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Special Issue "Production and Utilization of Biogas"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Bio-Energy".

Deadline for manuscript submissions: 31 July 2019

Special Issue Editor

Guest Editor
Dr. Wojciech Budzianowski

Wojciech Budzianowski Consulting Services, Poleska 11/37, PL-51354 Wrocław, Poland
Website | E-Mail
Phone: +0048 792781784
Interests: renewable energy, biogas, innovation management, business development

Special Issue Information

Dear Colleagues,

Biogas, although it is a mature renewable energy technology, still requires financial incentivization of commercial plants or end uses. Shortages of locally-available, very cheap digestible feedstocks restrain biogas productivity, so that biogas plants with a capacity greater than 1 MW are difficult to construct and operate in truly competitive markets. Research into innovations that could improve economic viability and resource flexibility of biogas technology is therefore needed. Potential improvements must be sought in the whole value chain of biogas: Cheaper feedstock production and collection including wastes, enhanced fermentation techniques, novel products that can be derived from feedstock processing or biogas, new end uses, integration with other technologies, market organization, etc. This Special Issue aims at encouraging researchers to address challenges associated with biogas production and utilization. It seeks research reports and innovative solutions that could contribute to the further development of biogas technology. In addition, the submission of review papers that systematically evaluate advances in biogass production and utilizaton with an emphasis on technological excellence and realistic commercial potential are also invited.

Dr. Wojciech Budzianowski
Guest Editor

Manuscript Submission Information

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Keywords

  • biogas
  • production
  • utilization
  • innovation
  • sustainability
  • technology
  • economics
  • value chain

Published Papers (18 papers)

