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Biogas for Rural Areas

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A4: Bio-Energy".

Deadline for manuscript submissions: closed (31 January 2020) | Viewed by 49367

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Special Issue Editors

Dr. Ivet Ferrer

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Guest Editor

Department of Civil & Environmental Engineering, Universitat Politecnica de Catalunya, Barcelona, Spain
Interests: biodegradable waste; microalgae, sewage sludge, biogas; anaerobic digestion; co-digestion; biomass pretreatment; life cycle assessment (LCA); low-tech digesters
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Dr. Stephanie Lansing

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Guest Editor

Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, USA
Interests: biogas; anaerobic digestion; life cycle assessment (LCA); wastewater treatment; manure; food waste; low-cost; algae

Dr. Jaime Martí-Herrero

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Guest Editor

Biomass to Resources Group, Universidad Regional Amazonica Ikiam, Via Tena-Muyuna, Km.7, Tena, Napo, Ecuador
Interests: anaerobic digestion; waste to energy; low technology; biogas; thermal performance

Special Issue Information

Dear Colleagues,

Bioenergy is renewable energy obtained from biomass—any organic material that has stored sunlight in the form of chemical energy. Biogas is among the biofuels that can be obtained from biomass resources, including biodegradable wastes like manure, sewage sludge, the organic fraction of municipal solid wastes, slaughterhouse waste, crop residues, and more recently lignocellulosic biomass and algae. Within the framework of the circular economy, biogas production from biodegradable waste is particularly interesting, as it helps to save resources while reducing environmental pollution. Besides, lignocellulosic biomass and algae do not compete for arable land with food crops (in contrast with energy crops). Hence, they constitute a novel source of biomass for bioenergy.

Biogas plants may involve both high-tech and low-tech digesters, ranging from industrial-scale plants to small-scale farms and even households. They pose an alternative for decentralized bioenergy production in rural areas. Indeed, the biogas produced can be used in heaters, engines, combined heat and power units, and even cookstoves at the household level. Notwithstanding, digesters are considered to be a sustainable technology that can improve the living conditions of farmers by covering energy needs and boosting nutrient recycling. Thanks to their technical, socio-economic, and environmental benefits, rural biogas plants have been spreading around the world since the 1970s, with a large focus on farm-based systems and households. There are several opportunities to introduce rural biogas plants in small and medium populations using wastewater, agriculture wastes, and organic municipal solid wastes. However, several challenges still need to be overcome in order to improve the technology, financial viability, and dissemination.

This Special Issue aims to gather research papers on recent developments for bioenergy supply in rural areas. Papers describing new insights on bioenergy production and utilization processes; the development of new efficient technologies for biogas production and utilization; full-scale case studies; and environmental, energy, or economic assessments of decentralized biogas plants are particularly expected. Review articles are also welcome.

Dr. Ivet Ferrer
Dr. Stephanie Lansing
Dr. Jaime Martí-Herrero
Guest Editors

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Keywords

medium- and small-scale biogas plants
household digesters
biogas and circular economy
biogas and decentralized waste treatment
decentralized bioenergy systems
life cycle assessment
environmental assessment
energy assessment
economic evaluation
digestate as fertilizer

Published Papers (12 papers)

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Research

22 pages, 13777 KiB

Open AccessArticle

Simultaneous Synergy in CH₄ Yield and Kinetics: Criteria for Selecting the Best Mixtures during Co-Digestion of Wastewater and Manure from a Bovine Slaughterhouse

