Archive for the ‘Aviation’ Category

From sunlight to Jet A1

In a world of near zero anthropogenic emissions of carbon dioxide, there remains the problem of finding a fuel or energy carrier of sufficiently high energy density that it remains practical to fly a modern jet aeroplane. Commercial aviation is heading towards some 1 billion tonnes of carbon dioxide per annum so doing nothing may not be an option.

Although planes will certainly evolve over the course of the century, the rate of change is likely to be slow and particularly so if a step change in technology is involved. In 100 years of civil aviation there have been two such step changes; the first commercial flights in the 1910s and the shift of the jet engine from the military to the commercial world with the development of the Comet and Boeing 707. The 787 Dreamliner is in many respects a world away from the 707, but in terms of the fuel used it is the same plane; that’s 60 years and there is no sign of the next change.

Unlike domestic vehicles where electricity and batteries offer an alternative, planes will probably still need hydrocarbon fuel for all of this century, perhaps longer. Hydrogen is a possibility but the fuel to volume ratio would change such that this could also mean a radical redesign of the whole shape of the plane (below), which might also entail redesign of other infrastructure such as airport terminals, air bridges and so on. Even the development and first deployment of the double decker A380, something of a step change in terms of shape and size, has taken twenty years and cost Airbus many billions.


For aviation, the simplest approach will probably be the development of a process to produce a look-alike hydrocarbon fuel. The most practical way to approach this problem is via an advanced biofuel route and a few processes are available to fill the need, although scale up of these technologies has yet to take place. But what if the biofuel route also proves problematic – say for reasons related to land use change or perhaps public acceptance in a future period of rising food prices? A few research programmes are looking at synthesising the fuel directly from water and carbon dioxide. This is entirely possible from a chemistry perspective, but it requires lots of energy; at least as much energy as the finished fuel gives when it is used and its molecules are returned to water and carbon dioxide.

Audi has been working on such a project and recently announced the production of the first fuel from their pilot plant (160 litres per day). According to their media release;

The Sunfire [Audi’s technology partner] plant requires carbon dioxide, water, and electricity as raw materials. The carbon dioxide is extracted from the ambient air using direct air capture. In a separate process, an electrolysis unit splits water into hydrogen and oxygen. The hydrogen is then reacted with the carbon dioxide in two chemical processes conducted at 220 degrees Celsius and a pressure of 25 bar to produce an energetic liquid, made up of hydrocarbon compounds, which is called Blue Crude. This conversion process is up to 70 percent efficient. The whole process runs on solar power.

Apart from the front end of the facility where carbon dioxide is reacted with hydrogen to produce synthesis gas (carbon monoxide and hydrogen), the rest of the plant should be very similar to the full scale Pearl Gas to Liquids (GTL) facility that Shell operates in Qatar. In that process, natural gas is converted to synthesis gas which is in turn converted to a mix of longer chain hydrocarbons, including jet fuel (contained within the Audi Blue Crude). The Pearl facility produces about 150,000 bbls/day of hydrocarbon product, so perhaps one hundred such facilities would be required to produce enough jet fuel for the world (this would depend on the yield of suitable jet fuel from the process which produces a range of hydrocarbon products that can be put to many uses). Today there are just a handful of gas-to-liquids plants in operation; Pearl and Oryx in Qatar, Bintulu in Malaysia and Mossel Bay in South Africa (and another in South Africa that uses coal as the starting feedstock). The final conversion uses the Fischer Tropsch process, originally developed about a century ago.

Each of these future “blue crude” facilities would also need a formidable solar array to power it. The calorific content of the fuels is about 45 TJ/kt, so that is the absolute minimum amount of energy required for the conversion facility. However, accounting for efficiency of the process and adding in the energy required for air extraction of carbon dioxide and all the other energy needs of a modern industrial facility, a future process might need up to 100 TJ/kt of energy input. The Pearl GTL produces 19 kt of product per day, so the energy demand to make this from water and carbon dioxide would be 1900 TJ per day, or 700,000 TJ per annum. As such,  this requires a nameplate capacity for a solar PV farm of about 60 GW – roughly equal to half the entire installed global solar generating capacity in 2013. A Middle East location such as Qatar receives about 2200 kWh/m² per annum, or 0.00792 TJ/m² and assuming a future solar PV facility that might operate at 35% efficiency (considerably better than commercial facilities today), the solar PV alone would occupy an area of some 250 km² , so perhaps 500 km² or more in total plot area (i.e. 22 kms by 22 kms in size) for the facility.