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Research

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Open AccessCommunication The Effect of Biochar Addition on the Biogas Production Kinetics from the Anaerobic Digestion of Brewers’ Spent Grain
Energies 2019, 12(8), 1518; https://doi.org/10.3390/en12081518
Received: 11 February 2019 / Revised: 12 April 2019 / Accepted: 16 April 2019 / Published: 22 April 2019
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Abstract
Biochar (BC) addition is a novel and promising method for biogas yield increase. Brewer’s spent grain (BSG) is an abundant organic waste with a large potential for biogas production. In this research, for the first time, we test the feasibility of increasing biogas [...] Read more.
Biochar (BC) addition is a novel and promising method for biogas yield increase. Brewer’s spent grain (BSG) is an abundant organic waste with a large potential for biogas production. In this research, for the first time, we test the feasibility of increasing biogas yield and rate from BSG digestion by adding BC, which was produced from BSG via torrefaction (low-temperature pyrolysis). Furthermore, we explore the digestion of BSG with the presence BCs produced from BSG via torrefaction (low-temperature pyrolysis). The proposed approach creates two alternative waste-to-energy and waste-to-carbon type utilization pathways for BSG: (1) digestion of BSG waste to produce biogas and (2) torrefaction of BSG to produce BC used for digestion. Torrefaction extended the short utility lifetime of BSG waste turned into BC. BSG was digested in the presence of BC with BC to BSG + BC weight ratio from 0 to 50%. The study was conducted during 21 days under mesophilic conditions in n = 3 trials. The content of dry mass 17.6% in all variants was constant. The kinetics results for pure BSG (0% BC) were: reaction rate constant (k) 1.535 d−1, maximum production of biogas (B0) 92.3 dm3∙kg−1d.o.m. (d.o.m. = dry organic matter), and biogas production rate (r), 103.1 dm3∙kg−1d.o.m.∙d−1. his preliminary research showed that the highest (p < 0.05) r, 227 dm3∙kg−1d.o.m.∙d−1 was due to the 5% BC addition. This production rate was significantly higher (p < 0.05) compared with all other treatments (0, 1, 3, 8, 10, 20, 30, and 50% BC dose). Due to the high variability observed between replicates, no significant differences could be detected between all the assays amended with BC and the variant 0% BC. However, a significant decrease of B0 from 85.1 to 61.0 dm3∙kg−1d.o.m. in variants with the high biochar addition (20–50% BC) was observed in relation to 5% BC (122 dm3∙kg−1d.o.m.), suggesting that BC overdose inhibits biogas production from the BSG + BC mixture. The reaction rate constant (k) was not improved by BC, and the addition of 10% and 20% BC even decreased k relatively to the 0% variant. A significant decrease of k was also observed for the doses of 10%, 20%, and 30% when compared with the 5% BC (1.89 d−1) assays. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
Open AccessArticle Identification of Context-Specific Knowledge as a Tool for Biogas Facilitators and Their Quality Involvement—Using Vietnamese Practice as an Example
Energies 2019, 12(7), 1326; https://doi.org/10.3390/en12071326
Received: 1 March 2019 / Revised: 28 March 2019 / Accepted: 1 April 2019 / Published: 6 April 2019
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Abstract
In Central Vietnam, two key actors are involved in the extension performance of biogas technology: The owners of biogas plants and facilitators. Facilitators as the immediate providers of advice and services are in direct contact with local farmers and belong to the Vietnamese [...] Read more.
In Central Vietnam, two key actors are involved in the extension performance of biogas technology: The owners of biogas plants and facilitators. Facilitators as the immediate providers of advice and services are in direct contact with local farmers and belong to the Vietnamese national extension network. This paper aims at identifying the current state of extension services and creating proper recommendations for further processes of training in the target area through the identification of context-specific knowledge (CSK). CSK can serve as a tool for facilitators and their quality involvement and for the improvement of current training practices in the area. It also provides performance indicators (PIs) for facilitators’ quality assessments. PIs should be consistent parts of the educational process for the evaluation of knowledge transmission success. More research in terms of facilitator’s impacts on the knowledge transition process towards the biogas owners should be done to prove the sustainability of the extension services. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Evaluation of Using Biogas to Supply the Dual Fuel Diesel Engine of an Agricultural Tractor
Energies 2019, 12(6), 1071; https://doi.org/10.3390/en12061071
Received: 30 January 2019 / Revised: 15 March 2019 / Accepted: 15 March 2019 / Published: 20 March 2019