by Zamir Sánchez, Davide Poggio, Liliana Castro and Humberto Escalante

Energies 2021, 14(2), 384; https://doi.org/10.3390/en14020384 - 13 Jan 2021

Cited by 8 | Viewed by 2130

Abstract

Usually, slaughterhouse wastewater has been considered as a single substrate whose anaerobic digestion can lead to inhibition problems and low biodegradability. However, the bovine slaughter process generates different wastewater streams with particular physicochemical characteristics: slaughter wastewater (SWW), offal wastewater (OWW) and paunch wastewater (PWW). Therefore, this research aims to assess the anaerobic co-digestion (AcoD) of SWW, OWW, PWW and bovine manure (BM) through biochemical methane potential tests in order to reduce inhibition risk and increase biodegradability. A model-based methodology was developed to assess the synergistic effects considering CH₄ yield and kinetics simultaneously. The AcoD of PWW and BM with OWW and SWW enhanced the extent of degradation (0.64–0.77) above both PWW (0.34) and BM (0.46) mono-digestion. SWW Mono-digestion showed inhibition risk by NH₃, which was reduced by AcoD with PWW and OWW. The combination of low CH₄ potential streams (PWW and BM) with high potential streams (OWW and SWW) presented stronger synergistic effects than BM-PWW and SWW-OWW mixtures. Likewise, the multicomponent mixtures performed overall better than binary mixtures. Furthermore, the methodology developed allowed to select the best mixtures, which also demonstrated energy and economic advantages compared to mono-digestions. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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17 pages, 2493 KiB

Open AccessArticle

Psychrophilic Full Scale Tubular Digester Operating over Eight Years: Complete Performance Evaluation and Microbiological Population

by Jaime Jaimes-Estévez, German Zafra, Jaime Martí-Herrero, Guillermo Pelaz, Antonio Morán, Alejandra Puentes, Christian Gomez, Liliana del Pilar Castro and Humberto Escalante Hernández

Energies 2021, 14(1), 151; https://doi.org/10.3390/en14010151 - 30 Dec 2020

Cited by 19 | Viewed by 3964

Abstract

Most biogas plants in the world run under psychrophilic conditions and are operated by small and medium farmers. There is a gap of knowledge on the performance of these systems after several years of operation. The aim of this research is to provide a complete evaluation of a psychrophilic, low-cost, tubular digester operated for eight years. The thermal performance was monitored for 50 days, and parameters such as pH, total volatile fatty acid (tVFA), chemical oxygen demand (COD) and volatile solids (VS) were measured every week for the influent and effluent. The digester operated at a stabilized slurry temperature of around 17.7 °C, with a mean organic load rate (OLR) equal to 0.52 kg VS/m³_digester *d and an estimated hydraulic retention time (HRT) of 25 days. The VS reduction in the digester was around 77.58% and the COD reduction was 67 ± 3%, with a mean value for the effluent of 3.31 ± 1.20 g COD/Lt, while the tVFA decreased by 83.6 ± 15.5% and the presence of coliforms decreased 10.5%. A BioMethane potential test (BMP) for the influent and effluent showed that the digester reached a specific methane production of 0.40 Nm³CH₄/kg VS and a 0.21 Nm³CH₄/m³_digester d with 63.1% CH₄ in the biogas. These results, together with a microbiological analysis, show stabilized anaerobic digestion and a biogas production that was higher than expected for the psychrophilic range and the short HRT; this may have been due to the presence of an anaerobic digestion microorganism consortium which was extremely well-adapted to psychrophilic conditions over the eight-year study period. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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17 pages, 3085 KiB

Open AccessArticle

Scaling-Up the Anaerobic Digestion of Pretreated Microalgal Biomass within a Water Resource Recovery Facility

by Rubén Díez-Montero, Lucas Vassalle, Fabiana Passos, Antonio Ortiz, María Jesús García-Galán, Joan García and Ivet Ferrer

