Tag Archives: anaerobic digestion

xxx N. Sjulander, V. Rooni, L. Rocha-Meneses and T. Kikas
Comparison of different chemical-free pretreatment methods for the production of sugars, ethanol and methane from lignocellulosic biomass
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Comparison of different chemical-free pretreatment methods for the production of sugars, ethanol and methane from lignocellulosic biomass

N. Sjulander¹*, V. Rooni¹, L. Rocha-Meneses² and T. Kikas¹*

¹Estonian University of Life Sciences, Institute of Forestry and Engineering, Chair of Biosystems Engineering, EE51014 Tartu, Estonia
²Renewable and Sustainable Energy Research Center, Technology Innovation Institute, P.O.Box: 9639, Masdar City, Abu Dhabi, United Arab Emirates
*Correspondence: nikki.sjulander@emu.ee; timo.kikas@emu.ee

Abstract:

Most pretreatment methods for lignocellulosic biomass use strong chemicals, such as sulphuric acid and ammonia, to open up the cellular structure of plant biomass. However, those chemicals are not environmentally friendly and their use leads to safety risks. As a result, different chemical-free pretreatment methods have been developed, which focus on the usage of pressure, high or low temperatures and mild chemicals. Freezing pretreatment and explosive decompression pretreatments, using different operating gases, such as nitrogen and steam, are compared in the context of glucose, ethanol and methane yield in this review. For the methane production, the stillage from bioethanol production is used. The usage of this waste improves the overall valorisation of lignocellulosic biomass. The review also investigates, whether the nitrogen explosive decompression pretreatment is suitable for the treatment of softwoods, hardwoods and herbaceous materials. In the comparison of different chemical-free pretreatment methods, it is concluded that heat and water are the most influential parameters for opening up the lignocellulosic biomass structure. The operating gas and pressure in the pretreatment reactor are less relevant. Steam explosion, nitrogen explosive decompression pretreatment and autohydrolysis pretreatment are the most suitable chemical-free pretreatment methods for lignocellulosic biomass.

Key words:

anaerobic digestion, biofuels, fermentation, lignocellulosic inhibitors, steam explosion

120-134 B. Jankovičová, M. Hutňan, Z. Imreová and R. Zakhar
Increased biogas production from lignocellulosic biomass by soaking in water
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Increased biogas production from lignocellulosic biomass by soaking in water

B. Jankovičová*, M. Hutňan, Z. Imreová and R. Zakhar

Slovak University of Technology in Bratislava, Faculty of Chemical and Food Technology, Department of Environmental Engineering, Radlinského 9, SK812 37 Bratislava 1, Slovakia
*Correspondence: barbora.jankovicova@stuba.sk

Abstract:

Due to its large production worldwide, lignocellulosic biomass represents a substrate with great potential to produce biogas. However, this type of biomass is characterized by a complex and solid structure, which is difficult to decompose by anaerobic microorganisms. Applying the correct pre-treatment method can increase its biodegradability. Lignocellulosic substrate was pre-treated by soaking in water for one day at room temperature to increase biogas production and monitoring of long-term operation of laboratory models of anaerobic reactors for anaerobic digestion of such pre-treated maize waste was employed. Monitoring results in two reactors, R1 with biogas produced from a substrate soaked in water for one day and R0 with the production of biogas from a substrate mixed with water just before dosing into the reactor, were compared showing positive effect of the pre-treatment method. This was expressed by higher values of biogas production and higher methane content in biogas from the substrate soaked in water for one day. The achieved specific biogas productions during four different phases of reactor operation in reactor R1 were in the range of 190–335 mL g^-1 of VS (volatile solids)
and 101–221 mL g^-1 of VS in reactor R0. Methane content of biogas during reactor operation was 49.3–55.2% in reactor R1 and 42.5–45.5% in reactor R0. During long-term operation of another reactor, pre-treated maize waste was used as a co-substrate for maize silage, in the ratio of 1:1 based on VS of the substrates proving as a suitable co-substrate for maize silage, as the achieved average value of specific biogas production during reactor operation at OLR (organic loading rate) = 1.75 kg VS m^-3 d^-1 was 510 mL g^-1 of VS and during first 67 days at OLR = 2 kg VS m^-3 d^-1 it was 454 mL g^-1 of VS.

