Grahame Buss ZAS0019
I was a Principal Scientist for Shell, for which I worked for 33 years. I have a degree in aeronautical engineering and a PhD in fluid mechanics. This contribution is my own although I draw in part on my time in Shell. Germane to this contribution is that I managed a ‘Gamechanger’ group that sought new business opportunities for Shell. Under my management the focus of this moved to renewable transport fuels and this became the primary focus of my budgets. I have worked with both Airbus and Boeing on the question of sustainable aviation. I also spent relevant time in the first incarnation of a Shell hydrogen business, arising from the Ballard fuel cell bubble.
In the latter parts of my career I moved to policy issues, particularly around land use. I worked with the DfT, DECC, US EPA. and the EU Commission. My engagement with the EU on the status of land post Kyoto lead to the question of carbon trading and offsetting. I remained in this area after I left shell up to 2020.
As a teenager the RAF awarded me a scholarship to learn to fly. I also joined the University Air Squadron. More recently, my concerns for our climate and environmental emergency have led me to stop flying. I wish to see a sustainable aviation industry that serves the public good. Hence, my contribution.
All routes so far have failed in the search for a substantive, sustainable, affordable fungible jet fuel. Nevertheless, there remain options. We should remain open but sceptical to these current options. We are not close to a substantive SAF industry. I reach a similar conclusion for hydrogen, while for battery technology there is no credible solution for mass transit aviation.
Land use concerns place significant constraints on the biomass derived SAF. This must be addressed.
The most significant operational efficiency change would to reduce the production of contrails. This means a change in scheduling and in some cases changing flights paths and altitude. The change would be immediate and highly significant.
We do not need to support the R&D phase or pilot plant stages of SAF. There is adequate private investment money available. The decision to build a working facility will need security on the price and this will in turn encourage more early stage investment. I make a number of proposals.
On offsetting and carbon trading my view is that, while it is entirely proper for governments to account across all sectors to arrive at the nation’s balance of carbon sinks and sources, industries should predominantly trade within their own sectors. Where it is a multisectoral business the carbon balances should be reported by sector not as a single number on the groups bottom line.
It would be foolish and indeed gravely irresponsible to base our current decision to allow the aviation industry to expand based on the presumption that we will eventually succeed with SAF. More than irresponsible it is illogical. We have a global carbon budget that we must not exceed. Future technologies, even certain technologies, do not licence current emissions. Our biosphere does not respond to promises, only to our actions.
For a non-technical reader, it is worth making clear that at small scale we can turn any biomass into a perfect jet fuel. If we have enough purification stages, if we are not concerned about the long-term behaviour of the catalysts, or the yields, the energy inputs, or the cost, then with a source of carbon and enough hydrogen we can make any hydrocarbon fuel. Investment in R&D is cheap compared to building operational facilities at scale so hope springs eternal. Many routes have been tried and failed. As yet we do not have that elusive reactor and that stable high yield catalyst that makes a credible process possible at an acceptable cost. But what is acceptable depends on circumstances and there are options available that prima facie may work.
The usual starting position is to presume that we can use a waste such as municipal solid waste (MSW). There are issues here and I was not supportive of this approach. Firstly, because this makes the processing difficult where catalysis is involved. Secondly, there are volume and logistical constraints with waste. It is in any event waste streams are not the basis of a global biofuel industry at the scale sought. One is inevitably driven to look at co-products, residues and primary crops such as sugar from sugarcane. This is the point at which the concerns arise.
As well as carbon, biodiversity is a key metric for decision making on land use changes. The destruction of our natural habitats and emissions from the agricultural sector contribute 25% of our greenhouse gases. If we are to achieve our targets of no more than +1.5 C we need to stop and restore our natural world. This is the opportunity cost of large-scale bioenergy feedstocks. The acceptance of biofuels at the large scale considered in the Shell scenarios for example, requires a successful implementation of this element of Nature Based Solutions (NBS). This has implications for animal feed, grazing and bioenergy as 77% of agricultural lands are for grazing and animal feed[1],[2]. Biofuels will struggle if seen or are perceived to be at the expense of nature. The most urgent Nature Based Solutions to address are the prevention of deforestation and loss of wetlands. Without significant action to address this it is difficult if not impossible to see how large-scale SAF supply could be seen as acceptable either to regulators or the public.