Energies 2020, 13(20), 5484; https://doi.org/10.3390/en13205484 - 20 Oct 2020

Cited by 11 | Viewed by 2388

Abstract

Microalgae-based wastewater treatment plants are low-cost alternatives for recovering nutrients from contaminated effluents through microalgal biomass, which may be subsequently processed into valuable bioproducts and bioenergy. Anaerobic digestion for biogas and biomethane production is the most straightforward and applicable technology for bioenergy recovery. However, pretreatment techniques may be needed to enhance the anaerobic biodegradability of microalgae. To date, very few full-scale systems have been put through, due to acknowledged bottlenecks such as low biomass concentration after conventional harvesting and inefficient processing into valuable products. The aim of this study was to evaluate the anaerobic digestion of pretreated microalgal biomass in a demonstration-scale microalgae biorefinery, and to compare the results obtained with previous research conducted at lab-scale, in order to assess the scalability of this bioprocess. In the lab-scale experiments, real municipal wastewater was treated in high rate algal ponds (2 × 0.47 m³), and harvested microalgal biomass was thickened and digested to produce biogas. It was observed how the methane yield increased by 67% after implementing a thermal pretreatment step (at 75 °C for 10 h), and therefore the very same pretreatment was applied in the demonstration-scale study. In this case, agricultural runoff was treated in semi-closed tubular photobioreactors (3 × 11.7 m³), and harvested microalgal biomass was thickened and thermally pretreated before undergoing the anaerobic digestion to produce biogas. The results showed a VS removal of 70% in the reactor and a methane yield up to 0.24 L CH₄/g VS, which were similar to the lab-scale results. Furthermore, photosynthetic biogas upgrading led to the production of biomethane, while the digestate was treated in a constructed wetland to obtain a biofertilizer. In this way, the demonstration-scale plant evidenced the feasibility of recovering resources (biomethane and biofertilizer) from agricultural runoff using microalgae-based systems coupled with anaerobic digestion of the microalgal biomass. Full article

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12 pages, 1919 KiB

Open AccessArticle

Potential Applications of Biogas Produced in Small-Scale UASB-Based Sewage Treatment Plants in Brazil

by Fabiana Passos, Thiago Bressani-Ribeiro, Sonaly Rezende and Carlos A. L. Chernicharo

Energies 2020, 13(13), 3356; https://doi.org/10.3390/en13133356 - 01 Jul 2020

Cited by 12 | Viewed by 2352

Abstract

Rural sanitation is still a challenge in developing countries, such as Brazil, where the majority population live with inadequate services, compromising public health and environmental safety. In this context, this study analyzed the demographic density of these rural agglomerations using secondary data from the Brazilian Institute of Geography and Statistics (IBGE). The goal was to identify the possibilities associated with using small-scale upflow anaerobic sludge blanket (UASB) reactors for sewage treatment, mainly focusing on biogas production and its conversion into energy for cooking, water heating and sludge sanitization. Results showed that most rural agglomerations lacking the appropriate sewage treatment were predominant from 500 to 1500 inhabitants in both northern and southern Brazilian regions. The thermal energy available in the biogas would be enough to sanitize the whole amount of sludge produced in the sewage treatment plants (STPs), producing biosolids for agricultural purposes. Furthermore, the surplus of thermal energy (after sludge sanitization) could be routed for cooking (replacing LPG) and for water heating (replacing electricity) in the northern and southern regions, respectively. This would benefit more than 200,000 families throughout rural areas of the country. Besides the direct social gains derived from the practice of supplying biogas for domestic uses in the vicinity of the STPs, there would be tremendous indirect gains related to the avoidance of greenhouse gas (GHG) emissions. Therefore, an anaerobic-based sewage treatment may improve public health conditions, life quality and generate added value products in Brazilian rural areas. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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19 pages, 1324 KiB

Open AccessArticle

Effects of Increasing Nitrogen Content on Process Stability and Reactor Performance in Anaerobic Digestion

by Ievgeniia Morozova, Nadiia Nikulina, Hans Oechsner, Johannes Krümpel and Andreas Lemmer

Energies 2020, 13(5), 1139; https://doi.org/10.3390/en13051139 - 03 Mar 2020

Cited by 15 | Viewed by 3278

Abstract

The aim of this study was to analyse the effect of different nitrogen increase rates in feedstock on the process stability and conversion efficiency in anaerobic digestion (AD). The research was conducted in continuously stirred tank reactors (CSTR), initially filled with two different inocula: inocula #1 with low and #2 with high nitrogen (N) concentrations. Three N feeding regimes were investigated: the “0-increase” feeding regime with a constant N amount in feeding and the regimes “0.25-increase” and “0.5-increase” where the N concentrations in feedstock were raised by 0.25 and 0.5 g·kg⁻¹, respectively, related to fresh matter (FM) every second week. The N concentration inside the reactors increased according to the feeding regimes. The levels of inhibition (Inhibition) in specific methane yields (SMY), related to the conversion efficiency of the substrates, were quantified. At the N concentration in digestate of 10.82 ± 0.52 g·kg⁻¹ FM measured in the reactors with inoculum #2 and “0.5-increase” feeding regime, the level of inhibition was equal to 38.99% ± 14.99%. The results show that high nitrogen increase rates in feeding regime are negatively related to the efficiency of the AD process, even if low volatile fatty acid (VFA) concentrations indicate a stable process. Full article