Key words:

anaerobic digestion, bioenergy, maize waste, methane, pre-treatment

1339-1350 V.P. Aravani, K. Tsigkou, M. Kornaros and V.G. Papadakis
Laboratory analyses for assessing the potential for biogas production of various agricultural residues in Greece
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Laboratory analyses for assessing the potential for biogas production of various agricultural residues in Greece

V.P. Aravani¹, K. Tsigkou², M. Kornaros²* and V.G. Papadakis¹*

¹Department of Environmental Engineering, University of Patras, 2 Seferi Str., GR30100 Agrinio, Greece
²Department of Chemical Engineering, University of Patras, 1 Karatheodori Str., University Campus- Rio, GR26504 Patras, Greece
*Correspondence: kornaros@chemeng.upatras.gr; vgpapadakis@upatras.gr

Abstract:

Greece produces significant amounts of agricultural and livestock waste. For the needs of this study, Greece was divided into a Northern and a Southern part and relevant proposals were made for residues that can be used for energy production, through anaerobic digestion. For Northern Greece, this study concluded that the most abundant residues and potential substrates for anaerobic digestion valorisation are those of maize, inedible vegetables (including greenhouse vegetables), cattle manure, as well as the residues of beer and wine industry. For Southern Greece, the corresponding substrates are those of maize, inedible vegetables, sheep/goat manure and residues of wine, tomato, orange and olive processing, respectively. Based on the physicochemical characterization of individual feedstocks, corn silage, tomato husks, watermelon, malt, cattle manure, orange, and olive processing residues (olive pomace) were considered as the most suitable feedstocks for anaerobic digestion. Biochemical Methane Potential (BMP) assays for Northern Greece were also performed, testing the most abundant and appropriate residues for anaerobic digestion (of this area), namely corn silage, cattle manure and malt, in order to define their BMP yield as well as their prospective optimum mixtures. It was concluded that the BMP of the mono-substrates is in accordance with literature, while there were no statistically significant differences in the methane yield of all tested mixtures. The residual biomass originating from the three main categories of the agricultural sector (crop residues, agro-industrial residues, and animal manure) in Northern Greece can be efficiently valorised via anaerobic co-digestion, without observing, though, any synergistic effects on methane production.

Key words:

agricultural residues, anaerobic digestion, biogas, BMP assays, Greece, residue characterization

1591–1598 V. Dubrovskis, I. Plume and I. Straume
The production of methane from the straw pellets with addition of enzymes
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The production of methane from the straw pellets with addition of enzymes

V. Dubrovskis*, I. Plume and I. Straume

Latvia University of Life Sciences and Technologies, Faculty of Engineering, Institute of Energetics, Cakstes blvd. 5, LV3001, Jelgava, Latvia
*Correspondence: vilisd@inbox.lv

Abstract:

Biogas production requires much cheaper raw materials. The use of straw, as not always the full use of agricultural residues, increases the methane yield in pelletised form compared to non-pelletised straw. Lack is the high ratio of carbon to nitrogen content of straw, which leads to a slow and incomplete breakdown of the matter, and less producing substances from which bacteria produce methane.Variety of additives can be used to improve anaerobic digestion process. This article shows the results of the study, where the enzymes alpha amylase and xylanase and catalysts Metaferm and Melafen mixture are used for the digestion process echancement. Investigation was provided in 16 bioreactors operated in batch mode at 38 °C. Additives were filled into 14 bioreactors and only inoculum were filled into two bioreactors for control. The yield of biogas from straw pellets without additives was 0.655 L g^-1_DOM and methane 0.301 L g^-1_DOM after 34 days of anaerobic digestion. The yield of biogas from straw pellets with added alpha amylase was 0.652 L g^-1_DOM and methane 0.318 L g^-1_DOM. The yield of biogas from straw pellets with added xylanase was 0.689 L g^-1_DOM and methane 0.347 L g^-1_DOM. The yield of biogas from straw pellets with added Metaferm and Melafen mixture was 0.638 L g^-1_DOM and methane 0.254 L g^-1_DOM. The study demonstrates that the adding of enzymes increases the production of methane.