This is certainly not inconceivable, but it is far larger than any solar PV facilities in operation today; the Topaz solar array in California is on a site 25 square kms in size with a nameplate capacity of 550 MW.  It is currently the largest solar farm in the world and produces about 1.1 million MWh per annum (4000 TJ), but the efficiency (23%) is far lower than my future assumption above. At this production rate, 175 Topaz farms would be required to power a refinery with the hydrocarbon output of Pearl GTL. My assumptions represent a packing density of solar PV some four times better than Topaz (i.e. 100 MW/km² vs 22 MW/km²).

All this means that our net zero emissions world needs to see the construction of some 100 large scale hydrocarbon synthesis plants, together with air extraction facilities, hydrogen and carbon monoxide storage for night time operation of the reactors and huge solar arrays. This could meet all the future aviation needs and would also produce lighter and heavier hydrocarbons for various other applications where electricity is not an option (e.g. chemical feedstock, heavy marine fuels). In 2015 money, the investment would certainly run into the trillions of dollars.

Getting to net-zero emissions

It is looking increasingly likely, but not a given, that a reference to global net-zero emissions or even a specific goal to achieve net-zero emissions by a certain date (e.g. end of the century) will appear in the climate deal that is expected to emerge from the Paris COP at the end of this year. But like many such goals, it is both open to interpretation and raises questions as to how it might actually be achieved.

The background to this is that the issue itself implies that this outcome is necessary. The IPCC says in its 5th Assessment Report;

Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. Limiting risks across RFCs (Reasons for Concern) would imply a limit for cumulative emissions of CO2. Such a limit would require that global net emissions of CO2 eventually decrease to zero and would constrain annual emissions over the next few decades (Figure SPM.10) (high confidence).

However, the term net-zero needs some sort of definition, although this is currently missing from the UNFCCC text. One online source offers the following;

Net phase out of GHG emissions means that anthropogenic emissions of greenhouse gases to the atmosphere decrease to a level equal to or smaller than anthropogenic removals of greenhouse gases from the atmosphere.

The above effectively means stabilization of the atmospheric concentration of CO2, which also aligns with the ultimate aim of the UNFCCC Convention (stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system). This could still leave room for some level of emissions in that climate models show atmospheric concentration of carbon dioxide will decline if anthropogenic emissions abruptly stopped. In a 450 – 500 ppm stabilization scenario emissions could remain in the range 7-10 billion tonnes CO2 per annum without driving the atmospheric concentration higher. This is far below current levels (35 billion tonnes per annum from the energy system alone), but it isn’t zero. It can be classified as net-zero though, in that the atmospheric concentration isn’t rising.

However, such an outcome, while stabilizing the atmospheric concentration may not be sufficient to prevent dangerous interference with the climate system. In that case an even lower level of emissions may be required, such that atmospheric concentrations do begin to fall and stabilize at a lower concentration.

Another definition of net-zero may simply apply to anthropogenic emissions directly, irrespective of what the concentration in the atmosphere might be doing. In this case, any remaining emissions from anthropogenic sources (and there will be some) would have to be offset with sequestration of carbon dioxide, either via CCS or a permanent forestry solution. In the CCS case, the carbon dioxide would need to come from a bio-source, such as the combustion of biomass in a power station. This is what the IPCC have termed BECCS.

A final step which goes beyond net-zero, is to have an anthropogenic net-negative emissions situation, which is drawing down on the level of carbon dioxide in the atmosphere through some anthropogenic process. This would be necessary to rapidly lower the concentration of carbon dioxide in the case of a significantly elevated level that comes about in the intervening years between now and the point at which the concentration stabilizes. Very large scale deployment of BECCS or an atmospheric capture solution with CCS would be required to achieve this.

