Project Case Study: Bioethanol Production from Waste

Project Duration: January 2023 to November 2023

Background:

The Energy Entrepreneurs Fund 9, supported by the UK Government’s Department for Energy Security and Net Zero (DESNZ), initiated an R&D study by ALPS to explore the feasibility of producing bioethanol from Organic Fraction of Municipal Solid Waste (OFMSW). The project aimed to assess the viability of dark fermentation as a method for bioethanol production.

Bioethanol Project Overview:

Over the course of 11 months, ALPS project team devised and executed a comprehensive study to evaluate the potential of dark fermentation and multi-stage anaerobic digestion for combined bioethanol and biomethane production from OFMSW. Utilising their knowledge and previous research, the team designed and built apparatuses to test various methodologies, including batch and continuous processes. Parameters such as pH, bacterial inoculum, and hydraulic retention time were systematically altered to identify the most successful combination.

Key Findings:

Feedstock Suitability: The study concluded that OFMSW was not a suitable feedstock for bioethanol production due to the complex composition of carbohydrates, which were not in the form of simple sugars required for fermentation.

Biogas Output: Despite the unsuitability for bioethanol production, the process effectively broke down the feedstock, leading to a significant increase in biogas output when utilised as a feedstock for anaerobic digestion. The methane yield increased from 469 mLCH4/gVS to 1033 mLCH4/gVS.

Process Optimisation: The study highlighted the effectiveness of the dark fermentation process as a pre-treatment method, operating at a lower temperature (37°C) compared to traditional methods (55°C). This lower temperature operation could enhance the economics of pre-treatment by dark fermentation.

Conclusion:

While the study did not yield the desired outcome for bioethanol production from OFMSW, it provided valuable insights into alternative applications of dark fermentation and endorses further development of multi-stage advanced anaerobic digestion. The significant increase in biogas output demonstrates the potential of utilising the process as an effective pre-treatment method for anaerobic digestion. Moving forward, the findings of this project add to ALPS significant body of work in this areas and signal opportunities for further research and development to optimise the dark fermentation process for enhanced waste-to-energy conversion.

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