The claim that the hydrogen from one cow’s poop will power a car for one year is pure Bull Shiite. 40 years ago I researched the possibility to generate power from methane from cow poop. I ran the numbers and concluded it was not economically feasible, not by a long shot.
Saw your post wanted to run the math... Here is the math.
“Manure - A cow produces 65 lbs. (29.5 kg) of feces or manure daily - that’s 12 tons (10767 kg) a year. A cow can poop up to 15 times a day.”
“In August 2021, the second-generation Mirai set a world record of traveling 1,360 km (845 mi) with a full tank of 5.65 kg hydrogen. “
Average driving distance annually is 13500 miles verified by data collected from state registration data from the NHTSA
(5.65/845)*13500= 93.06 kg of H2 per year to cover the average distance with the super efficient fuel cell power train.
So the question is how much methane does 10000+ kg of manure ferment too then since methane is CH4 one molecule of methane is two molecules of H2 gas plus a single solid carbon atom.
Penn State has the numbers for methane production in a digester.
“In Pennsylvania, dairy cows produce an estimated 5.5 million tons of reclaimable manure each year. Given the gas production rate of the Penn State digester, a net daily biogas output of 40 cubic feet (1.2 m3) per cow,”
Since we know a cow on avg makes 65lbs of manure per day and now know that turns into 40 cubic feet per day. Going to a whole year would be
14,600 CF with methane at 1010 btu per cubic foot that’s 14,746,000 btu per year. H2 is 113,839.74 btu per KG so just on a BTU basis 129.5 kg worth of energy in that methane. So the Toyota scientists were right since they are the world’s leader in hydrogen vehicles one would expect them to be right.
Turning methane into pure H2 can be done a few ways the cheapest is SMR
Steam-methane reforming reaction
CH4 + H2O (+ heat) → CO + 3H2
Water-gas shift reaction
CO + H2O → CO2 + H2 (+ small amount of heat)
Driven by these reactions:
Partial oxidation of methane reaction
CH4 + ½O2 → CO + 2H2 (+ heat)
CO + ½O2 → CO2 (+ heat)
The net result is CO2 + H2 with a over all net exothermic reaction with high temperature steam the reaction can be driven endothermicly with the SMR and water water gas shift turning more H20 into CO2 + H2 doubling the yield of H2 per cubic foot of methane as each carbon molecule takes two O molecules yielding two H2 from each two H2O consumed in the water gas shift reaction. The 700 degree steam can be sourced from solar thermal, resistance heaters powered by wind or solar or a gas cooled nuke to make zero carbon steam. Either way the fuel cell is so efficient yes a single cows waste has more than enough hydrogen in it’s produced methane to drive that car much farther than the average American drives. Cheers curiosity satisfied.