Not sure I believe that. It takes less energy to keep a vehicle moving than it does to accelerate it. That’s not going to change whether it’s gas or electric.

Merry Christmas, it’s physics time. When a vehicle is in motion, the forces the motors must fight are governed by the following equations: F_total= F_drag + F_rolling= 0.5ρv²C_DA + Nμ_R , where:

• ρ = air density (kg/m^3)
• v = velocity (m/s)
• C_D = coefficient of drag, defined by the shape of the car.
• A = cross-sectional front-facing area of the car (m²)
• μ_R = rolling resistance coefficient, which is calculated separately and depends mostly on tire pressure and surface quality. It changes a tiny bit with speed. In the example below, it’s 0.011.
• N = Normal force, or weight of the car (N)

If we take F_total and multiply it by the speed of the vehicle, we find the energy wasted per second, or the power needed to maintain that speed. Filling in the blanks for a Tesla Model 3 (because it’s easy to find the numbers) at 120kph (and ideal circumstances!), we find that F_total = 347.4 N + 196.4 N, and so P_wasted = 18.13 kJ/s or 18.13 kW. For a battery with 74 kWh usable, this translates to 489.8 km. Inside EVs tested their Model 3 at 112.6 kph and got 498.9 km, so this seems about right.

Now let’s slow things down to 70 kph. F_total = 118.2 N + 196.4 N, and our range jumps to 846.7 km. That’s a lot, but hypermilers have gotten more in this particular vehicle. Now, I never said the 70kph example would have stops and starts, but since you brought them up, let’s see if we can recalculate with those in mind.

The energy needed to bring a vehicle up to 70 kph is the kinetic energy adjusted up for a motor’s electrical efficiency, E = (1/.96)(1/2)mv² = 358.4 kJ or 0.0996 kWh. The energy recuperated when using regen braking is the same, but adjusted down for the regen’s electrical efficiency, E = (0.7)(1/2)mv² = 240.8 kJ or 0.0669 kWh. So a single stop-start cycle uses a net 0.0327 kWh. I’ll add one such 10-second start-stop cycle every 2 minutes (just spitballing), and recalculate for drag at the new speeds. We end up with an estimate of 733 km. This matches EV-database’s city range estimates in mild weather.

Now, this may seem a bit startling, but the fact that EVs are more efficient in traffic than on the highway has been empirically measured. Personally, I can confirm that my range in my Clarity PHEV is about 50% longer at 45 mph than it is at 75 mph.

It mostly depends on speed. Need to go 500km at 70kph? Easy. Most EVs can do that. 500km at 120kph? Not so much. If you need the latter, I’d recommend looking at PHEVs.

(Temperature also plays a role, but it’s less significant than speed, especially with all the heat pumps these days.)

Tailpipe emissions? No. Round-trip emissions? Yes.

Biofuel sucks CO2 from the atmosphere while the plants or algae grow, then releases it again when the fuel is burned. It’s net-zero in the literal sense. They only have a GHG footprint if fossil fuels are used during the processing. In the US for example, during the processing of corn into ethanol, they burn natural gas for heat because it’s convenient and cheap. So the GHG footprint of American corn ethanol is approximately the same as gasoline.

Make no mistake, this is a publicity stunt and you shouldn’t expect Virgin Atlantic to follow through. But SAF is feasible.

Cost: Currently, according to Argus Media, SAF is around $6.69/gal compared to $2.85/gal for jet fuel. Jet fuel accounts for between 15% and 20% of airline operating costs per US BTS reports. So using SAF would increase operating costs by 22-35%. Given that airfare fluctuates around 20% depending on whether or not it’s a tuesday, that’s actually not bad at all. (Also, I think the airlines could fully absorb that price increase if it weren’t for the deadweight of shareholders, stock value manipulation, and executive bonuses.)

Scaling: Despite how hard America tries, there’s only so much used fry oil. Biofuel needs farmland, and there isn’t enough farmland to serve the automotive sector. Given typical yields, we would need about 373m acres of biofuel farmland, which is every last inch of unused farmable land the US has. But aviation is a different story. According to the EIA, the US uses 8.81 million barrels of gasoline a day, 2.98 mb/d of diesel, but only 1.5mb/d of jet fuel. That’s an order of magnitude less fuel, and an order of magnitude less farmland.

Sustainability: This one’s trickier. Biofuel doesn’t need to be produced using fossil fuels, but usually is. The US’s 893m acres of farmland produce only 10.6% of our GHG emissions. I think the biggest concerns would be increased water, pesticide, and herbicide usage. I am also not sure of the impacts on other nations with different geography or agricultural potential. I am not well-equipped to quantify those impacts.