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13 pages, 1092 KiB

Open AccessArticle

Enhanced Biogas Production of Cassava Wastewater Using Zeolite and Biochar Additives and Manure Co-Digestion

by Chibueze G. Achi, Amro Hassanein and Stephanie Lansing

Energies 2020, 13(2), 491; https://doi.org/10.3390/en13020491 - 19 Jan 2020

Cited by 21 | Viewed by 6523

Abstract

Currently, there are challenges with proper disposal of cassava processing wastewater, and a need for sustainable energy in the cassava industry. This study investigated the impact of co-digestion of cassava wastewater (CW) with livestock manure (poultry litter (PL) and dairy manure (DM)), and porous adsorbents (biochar (B-Char) and zeolite (ZEO)) on energy production and treatment efficiency. Batch anaerobic digestion experiments were conducted, with 16 treatments of CW combined with manure and/or porous adsorbents using triplicate reactors for 48 days. The results showed that CW combined with ZEO (3 g/g total solids (TS)) produced the highest cumulative CH₄ (653 mL CH₄/g VS), while CW:PL (1:1) produced the most CH₄ on a mass basis (17.9 mL CH₄/g substrate). The largest reduction in lag phase was observed in the mixture containing CW (1:1), PL (1:1), and B-Char (3 g/g TS), yielding 400 mL CH₄/g volatile solids (VS) after 15 days of digestion, which was 84.8% of the total cumulative CH₄ from the 48-day trial. Co-digesting CW with ZEO, B-Char, or PL provided the necessary buffer needed for digestion of CW, which improved the process stability and resulted in a significant reduction in chemical oxygen demand (COD). Co-digestion could provide a sustainable strategy for treating and valorizing CW. Scale-up calculations showed that a CW input of 1000–2000 L/d co-digested with PL (1:1) could produce 9403 m³ CH₄/yr using a 50 m³ digester, equivalent to 373,327 MJ/yr or 24.9 tons of firewood/year. This system would have a profit of $5642/yr and a $47,805 net present value. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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13 pages, 2490 KiB

Open AccessArticle

Evaluation of Hydrogen Sulfide Scrubbing Systems for Anaerobic Digesters on Two U.S. Dairy Farms

by Abhinav Choudhury, Timothy Shelford, Gary Felton, Curt Gooch and Stephanie Lansing

Energies 2019, 12(24), 4605; https://doi.org/10.3390/en12244605 - 04 Dec 2019

Cited by 34 | Viewed by 4727

Abstract

Hydrogen sulfide (H₂S) is a corrosive trace gas present in biogas produced from anaerobic digestion systems that should be removed to reduce engine-generator set maintenance costs. This study was conducted to provide a more complete understanding of two H₂S scrubbers in terms of efficiency, operational and maintenance parameters, capital and operational costs, and the effect of scrubber management on sustained H₂S reduction potential. For this work, biogas H₂S, CO₂, O₂, and CH₄ concentrations were quantified for two existing H₂S scrubbing systems (iron-oxide scrubber, and biological oxidation using air injection) located on two rural dairy farms. In the micro-aerated digester, the variability in biogas H₂S concentration (average: 1938 ± 65 ppm) correlated with the O₂ concentration (average: 0.030 ± 0.004%). For the iron-oxide scrubber, there was no significant difference in the H₂S concentrations in the pre-scrubbed (450 ± 42 ppm) and post-scrubbed (430 ± 41 ppm) biogas due to the use of scrap iron and steel wool instead of proprietary iron oxide-based adsorbents often used for biogas desulfurization. Even though the capital and operating costs for the two scrubbing systems were low (<$1500/year), the lack of dedicated operators led to inefficient performance for the two scrubbing systems. Full article

