One exception to note: If the food's sitting in an environment where the temperature is over 90Â°F, the USDA says the food should only be left out for one hour, so keep an eye on the clock if you're serving food on a hot day!
Estimated cost of hydrogen per kilogram in a variety of scenarios. With all of this in mind, here are the cost estimates per kilogram (which each include $1.25 for taxes): Hydrogen from natural gas (produced via steam reforming at fueling station). $4 â $5 per kilogram of hydrogen.
(Note that meant that in 2003, the two pounds of Hydrogen necessary to have the same amount of chemical energy (126,000 Btus) as one gallon of gasoline would have involved TWO K-size tanks and cost around $85!) In 2006, the price was still about the same for a K-tank of compressed Hydrogen.