Stephen Dooley, Associate Professor in the School of Physics and researcher in the Ryanair Sustainable Aviation Research Centre, looks at the cost of travel and the future of sustainable aviation, including biofuels and storing excess energy from wind and solar.

I grew up with a good explainer. My Dad was a maths and science teacher and he was generally ready to answer all my questions. He had been explaining pollution. I grasped that once you ignite a reaction in a car engine say, with a carbohydrate fuel or a fossil fuel, you should get two things, carbon dioxide and water. I thought, ‘it should be as simple as that.’ We were driving one day, maybe on one of the long journeys we would take to Donegal – where Mum and Dad are from - or Galway. Long enough to be bored and go into another explanation of gases, combustion and emissions. We passed a souped-up car with two exhausts. I asked him, ‘Does that car have a pipe for each compound?’ meaning CO2 and H2O, one exhaust for each. He laughed at that; if only things were so simple! The irony is that, after all this time, the work we are doing at Trinity goes straight to that simple question of carbon cycles, carbon emissions and carbon capture. What is happening when we use energy? How do we organise ourselves better to fulfil our requirements while reducing the harm we do? I found my way into the science of fuels and combustion through some other mentors: my brother first, who would become a mechanical engineer, and who had an obsession with planes, rockets, military things; later I found my way to Professor John Simmie at NUI Galway, a leading expert on combustion and energy science in Ireland and founder of the Combustion Institute. Studying with John, the concern for the environment that I’d retained from childhood found a clear form: try to master the science, go out into the community or the wider world and apply it, almost a return on the investment that society has made in you and your education.

My PhD got some positive attention and I followed an opportunity to work and learn with Frederick Dryer in Princeton, the home of combustion science. There, through the School of Mechanical Engineering, I jumped right into a contract with the Air Force to optimize SAF – Synthetic Aviation Fuel. There is a continuity from that experience right through to our research today with Ryanair and the aviation industry at large. Just one difference. We look for Sustainable Aviation Fuel now. No need to change the first letter. The core question of carbon was there when I went to work on engine fuels with Cummins Engines in the UK. It was applied science, proper engineering with greasy hands, running engines and test cycles. We were measuring how much carbon dioxide was being produced and assessing the accuracy of their own measurement of carbon release per unit of power. Not far from what happens at the Ryanair Sustainable Aviation Research Centre. I was glad to return to Ireland, first to teach in Limerick. The environmental science priority and resulting funding and hiring policies had taken hold at home. Trinity also had a vision to do something pioneering in energy and environment, and I was hired by the School of Physics. That started me down another interdisciplinary path. But the central problem remained: how to measure carbon, how to manage it, how to keep it from spilling excessively into our atmosphere. How to decarbonize society without damaging the economy?

This is an idea that has traction in Ireland, but when it comes to transport, reducing the CO2 releases has been hard. As well as being an island, remote and full of remote spaces and places, we are now so invested in aviation as an industry, with Ryanair’s prominence and the lesser known but highly important aircraft leasing sector – for which Ireland is the world centre. This is an industry (global aviation) that uses 96 billion gallons of fossil fuels yearly. So how do we start to replace that? That is precisely why the support from the industry for the Ryanair Sustainable Aviation Research Centre is so important. Along with growth and recovery post-pandemic, the leaders don’t want their industry to be – or to be perceived as – the main driver of global arming, and this is a sign of a willingness to take action. The initial purse (€1.5 million) has been distributed across two main activity paths over the past year: in each of them, the familiar question of precise CO2 measurement returned. On the one hand we developed calculation methodologies to determine the greenhouse gas intensity of sustainable aviation fuels, while we iterated different varieties of fuel ourselves.

On the other we began to create a mapping of the CO2 intensity of aviation as it is now. We wanted to look at each link on the supply chain of flying and find out its carbon cost. This is a complex process involving datasets from multiple sources and a lot of pure mathematics – the opposite of the engine room work of making fuel batches. We will be able to remake leaner processes for each link in the chain in terms of carbon footprint. This requires many layers of cooperation and has potential to shine a light beyond the immediate concern of the craft and the airport. In that vein we have already started a collaboration with the Spanish tourism body to assess the carbon cost of Spain’s tourism industry. That centres our work on the phenomenon of travel: what is the cost of the journey, including the taxi, the hotel and the rest? Working with so much data incoming from different sources, we must attempt to “trust but verify,” as Ronald Reagan put it, when making judgement calls on information. We hope that the methods that emerge can be followed and elaborated on.

When it comes to the fuels, it can stir amazement in the casual observer that we might one day fly planes on vegetable waste: it is partly true. Right now the principal advanced biofuel recipe relies on corn cobs. We have an elaborate procedure that chemically converts to an optimum ethanol to blend with gasoline and diesel fuels. The experimentation is not market-agnostic either: we will constantly assess the scalability of the fuel solutions. If they cannot work for the industry and its 96-billion-gallon thirst, we go back to our testing ‘cell’.

The plant-based biofuels are not the only focus: we are also working on ways of dealing with the excess energy created by sustainable methods with big fluctuations in power, like solar and wind. Can we work out a way to create an electrochemical reaction that will store as simple fuel-like molecules, ie methanol, methane hydrogen, that we can transport and use? That will be a longer time to realise in terms of a solution ready for private enterprise. But all the interdisciplinary work, the closer contact with industry executives and other stakeholders in the world of travel, energy and environment – all this will help to make things happen faster. It is excellent that Trinity and the wider research world is coming around to the necessity of improving our understanding of energy. It is a peculiar, complex and – to me – utterly fascinating science where the breakthroughs that we can see coming are the ones the world clearly needs.

 Trinity Today Autum 2022