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12 pages, 1937 KiB

Open AccessArticle

Methane and Hydrogen Sulfide Production from Co-Digestion of Gummy Waste with a Food Waste, Grease Waste, and Dairy Manure Mixture

by Abhinav Choudhury and Stephanie Lansing

Energies 2019, 12(23), 4464; https://doi.org/10.3390/en12234464 - 23 Nov 2019

Cited by 6 | Viewed by 3798

Abstract

Co-digestion of dairy manure with waste organic substrates has been shown to increase the methane (CH₄) yield of farm-scale anaerobic digestion (AD). A gummy vitamin waste (GVW) product was evaluated as an AD co-digestion substrate using batch AD testing. The GVW product was added at four inclusion levels (0%, 5%, 9%, and 23% on a wet mass basis) to a co-digestion substrate mixture of dairy manure (DM), food-waste (FW), and grease-waste (GW) and compared to mono-digestion of the GVW, DM, FW, and GW substrates. All GVW co-digestion treatments significantly increased CH₄ yield by 126–151% (336–374 mL CH₄/g volatile solids (VS)) compared to DM-only treatment (149 mL CH₄/g VS). The GVW co-digestion treatments also significantly decreased the hydrogen sulfide (H₂S) content in the biogas by 66–83% (35.1–71.9 mL H₂S/kg VS) compared to DM-only (212 mL H₂S/kg VS) due to the low sulfur (S) content in GVW waste. The study showed that GVW is a potentially valuable co-digestion substrate for dairy manure. The high density of VS and low moisture and S content of GVW resulted in higher CH₄ yields and lower H₂S concentrations, which could be economically beneficial for dairy farmers. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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13 pages, 619 KiB

Open AccessArticle

Energy and Nutrients’ Recovery in Anaerobic Digestion of Agricultural Biomass: An Italian Perspective for Future Applications

by Federico Battista, Nicola Frison and David Bolzonella

Energies 2019, 12(17), 3287; https://doi.org/10.3390/en12173287 - 26 Aug 2019

Cited by 32 | Viewed by 3448

Abstract

Anaerobic digestion (AD) is the most adopted biotechnology for the valorization of agricultural biomass into valuable products like biogas and digestate, a renewable fertilizer. This paper illustrates in the first part the actual situation of the anaerobic digestion sector in Italy, including the number of plants, their geographical distribution, the installed power and the typical feedstock used. In the second part, a future perspective, independent of the actual incentive scheme, is presented. It emerged that Italy is the second European country for the number of anaerobic digestion plants with more than 1500 units for a total electricity production of about 1400 MW_el. More than 60% of them are in the range of 200 kW–1 MW installed power. Almost 70% of the plants are located in the northern part of the Country where intensive agriculture and husbandry are applied. Most of the plants are now using energy crops in the feedstock. The future perspectives of the biogas sector in Italy will necessarily consider a shift from power generation to biomethane production, and an enlargement of the portfolio of possible feedstocks, the recovery of nutrients from digestate in a concentrated form, and the expansion of the AD sector to southern regions. Power to gas and biobased products will complete the future scenario. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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17 pages, 4942 KiB

Open AccessArticle

Development of a Modified Plug-Flow Anaerobic Digester for Biogas Production from Animal Manures

by Daniel Gómez, Juan Luis Ramos-Suárez, Belén Fernández, Eduard Muñoz, Laura Tey, Maycoll Romero-Güiza and Felipe Hansen

