Special Issue "New Frontiers in Anaerobic Digestion (AD) Processes"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: 18 December 2022 | Viewed by 6279

Special Issue Editors

Prof. Dr. Sonia Heaven
E-Mail Website
Guest Editor
Faculty of Engineering and Physical Sciences, University of Southampton, Southampton Boldrewood Innovation Campus, Southampton SO16 7QF, UK
Interests: optimised process configurations and operating regimes for renewable energy production through anaerobic digestion; biomass production for biorefineries; valorisation of food waste; algal biomass systems; membrane bioreactors; bioprocessing of biodegradable municipal waste; industrial wastewaters
Dr. Sigrid Kusch-Brandt
E-Mail Website
Guest Editor
Department of Civil, Environmental and Architectural Engineering ICEA, University of Padova, 35122 Padova, Italy
Interests: biological process engineering; anaerobic digestion (biogas); organic resources; food waste; circular economy; solid waste management; environmental engineering; environmental sustainability
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Charles Banks
E-Mail Website
Guest Editor
Faculty of Engineering and Physical Sciences, University of Southampton, Southampton Boldrewood Innovation Campus, Southampton SO16 7QF, UK
Interests: innovative technology for environmental protection; controlled anaerobic and aerobic biodegradation of municipal and industrial solid wastes; treatment of liquid industrial effluents by biological systems; energy production from digestion of crops and agricultural wastes; development of operating protocols for anaerobic digestion to maximise rates of substrate conversion and biogas yield

Special Issue Information

Dear Colleagues,

Anaerobic digestion (AD) is widely used to process a variety of organic materials, but a major share of its full potential currently remains unlocked.

This Special Issue on “New Frontiers in Anaerobic Digestion (AD) Processes” seeks original contributions that focus on recent developments and advanced concepts related to the valorisation of biomass under application of anaerobic digestion. Topics of interest include, but are not limited to:

  • optimised operating regimes for AD processes;
  • novel or significantly improved reactor configurations;
  • progress in overcoming process inhibitions and ensuring process stability;
  • modelling and control strategies;
  • valorisation of biogas components in high-value applications;
  • integrating AD into biorefinery concepts;
  • integrating AD and renewables in power-to-gas applications;
  • synergistic integration of AD into chemical and biochemical processes;
  • AD process integration at the industrial scale; and
  • sustainable concepts for decentralised, small-scale AD processes.

Prof. Dr. Sonia Heaven
Dr. Sigrid Kusch-Brandt
Prof. Dr. Charles Banks
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • operating regimes and reactor configuration for anaerobic digestion processes
  • modelling and control
  • process inhibition and stability
  • biorefinery concepts
  • integration with other processes and renewables
  • large and small-scale applications
  • biogas production

Published Papers (7 papers)