Finally, there is the consideration that needs to be given to greenhouse gases other than carbon dioxide. Methane for example, while a potent greenhouse gas, is relatively short lived (a decade) in the atmosphere so will require some thought. Even in a zero energy emissions system, methane from agriculture and cattle will doubtless remain a problem.

Both of the Shell New Lens scenarios end in a  net zero emissions outcome by the end of the century, but this is within the energy system itself and does not encompass the full range of other sources of CO2 emissions and other long lived greenhouse gases. Nevertheless, with extensive deployment of CCS the Mountains scenario heads into negative emissions territory by 2100 and the Oceans scenario soon after that (which means there is potential to offset remaining emissions from very difficult to manage sources). Oceans relies on this approach in a major way to even approach zero in the first instance

Many look to renewable energy as a quick solution to the emissions issue, but the reality is far more complex. While we can imagine a power generation system that is at near zero emissions, made up of nuclear, renewables and fossil fuels with CCS, this is far from a complete solution. Electricity currently represents only 20% of the global final energy mix (see below, click for a larger image: Source IEA).

Global final energy 2012

Solutions will need to be found for a broad range of goods and services that give rise to greenhouse gas emissions, including non-energy sources such as limestone calcination for cement and cattle rearing for dairy and direct consumption. While we can also imagine a significant amount of global light transport migrating to electricity, shipping, heavy transport and aviation will not be so simple. Aviation in particular has no immediate solution other than through a biofuel route although there is some experimentation underway using high intensity solar to provide the energy for synthesis gas manufacture (from carbon dioxide and water), which is then converted to jet fuel via the well-established Fischer–Tropsch process. There are also dozens of industrial processes that rely on furnaces and high temperatures, typically powered by fuels such as natural gas. Metal smelting currently uses coal as the reducing agent, so a carbon based fuel is intrinsic to the process. Solutions will be required for all of these.

Whether we aim for a very low level of emissions, true net-zero anthropogenic emissions or negative emissions is somewhat academic today, given the current level of emissions. All the aforementioned outcomes are going to require a radical re-engineering of the energy system in a relatively short amount of time (< 80 years).

Selling CCS at a climate conference

As COP 19 rolls on in Warsaw, both delegates and observers that I have talked to are seeing little agreement, despite the sometimes upbeat assessment coming from the UNFCCC. It may well be late on Friday or even Saturday before something appears from this COP.

Meanwhile the side event and external (to the formal COP) conference programmes continue. It is through these processes that participants can meet and discuss various aspects related to climate change. This being a meeting about climate change, it might be expected that attendees would be interested in hearing about carbon capture and storage (CCS), but it turns out this is a hard sell here. The problem seems to start at the COP venue itself, where the meeting room banners feature various approaches to energy and environmental management. CCS doesn’t get a mention.

 COP Banners

All I could find were Energy Efficiency, Renewable Energy Sources, Air Protection and Water & Wastewater Management.

This theme continues in many presentations, speeches, dinner conversations and panel discussions. While CCS does of course feature when organizations such as GCCSI hold events, at more general climate solution events it struggles to hold its own. Rather the focus is solidly on energy efficiency and renewables. Neither of these are anything close to sufficient solutions to the climate problem as it stands today, yet you could sometimes come to the conclusion that this is what the COP is actually about.

Energy efficiency has transformed global industry since the first day of the industrial revolution. Everything we do is possible through a combination of technology innovation and energy efficiency, from power stations to vehicles to mobile phones. The result of this has been tremendous growth, but with it has come a continuous rise in greenhouse gas emissions, particularly CO2. We use more goods and services, buy more stuff and travel further than at any point in human history and there is no apparent let up in this trend as it continues to pervade the entire global economy. But now energy efficiency is being sold as a mechanism for reducing emissions, throwing into reverse a trend that has been with us for over 200 years and fundamentally challenging economic building blocks such as Jevons Paradox. A parade of people representing business organizations, environmental NGOs and multilateral institutions will wax lyrical about energy efficiency. In one presentation an airline industry spokesperson talked about the tremendous improvements in efficiency the industry was making, through engine design, light weighting, route optimization and arrival and departure planning. There is no doubt that this is happening, but it is also bringing cheaper air travel to millions of people and of course forcing up emissions for the industry as a whole. There is no sign of this trend reversing itself. Adding a carbon price to the energy mix is the way to change this trend and still make energy efficiency improvements. 

