16% C18, which makes the extractives appropriate materials to convert into biodiesel. Results from Fourier transform infrared spectroscopy (FT-IR) further support that lignin and FAME extracted from SCG have structures similar to previously reported extractives from other lignocellulosic biomasses. The solid residue remaining after lignin and FAME extraction was anaerobically digested under mesophilic conditions, resulting in a methane yield of 36.0 mL-CH₄/g-VS_added. This study is the first to introduce an integrated resource recovery platform capable of valorization of a municipal solid waste stream. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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15 pages, 3327 KiB

Open AccessArticle

Performance and Microbial Community Dynamics in Anaerobic Digestion of Waste Activated Sludge: Impact of Immigration

by Juhee Shin, Si-Kyung Cho, Joonyeob Lee, Kwanghyun Hwang, Jae Woo Chung, Hae-Nam Jang and Seung Gu Shin

Energies 2019, 12(3), 573; https://doi.org/10.3390/en12030573 - 12 Feb 2019

Cited by 28 | Viewed by 4497

Abstract

Waste activated sludge (WAS) is a byproduct of municipal wastewater treatment. WAS contains a large proportion of inactive microbes, so when it is used as a substrate for anaerobic digestion (AD), their presence can interfere with monitoring of active microbial populations. To investigate [...] Read more.

Waste activated sludge (WAS) is a byproduct of municipal wastewater treatment. WAS contains a large proportion of inactive microbes, so when it is used as a substrate for anaerobic digestion (AD), their presence can interfere with monitoring of active microbial populations. To investigate how influent cells affect the active and inactive microbial communities during digestion of WAS, we operated model mesophilic bioreactors with conventional conditions. Under six different hydraulic retention times (HRTs; 25, 23, 20, 17, 14, and 11.5 d), the chemical oxygen demand (COD) removal and CH₄ production of the AD were within a typical range for mesophilic sludge digesters. In the main bacteria were proteobacteria, bacteroidetes, and firmicutes in both the WAS and the bioreactors, while in main archaeal methanogen group was Methanosarcinales in the WAS and methanomicrobiales in the bioreactors. Of the 106 genera identified, the estimated net growth rates were negative in 72 and positive in 34. The genera with negative growth included many aerobic taxa. The genera with positive growth rates included methanogens and syntrophs. In some taxa, the net growth rate could be positive or negative, depending on HRT, so their abundance was also affected by HRT. This study gives insights into the microbial dynamics of a conventional sludge anaerobic digester by distinguishing potentially active (growing) and inactive (non-growing, dormant) microbes and by correlating population dynamics with process parameters. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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Review

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20 pages, 1155 KiB

Open AccessReview

Granular Sludge Bed Processes in Anaerobic Digestion of Particle-Rich Substrates

by Fasil Ayelegn Tassew, Wenche Hennie Bergland, Carlos Dinamarca, Roald Kommedal and Rune Bakke

Energies 2019, 12(15), 2940; https://doi.org/10.3390/en12152940 - 31 Jul 2019

Cited by 5 | Viewed by 3645

Abstract

Granular sludge bed (GSB) anaerobic digestion (AD) is a well-established method for efficient wastewater treatment, limited, however, by the wastewater particle content. This review is carried out to investigate how and to what extent feed particles influence GSB to evaluate the applicability of [...] Read more.

Granular sludge bed (GSB) anaerobic digestion (AD) is a well-established method for efficient wastewater treatment, limited, however, by the wastewater particle content. This review is carried out to investigate how and to what extent feed particles influence GSB to evaluate the applicability of GSB to various types of slurries that are abundantly available. Sludge bed microorganisms evidently have mechanisms to retain feed particles for digestion. Disintegration and hydrolysis of such particulates are often the rate-limiting steps in AD. GSB running on particle-rich substrates and factors that affect these processes are stdied especially. Disintegration and hydrolysis models are therefore reviewed. How particles may influence other key processes within GSB is also discussed. Based on this, limitations and strategies for effective digestion of particle-rich substrates in high-rate AD reactors are evaluated. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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25 pages, 1605 KiB

Open AccessReview

A Review on Anaerobic Co-Digestion with a Focus on the Microbial Populations and the Effect of Multi-Stage Digester Configuration

by Anahita Rabii, Saad Aldin, Yaser Dahman and Elsayed Elbeshbishy

Energies 2019, 12(6), 1106; https://doi.org/10.3390/en12061106 - 21 Mar 2019

Cited by 221 | Viewed by 9978

Abstract

Recent studies have shown that anaerobic co-digestion (AnCoD) is superior to conventional anaerobic digestion (AD). The benefits of enhanced bioenergy production and solids reduction using co-substrates have attracted researchers to study the co-digestion technology and to better understand the effect of multi substrates [...] Read more.

Recent studies have shown that anaerobic co-digestion (AnCoD) is superior to conventional anaerobic digestion (AD). The benefits of enhanced bioenergy production and solids reduction using co-substrates have attracted researchers to study the co-digestion technology and to better understand the effect of multi substrates on digester performance. This review will discuss the results of such studies with the main focus on: (1) generally the advantages of co-digestion over mono-digestion in terms of system stability, bioenergy, and solids reduction; (2) microbial consortia diversity and their synergistic impact on biogas improvement; (3) the effect of digester mode, i.e., multi-stage versus single stage digestion on AnCoD. It is essential to note that the studies reported improvement in the synergy and diverse microbial consortia when using co-digestion technologies, in addition to higher biomethane yield when using two-stage mode. A good example would be the co-digestion of biodiesel waste and glycerin with municipal waste sludge in a two-stage reactor resulting in 100% increase of biogas and 120% increase in the methane content of the produced biogas with microbial population dominated by Methanosaeta and Methanomicrobium. Full article

(This article belongs to the Special Issue Anaerobic Digestion for the Production of Energy and Chemicals)

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