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Research

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Article
Potential for Biomethanisation of CO2 from Anaerobic Digestion of Organic Wastes in the United Kingdom
Processes 2022, 10(6), 1202; https://doi.org/10.3390/pr10061202 - 16 Jun 2022
Viewed by 397
Abstract
The United Kingdom (UK) has a decarbonisation strategy that includes energy from both hydrogen and biomethane. The latter comes from the growing anaerobic digestion (AD) market, which in 2020 produced 23.3 TWh of energy in the form of biogas. According to the strategy, [...] Read more.
The United Kingdom (UK) has a decarbonisation strategy that includes energy from both hydrogen and biomethane. The latter comes from the growing anaerobic digestion (AD) market, which in 2020 produced 23.3 TWh of energy in the form of biogas. According to the strategy, this must be upgraded to biomethane by removal of carbon dioxide (CO2): a goal that could also be fulfilled through CO2 biomethanisation, alleviating the need for carbon capture and storage. Results are presented from a survey of publicly available datasets coupled with modelling to identify potential scale and knowledge gaps. Literature data were used to estimate maximum biomethane concentrations by feedstock type: these ranged from 79% for food wastes to 93% for livestock manures. Data from various government sources were used to estimate the overall potential for CO2 biomethanisation with current AD infrastructure. Values for the uplift in biomethane production ranged from 57% to 61%, but the need for more consistent data collection methodologies was highlighted. On average, however, if CO2 biomethanisation was applied in all currently operating UK AD plants an energy production uplift of 12,954 GWh could be achieved based on 2020 figures. This is sufficient to justify the inclusion of CO2 biomethanisation in decarbonisation strategies, in the UK and worldwide. Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
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Article
Hydrothermal Pretreatment of Wheat Straw—Evaluating the Effect of Substrate Disintegration on the Digestibility in Anaerobic Digestion
Processes 2022, 10(6), 1048; https://doi.org/10.3390/pr10061048 - 24 May 2022
Viewed by 379
Abstract
The increasing demand for renewable energy sources and demand-oriented electricity provision makes anaerobic digestion (AD) one of the most promising technologies. In addition to energy crops, the use of lignocellulosic residual and waste materials from agriculture is becoming increasingly important. However, AD of [...] Read more.
The increasing demand for renewable energy sources and demand-oriented electricity provision makes anaerobic digestion (AD) one of the most promising technologies. In addition to energy crops, the use of lignocellulosic residual and waste materials from agriculture is becoming increasingly important. However, AD of such feedstocks is often associated with difficulties due to the high content of lignocellulose and its microbial persistence. In the present work, the effect of hydrothermal pretreatment (HTP) on the digestibility of wheat straw is investigated and evaluated. Under different HTP temperatures (160–180 °C) and retention times (15–45 min), a significant increase in biomethane potential (BMP) can be observed in all cases. The highest BMP (309.64 mL CH4 g−1 volatile solid (VS) is achieved after pretreatment at 160 °C for 45 min, which corresponds to an increase of 19% of untreated wheat straw. The results of a multiple linear regression model show that the solubilization of organic materials is influenced by temperature and time. Furthermore, using two different first-order kinetic models, an enhancement of AD rate during hydrolysis due to pretreatment is observed. However, the increasing intensity of pretreatment conditions is accompanied by a decreasing trend in the conversion of intermediates to methane. Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
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Article
Exploring Farm Anaerobic Digester Economic Viability in a Time of Policy Change in the UK
Processes 2022, 10(2), 212; https://doi.org/10.3390/pr10020212 - 24 Jan 2022
Cited by 1 | Viewed by 855
Abstract
The combination of a post-Brexit agricultural policy, the Global Methane Pledge announced during the last United Nations Climate Change Conference in Glasgow (COP26), and urgency of meeting climate goals means the UK has a unique opportunity to create an exemplar through recognition of [...] Read more.
The combination of a post-Brexit agricultural policy, the Global Methane Pledge announced during the last United Nations Climate Change Conference in Glasgow (COP26), and urgency of meeting climate goals means the UK has a unique opportunity to create an exemplar through recognition of the benefits of small-scale farm anaerobic digesters that valorise on-site wastes for renewable electricity and heat, cushioning agri-businesses against energy perturbations. To explore economic viability of farm-based biogas production, combinations of support levels, energy prices, capital cost, internal rate of return (IRR), and digestate value were analysed, employing a 550-cow dairy farm with access to other agricultural wastes. A 145 kWe system utilising 100% of CHP electricity (grid value: £0.1361 per kWh) and 70% of the heat (heating oil value: £0.055 per kWh) could achieve an IRR above 15.5% with a median electricity tariff of £0.1104 per kWh at a heat tariff from £0.0309 to £0.0873 per kWh thermal. Under a subsidy-free regime, the same system could achieve a 10% IRR with electricity prices in the range £0.149 to £0.261 per kWh. High fertiliser prices could increase digestate value, further improving viability. With late-2021 high energy prices, the technology approaches subsidy-free viability, but uptake is unlikely unless wider environmental and societal benefits of on-farm systems can be explicitly valued. Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
Article
Estimating the Methane Potential of Energy Crops: An Overview on Types of Data Sources and Their Limitations
Processes 2021, 9(9), 1565; https://doi.org/10.3390/pr9091565 - 01 Sep 2021
Cited by 3 | Viewed by 835
Abstract
As the anaerobic digestion of energy crops and crop residues becomes more widely applied for bioenergy production, planners and operators of biogas plants, and farmers who consider growing such crops, have a need for information on potential biogas and methane yields. A rich [...] Read more.
As the anaerobic digestion of energy crops and crop residues becomes more widely applied for bioenergy production, planners and operators of biogas plants, and farmers who consider growing such crops, have a need for information on potential biogas and methane yields. A rich body of literature reports methane yields for a variety of such materials. These data have been obtained with different testing methods. This work elaborates an overview on the types of data source available and the methods that are commonly applied to determine the methane yield of an agricultural biomass, with a focus on European crops. Limitations regarding the transferability and generalisation of data are explored, and crop methane values presented across the literature are compared. Large variations were found for reported values, which can only partially be explained by the methods applied. Most notably, the intra-crop variation of methane yield (reported values for a single crop type) was higher than the inter-crop variation (variation between different crops). The pronounced differences in reported methane yields indicate that relying on results from individual assays of candidate materials is a high-risk approach for planning biogas operations, and the ranges of values such as those presented here are essential to provide a robust basis for estimation. Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
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Article
Operation of Submerged Anaerobic Membrane Bioreactors at 20 °C: Effect of Solids Retention Time on Flux, Mixed Liquor Characteristics and Performance
Processes 2021, 9(9), 1525; https://doi.org/10.3390/pr9091525 - 29 Aug 2021
Viewed by 929
Abstract
Four flat-sheet submerged anaerobic membrane bioreactors ran for 242 days on a simulated domestic wastewater with low Chemical Oxygen Demand (COD) and high suspended solids. Organic loading was maintained around 1.0 g COD L−1 day−1, while solids retention time (SRT) [...] Read more.
Four flat-sheet submerged anaerobic membrane bioreactors ran for 242 days on a simulated domestic wastewater with low Chemical Oxygen Demand (COD) and high suspended solids. Organic loading was maintained around 1.0 g COD L−1 day−1, while solids retention time (SRT) was varied from 20–90 days. This was achieved at a constant membrane flux, maintained by adjusting transmembrane pressure (TMP) in the range 1.8–9.8 kPa. Membrane fouling was assessed based on the required TMP, with mixed liquors characterised using capillary suction time, frozen image centrifugation and quantification of extracellular polymeric substances (EPS). SRT had a significant effect on these parameters: fouling was least at an SRT of 30 days and highest at 60 days, with some reduction as this extended to 90 days. Operation at SRT < 30 days showed no further benefits. Although operation at a short SRT was optimal for membrane performance it led to lower specific methane productivity, higher biomass yields and higher effluent COD. Short SRT may also have accelerated the loss of essential trace elements, leading to reduced performance under these conditions. A COD-based mass balance was conducted, including both biomass and methane dissolved in the effluent. Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
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Article
Batch and Semi-Continuous Anaerobic Digestion of Industrial Solid Citrus Waste for the Production of Bioenergy
Processes 2021, 9(4), 648; https://doi.org/10.3390/pr9040648 - 08 Apr 2021
Cited by 2 | Viewed by 1023
Abstract
The aim of this paper is to describe a study of the anaerobic digestion of industrial citrus solid waste (ISCW) in both batch and semi-continuous modes for the production of bioenergy without the elimination of D-limonene. The study was conducted at the pilot [...] Read more.
The aim of this paper is to describe a study of the anaerobic digestion of industrial citrus solid waste (ISCW) in both batch and semi-continuous modes for the production of bioenergy without the elimination of D-limonene. The study was conducted at the pilot plant level in an anaerobic reactor with a working volume of 220 L under mesophilic conditions of 35 ± 2 °C. Cattle manure (CM) was used as the inoculum. Three batches were studied. The first batch had a CM/ISCW ratio of 90/10, and Batches 2 and 3 had CM/ISCW ratios of 80/20 and 70/30, respectively. In the semi-continuous mode an OLR of approximately 8 g total chemical oxygen demand (COD)/Ld (4.43 gVS/Ld) was used. The results showed that 49%, 44%, and 60% of volatile solids were removed in the batch mode, and 35% was removed in the semi-continuous mode. In the batch mode, 0.322, 0.382, and 0.316 LCH4 were obtained at STP/gVSremoved. A total of 24.4 L/d (34% methane) was measured in the semi-continuous mode. Bioenergy potentials of 3.97, 5.66, and 8.79 kWh were obtained for the respective batches, and 0.09 kWh was calculated in the semi-continuous mode. The citrus industry could produce 37 GWh per season. A ton of processed oranges has a bioenergy potential of 162 kWh, which is equivalent to 49 kWh of available electricity ($3.90). Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
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Review