Energies 2019, 12(13), 2628; https://doi.org/10.3390/en12132628 - 08 Jul 2019

Cited by 16 | Viewed by 7744

Abstract

Traditional plug-flow anaerobic reactors (PFRs) are characterized by lacking a mixing system and operating at high total solid concentrations, which limits their applicability for several kinds of manures. This paper studies the performance of a novel modified PFR for the treatment of pig manure, characterized by having an internal sludge mixing system by biogas recirculation in the range of 0.270–0.336 m³ m⁻³ h⁻¹. The influence on the methane yield of four operating parameters (recirculation rate, hydraulic retention time, organic loading rate, and total solids) was evaluated by running four modified PFRs at the pilot scale in mesophilic conditions. While the previous biodegradability of organic matter by biochemical methane potential tests were between 31% and 47% with a methane yield between 125 and 184 L_CH4 kgVS⁻¹, the PFRs showed a suitable performance with organic matter degradation between 25% and 51% and a methane yield of up to 374 L_CH4 kgVS⁻¹. Operational problems such as solid stratification, foaming, or scum generation were avoided. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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14 pages, 735 KiB

Open AccessArticle

Effect of Mixing Regimes on Cow Manure Digestion in Impeller Mixed, Unmixed and Chinese Dome Digesters

by Abiodun O. Jegede, Grietje Zeeman and Harry Bruning

Energies 2019, 12(13), 2540; https://doi.org/10.3390/en12132540 - 02 Jul 2019

Cited by 9 | Viewed by 3046

Abstract

This study examines the effect of mixing on the performance of anaerobic digestion of cow manure in Chinese dome digesters (CDDs) at ambient temperatures (27–32 °C) in comparison with impeller mixed digesters (STRs) and unmixed digesters (UMDs) at the laboratory scale. The CDD is a type of household digester used in rural and pre-urban areas of developing countries for cooking. They are mixed by hydraulic variation during gas production and gas use. Six digesters (two of each type) were operated at two different influent total solids (TS) concentration, at a hydraulic retention time (HRT) of 30 days for 319 days. The STRs were mixed at 55 rpm, 10 min/hour; the unmixed digesters were not mixed, and the Chinese dome digesters were mixed once a day releasing the stored biogas under pressure. The reactors exhibited different specific biogas production and treatment efficiencies at steady state conditions. The STR 1 exhibited the highest methane (CH₄) production and treatment efficiency (volatile solid (VS) reduction), followed by STR 2. The CDDs performed better (10% more methane) than the UMDs, but less (approx. 8%) compared to STRs. The mixing regime via hydraulic variation in the CDD was limited despite a higher volumetric biogas rate and therefore requires optimization. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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15 pages, 2285 KiB

Open AccessArticle

Development of an Optimised Chinese Dome Digester Enables Smaller Reactor Volumes; Pilot Scale Performance

by Abiodun O. Jegede, Grietje Zeeman and Harry Bruning

Energies 2019, 12(11), 2213; https://doi.org/10.3390/en12112213 - 11 Jun 2019

Cited by 4 | Viewed by 3659

Abstract

Chinese dome digesters are usually operated at long hydraulic retention times (HRT) and low influent total solids (TS) concentration because of limited mixing. In this study, a newly optimised Chinese dome digester with a self-agitating mechanism was investigated at a pilot scale (digester volume = 500 L) and compared with a conventional Chinese dome digester (as blank) at 15% influent TS concentration at two retention times (30 and 40 days). The reactors were operated at ambient temperature: 27–33 °C. The average specific methane production, volatile fatty acids and percentage of volatile solids (VS) reduction are 0.16 ± 0.13 and 0.25 ± 0.05L CH₄/g VS; 1 ± 0.5 and 0.7 ± 0.3 g/L; and 51 ± 14 and 57 ± 10% at 40 days HRT (day 52–136) for the blank and optimised digester, respectively. At 30 days HRT (day 137–309) the results are 0.19 ± 0.12 and 0.23 ± 0.04 L CH₄/g VS; 1.2 ± 0.6 and 0.7 ± 0.3 g/L; and 51 ± 9 and 58 ± 11.6%. Overall, the optimised digester produced 40% more methane than the blank, despite the high loading rates applied. The optimised digester showed superior digestion treatment efficiency and was more stable in terms of VFA concentration than the blank digester, can be therefore operated at high influent TS (15%) concentration. Full article

(This article belongs to the Special Issue Biogas for Rural Areas)

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