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Abstract
It is known that biogas without prior purification to biomethane is a commonly used fuel only for the stationary internal combustion engines but not for vehicle engines. The current study evaluates the use of biogas without its prior upgrading to biomethane as fuel [...] Read more.
It is known that biogas without prior purification to biomethane is a commonly used fuel only for the stationary internal combustion engines but not for vehicle engines. The current study evaluates the use of biogas without its prior upgrading to biomethane as fuel for tractor engines. The following tests were carried out: biochemical methane potential tests, dynamometer engine tests, and field tests with the use of a tractor. The average methane content in biogas obtained from vegetable wastes exceeded 60%. The tests performed on the engine dynamometer showed that the engine powered by dual fuel worked stably when diesel was replaced by 40% biogas (containing 50% of CO2) or 30% methane. Dual fuel supplying of the engine caused an increase in the concentration of hydrocarbons and carbon monoxide in the exhaust gases and a decrease or no effect in the concentration of particulate matter and nitrogen oxides. It did not significantly affect the dynamics of the vehicle and its useful properties. Biogas that contains a maximum of 50% CO2 and from which H2S, moisture, and siloxanes have been largely removed, is suitable as a fuel for tractors. Such biogas can be obtained in biogas plants from different substrates, e.g., vegetable or agriculture wastes as well as biodegradable municipal wastes. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Feasibility Study of Biogas Production from Hardly Degradable Material in Co-Inoculated Bioreactor
Energies 2019, 12(6), 1040; https://doi.org/10.3390/en12061040
Received: 27 February 2019 / Revised: 13 March 2019 / Accepted: 15 March 2019 / Published: 18 March 2019
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Abstract
Anaerobic technology is a well-established technique to wean the fossil fuel-based energy off with various positive environmental inferences. Biowaste treatment is favorable due to its low emissions. Biogas is merely regarded as the main product of anaerobic digestion with high energy value. One [...] Read more.
Anaerobic technology is a well-established technique to wean the fossil fuel-based energy off with various positive environmental inferences. Biowaste treatment is favorable due to its low emissions. Biogas is merely regarded as the main product of anaerobic digestion with high energy value. One of the key concerns of the waste water treatment plants is the vast amount of cellulosic residuals produced after the treatment of waste waters. The fine sieve fraction, collected after the primary sludge removal, has great energy value. In this study, the economic performance of a biogas plant has been analyzed based on net present value and pay-back period concepts. The plant in the base scenario produced 309,571 m3 biogas per year. The annual electricity production has been 390,059 kWh. The producible heat energy has been 487,574 kWh or 1755 GJ per year. The plant depicts a positive economic situation with 11 years pay-back time, earning low profits and showing a positive net present value of 11,240 €. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessFeature PaperArticle Is the Fischer-Tropsch Conversion of Biogas-Derived Syngas to Liquid Fuels Feasible at Atmospheric Pressure?
Energies 2019, 12(6), 1031; https://doi.org/10.3390/en12061031
Received: 11 January 2019 / Revised: 8 March 2019 / Accepted: 11 March 2019 / Published: 16 March 2019
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Abstract
Biogas resulting from anaerobic digestion can be utilized for the production of liquid fuels via reforming to syngas followed by the Fischer-Tropsch reaction. Renewable liquid fuels are highly desirable due to their potential for use in existing infrastructure, but current Fischer-Tropsch processes, which [...] Read more.
Biogas resulting from anaerobic digestion can be utilized for the production of liquid fuels via reforming to syngas followed by the Fischer-Tropsch reaction. Renewable liquid fuels are highly desirable due to their potential for use in existing infrastructure, but current Fischer-Tropsch processes, which require operating pressures of 2–4 MPa (20–40 bar), are unsuitable for the relatively small scale of typical biogas production facilities in the EU, which are agriculture-based. This paper investigates the feasibility of producing liquid fuels from biogas-derived syngas at atmospheric pressure, with a focus on the system’s response to various interruption factors, such as total loss of feed gas, variations to feed ratio, and technical problems in the furnace. Results of laboratory testing showed that the liquid fuel selectivity could reach 60% under the studied conditions of 488 K (215 °C), H2/CO = 2 and 0.1 MPa (1 bar) over a commercial Fischer–Tropsch catalyst. Analysis indicated that the catalyst had two active sites for propagation, one site for the generation of methane and another for the production of liquid fuels and wax products. However, although the production of liquid fuels was verified at atmospheric pressure with high liquid fuel selectivity, the control of such a system to maintain activity is crucial. From an economic perspective, the system would require subsidies to achieve financial viability. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Italian Biogas Plants: Trend, Subsidies, Cost, Biogas Composition and Engine Emissions