Key words:

alpha amylase, anaerobic digestion, methane, straw pellets, xylanase

1881–1890 V. Dubrovskis, I. Plume and I. Straume
Use of ethanol production and stillage processing residues for biogas production
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Use of ethanol production and stillage processing residues for biogas production

V. Dubrovskis*, I. Plume and I. Straume

Latvia University of Life Sciences and Technologies, Liela street 2, LV 3001 Jelgava, Latvia
*Correspondence: vilisd@inbox.lv

Abstract:

In Latvia, ethanol is produced mainly from wheat grains. The production process involves the formation of the by-products of wheat bran, grains residues and stillage. By-products from production of alcohol distilling dregs (stillage) contain much organic matter therefore could be useful for the production of the biogas The product with high protein content usable for feed can be produced from the stillage too. A liquid residue is formed during the production process. Purpose of study is the assessment of the methane volume obtainable from the stillage processing residue mixed with wheat brans and grains residues in anaerobic fermentation process and from wheat brans and grains residues mixed only with inoculum. Investigation was provided in 16 bioreactors operated in batch mode at 38 °C. Stillage processing residues mixed with the wheat brans and inoculum were filled into 4 bioreactors, mixed with grains residues were filled into 4 bioreactors and only inoculum was filled into two bioreactors for control. Wheat brans with inoculum were filled into 3 bioreactors. Into others 3 bioreactors were filled grains residues with inoculum. The yield of biogas from wheat brans was 1.151 L g^-1DOM and methane 0.593 L g^-1DOM after 30 days of anaerobic digestion. The yield of biogas from wheat brans with stillage processing residue was 1.098 L g^-1DOM and methane 0.600 L g^-1DOM. The yield of biogas from grains residues was 0.915 L g^-1DOM and methane 0.451 L g^-1DOM. The yield of biogas from grains residues with stillage processing residue was 1.01 L g^-1DOM and methane 0.523 L g^-1DOM. The study demonstrates that the investigated products are very good raw material for the production of methane. Stillage processing residue acted as a catalyst for the process.

Key words:

anaerobic digestion, grains residues, methane, stillage, stillage processing residue, wheat brans

1642-1648 V. Dubrovskis, I. Plume and I. Straume
Suitability of Common nettle (Urticadioica) and Canadian goldenrod (Solidagocanadensis) for methane production
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Suitability of Common nettle (Urticadioica) and Canadian goldenrod (Solidagocanadensis) for methane production

V. Dubrovskis*, I. Plume and I. Straume

Latvia University of Life Sciences and Technologies, Faculty of Engineering, Institute of Energetics, Cakstesblvd. 5, LV3001 Jelgava, Latvia
*Correspondence: vilisd@inbox.lv

Abstract:

Support for biogas production in Latvia was decreased. There is an urgent need to investigate the suitability of various inexpensive renewable biomass resources for energy production. Also, itis necessary to explore the possibilities to improve the anaerobic fermentation process with the help of various catalysts. Biocatalyst Metaferm produced in Latvia was used in previous studies with other biomass and showed increase in biogas and methane production. The article shows the results of studies on biogas (methane) production from chopped fresh Common nettle (Urtica dioica) and Canadian goldenrod (Solidago canadensis) biomass and effect of catalyst Metaferm in anaerobic fermentation process. The anaerobic digestion process was performed in 0.75 L laboratory digesters, operated in batch mode (38 ± 1.0 °C, 35 days). The average specific biogas or methane production per unit of dry organic matter added (DOM) from Common nettle was 0.709 L g^-1_DOM or was 0.324 L g^-1_DOM respectively. Average specific biogas or methane volume produced from chopped Canadian goldenrod in anaerobic fermentation was 0.548 L g^-1_DOM or 0.267 L g^-1_DOM respectively. Average biogas or methane yield from digestion of chopped Common nettle with 1 mL Metaferm was 0.752 L g^-1_DOM or 0.328 L g^-1_DOM respectively. Average specific biogas or methane yield from anaerobic fermentation of chopped Canadian goldenrod with 1 mL Metaferm was 0.624 L g^-1_DOM or 0.276 L g^-1_DOM respectively. Adding of catalyst Metaferm increases methane yield from chopped nettle or Canadian goldenrod by 1.2% or 3.4% respectively. All investigated biomass resources can be used for methane production.

