Can flying ever go green?

Define green.

Today I learned that United Airlines uses biofuels from municipal sewage for a portion of their jet fuel for flights out of LAX.  In 2016, they contracted to purchase up to 15 Million gallons of biofuel over 3 years.  At the end of the contract, they signed up to purchase up to 10 M gal/year, doubling their use.

In 2016, WaPost wrote that the biofuel would be blended in a mixture of 30 percent biofuel and 70 percent traditional fuel.

But the use of biofuels is one possibility for existing machines to cut down on their emissions without having to upgrade their engines or other aspects of their design or engineering. “Drop-in” fuels are renewable fuels that are designed to work safely with existing engines, although as in the case of the United flights, they sometimes require mixing with traditional fuels.

This is analogous to cars in California using a blend of 15% bioethanol and 85% gasoline. If the ethanol comes from grains like corn, then the carbon savings is minimal.  If the bioethanol and biomethane comes from food waste, then the payoff is bigger.

Putting it in perspective.  United Airlines used 4292 Million gallons of fuel in 2019, of which 5 M gal was biofuel.  Even if they were to double that to 10 M gal/year, that would be 0.2% of their fuel use.

So, biofuels in airplanes is better than diesel.  But it's even better if we cut down on our flying overall.  It doesn't have to be much.  Cut down on one round trip long haul flight per year and it's as much carbon savings as if you traded in your gasoline-powered car for an electric car.

I copied the figure from Quantifying the potential for climate change mitigation of consumption options, which I also wrote about in New Paper on Global Data-Driven Climate Actions.

We cut back on personal flights so that we make one long-haul trip every few years.  I was supposed to fly home from Germany yesterday-today.  Bad Dad was going to represent his family at the commemoration of the liberation of Bergen Belsen 75 years ago.  The ceremony will be postponed.

We don't fly long distances for short trips.  We make fewer, longer trips.  We had planned to spend 3 weeks, visiting Berlin, Munich and some smaller towns in between.  I even planned to show him the small town where I had been an exchange student in high school (German Gymnasium.)  It will have to wait.

Poor planning and governance, not density, is the problem

I want to push back against the idea that density and transit necessarily have to spread COVID-19. Dense NYC may be the site of a particularly bad outbreak, but much denser Asian and European cities did much better despite high transit use. The difference is in better institutional planning and personal actions for disease containment.

Density is not the problem. It's the type of density. If you ban Asian metropolis-style apartment buildings, you get low-paid workers crammed 4 to a bedroom in a single-family home in Elmhurst, Queens, NYC. Or 23 people in a house in northeast Los Angeles.

In the words of Richard Florida

But even in the U.S., it is not density in and of itself that seems to make cities susceptible, but the kind of density and the way it impacts daily work and living. That’s because places can be dense and still provide places for people to isolate and be socially distant. Simply put, there is a huge difference between rich dense places, where people can shelter in place, work remotely, and have all of their food and other needs delivered to them, and poor dense places, which push people out onto the streets, into stores and onto crowded transit with one another.

New Paper on Global Data-Driven Climate Actions

Local experience is not always generalizable. But, you sum up research on a bunch of places, and then patterns emerge. In Data-Driven Climate Action (for Los Angeles) I said:

In summary, decarbonizing transportation has the highest potential for stopping Climate Change, but it requires collective action. We can’t choose to bike along a street that doesn’t create a safe space for us or take a bus to an evening concert if the buses don’t operate at night. An urban area is precisely where these two modes can excel, if we let them. We don’t need a solution that works in Iowa or New Hampshire or even Fresno. We have the existing density and the weather to do this right here, right now. Let’s paint those streets Green (bike lane) & Red (bus lane).

A recent meta-analysis by Diana Ivanova, John Barrett, Dominik Wiedenhofer, Biljana Macura, Max W Callaghan and Felix Creutzig, examined

6,990 records in the Web of Science Core Collections and Scopus. Searches were restricted to 1) reviews of lifecycle assessment studies and 2) multiregional input-output studies of household consumption, published after 2011 in English. We selected against pre-determined eligibility criteria and quantitatively synthesized findings from 53 studies in a meta-review. We identified 771 original options, which we summarized and presented in 61 consumption options with a positive mitigation potential.

They really did their homework on a global scale.  Climate mitigation measures were broadly separated into transportation, food, housing and other.  The combined findings are plotted together on a single box and whiskers chart.