Energies 2019, 12(6), 979; https://doi.org/10.3390/en12060979
Received: 31 January 2019 / Revised: 21 February 2019 / Accepted: 7 March 2019 / Published: 13 March 2019
Cited by 1 | PDF Full-text (667 KB) | HTML Full-text | XML Full-text
Abstract
Italy is one of the leading nations in the biogas sector. Agricultural, landfill, sewage and manure substrates are converted into biogas using anaerobic digestion and, then, into electricity and heat by means of properly arranged internal combustion engines. In this study, after an [...] Read more.
Italy is one of the leading nations in the biogas sector. Agricultural, landfill, sewage and manure substrates are converted into biogas using anaerobic digestion and, then, into electricity and heat by means of properly arranged internal combustion engines. In this study, after an overview of the European context, the authors present the Italian biogas sector status in terms of development trends and factors that favour/block biogas spread. Despite the fact that biogas is a renewable fuel and a consolidate technology, it is mandatory to examine its real costs, biogas composition and engine combustion products. For this purpose, in the present work, the authors selected six in-operation biogas plants fed by different substrates, investigate plants construction and operation costs and measure both biogas and engine emissions compositions. Biogas status analysis shows a high growth rate until the end of 2012 due to generous Government subsidies while, after supports reduction, a continuous depletion of biogas installations is observed. Alongside the development, established supports overlook also the plant size as well as the cost. In fact, the most widespread plant nameplate electric power is 1 MW while its construction cost ranges between 4.2–4.8 millions of Euros. Real on-site measurements show variable biogas composition while engine emissions are comparable with the natural gas ones. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Systems Analysis of Biogas Production—Part I Research Design
Energies 2019, 12(5), 926; https://doi.org/10.3390/en12050926
Received: 28 December 2018 / Revised: 1 March 2019 / Accepted: 6 March 2019 / Published: 10 March 2019
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Abstract
Striving towards a resource efficient society requires an adjustment of energy systems towards renewable options. It is also of high importance to make use of products and materials to a higher degree. Biogas production has the potential to recover nutrients and energy from [...] Read more.
Striving towards a resource efficient society requires an adjustment of energy systems towards renewable options. It is also of high importance to make use of products and materials to a higher degree. Biogas production has the potential to recover nutrients and energy from organic by-products, as well as to substitute fossil fuels in the energy system. Resource efficiency relates to the economic, energy and environmental performance of the system studied. A comprehensive research design for assessment of the resource efficiency of biogas production systems is described in this paper. The research design includes the following parts: identification of cases, defining scenarios, system development, evaluation perspectives and systems analysis. The analysis is performed from three perspectives; economy, energy and environment. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Biofuel Produced from Solid-State Anaerobic Digestion of Dairy Cattle Manure in Coordination with Black Soldier Fly Larvae Decomposition
Energies 2019, 12(5), 911; https://doi.org/10.3390/en12050911
Received: 28 December 2018 / Revised: 28 February 2019 / Accepted: 2 March 2019 / Published: 8 March 2019
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Abstract
This study was conducted to evaluate the feasibility of applying a two-step biological treatment process, solid-state anaerobic digestion (SSAD) and black soldier fly larvae (BSFL) composting, for the treatment of dairy cattle manure. Biogas from the SSAD of dairy cattle manure, and the [...] Read more.
