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.
Steam-Methane Reforming. Most hydrogen produced today in the United States is made via steam-methane reforming, a mature production process in which high-temperature steam (700Â°Câ1,000Â°C) is used to produce hydrogen from a methane source, such as natural gas.