Key words:

anaerobic digestion, biogas, Canadian goldenrod, methane, nettle

769-783 K. Krištof and J. Gaduš
Effect of alternative sources of input substrates on biogas production and its quality from anaerobic digestion by using wet fermentation
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Effect of alternative sources of input substrates on biogas production and its quality from anaerobic digestion by using wet fermentation

K. Krištof¹* and J. Gaduš²

¹Slovak University of Agriculture in Nitra, Faculty of Engineering, Department of Machines and Production Biosystems, Tr.A. Hlinku 2, SK949 76 Nitra, Slovakia
²Slovak University of Agriculture in Nitra, Faculty of European Studies and Regional Development, Department of Regional Bioenergy, Tr.A. Hlinku 2, SK949 76 Nitra, Slovakia
*Correspondence: koloman.kristof@uniag.sk

Abstract:

The aim of the study was to confirm the suitability of alternative input substrates for production of biogas in order to decrease the need of utilization of high quality maize silage. All of the experiments were conducted by employment of wet fermentation process in mesophilic conditions (temperature in fermentor 40 ± 1 °C) in experimental fermentor with volume 5 m³. The experiments were realised in operating conditions of biogas station designed for utilization of agricultural biowaste. The experiments were divided into two alternatives (I and II cycle) and one control input substrates. In the first alternative (I cycle) was daily dosage formed by 33 kg of Amaranth and 250 L of control manure mixture. In this cycle, more than 3–times greater specific production of biogas was observed with average methane content 63.9% in comparison with control manure mixture (80 : 20%, liquid manure and manure). In the second alternative (II cycle) was daily dosage formed by 19.5 kg of sugar beer cuts, 3.3 kg of maize silage, 1.9 kg of oil-seed rape moldings, 2.5 kg of glycerin and 250 L of control manure mixture. In this cycle, more than 5.9–times greater specific production of biogas was observed. The decrease in average methane content 55.1% however also decrease in average content of hydrogen sulfide (128 ppm) was observed as well. An unquestionable advantage for both tested alternative mixed substrates was increase in biogas production and its quality in comparison with control substrate based on manure. At the basis of these findings can be concluded that both tested alternative input substrate mixtures are suitable as co–fermentation substances with great potential to increase the biogas production and its quality in case of wet fermentation processes.

Key words:

anaerobic digestion, biogas, co-fermentation, co-substrates, wet fermentation

688-695 V. Dubrovskis, I. Plume and I. Straume
Anaerobic co-fermentation of molasses and oil with straw pellets
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Anaerobic co-fermentation of molasses and oil with straw pellets

V. Dubrovskis*, I. Plume and I. Straume

Latvia University of Life Sciences and Technologies, Faculty of Engineering, Institute of Energetics, Cakstes blvd. 5, LV3001 Jelgava, Latvia
*Correspondence: vilisd@inbox.lv

Abstract:

The average grain and straw production in Latvia is increasing in last decade. Straw is not always managed properly and its utilisation in biogas plants can be considered as an alternative. Straw is not the best feedstock for methane production, because it has high C/N ratio. Co-fermentation with other biomass with higher N content can improve the methane production. Purpose of investigation is to evaluate the wheat straw pellets biomass suitability for production of the methane and effect of its co-fermentation with molasses, fried sunflower oil and catalyst Metaferm. The anaerobic digestion process for biogas production was investigated in 0.75 L digesters, operated in batch mode at temperature 38 ± 1.0°C. The average biogas yield per unit of dry organic matter added from digestion of wheat straw pellets was 0.540 L g^-1_DOM and methane yield was 0.285 L g^-1_DOM. Average biogas yield from co-fermentation of wheat straw pellets and molasses was 0.777 L g^-1_DOM and methane yield was 0.408 L g^-1_DOM. Average biogas yield from fermentation of wheat straw pellets with 1ml Metaferm was 0.692 L g^-1_DOM and methane yield was 0.349 L g^-1_DOM. Average biogas yield from co-fermentation of wheat straw pellets and sunflowers oil was 1.041 L g^-1_DOM and methane yield was 0.639 L g^-1_DOM. All investigated biomasses can be used for methane production.