This study was conducted to evaluate the feasibility of applying a two-step biological treatment process, solid-state anaerobic digestion (SSAD) and black soldier fly larvae (BSFL) composting, for the treatment of dairy cattle manure. Biogas from the SSAD of dairy cattle manure, and the digestate of SSAD was fed to BSFL. In turn, BSFL can be fed to animals as a protein supplement. Adjustment of the pH and 30% inoculation ratio (IR30) during SSAD produced the highest theoretical methane yield, 626.1 ± 28.7 L CH4/kg VSdes, with an ultimate methane yield of 96.81 ± 2.0 L CH4/kg VSload. For BSFL composting, the groups with a feeding rate of 75 and 100 mg/day/larvae had the highest body weight change, which was 969.6 ± 28.4% and 984.1 ± 177.6%, respectively. The combination process of SSAD and BSFL composting increases the incentive for dairy cattle manure treatment instead of conventional composting and produced more valuable products. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Environmental Life Cycle Assessment of Biogas as a Fuel for Transport Compared with Alternative Fuels
Energies 2019, 12(3), 532; https://doi.org/10.3390/en12030532
Received: 30 December 2018 / Revised: 26 January 2019 / Accepted: 1 February 2019 / Published: 7 February 2019
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Abstract
Upgraded biogas, also known as biomethane, is increasingly being used as a fuel for transport in several countries and is regarded as an environmentally beneficial option. There are, nevertheless, few studies documenting the environmental impacts of biogas as a transport fuel compared with [...] Read more.
Upgraded biogas, also known as biomethane, is increasingly being used as a fuel for transport in several countries and is regarded as an environmentally beneficial option. There are, nevertheless, few studies documenting the environmental impacts of biogas as a transport fuel compared with the alternatives on the market. In this study, life cycle assessment (LCA) methodology was applied to compare the environmental performance of biogas used as a fuel for bus transport with natural gas, electricity fueled buses, biodiesel, and fossil diesel. A sensitivity analysis was performed for the biogas alternative to assess the importance of the underlying assumptions. The results show that biogas has a relatively low contribution to the environmental impact categories assessed. Emissions of greenhouse gases are dependent on assumptions such as system boundaries, transport distances and methane leakages. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle System Analysis of Biogas Production—Part II Application in Food Industry Systems
Energies 2019, 12(3), 412; https://doi.org/10.3390/en12030412
Received: 28 December 2018 / Revised: 25 January 2019 / Accepted: 26 January 2019 / Published: 28 January 2019
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Abstract
Biogas production from organic by-products is a way to recover energy and nutrients. However, biogas production is not the only possible conversion alternative for these by-products, and hence there is interest in studying how organic by-products are treated today and which alternatives for [...] Read more.
Biogas production from organic by-products is a way to recover energy and nutrients. However, biogas production is not the only possible conversion alternative for these by-products, and hence there is interest in studying how organic by-products are treated today and which alternatives for conversion are the most resource efficient from a systems perspective. This paper investigates if biogas production is a resource efficient alternative, compared to business as usual, to treat food industry by-products, and if so, under what circumstances. Five different cases of food industries were studied, all with different prerequisites. For all cases, three different scenarios were analysed. The first scenario is the business as usual (Scenario BAU), where the by-products currently are either incinerated, used as animal feed or compost. The second and third scenarios are potential biogas scenarios where biogas is either used as vehicle fuel (Scenario Vehicle) or to produce heat and power (Scenario CHP). All scenarios, and consequently, all cases have been analysed from three different perspectives: Economy, energy, and environment. The environmental perspective was divided into Global Warming Potential (GWP), Acidification Potential (AP), and Eutrophication Potential (EP). The results show, in almost all the systems, that it would be more resource efficient to change the treatment method from Scenario BAU to one of the biogas scenarios. This paper concludes that both the perspective in focus and the case at hand are vital for deciding whether biogas production is the best option to treat industrial organic by-products. The results suggest that the food industry should not be the only actor involved in deciding how to treat its by-products. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Struvite—An Innovative Fertilizer from Anaerobic Digestate Produced in a Bio-Refinery
Energies 2019, 12(2), 296; https://doi.org/10.3390/en12020296
Received: 7 December 2018 / Revised: 11 January 2019 / Accepted: 15 January 2019 / Published: 18 January 2019
