Two stories about sustainability and aviation reveal the confusion about how we can reduce the polluting effects of aviation. We are slow to accept that we live in a finite world and that our atmosphere is finite too. It was in the early 19th century that the natural greenhouse effect was first identified. By the 1990s, a broad consensus had emerged amongst scientists that greenhouse gas emissions arising from the burning of fossil fuels were resulting in climate change. If there are also natural causes, they are secondary, and while we could reduce emissions from our burning of fossil fuels, we cannot reduce natural causes.
The dominant theories and models of economics used by academics, policy makers, regulators, and businesses dismiss greenhouse gas emissions as mere externalities; they are not included in the cost side of calculations. These pollution costs, like climate change, impose very substantial costs on others, but the polluter does not bear the cost; others do.
I now vaguely recall the Polluter Pays Principle (PPP) first introduced in 1972 by the Organization for Economic Cooperation and Development (OECD), where the polluter was kept responsible for the pollution. It was reaffirmed globally in the 1992 Rio Declaration on Environment and Development. Aviation is just one of the industries where the polluter does not pay.
Aviation fuel production, drilling, refining, and delivery are not without externality costs. However, the real environmental damage is caused by the burning of the fuel. Bristol-based Firefly Green Fuels, about its company’s plans to turn sewage into sustainable aviation fuel.
Taking sewage sludge from water utilities, Firefly puts it into a high-pressure reactor to separate it into two useful materials: Biochar, a fertiliser for the agriculture industry, and bio-crude, which can be refined into jet fuel.
“Firefly’s route to sustainable aviation fuel (SAF) is unique in that it uses a completely biogenic and otherwise problematic material as a feedstock – sewage,” James Hygate, Firefly Green Fuels CEO, said. “This cheap and abundant feedstock will never run out and the SAF we can produce with it is almost identical to fossil jet fuel.”
The SAF it produces will then be “almost identical to fossil jet fuel,” burnt in the same jet engines it will produce very similar emissions. Some biofuels do burn without greenhouse gas emissions, but those based on sewage will not reduce emissions – and emissions are the issue.
Peer reviewed research published by Cambridge University engineers reveals that reducing contrails could reduce aviation’s global warming impact by nearly half. “aviation contributes around 2–3% of global carbon dioxide emissions, but its total climate impact is larger because of non-CO₂ effects such as contrails. Interest in contrail avoidance has grown rapidly in recent years as governments and airlines search for ways to reduce aviation’s climate impact while the sector transitions to lower-carbon fuels.”
Lead author Dr Jessie Smith, from Cambridge’s Department of Engineering says “Contrail avoidance can often be as simple as changing the flight paths, Often it’s even simpler than that – just moving slightly to a higher or lower altitude to avoid the areas of the atmosphere where contrails form.”