Vegetable-oil are liquids with a high energy density. The main options are palm oil, rapeseed and soy. These can be hydrotreated to give jet fuels but cannot deliver the volumes required and will remain a marginal contribution. Shell chose not to invest in a process for hydrotreating vegetable oils as the feedstock was predominantly palm oil. There are rightly profound concerns about the provenance of palm oil. The DfT does not permit the use of vegetable oils unless it is a ‘waste’ product, such as used cooking oil. The EU is phasing out palm oil derived diesel as the bulk of the feedstock comes from the deforestation of high carbon stock tropical forests. Soy is equally challenging[3].
Sugar and starch crops are feedstocks for ethanol. In Brazil ethanol from sugarcane is a major transport fuel alongside petrol. In principle ethanol can be converted to jet fuel and there are proposals to do this. Governments are more supportive of starting from lignocellulosic feedstocks than sugars and starches - such as residues from the timber industry, stover, bagasse. and purpose grown lignocellulosic crops. These are significantly harder to process. Many routes have been tried and failed, but there remain choices. I do not go into these here. In my experience this is not an area where there is shortage of investment.
The manufacturing plant cannot be too big (far smaller than a conventional refinery). This is determined by the logistics of moving bulky low-density feedstocks from a large area to a point in the centre. The traffic movements alone can make the project unworkable. An exception to this is Drax where the rail infrastructure exists to take wood chips from ships to the power station. Most biomass power stations are small and so will SAF manufacturing facilities.
Ultimately all inputs including energy, and outputs including wastewater have to have a low or zero carbon intensity contribution. This makes the process more expensive. In practice a compromise is attempted that gives not a zero-carbon intensity fuel (from a Life Cycle Analysis) but a lower value than fossil jet fuel. In time we might expect from learning curves (and those of equipment suppliers) to reduce the costs and carbon intensity. This requires the roll out of the manufacturing infrastructure at large scale with many small distributed manufacturing plants. This will take decades[4].
It is unwise to see biofuels as ‘transitional’ fuel until we know what the transition is to and when it will occur. The investment and the rate at which industries grow rules it out. This industry would need to stand or fall on its own merits. Investment in R&D is one thing but building at scale an industry that is time limited is to create a white elephant at threat from something better. Or, perhaps worse to delay the implementation of something better. More credible is that the industries serving the same needs would exist together – as we see now.
Shell has considered hydrogen as a fuel on a number of occasions. I was involved in a some of these programmes. We looked at liquid hydrogen, compressed hydrogen and the storage of hydrogen in hydrides. This was considered for road vehicles. It was not thought credible for aviation. Of the three, compressed hydrogen is the better option for long distance trucks and buses. Airbus is proposing to have liquid hydrogen passenger aircraft developed by 2035. There are problems with compressed hydrogen because of the weight of the storage tanks, while liquifying the hydrogen takes about 1/3rd of the energy in the hydrogen. Airbus clearly recognises the profound technical changes required. 14 years is not long to achieve this development, particularly as the aircraft proposed is a fuel cell hybrid and the fuel is stored at around -253 C. There is a long way between having an aircraft developed and having a global industry using these aircraft. Boeing remain unconvinced that we will see this development before 2050. Let us not forget that we are still flying 747s that first flew in 1969.
As well as the aircraft we will need the production and then storage infrastructure for liquid green hydrogen at the airports. There is also an opportunity cost. If we assume – as we should – that the hydrogen comes from the electrolysis of water, then we need to consider if this is a sensible use of the renewable power infrastructure. It is not just the aviation industry who want this resource.
We should dismiss the idea of battery powered aircraft as anything other than small executive jets and luxury taxis (rather like the current use of helicopters as taxis across London or Sao Paulo). It beggar’s belief that we would assert this as a credible option. Despite the research effort we have not significantly bettered lithium ion batteries in terms of storage density, and these are now approaching their limit. The (much higher) theoretical limit for batteries is around 2 MJ/kg. Jet fuel is 43 MJ/kg. There are limits to the aerodynamic efficiencies of aircraft so we will inevitable have to trade payload for batteries. Jet fuel can be 40% of the maximum take-off weight of a large passenger aircraft.
