Sunday, 1 March 2020

4 strategies to fix carbon emissions

Greta Thunberg, school children and others are loud in their condemnation of our government's failure to address climate change [1] and they are right to be so. But it is notable that they never offer a plan of action. To do so would invite (even more) criticism because all options are unpopular with at least some people. I try to highlight some of this dilemma when I am giving a talk about personal actions to reduce GHG emissions. It is slightly off topic but I think it is important. It also raises the hope that some of these problems may be temporary.

I always start with air travel because it is such a nice example. The emissions from air travel are staggering. One return flight to New York (economy class) emits nearly 2 tonnes of CO2 equivalent, about a quarter of the average UK resident's annual total. 

So what to do about it. I offer four different strategies:
  1. Austerity: do not fly (like Greta Thunberg)
  2. Demand management by market manipulation: Use taxes or ration flying so everyone gets a fair share
  3. Technology fixes: Zero carbon aircraft
  4. Damage repair: Carbon offset or capture and store the emissions
Unsurprisingly, option 1 is never popular. You can also apply the same strategies in other sectors; below I consider meat eating and home heating as well as flying,

Austerity is not a popular solution.
The Greta Thunberg solution works for some. In fact about half the population in the UK do not fly as it is. Some people have to fly for business but probably less than you think: the vast majority (80%) of flights are for holidays or visiting friends. Amongst young people, a third to a half of flights are for stag parties and hen nights [3]. Do we really need to go abroad to throw a party? Still, the no-fly at all option is not popular among the groups where I have discussed the issue. I see that FlightFree 2020 has only 25,000 signups so far this year. [4]

Rationing or taxation could be a fairer approach.
Rationing is a possibility. A few frequent flyers are responsible for most flights (15% of people take 70% of flights [5]. To discourage this, the organisation afreeride recommends a tax on frequent flyers - the more you fly the more you pay. The Committee for Climate Change seems to support the idea too [5]. I can foresee some difficulties with implementation - such as how to stop people taking the train to Paris and flying from there? Anyway, with current technology we cannot afford the emissions for everyone to take even just one flight. A simpler approach would be to tax flying more broadly possibly with a general carbon tax. This would reduce demand but probably exacerbate the existing inequality in access.

The technical solution is not here yet.
Then there is the technical solution - carbon free flights. The aircraft industry is working on it but they are nowhere near a solution as yet. Electric planes could be truly carbon free but so far there are none that can carry an economically viable number of passengers a reasonable distance. July 2019 saw the launch of the first prototype commercial all electric plane by Israeli firm Eviation [6]. It will carry nine passengers 650 miles - so from London to Zurich, but not to New York (not that I wish to go to New York but apparently many people do).

There are other approaches on the drawing board, such as fuel made from waste or biomass. Supplies are limited and I do not believe there will ever be carbon free flying on a mass scale. But for some people some of the time, yes that is plausible.

Carbon offset.
We can pay someone else to save emissions equivalent to our flights. Some airlines make this as easy as ticking a box when you book the flight (and paying a little extra)[7]. The offsetting industry requires careful auditing to make sure that carbon savings are real, permanent and additional - i.e. they would not have happened anyway. Most offsetting projects are in developing countries which makes them cheap. ClimateCare will offset the 2 tonne New York trip for £15. Offsetting is not sustainable in the long term and in any case it would be better to fund these projects as charity or direct aid.

Direct Air Capture and Storage.
Another approach is to capture and store an equivalent amount of carbon from the air where we have just put it (Direct Air Capture and Storage: DACS). To make sure this is permanent, the carbon should be incorporated into stone: this is called mineralisation. In fact the mineralisation bit is relatively easy, it is the capture bit that is expensive. A subscription with Climeworks to capture and store a quarter of a ton per year costs EUR 25/month. For 2 tonnes: EUR 2,400 ! (It is much easier to capture carbon from a concentrated source such as a power station exhaust.) Arguably we may need to deploy DAC on a large scale in the future so it is good to support its development and bring down costs.

Which of these solutions do you think are best? In practice there will be a combination. I'd really like to see a tax on the aircraft industry to fund carbon capture and storage. That would make flying a lot more expensive, at least in the short term.

