BA overestimates the potential of its biofuel plan
UK flag carrier British Airways (BA)’s plan to create fuel from domestic waste has a significant flaw. According to blog Carbon Commentary, the airline has over-egged the amount of biofuel it would be able to produce by “a factor of ten”.
In the post, author Chris Goodall compares figures projected by BA’s head of environment with government waste statistics and adjustments for efficiency of converting waste into fuel.
In the Guardian, Damian Carrington quotes BA’s expectation that the UK produces around 200 million tones of waste suitable for conversion using a gasification process into low carbon aviation fuel. This kind of thinking is important because, as Goodall points out:
“As the number of flights increases in the industrialising world, it is not far-fetched to see aviation using up the entire global CO2 budget in 2050.”
BA’s head of environment says half a million tones of this waste converted at its new gasification plant could produce around 50,000 tonnes of aviation fuel – a ratio of about ten to one – along with around 33 megawatts of electricity.
Problem 1: We’re less wasteful than we think
Goodall says BA has first of all overestimated the kind of waste that can be converted. Of the 200 million tonnes of waste the UK produces per year, he says:
“[…] only a small fraction of this is in the form of hydrocarbons that can be converted to energy-laden fuels.”
This particular waste must contain the “right chemical elements,” Goodall explains. Sources could be “food waste, rubber, textiles, paper and other products containing carbon and hydrogen”. In the last financial year, he says:
“[â?¦] the UK’s households produced about 23.5 million tonnes of waste, not much more than 10% of the total national figure. About 9.5 million tonnes of this was recycled, composted or reused, leaving about 14 million tonnes of true waste.
In addition to this, just under 4 million tonnes of other waste collections, not from households, were of animal or vegetable origin. (If it isn’t of this origin, it won’t contain usable amounts of carbon or hydrogen for fuel). So the absolute maximum amount of UK waste available to be converted into complex hydrocarbons for fuel is about 13.5 million tonnes.”
This high-end figure is less than seven per cent of BA’s prediction for the amount of feedstock its plant will have – and it’s set to reduce because household recycling figures increase.
Problem 2: even if we have the right kind of waste, it still produces less fuel than BA thinks
The second problem is that municipal waste is estimated to have an energy value of around six to seven gigajoules per tonne – about a seventh of that of conventional, dirty aviation fuel. Goodall adds:
“Moreover the process of changing waste into fuel must involve losses of energy – all energy conversion processes result in the production of low grade waste heat. The very best gasification technologies only capture 50% of the energy in the feedstock and the BA plant is probably much less.”
So the ratio of tonnes of waste to tonnes of fuel will be “at best, 14 to one and probably far worse,” Goodall says.
“In other words, instead of the BA fuel production process producing 50,000 tonnes of aviation kerosene from half a million tonnes of rubbish, it can only possibly produce 30,000 tonnes. This is still a worthwhile amount, but significantly below what BA says.”
By taking these factors into account, BA’s estimated yield of 20 million tonnes of fuel is reduced to one million tonnes or around eight per cent of the UK’s total use of aviation fuel, Goodall says. He adds that the ramping-up of recycling measures could mean the UK’s “total amount of carbon-based waste falls to well below 10 million tonnes” – meaning the absolute maximum fuel output “will fall to not much more than five per cent of aviation needs.
Goodall concludes:
“The false promise of biofuels (such as aviation fuel from municipal waste or ethanol from corn) is that we will get low-carbon energy from a plentiful supply of biological material, whether it be waste or US corn crops. The promise always fails when it hits biological limits. Our needs for transport fuels are simply far too great – by between one and two orders of magnitude -ever to be met from organic sources such as waste or agricultural crops.”
As Goodall says, there is intrinsic merit in airlines doing this kind of work. Clearly, rubbish going into making low-carbon aviation fuel and electricity instead of landfill or the sea is still a good thing. And if such a scheme were to be rolled out, it would presumably lead to dialogue with local authorities on how to manage recycling given the existence of new fuel conversion plants. But Goodall’s analysis shows BA is going to have to do a lot more thinking if it wants to help the aviation industry avoid the huge emissions levels it could easily reach in the future.