The most significant operational efficiency is to reduce the production of contrails. This means a change in scheduling and in some cases changing flights paths and altitude. The change would be immediate and highly significant. This would require scheduling changes and there would be a reduction in overall flights in some regions. It should be within the power of the UK CAA to impose this on aircraft arriving and leaving the UK. The EU is proposing to introduce this change over the next five years[5]. Now we are out of the EU we can do this ourselves and faster. It would be interesting to know the industry view on this as it will be a measure of their seriousness.
All the measures suggested are sensible, although I would not ban domestic flight. I have already contributed to the Treasury on this issue, but in brief. More bands for APD, a reduction of flights in line with IPCC recommendations on greenhouse gas reductions (halved by 2030), and a frequent flyer levy (FFL) with a high escalator on the levy with flights. The revenue should be used in part to support those flying infrequently (once or less per year) and the development of the industry (see below).
In my view we do not need to support the R&D phase or pilot plant. There is plenty of investment money available. The decision to build a working facility will need security on the price and this will in turn encourage more early stage investment. One option for working facilities would be a reverse auction (as we have seen for example in the forestry sector). This would be financed from revenue raised by the airlines and airports.
Most of the manufacturing will be outside of the UK, in which case there are other options. The most appropriate would be a carbon tax to encourage the industry to use the fuel. The APD or a FFL are appropriate – most of the ‘environmental’ taxes raised by government are not spent on the environment. This needs to change. in the early days the blend ratios will be small so this carbon price would not be onerous on a volume basis. Of course, if not onerous it will also not be significant. See my remarks on CORSIA below.
In my latter years I worked with DECC, the DfT, the EU Commission and the US EPA on policy issues around land use and biofuels. This inevitable leads to a consideration of offsetting as other land use is an opportunity cost for the use of biomass. My summary here is that: while it is entirely proper for governments to account across all sectors in arriving at the balance of carbon emissions and recoveries for the state, industries should predominantly trade offsets within their own or closely related sectors.
We see this recognised within the EU ETS where large industrial activities work with a cap and trade system. The ETS includes the aviation sector at this time. In my view this is not where it belongs, but it at least has the advantage that the ETS cannot trade with the Land Use, Land Use Change and Forestry sector (LULUCF). Other sectors fall within the Effort Sharing Decision and are regulated separately depending on the capacities and needs of each individual sector.
We see this same sector by sector principle in the UK and in the US EPA regulations. APD is not the same as fuel duty. Farming emissions are dealt with differently to industrial waste handling. The effective carbon and environmental prices differ across sectors. Were we to introduce a single carbon price with trading across sectors we would see arbitrage - driving all activity to the cheapest possible option. In the aviation sector this would ensure that were the technology ever developed it would not be implemented.
CORSIA will look for the cheapest possible offset. This will be forestry. The industry will claim that they have reduced their net emissions and their failure to reduce their actual emissions will be hidden. A threat that the industry would shrink would drive far greater rates of change that giving them an (almost) free pass.
Another and perhaps more pressing reason to not allow this cross-sector offsetting is that there are no sectors that have an excess of capacity to address our climate crisis. All will struggle to meet the IPCC recommendations. Investing in forests is a necessary action for the LULUCF sector.
I would be in favour of the aviation industry – indeed any industry – investing in the protection of the natural world, but this activity should not be added to the bottom line with the emissions from their own sector. This is an obfuscation. Rather, the accounting should be transparent and recorded by sector with no integrated bottom line. I note that Shell in investing in nature-based solutions (NBS) will include these activities in its bottom line as a reduction in the carbon intensity of the whole business. This is misleading. It apes the legitimate position of governments to account across sectors to determine their emissions and recovery contributions to their NDCs.
September 2021
[1] Wirsenius, S., 2003a. The biomass metabolism of the food system: a model-based survey of the global and regional turnover of food biomass. Journal of Industrial Ecology 7, 47–80.
[2] Ourworldindata.org
[3] Land Use Change and the European Biofuels Policy: The expansion of oilseed feedstocks on lands with high carbon stocks January 2019 DOI: 10.13140/RG.2.2.35349.58081
[4] Kramer, G. J. & Haigh, M. No quick switch to low-carbon energy. Nature 462, 568–569 (2009)
[5] EASA, 2020, Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to the Emissions Trading System Directive Article 30(4).