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Abstract
This paper presents the results of a pot experiment aimed at the assessment of the fertilizer value of struvite, a precipitation product obtained from a liquid fraction of the digestate. The effects of struvite (STR), struvite + ammonium sulphate (STR + N) and [...] Read more.
This paper presents the results of a pot experiment aimed at the assessment of the fertilizer value of struvite, a precipitation product obtained from a liquid fraction of the digestate. The effects of struvite (STR), struvite + ammonium sulphate (STR + N) and ammonium phosphate (AP) treatments were examined on maize and grass cultivation on silty loam and loamy sand soil. The crop yields were found to depend on both the soil type and experimental treatment. Crop yields produced under STR and STR + N exceeded those under the control treatments by respectively 66% and 108% for maize, and 94% and 110% for grass. Crop yields under STR + N were similar or greater than those under the AP treatment. The nitrogen recovery by maize and grass reached respectively 68% and 62% from the struvite and 78% and 52% from AP. The phosphorus recovery by maize and grass reached 7.3% and 4.8%, respectively, from struvite (i.e., STR and STR + N), which was lower than that from the AP (18.4% by maize and 8.1% by grass). Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Effect of Combined Inoculation on Biogas Production from Hardly Degradable Material
Energies 2019, 12(2), 217; https://doi.org/10.3390/en12020217
Received: 6 December 2018 / Revised: 27 December 2018 / Accepted: 3 January 2019 / Published: 11 January 2019
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Abstract
The goal of this research was to appraise the effect of combined inoculation on the performance of anaerobic digesters treating hardly degradable material, and particularly the pressed fine sieved fraction (PFSF) derived from wastewater treatment plants (WWTPs). Batch tests were conducted in mesophilic [...] Read more.
The goal of this research was to appraise the effect of combined inoculation on the performance of anaerobic digesters treating hardly degradable material, and particularly the pressed fine sieved fraction (PFSF) derived from wastewater treatment plants (WWTPs). Batch tests were conducted in mesophilic conditions in order to examine the optimal mixing ratio of inoculums. Mixing ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 of three different inoculums were applied in the batch tests. The findings indicated that the inoculation of digested activated sludge with digested organic fraction of municipal solid waste (MSW) in the ratio 25:75 resulted in a higher PFSF degradation and a higher biogas yield. The results from the kinetic analysis fit well with the results from the batch experiment. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle A Bio-Refinery Concept for N and P Recovery—A Chance for Biogas Plant Development
Energies 2019, 12(1), 155; https://doi.org/10.3390/en12010155
Received: 1 December 2018 / Revised: 20 December 2018 / Accepted: 31 December 2018 / Published: 2 January 2019
Cited by 2 | PDF Full-text (1604 KB) | HTML Full-text | XML Full-text
Abstract
Biogas is an alternative source of energy for fossil fuels. In the process of transforming organic materials into biogas significant amounts of valuable digestate are produced. In order to make the whole process sustainable digestate should be utilized this is a constraining factor [...] Read more.
Biogas is an alternative source of energy for fossil fuels. In the process of transforming organic materials into biogas significant amounts of valuable digestate are produced. In order to make the whole process sustainable digestate should be utilized this is a constraining factor in the development of the biogas industry. Consequently, there is an on-going search for new technologies to process digestate, allowing to broaden the range of possible ways of digestate utilization. One of such possibilities is technology of nitrogen (N) and phosphorus (P) recovery from the anaerobic digestate. In this study results of physicochemical analysis of materials flowing through the farm-scale bio-refinery producing struvite (STR) and ammonium sulphate (AS) are presented. Struvite was precipitated from the liquid fraction of digestate (LFDS). Ammonia was bound by sulphuric acid resulting in obtaining ammonium sulphate. The STR obtained was of medium purity and contained other macronutrients and micronutrients that further enhanced its agronomic value. The P recovery effectiveness, counted as the difference between the Ptot content in the material before and after STR precipitation was 43.8%. The AS was characterized by relatively low Ntot and Stot content. The Ntot recovery efficiency reached 43.2%. The study showed that struvite precipitation and ammonia stripping technologies can be used for processing digestate however, the processes efficiency should be improved. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessFeature PaperArticle Biogas and Ethanol from Wheat Grain or Straw: Is There a Trade-Off between Climate Impact, Avoidance of iLUC and Production Cost?