The renewable energy story is told in a similar way. While there is also no doubt that the application of renewable energy is bringing benefits to many countries, offering distributed energy, providing off-grid electricity and supplementing the global energy supply in a tangible way, the global average CO2 intensity of energy has remained stubbornly the same since the 1980s when it dropped on a relative scale (1990 = 100) from 107 in 1971 to 100 in 1987 (Source: IEA). It was still at 100 in 2011. This is not to say it will never change, but simply advocating for renewable energy is very unlikely to take us to net zero emissions before the end of this century. The fossil fuel base on which the economy rests is also growing as demand for energy grows. As recent IEA World Energy Outlooks have repeatedly shown, much of this new demand is being met with coal. The only way to manage emissions from coal is the application of CCS, yet this seemingly falls on deaf ears here in Warsaw.

When CCS does get a mention, it is increasingly phrased as CCUS, with the “U” standing for “use”. In her one upbeat mention of CCS that I have heard, UNFCCC Executive Secretary also referred to it as CCUS. In another forum, one participant even talked about “commoditizing” CO2 to find a range of new uses. The problem is that CO2 really can’t be used for much of anything, with one modest (compared to the scale of global emissions) but important exception. The largest use today is for enhanced oil recovery where the USA has a mature and growing industry. It was originally built on the back of natural CO2 extracted from the sub-surface, but the industry now pays enough for CO2 that it can provide support to carbon capture at power plants and other facilities (usually with some capital funding from the likes of DOE).  This has helped the US establish a CCS demonstration programme of sorts.

There are other minor industrial gas uses (soft drinks), some scope for vegetable greenhouses such as the Shell project in the Netherlands (which provides refinery CO2 to Rotterdam greenhouses for enhanced growing, rather than have them produce it by burnaing natural gas) and a technology that quickly absorbs CO2 in certain minerals to make a new material for building, but all of these are tiny. The problem is that CO2 is the result of combustion and energy release and therefore any chemistry that turns it into something useful again requires lots of energy – nature does this and uses sunlight. Even if such a step were possible, this wouldn’t change the CO2 balance in the atmosphere, just as any bio process doesn’t change the overall balance in the atmosphere. Only sequestration, either natural or anthropogenic, changes that balance.

In a year which saw extreme weather rise up the political agenda and the consequences of a changing climate starting to sink into our collective psyche, action to actually address the issue of rising levels of CO2 in the atmosphere remained limited.

With regards issue recognition and despite arguments about attribution, the Bloomberg Businessweek headline after Hurricane Sandy was a telling moment. But events such as this seem to have a short half life, so it remains to be seen how lasting this will be.

 The principal policy instrument to trigger action, a price on CO2 emissions, did gain political traction and coverage, but its impact remained mute. Several jurisdictions introduced carbon pricing and others continued developing approaches and/or starting up schemes already in the pipeline. Notably, despite industry resistance, Japan introduced a modest carbon tax (although there has been a change in government since then so watch this space) and Kazakhstan leapt ahead of the pack by introducing an emissions trading system for startup this week. The Chinese trial systems began to take shape and there is now serious discussion about national implementation in the 2016 5-year plan. As of January 1st the California ETS is up and running, as is the Quebec system. The Australian carbon price mechanism started in 2012 and importantly the Australian Government passed legislation to link their system with the EU ETS. But fierce opposition forced the EU to take a step back with regards its plans to cover international aviation under the EU ETS.