Key words:

anaerobic digestion, biogas, methane, molasses, sunflower oil, wheat straw pellets

398-409 A. Gruduls, K. Balina, K. Ivanovs and F. Romagnoli
Low temperature BMP tests using fish waste from invasive Round goby of the Baltic Sea
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Low temperature BMP tests using fish waste from invasive Round goby of the Baltic Sea

A. Gruduls*, K. Balina, K. Ivanovs and F. Romagnoli

Riga Technical University, Institute of Energy Systems and Environment, Azenes street 12-K1, LV-1048 Riga, Latvia
*Correspondence: Arturs.Gruduls@rtu.lv

Abstract:

Round goby (Neogobius melanostomus) is an invasive fish species in the Baltic Sea. While meat can be used for human consumption, fish processing residues are considered as a waste. Within circular economy and bio-economy perspectives fish waste could be used as a valuable feedstock for biogas production. However, the research is mostly focused on evaluating biogas yield at mesophilic conditions (i.e. 37 °C). In this study the impact of low temperature on Biochemical Methane Potential (BMP) tests has been investigated. Round goby’s processing leftovers – heads, intestines and skin/bone mixture were tested in codigestion with sewage sludge. Anaerobic digestion (AD) was carried out in 100 mL batch tests at low temperature 23 °C and 37 °C conditions, over an incubation period of 31 days. The results show that AD at low temperature occurs twice as slowly as under 37 °C conditions. However, after 31 days the BMP values for 23 °C samples were only 2% lower than for high temperature samples. Heads and skins showed similar BMP values reaching on average 502 L CH₄ kgVS^-1 and 556 L CH₄ kgVS^-1 respectively. BMP for fish intestines was higher, reaching on average 870 L CH₄ kgVS^-1. Average BMP for mixes of fish heads, skins, intestines and bones was 660 L CH₄ kgVS^-1. Acquired BMPs were further compared with the theoretical BMPs from Buswell’s formula. Research results suggests that anaerobic digestion of fish waste under low temperature conditions could be feasible as the process still efficiently occurs, in fact opening a new opportunity to explore the overall sustainability of technologies based on these conversion processes.

Key words:

anaerobic digestion, biomethane, fish waste, low temperature, Neogobius melanostomus

674–679 V. Dubrovskis and I. Plume
Suitability of oat bran for methane production
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Suitability of oat bran for methane production

V. Dubrovskis* and I. Plume

Latvia University of Agriculture, Faculty of Engineering, Institute of Energetics, Cakstes blvd 5, LV 3001 Jelgava, Latvia
*Correspondence: vilisd@inbox.lv

Abstract:

There is need to investigate the suitability of various cheaper biomasses for energy production. It is necessary to explore ways to improve the anaerobic fermentation process with the help of various catalysts. Biocatalyst Metaferm produced in Latvia previous studies with other biomass gave an increase in production. The purpose of study is evaluation of suitability of granular and crushed oat bran waste biomass for the production of methane and influence of catalyst Metaferm on anaerobic digestion (AD) process. The biomass anaerobic digestion process was investigated in 0.75 L digesters, operated in batch mode at temperature 38 ± 1.0 °C. The average biogas yield per unit of dry organic matter added (DOM) from digestion of granular oat bran was 0.400 L g^-1 DOM and methane yield was 0.193 L g^-1 DOM. Average biogas yield from digestion of crushed oat bran was 0.439 L L g^-1 DOM and specific methane yield was 0.193 L L g^-1 DOM. Adding of 1 mL Metaferm in substrates with not crushed or crushed oat bran increases specific methane yield by 0.227 L g^-1
DOM or 0.236 L g^-1 DOM respectively. Investigated oat bran can be used for methane production, but methane production was less than from traditional biomass, e.g. maize silage.

Key words:

additive Metaferm, anaerobic digestion, biogas, methane, oat bran