The same principles can be applied to meat eating.
The same principles can apply to other problem areas and the answers may be different. Consider meat eating.
  1. Austerity: don't eat meat. Many of my friends are vegan or nearly so. However, this is going further than necessary - few scientists say we have to give meat up altogether.
  2. Market manipulation: discourage consumption by taxing meat. This suggestion pops up in the news fairly regularly, most recently prompted by a report from the TAPP Coalition (True Animal Protein Price Coalition) [8]. There are also health benefits from reducing red meat consumption.
  3. Technical solution - meat alternatives. Pseudo products made from various vegetable sources are widely available in supermarkets and even fast food outlets such as MacDonalds. Lab grown meat, made from animal cells but not from a live animal is another approach attracting a lot of development effort. Some say it is close - such as startup company Just Eat [9]. They already have an egg product. A partial technical solution could involve feed additives for cows to reduce the amount methane they belch out [10].
  4. Carbon storage - UK farmers have a plan to offset some unavoidable emissions by a range of techniques including tree planting [11].
Low carbon heat too.
Also the problem of low-carbon heat for our homes - most people use gas which is a fossil fuel and inherently high in emissions (though not as bad as coal or oil).
  1. Austerity: don't heat our homes - again not a popular option, though cutting back is certainly doable for most people. We just have to adjust our thermostats and wear warmer clothes ...
  2. Market manipulation: tax the fuel we use to heat our homes. It is notable that businesses have paid carbon taxes for nearly 20 years (Climate Change Levy) but domestic fuel has always been exempt.
  3. Technical solutions abound but all have limitations. Electric heat pumps are large and need low temperature radiators (see Low carbon heating in real houses); renewable gas requires too much land to grow the biomass source (How is a house like 3/4 of a cow); district heating with waste heat can work in some places but not others.
  4. Carbon capture and storage - well actually I don't see how that can help in this instance as the other solutions are cheaper.
For low carbon heating, the technical solutions are close and arguably market manipulation could tip the balance to make them financially attractive. However, market based solutions are hampered by the fact our housing market is so tight. It is rarely possible for someone with a hard-to-heat house move away to somewhere better. This means a pure market based solution is bound to bring hardship to many. We don't need to take holidays abroad and we don't need to eat meat to stay healthy, but we do need to keep reasonably warm.

What do I think?

For the flying problem I have already mentioned I like the idea of market manipulation, forcing the airlines to fund remedial measures such as carbon storage. This will increase prices and reduce demand in the frivolous cases. Similarly I would be happy with a tax on meat and in this instance some alternative choices are here already. The hardest case is the low carbon heat for our homes. I fear this needs more time for technology to improve on the current solutions. In the interim some turning down of thermostats would help a lot. Perhaps a tax on domestic fuel combined with a subsidy for the fuel poor would be a fair way to manipulate the market. This actually sounds quite a lot like Carbon Fee and Dividend!

However it is not for me to decide. Hopefully the Climate Citizens Assembly will consider some of these options and decide which are the most acceptable in the short to medium term. In the longer term, technology will doubtless provide more choices.

[2] Aviation statistics AVI0108 (
[3] Should Hens Fly(Hubbub ) Feb 2019
[4] Flight Free 2020& (westayontheground)
[5] Introduce frequent flyer levy to fight emissions, government told (BBC) Sep 2019
[6] Why the age of flight is finally upon us (BBC) July 2019
[7] Can carbon offsets tackle airlines emissions problem (Guardian) Nov 2019
[8] EU urged to adopt meat tax to tackle climate emergency (Guardian) Feb 2020
[9] Out of the lab and into your frying pan: the advance of cultured meat (Guardian) Jan 2020
[10] Beefing about meat (This blog) Jan 2020
[11] Five ways UK farmers are tackling climate change (BBC) Sep 2019


  1. You don't even mention electro-fuels as a mechanism for flight decarbonisation (by about 5-70%, because the rest is cloud formation which remains so long as we have jet engines.

    Electro-fuels seems a lot more plausible to me as a large-scale aviation decarbonisation mechansim than biofuels, which SFAICT are quite limited in volume (without unacceptable impacts on land-use/biodiversity/food production). Worldwide Aviation fuel use was about 575 million litres/day in 2016. Cars seems to be about 7 billion litres/day. And biofuels were 3.5% of that (in 2016). Whic his 250 million litres/day. So we do only need to double/triple biodfuel production to run all the planes so long as we swtich cars off it completely. That is more practical than I thought, although still moderately heroic.
    Switching refineries to do hydrolysis then generate carbon fuels (preferably using atmosphere-scrubbed carbon) may well be a better approach. It's certainly much more efficient and will use dramatically less land.

    Have you read Chris Goodall's new book ('What we need to do now') where he proposes a renewables+hydrogen (and electrofuels) system. Still quite heroic, but it all seems plausible.


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