The findings for each study are plotted with circles.  The extreme values are marked with "whiskers" at the end of the bars showing the full range of values. The 25th and 75th percentiles bound the "box". The average value is marked with a large X. The median is marked with a vertical line. 

For context, we need to reduce global CO2 productions by 55% to limit climate change to a global average of 1.5℃ (We've already warmed up 0.8℃ and 1.0℃ is already baked in due to past emissions alone.)  That means each person on earth can contribute 2.1 tCO2eq/cap (metric tons of CO2 or equivalent of emissions  per capita per year.) Americans and Australians contribute 16.7 and 16.2 tCO2eq/cap of emissions.

Note that some of the mitigation strategies can cause negative reductions or increases in CO2 emissions. The authors call that rebound--when the cure is worse than the disease.

The biggest difference that we can make, with the least cost and risk, is to live car-free. I get a lot of eye-rolling, mainly from older people in the US, when I mention this. We are apparently so exceptional in the US that physics and logic could simply not apply to us.

We know how this worked out for COVID-19. Ignore scientists and the results are apparent in a few weeks.

We have been telling you to get out of your car to save the planet for decades, and the result is so slow-moving, that we've been ignored or told we are crazy.

Physics and viruses don't care. They do what they are going to do.

Here's a closer look at just the transportation sector. See the range of values for "Live car-free?" The extreme high value is for ditching an SUV, which also happens to be the most popular car style in America. Losing the family SUV is a huge savings of about 3.6 metric tons of CO2 per capita per year.

I can already hear the, "Yes, but" crowd pointing to the Battery Electric Vehicles (BEV).  Don't they offer almost as much CO2 reduction?

The answer is maybe.  Notice that a significant chunk of the data points for BEV fall in the pink, rebound area, where they cause a net INCREASE in CO2 emissions.  E.g. the BEV is charged with fossil fuel-generated electricity or other externalities that cause other emissions to go up.  Los Angeles falls in the pink area for the reasons I explained in Data-Driven Climate Action (for Los Angeles).

Notice Fuel Cell Vehicles (FCVs) at the bottom?  Hydrogen fuel cells get a lot of hype, but don't save CO2 emissions and they run a huge rebound risk.

I've been accused of confirmation bias because I keep pointing to cars as the culprit for so many ills.  Look at the data.  The biggest bang for the buck is to reduce the distances that you travel, and then travel in the most environmentally-light way.  Walk, bike,  eBike, eScooter, transit, carpool, drive a fuel-efficient car (small and/or hybrid, or BEV.)

Our family made the calculation that, a BEV would be a fine SECOND car, but not our ONLY car.  We drive to SF visit family and have seen the waits to use the fast chargers on Interstate 5.  We also like to take family car trips to remote places with no BEV chargers.

I have seen the South Bay CCOG statistics of car ownership.  I've seen the Vehicle Miles Traveled (VMT) data for Los Angeles county.  In the relatively affluent South Bay, there is about one car per licensed driver.  We have 1 car for 3 drivers. We've essentially taken 2 cars off the road compared to our neighbors.

By having only one car, and making it a fuel-efficient hybrid, our entire family has had to learn how go about our daily routines without a car.  This leads to non-linear savings.  If you always have a car available to you, you use it.  If you can't count on having a car available, then you learn to make most of your trips without a car.

Learning to live "car-light" saves us money, reduces air & water pollution, mitigates climate change, reduces competition for parking spaces in our neighborhood and forces us to get more exercise.  Those are all very positive outcomes and does not require us to wait for a build-out of BEV charging infrastructure.

Ivanova et al strikes an optimistic note.  If you just do the top 10 changes, we make substantial global progress.

The top consumption options (by medians) include substantial changes in car travel (living car-free, shifting to electric vehicles and public transport), air travel reductions, use of renewable electricity and more sustainable heating (renewable-based heating and heat pump), refurbishment and renovation, a shift to a plant-based diet and improved cooking equipment. The top 10 consumption options together (accounting for the overlap of car travel alternatives) yield an average annual mitigation potential of 9.2 tCO2eq/cap. While crudely estimated, this indicates a substantial mitigation potential of already available low-carbon consumption options towards achieving the 1.5-2°C target.

Make the changes that you can, given the society that we live in. Then organize to create a society where more of us can make choices that are better for the planet. We collectively built the auto-centric landscape in the past 70 years. We can collectively rebuild it.