Opinion: while there are challenges to overcome, the production of ethanol and butanol at a large scale seems promising

The ever-increasing emissions worldwide in greenhouse gases and carbon dioxide has caused global warming and climate change. The Energy-related CO2 Emissions in Ireland 2005-2016 report showed that CO2 emission was 40 metric tons (Mt) in Ireland in 2016, with transport and residential housing accounting for 62% of these emissions.  In the last three years alone, the national total emissions increased by 6.4%, with the number of vehicles on our roads reaching 2.6 million in 2015, an increase of 181% in comparison to 1985.

This massive rise in vehicles and the spread of industry has lead to both an increase in carbon emissions and the emission of other toxic gases such as carbon monoxide. Produced from steel manufacture and oil refining industries, vehicle exhausts and residential homes with fossil fuel heating, carbon monoxide intensifies air pollution in winter.

From RTÉ Radio 1's Morning Ireland, Dr Eimear Cotter from the EPA on the agency's October 2019 report that Ireland had exceeded its annual EU emissions target by 5m tonnes

The increasing demand for fuels and their gradual depletion requires the development of new technologies for fuel production, such as biofuels. Biofuels are fuels such as alcohols produced by microorganisms directly or indirectly from organic material. Alcohols such as ethanol and butanol are fossil fuel alternatives. For example, a mixture of 10% ethanol and above 90% butanol could be a substitute for petrol. Bioethanol is currently the most produced biofuel, corresponding to 117.7 million m³ in 2016.

The traditional production of ethanol and butanol is from corn or sugar, which may result in food-fuel competition. Biofuel production from carbon dioxide and carbon monoxide has recently gained more attention as it helps to reduce air pollution and also simultaneously generates valuable chemicals.

From RTÉ Radio 1's Countrywide, Billy Costello from the Costello Group explains how anaerobic digesters work on their farms

Anaerobic sludge is a solid waste from wastewater treatment plants. Some wastewater treatment methods can lead to environmental issues due to the large numbers of bacteria involved in the process, which can potentially be harmful and cause illness. At the same time, the production of biofuels rely greatly on the work of these micro-organisms. Some microorganisms such as Clostridium species may use carbon dioxide and carbon monoxide to produce biofuels, while some of them produce methane and hydrogen. Clostridium species can often resist extreme conditions, such as high temperatures of over 80°C so pre-treatment methods, like heating to 90°C, are used to select Clostridium species

The production of ethanol and butanol from carbon dioxide and carbon monoxide by selected microorganisms has been applied at laboratory scale. The predominant functional bacteria are called Clostridium species which play the main role in the conversion of waste gas to biofuel as they are equipped with a special enzyme called carbon monoxide dehydrogenase, which makes Clostridium overcome the toxicity of carbon monoxide. They convert carbon dioxide and carbon monoxide via the Wood-Ljungdahl pathway, which is the most effective, non-photosynthetic carbon fixation pathway in the biofuel production process. 

From RTÉ Prime Time Explained, Fran McNulty and Aisling Moloney look at Ireland's agricultural emissions

There are still many challenges to overcome in biofuel production research. However, by combining recent research with genetic tools obtained from commercialized Clostridium strains, the production of ethanol and butanol at a large scale seems promising. The first industrial trial has successfully applied on waste gases from a steel mill where by a mixture of carbon monoxide, carbon dioxide and hydrogen were used to produce the biofuel, butanol.

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Other potentially functional bacteria which are separated from waste solids like sludge, animal manure, such as pig, cow and chicken manure, are also currently being researched. Biofuels produced from carbon dioxide and carbon monoxide will undoubtedly become a contributing factor in future solutions for relieving greenhouse gas emission and energy shortages in the future. 


The views expressed here are those of the author and do not represent or reflect the views of RTÉ