Energies 2018, 11(10), 2633; https://doi.org/10.3390/en11102633
Received: 27 August 2018 / Revised: 21 September 2018 / Accepted: 27 September 2018 / Published: 2 October 2018
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Abstract
Current EU policy calls for decreased emissions of greenhouse gases (GHG) by i.e., replacing fossil fuel in the transportation sector with sustainable biofuels. To avoid indirect land use change (iLUC), the EU at the same time strives to limit the use of crops [...] Read more.
Current EU policy calls for decreased emissions of greenhouse gases (GHG) by i.e., replacing fossil fuel in the transportation sector with sustainable biofuels. To avoid indirect land use change (iLUC), the EU at the same time strives to limit the use of crops and to increase the use of residues. In this study we compare climate impact and production cost for biogas and ethanol based on wheat grain and straw, respectively, in a Swedish context. The economic competitiveness for ethanol from straw vs. grain is evaluated based on the mandatory emission reduction for fossil vehicle fuels implemented since July 2018 in Sweden. The result of this study clearly shows that biogas and ethanol from straw have the lowest GHG emissions regardless of the calculation method used, although biofuels from grain also fulfill EU GHG reduction criteria even when suggested iLUC factors are included. It was also shown that the cost of producing straw-based biofuels was higher, thus there is a trade-off between climate impact and costs. The GHG reduction mandate adopted in Sweden partly compensates for this, but is not enough to make ethanol from straw competitive from an economic perspective. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessArticle Biogas from Fresh Spring and Summer Grass: Effect of the Harvesting Period
Energies 2018, 11(6), 1466; https://doi.org/10.3390/en11061466
Received: 3 May 2018 / Revised: 1 June 2018 / Accepted: 4 June 2018 / Published: 6 June 2018
Cited by 8 | PDF Full-text (3315 KB) | HTML Full-text | XML Full-text
Abstract
Yard trimmings, landscape management and agricultural practices determine the collection of biomass currently destined mainly to the production of a valuable soil amendant by composting. While composting requires energy, especially for the turning/aeration phases and for air treatment (i.e., biofilters in the case [...] Read more.
Yard trimmings, landscape management and agricultural practices determine the collection of biomass currently destined mainly to the production of a valuable soil amendant by composting. While composting requires energy, especially for the turning/aeration phases and for air treatment (i.e., biofilters in the case of enclosed systems), anaerobic digestion represents an energy positive process that results in production of biogas and digestate, which can be used as fuel and fertilizer, respectively. The focus of the present research was the evaluation of biogas and methane potential of grass collected in two different periods of the year (spring and summer) from riverbanks located in Northern Italy. The conversion to biogas of feedstocks is greatly influenced by the composition of the organic matter, content of cellulose, and lignin in particular. The production of biomass per hectare and the consequent biogas production were also evaluated. The experimental tests were performed on both samples of fresh grass in laboratory scale batch reactors, characterized by 4.0 L of volume and operated in mesophilic conditions (38 °C), for 40 days per cycle. The anaerobic digestion process was performed on a mixture of inoculum and grass, characterized by inoculum:substrate VS (volatile solids) ratio equal to 2. The inoculum was represented by digestate from a full-scale anaerobic digestion plant fed with dairy cow manure. The results in terms of biogas production, biogas quality (CH4, CO2, H2S), and emissions from digestates (NH3, CO2 and CH4) are presented in the paper. Total solids (TS), volatile solids (VS), pH, volatile fatty acids (VFA), alkalinity, acidity vs. alkalinity ratio, fibers (cellulose, lignin), and total Kjieldahl nitrogen (TKN) were determined both on input and output of the process. The biogas yield obtained from grass resulted higher than expected, quite similar to the yield obtained from energy crops, with Biomethane Potential (BMP) of 340.2 NL·kg−1VS and of 307.7 NL·kg−1VS, respectively, for spring and summer grass. Biogas quality was slightly lower for summer grass, perhaps in relation to the higher content of fibers (lignin). Alternatively, the yield of grass per surface was significantly different between spring and summer with the highest production in the summer. In fact, the results revealed a methane yield of 263 Nm3·ha−1 and of 1181 Nm3·ha−1, respectively for spring and summer grass. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Review

