Improvement of Biogas Quality and Quantity for Small-Scale Biogas-Electricity Generation Application in off-Grid Settings: A Field-Based Study

Henry Wasajja,Antonella L Piaggio,Pamela Ceron-Chafla,Ralph E F Lindeboom,Jules B Van Lier,Saqr A A Al-Muraisy,Henri Spanjers,Purushothaman Vellayani Aravind

doi:10.3390/en14113088

Henry Wasajja, Antonella L Piaggio + Show 6 more

Open Access

https://doi.org/10.3390/en14113088

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Journal: Energies	Publication Date: May 26, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: Ndejje University, Delft University of Technology

Abstract

Small-scale electrical power generation (<100 kW) from biogas plants to provide off-grid electricity is of growing interest. Currently, gas engines are used to meet this demand. Alternatively, more efficient small-scale solid oxide fuel cells (SOFCs) can be used to enhance electricity generation from small-scale biogas plants. Most electricity generators require a constant gas supply and high gas quality in terms of absence of impurities like H2S. Therefore, to efficiently use the biogas from existing decentralized anaerobic digesters for electricity production, higher quality and stable biogas flow must be guaranteed. The installation of a biogas upgrading and buffer system could be considered; however, the cost implication could be high at a small scale as compared to locally available alternatives such as co-digestion and improved digester operation. Therefore, this study initially describes relevant literature related to feedstock pre-treatment, co-digestion and user operational practices of small-scale digesters, which theoretically could lead to major improvements of anaerobic digestion process efficiency. The theoretical preamble is then coupled to the results of a field study, which demonstrated that many locally available resources and user practices constitute frugal innovations with potential to improve biogas quality and digester performance in off-grid settings.

Highlights

Biomass is a traditional source of energy for resource-constraint communities, which are disconnected from the central grid [1]
With the introduction of state-of-the-art small-scale solid oxide fuel cells (SOFCs) with a power output of less than 5 kW [4], a significant electrical efficiency gain could be made that could accelerate the integration of biogas in rural electrification schemes
Note that the observed CH4 and CO2 composition is suitable for electricity generation, especially if dry reforming in SOFCs is envisaged [65,66,67]

Summary

Introduction

Biomass is a traditional source of energy for resource-constraint communities, which are disconnected from the central grid [1]. Biogas production from biomass could mitigate these negative health and environmental effects, while safeguarding energy access for disadvantaged communities, especially if local residues such as faecal matter and animal waste are utilized as feedstock. Electricity production from small-scale biogas installations using conventional technologies such as internal combustion engines (ICEs) can be economically advantageous compared to subsidised costs of electricity from fossil fuels, which require large-scale infrastructure [3]. From our previous reviews [5,6], small-scale electricity generation using biogas as a SOFC fuel would require a different biogas quality compared to ICEs. For the SOFC, macro-pollutants like CO2 and water vapour have no negative impact and may be used for dry and steam reforming, thereby omitting the need for biogas upgrading. It should be noted that both technologies will require biogas cleaning since reported H2S concentrations in biogas may reach values as high as 2000 ppm, depending on the used feedstock [9,11]

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Discussion

Conclusion