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Review
Review of Soft Sensors in Anaerobic Digestion Process
Processes 2021, 9(8), 1434; https://doi.org/10.3390/pr9081434 - 19 Aug 2021
Cited by 1 | Viewed by 649
Abstract
Anaerobic digestion is associated with various crucial variables, such as biogas yield, chemical oxygen demand, and volatile fatty acid concentration. Real-time monitoring of these variables can not only reflect the process of anaerobic digestion directly but also accelerate the efficiency of resource conversion [...] Read more.
Anaerobic digestion is associated with various crucial variables, such as biogas yield, chemical oxygen demand, and volatile fatty acid concentration. Real-time monitoring of these variables can not only reflect the process of anaerobic digestion directly but also accelerate the efficiency of resource conversion and improve the stability of the reaction process. However, the current real-time monitoring equipment on the market cannot be widely used in the industrial production process due to its defects such as expensive equipment, low accuracy, and lagging analysis. Therefore, it is essential to conduct soft sensor modeling for unmeasurable variables and use auxiliary variables to realize real-time monitoring, optimization, and control of the an-aerobic digestion process. In this paper, the basic principle and process flow of anaerobic digestion are first briefly introduced. Subsequently, the development history of the traditional soft sensor is systematically reviewed, the latest development of soft sensors was detailed, and the obstacles of the soft sensor in the industrial production process are discussed. Finally, the future development trend of deep learning in soft sensors is deeply discussed, and future research directions are provided. Full article
(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)
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