Process Intensification of Biological Methanation (BM) Systems

Lead Research Organisation: University of Sheffield
Department Name: Mechanical Engineering

Abstract

This project seeks to explore the idea of using biological enzymes immobilised on a biochar framework to convert carbon dioxide (CO2) to methanol (CH3OH). Biological enzymes present a powerful and sustainable alternative to inorganic catalysis; however, they also present a challenge. Enzymes must be robust enough to work within adverse environments, such as CO2 exhaust outflows. Free enzymes in solution also create unfeasibly high operational costs due to low recovery rates.

One of the most effective ways to solve these issues is through immobilization; unfortunately, many studies are limited by complex methodology and loss of enzyme activity. Biochar has recently emerged as a stable, inert, and economical matrix for enzyme immobilisation that could overcome these limitations. As opposed to being bound onto the matrix - which impacts activity - enzymes are instead held in place on the biochar by surface functional groups. This could create a bio-catalytic system that provides enzyme stability without affecting functionality; offering industries struggling to decarbonise a CO2-capture technology that generates an economic return on the significant investment required to implement capture-based solutions.

This study will begin by engineering biochar from sustainable UK-based forestry products to ensure its physiochemistry facilitates optimal enzyme attachment and activity. Then, it will determine the optimal conditions (pH, time, temperature, enzyme and ionic concentration) for enzyme binding. It will then test bio-catalysis of CO2 to methanol in pure CO2 and flue gas. Finally, if the study proof-of-concept is achieved, I hope to conduct lifecycle, technoeconomic and pathways-to-market analyses to determine process sustainability and identify pathways to accelerate technology uptake and adoption.

In 2018 alone, methanol production from fossil fuels contributed 211 million tonnes of CO2 emissions into the atmosphere. If proof of concept is achieved; this novel technology could replace the use of fossil fuels in methanol manufacturing, demand for which has reached 98 million tonnes in 2018 and is increasing. It could also create an opportunity for CCUS investment in growing industries struggling to eliminate CO2 emissions, such as the cement and steel industry, which contribute over 9% of global CO2 emissions. Methanol will also continue to be in demand in the future as a source of hydrogen for fuel cell vehicles and for conversion to dimethyl ether - a super clean diesel fuel for transport. This provision of sustainable methanol could assist in transport decarbonisation, transport is currently responsible for 6% of global CO2 output.

The leading method for CO2 capture and conversion to methanol is via rare-metal catalysis, which is associated with expense and sustainability concerns. This biocatalytic method will overcome these barriers by utilising biochar as the reaction matrix, to which the enzymes are attached. Biochar and enzymes are renewable, widely available, and affordable, which could result in a lower carbon footprint and a more competitive process. Also, the enzyme-mediated conversion performs optimally at lower temperatures and pressures, making it more energy-efficient.

This would be the first study of its kind to use biochar in a multi-enzyme cascade system. It is hoped that proof of the system's concept will incentivise further investigations into enzyme-mediated carbon capture.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022996/1 30/09/2019 30/03/2028
2280623 Studentship EP/S022996/1 30/09/2020 29/09/2024 Jennifer Hancock