Jump to: Research

Open AccessReview A Brief Review of Anaerobic Digestion of Algae for Bioenergy
Energies 2019, 12(6), 1166; https://doi.org/10.3390/en12061166
Received: 7 March 2019 / Revised: 21 March 2019 / Accepted: 23 March 2019 / Published: 26 March 2019
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Abstract
The potential of algal biomass as a source of liquid and gaseous biofuels has been the subject of considerable research over the past few decades, with researchers strongly agreeing that algae have the potential of becoming a viable aquatic energy crop with a [...] Read more.
The potential of algal biomass as a source of liquid and gaseous biofuels has been the subject of considerable research over the past few decades, with researchers strongly agreeing that algae have the potential of becoming a viable aquatic energy crop with a higher energy potential compared to that from either terrestrial biomass or municipal solid waste. However, neither microalgae nor seaweed are currently cultivated solely for energy purposes due to the high costs of harvesting, concentrating and drying. Anaerobic digestion of algal biomass could theoretically reduce costs associated with drying wet biomass before processing, but practical yields of biogas from digestion of many algae are substantially below the theoretical maximum. New processing methods are needed to reduce costs and increase the net energy balance. This review examines the biochemical and structural properties of seaweeds and of microalgal biomass that has been produced as part of the treatment of wastewater, and discusses some of the significant hurdles and recent initiatives for producing biogas from their anaerobic digestion. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessReview The Future Agricultural Biogas Plant in Germany: A Vision
Energies 2019, 12(3), 396; https://doi.org/10.3390/en12030396
Received: 31 December 2018 / Revised: 24 January 2019 / Accepted: 24 January 2019 / Published: 27 January 2019
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Abstract
After nearly two decades of subsidized and energy crop-oriented development, agricultural biogas production in Germany is standing at a crossroads. Fundamental challenges need to be met. In this article we sketch a vision of a future agricultural biogas plant that is an integral [...] Read more.
After nearly two decades of subsidized and energy crop-oriented development, agricultural biogas production in Germany is standing at a crossroads. Fundamental challenges need to be met. In this article we sketch a vision of a future agricultural biogas plant that is an integral part of the circular bioeconomy and works mainly on the base of residues. It is flexible with regard to feedstocks, digester operation, microbial communities and biogas output. It is modular in design and its operation is knowledge-based, information-driven and largely automated. It will be competitive with fossil energies and other renewable energies, profitable for farmers and plant operators and favorable for the national economy. In this paper we discuss the required contribution of research to achieve these aims. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Open AccessReview Process Disturbances in Agricultural Biogas Production—Causes, Mechanisms and Effects on the Biogas Microbiome: A Review
Energies 2019, 12(3), 365; https://doi.org/10.3390/en12030365
Received: 20 December 2018 / Revised: 12 January 2019 / Accepted: 19 January 2019 / Published: 24 January 2019
Cited by 2 | PDF Full-text (3199 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Disturbances of the anaerobic digestion process reduce the economic and environmental performance of biogas systems. A better understanding of the highly complex process is of crucial importance in order to avoid disturbances. This review defines process disturbances as significant changes in the functionality [...] Read more.
Disturbances of the anaerobic digestion process reduce the economic and environmental performance of biogas systems. A better understanding of the highly complex process is of crucial importance in order to avoid disturbances. This review defines process disturbances as significant changes in the functionality within the microbial community leading to unacceptable and severe decreases in biogas production and requiring an active counteraction to be overcome. The main types of process disturbances in agricultural biogas production are classified as unfavorable process temperatures, fluctuations in the availability of macro- and micronutrients (feedstock variability), overload of the microbial degradation potential, process-related accumulation of inhibiting metabolites such as hydrogen (H2), ammonium/ammonia (NH4+/NH3) or hydrogen sulphide (H2S) and inhibition by other organic and inorganic toxicants. Causes, mechanisms and effects on the biogas microbiome are discussed. The need for a knowledge-based microbiome management to ensure a stable and efficient production of biogas with low susceptibility to disturbances is derived and an outlook on potential future process monitoring and control by means of microbial indicators is provided. Full article
(This article belongs to the Special Issue Production and Utilization of Biogas)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Production Techniques And Energetic Performance of Biogas In Rural Environment. A Review
Authors: Alvaro Ramirez Gomez; email: [email protected]
Abstract: The use of biogas produces a global benefit by reducing emissions of greenhouse gases such as CO2 and CH4. In rural areas, it is a substitute for conventional solid or liquid fuels such as kerosene or firewood, which contributes to the improvement of people's quality of life, and reduces the negative impact of the use of chemical fertilizers due to the accumulation of heavy metals in soil and groundwater.
The biogas has a calorific value between 16-20 MJ/m3 depending on the organic waste from which it is produced and the content of nutrients (proteins, fats, carbohydrates) in the substrates. It represents a low cost energy alternative, being used as fuel in kitchens, for heat generation and lighting in rural industries and production of electric power for small engines. Thus, for example, in countries such as China, India and Nepal, biogas is commonly used.
This work will present an exhaustive review of the factors that affect the performance of the process of generation and consumption of biogas in the rural environment. Aspects such as production rate and biogas quality per unit of potentially digestible material are addressed, depending on their composition, type of digester, pretreatments and operating conditions, as well as the performance obtained in its various applications for heating water, heating, steam generation and electricity production. We analyze the means used and available for the generation of biogas in rural areas, such as bags, buried drums and reactors, as well as operating variables such as temperature (optimum around 35 ºC), and maintenance of the acid-base balance during the digestion process (pH 6.6-7.6). In addition, the parameters of operation and energetic performance of rural consumption devices and domestic appliances (stoves and kitchens) are reviewed, conditioned by factors such as methane content (50-70%), relative density (0.7-0.9) of the biogas generated, as well as its supply pressure (around 10 bar).

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