The EU did however take one major step forward during 2012, in its recognition that a carbon market created as a result of an ETS may need some government intervention from time to time to keep it on track and relevant. Although the issue is far from settled, there is at least a proposal on the table aimed at supporting the weak market in the EU. The move also establishes an important precedent for the future, not just in the EU but probably in the minds of policy makers globally.

With global carbon prices remaining low, the one critical technology for actually rescuing the emissions problem, carbon capture and storage (CCS), struggled badly. Shell did announce an important project in its oil sands in Alberta, but other than this little else happened. At the end of the year the EU managed to deliver a damaging blow to the technology by not coming up with a single project to support with its NER300 CCS funding mechanism, despite having nearly €2 billion in hand to spend. Instead, the money went to some twenty or so small renewable energy projects. It’s hard to overstate the importance of CCS, yet it seems increasingly distant in terms of commercialization and deployment.

From a climate perspective, the year concluded in Doha with two weeks of talks that did a lot to tidy up the UNFCCC process, but hardly pushed the agenda forward at all. If the “holy grail” of a global deal really is to be agreed by 2015, then something remarkable needs to happen during 2013.

Happy New Year!

Where to now for aviation?

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Last week’s first commercial flight of the Boeing 787 Dreamliner potentially marks the beginning of a new era for the aviation industry. Its composite construction and 20% better fuel efficiency (than the 767) continues a long term trend of improvement by Boeing. But the numbers behind this essential global industry are daunting, albeit with impressive strides forward such as the 787.

Revenue Passenger Kilometres (RPK) have more than doubled since 1990 and the Boeing Current Market Outlook for the period 2011 to 2030 has RPK growth rates surging ahead in many parts of the world at well over 5% p.a. such that by 2030 RPK in the Asia Pacific area alone is nearly 4 trillion. Globally, 2030 traffic is forecast to be about triple that of today.

Total CO2 emissions (Source: IEA) have risen as well, but since 1990 the growth has been “only” 50%, compared with the more than doubling of activity. This points to the impressive jumps in fuel efficiency, with the Dreamliner delivering yet again.

The chart above gives an indication of the improvements achieved by plane type. I wasn’t able to locate actual efficiency figures, so the chart has been derived from the fuel capacity, passenger carrying capacity and range of various aircraft plotted against the year of release for the aircraft in question. Clearly the trend has been strongly down, starting with the Boeing 707 in the 1950s. But how much further can this impressive trend extend? Airlines are also pressing hard to increase efficiency of their legacy fleets by taking steps such as reducing weight, incentivizing passengers to do the same with their baggage, optimizing schedules and pushing air traffic control and airports to improve landing, takeoff and taxiing procedures.

But if air traffic is to triple in just 20 years, efficiency will have to jump by even more than it has to date to deliver any sort of sustainable service. Increasing Kerosene (Jet A1) demand will not only put pressure on crude oil demand, but will also pressure the yield of kerosene from the barrel. This will require refiners to become more inventive in the processing of crude oil and could well point to even higher energy demand by refineries to make more transport fuel from the barrels of crude available. It may also point to an even faster turnover of the fleet as airlines scramble to upgrade to the next generation of fuel efficient aircraft – planes such as the 787 Dreamliner, A380 and upcoming A350 series from Airbus.

Many airlines are now starting to experiment with biofuels and new production processes such as Fischer-Tropsch based Gas-to-Liquids with its high kerosene yields will add to the aviation fuel pool. But revolutionary step change airframes that might make up a future Boeing 800 or Airbus 400 series are unlikely to impact this 20 year picture, they just won’t be here in time or in sufficient numbers to make a difference (the Dreamliner was first mooted in the late 1990s). The2030 die is now largely cast with what we have and know about.

The challenge of an absolute reduction in CO2 emissions from aviation is also an unlikely prospect given the above figures. Yet by 2030 global emissions need to have peaked and be showing real falls. Although aviation may well continue to show impressive efficiency improvements and could have introduced biofuels into the mix by 2030, sheer demand will probably mean a rise in emissions. This then puts more pressure on other sectors to reduce, such as power generation and road transport.