Until the last few years, almost all of my writings were business or technical in nature. With this essay, it seems I have reverted back to my original form. I apologize for that, but like the old story about the scorpion and the turtle crossing the river, I couldn’t help myself; it is just in my nature.
There have been myriads of papers published extolling the ecological benefits of switching to electric vehicles to reduce our dependence on fossil fuels and reduce CO2 (Carbon Dioxide) emissions. And, if the electricity needed is produced by non-polluting sources, those claims are valid.
But what about cars running on hydrogen? You occasionally hear or read about automobiles from Honda, Toyota, and Hyundai that utilize fuel cells and run on hydrogen gas, which seems to be gaining popularity in California. Also, if you follow the financial market, there were recently boom and bust stories about a company named Nikola. This upstart company raised billions of dollars with its plans to build hydrogen-fueled semi-trailer trucks.
So, that got me pondering which technology was greener, electricity or hydrogen gas?
The husband of my wife’s friend is a Dutch chemical engineer. During dinner at my house, Frits, the husband, told me about a recently involved study he did as a consultant. The study entailed producing hydrogen for use by cars and trucks using renewable energy sources to separate hydrogen from water using a simple electrolysis technique.
From what I can remember, Frits’s conclusions only had to do with reducing CO2 and saving or eliminating the use of fossil fuels, the same as always had been done previously when justifying electric vehicles.
But that got me thinking, were there any additional savings? What about saving oxygen? We keep hearing or reading about the depleting of trees in the Brazilian rain forest. Since trees are a significant oxygen source, I wondered how many trees it takes to produce the oxygen an automobile needed to run?
I was going to ask Frits to figure it out for me, but since I have a strong engineering and physics background, I decided I could do that myself, which I did.
Doing the analysis entailed a little mathematics and making assumptions about the average car’s displacement and its average engine speed when running, which I assumed was 2 liters and 2000 RPM. I also had to do a bit of research on the Internet, and I learned an average tree produces 260 pounds of oxygen each year.
Using those numbers, I was shocked to learn my average car consumed the amount of oxygen it took 1339 trees to produce when running. Think about it, each car requires 1339 trees when running! Of course, you don’t drive your vehicle 24 hours a day, so, fortunately, on average, it isn’t nearly that bad.
According to AAA, the average car is only driven 293 hours each year, which means in one year, which has 8760 hours, the vehicle is only driven 3.3 percent of the time. So, if you are the average driver, you only need 44 trees to sustain your car.
If you buy an electric vehicle, and — the big one. If the electricity is entirely produced by renewable sources, it could be the same as planting about 44 trees. However, if you plug into the grid, as most of you would do, that amount will not entirely happen in the near future.
I then wanted to know how many trees would be saved by using hydrogen fuel cell cars. To figure that one out, I used the Honda Clarity as my example, which is now in its third iteration. According to its advertisements, it consumes 5.46 kilograms of hydrogen to go 360 miles.
Since hydrogen fuel cells produce water as a by-product, the reaction implies that for every two molecules of hydrogen needed, one molecule of oxygen was required in the process. Working those calculations at an average speed of 30 miles/hour, I determined that a hydrogen fuel cell vehicle consumed the amount of oxygen it took 271 trees to produce when running or, on a yearly average as above, 9 trees. That still would be a net annual savings of 35 trees over my typical fossil fuel burning vehicle.
Going back to Frits’s project, producing hydrogen by electrolysis using renewable energy, there are more savings. The electrolysis process releases enough surplus oxygen back into the air to offset the 271 trees needed to run a hydrogen fuel cell car. So, again eventually, the end result would be a maximum total savings of 1339 trees when the vehicle is running or an average annual savings of 44 trees.
So, which one is better? If your incentive is to go green, you can save about 35 trees by going with a hydrogen car, even without renewable energy.
Also, although there are few hydrogen filling stations, it is much faster to refuel your vehicle with hydrogen than recharging a battery. However, for me personally, nothing beats the convenience of refueling my car at home, so I plan to buy an electric car and put a charger in my garage. I also might install solar panels to charge it and save even more trees?
As a footnote, Frits reviewed my calculation for accuracy and has informed me that according to the EPA, a typical USA car emits 4600 kg of CO2 per year, and about 54 trees would be required to absorb the CO2.
I’m not a biologist, but I suspect, based on the similarity of the two numbers (44 vs. 54), that the amount of CO2 a tree absorbs is basically the same as the amount of oxygen it emits.
