Carbon Dioxide: Friend not Foe

Carbon Dioxide: Friend not Foe
Admin 26.10.2018

A UK-Brazilian approach to a global problem.

Michael North, Green Chemistry Centre of Excellence, University of York

Since the UK started the industrial revolution in the 19th century, atmospheric levels of carbon dioxide have increased by around 50%, from 0.028% to 0.041% in 2018, primarily due to the burning of the fossil fuels: coal, oil and gas. As carbon dioxide is good at adsorbing heat, atmospheric carbon dioxide is responsible for global warming and consequently for planet-wide effects such as climate change, melting of glaciers and ice-caps, and rises in sea level. Finding ways of allowing humankind to continue to generate the energy needed to support the lifestyle enjoyed by developed countries and to which the developing world aspires, without further increasing atmospheric carbon dioxide levels, will probably be the biggest challenge of the 21st century. Ultimately, humankind will address this issue by moving energy generation away from burning fossil fuels to renewable and sustainable energy sources such as wind, sunlight, waves and biomass combustion. The UK and Brazil have adopted leading positions in this transition through a UK commitment to cease generating electricity by burning coal by 2025 and the Brazilian use of bio-derived ethanol as an alternative to petrol to power motor vehicles. However, globally, this will be a slow transition likely to take most of the 21st century, so the challenge is what to do with all the carbon dioxide generated in the meantime.

There are two approaches proposed to allow society to continue burning fossil fuels without further increasing atmospheric carbon dioxide levels. These are carbon capture and storage (CCS) and carbon capture and utilisation (CCU). CCS treats carbon dioxide as a waste to be stored underground or undersea in the hope that it will stay where it is put and that future generations will be able to deal with it. This is a continuation of the ‘use once and dispose of’ approach on which our modern society is largely based. In contrast, CCU treats carbon dioxide as a valuable source of carbon for the production of a wide range of chemicals and fuels. CCU is a circular economy approach to addressing the challenge of global carbon dioxide emissions. Major carbon dioxide emission sources occur globally and the atmospheric concentration of carbon dioxide is the same everywhere, so carbon dioxide, unlike the original fossil fuels from which much of it derives, is an ideal source of carbon for the developing world as it is freely available and has complete security of supply.

CCU is not a new idea: urea is used by farmers as a fertiliser and is made from carbon dioxide. Similarly, aspirin has been made by a route that involves use of carbon dioxide for over 100 years. To utilise carbon dioxide within CCU, however, it is essential that the other chemicals needed, and any energy required, are supplied renewably. Brazil is an ideal country in which to develop such sustainable CCU systems. It has a large and diverse landmass supporting a wide variety of biomass from the Amazon rainforest to sugar cane plantations. The sustainable use of, preferably waste, biomass can then provide the other chemicals needed to facilitate CCU.

This approach is being taken by a Royal Society funded GCRF project between the University of York in the UK and the Federal University of Rio de Janeiro in Brazil. The aim is to develop a completely sustainable synthesis of a class of chemicals called cyclic carbonates, which are crucially used as the electrolytes in lithium ion batteries. These batteries power the mobile electronic devices such as mobile phones, tablets and laptop PCs prevalent in modern society, and even more vitally the next generation of electric vehicles that will assist in the transition to a sustainable economy. The teams of chemists and chemical engineers are developing ways to utilise waste carbon dioxide sources in Brazil, such as from gas fields and bio-ethanol production sites, and then combine the carbon dioxide with chemicals available from Brazilian biomass to provide a sustainable route for the large-scale preparation of cyclic carbonates. If successful, the project will help Brazil to continue developing its economy whilst avoiding further increases in carbon dioxide emissions.

Categorias: Blog