Hydrogen has Very Low Energy Density; But H2 Still has Value

It is clear from the table of energy densities below, that the energy from a nuclear reaction such as fission far outstrips energy from chemical reactions such as combustion. But since it is neither practical nor safe to place a fission reactor in every household, every town, or every motor vehicle, there will always be a place for combustion reaction energy.

What fuels of combustion are most practicable, according to their energy density? The table gives us a few ideas. We will tend to avoid hydrogen gas for motor vehicles which require any significant range of travel, for example. For stationary applications -- such as fuel cell CHP generators and backup -- H2 can be valuable.

But an even greater value for H2 is for use in industrial processes, such as in turning low value bio-molecules into high value hydrocarbons [eg Neste], and in the refining of sour crude oil, among many other high-value processes. In other words, H2 production for the chemicals and fuel refining industries could become a lucrative enterprise.

Another common gas likely to grow in demand in the microbial fuels industry is CO2. Not dilute CO2 as in the measly 0.04% CO2 in the atmosphere. No. Clean, concentrated CO2 reagent grade, suitable to be fed to microbes and biomass crops (such as seaweed and giant king grass farms). Imagine getting rich from supplying H2 and CO2 to synth-fuels industries!
Source for the table of energy densities below

Material	Volumetric	Gravimetric
Fission of U-235	4.7x1012 Wh/l	2.5x1010 Wh/kg
Boron	38,278 Wh/l	16361 Wh/kg
JP10 (dicyclopentadiene)	10,975 Wh/l	11,694
Diesel	10,942 Wh/l	13,762 Wh/kg
Gasoline	9,700 Wh/l	12,200 Wh/kg			$0.0814/kwh 11-2007
Black Coal solid =>CO2	9444 Wh/l	6667 Wh/kg
LNG	7,216 Wh/l	12,100 Wh/kg
Propane (liquid)	7,050 +/-450 Wh/l	13,900 Wh/kg
Black Coal Bulk =>CO2	6278 Wh/l	6667 Wh/kg
Ethanol	6,100 Wh/l	7,850 Wh/kg
hydrazine (Mono-propellant)	5,426 Wh/l	5,373 Wh/kg
Thermite Fe2O3(s) + 2Al(s) -> Al2O3(s) + 2Fe(s) (mono fuel)	5,114 Wh/l	1,111 Wh/kg
Methanol	4,600 Wh/l	6,400 Wh/kg
Ammonia	4,325 Wh/l	4,318 Wh/kg
Sodium Borohydride Theoretical Hydrogen battery real is about 40% efficient	7,314 Wh/l theoretical 2,925 Wh/l real	7,100 Wh/kg theoretical 2,840 Wh/kg real
Liquid H2	2,600 Wh/l	39,000† Wh/kg
Hydrogen Peroxide 100% (mono-propellant rocket fuel) Often used at 30% or 90% and correspondingly less dense. when used, not all decomposes consider this a maximum	1,187 Wh/l	813 Wh/kg
LiFePO4	970 Wh/l	439 Wh/kg	1000 ? method not specified..
Wood Varies with type of wood and moisture content	700 +/-200 Wh/l	3154 +/-1554 Wh/kg
150 Bar H2	405 Wh/l	39,000 † Wh/kg
Secondary Lithium - ion Polymer	300 Wh/l ??	130 - 1200 Wh/kg
Secondary Lithium-Ion	300 Wh/l	110 Wh/kg
Primary Zinc-Air	240 Wh/l 1000Wh/l ??Best?	300 Wh/kg 440Wh/kg>
Dry ice sublimation	248 Wh/l	159 Wh/kg
Primary Lithium Sulfur Dioxide	190 Wh/l	170 Wh/kg
Nickel Metal Hydride (not discounted for high discharge rates)	100 Wh/l	60 Wh/kg
Wood pellets (pelletizing energy subtracted?)	100 †† Wh/l	4,700 Wh/kg
Flywheel	210 Wh/l	120 Wh/kg
Ice to water	92.6 Wh/l	92.6 Wh/kg
Liquid N2	68 Wh/l	55 Wh/kg
Lead Acid Battery	40 Wh/l	25 Wh/kg	300		$1.58/kWh
Propane (Gas - 1 bar)	28.1 Wh/l	13,900 Wh/kg
Compressed Air	17 Wh/l	34 Wh/kg
STP H2	2.7 Wh/l	39,000 † Wh/kg
Boost cap	1.72 Wh/l	2.98 Wh/kg

Table Source

University of Washington scientists are devising ways to rev up H2 production using photosynthetic microbes.

As discussed previously, artificial photosynthesis methods (artificial leaves) also split water to produce H2 (and O2).

University of Minnesota researchers are using microbes to produce fuels with sunlight and CO2. In this case the microbes are splitting water to produce hydrogen, and fixing carbon from CO2 to build biomass and specific product. But the pathetically small amount of CO2 in the atmosphere will simply not do. They will need to buy lots and lots of pure CO2 -- perhaps from you?

BARD of Morrisville, PA, intends to hit the algal fuels market in a big and fast way! Assuming BARD spokespersons are honest in their claims, they will need a HUGE amount of CO2 to produce their algal fuels. Where will they get it? How much are they willing to pay?

Innovative Energy Inc. from the St. Louis, MO, neighborhood, manufactures gasifiers capable of taking any carbonaceous material and turning it into syngas -- to generate power and process heat. Of course, one of the components of syngas is H2. Tweaking the gasifier and feedstock can alter the composition of your syngas according to desired product -- for immediate combustion or for later use in catalytic synthesis of fuels and chemicals.

University of Connecticut researchers have developed continuous process reactors to quickly and efficiently separate glycerine from biodiesel in biodiesel processing plants. But of course a better way of making biodiesel (besides esterification) is via the use of hydrotreating with H2 -- if you have the H2!

Highmark Renewables Research of Canada is developing an anaerobic digester to be used in conjunction with multiple other bio-reactors for producing multiple bio-fuels. Of course, this is the way of the future in biofuels and bioreactor companies -- combine and conquer.

While you may not see the same company owning the full cluster of diverse and complementary bioreactors, you will begin to see more co-location of various types of bioreactors and feedstock pre-processing, processing, refining, and more sophisticated catalytic synthesis.

And always, you will find H2 and CO2 to be in high demand. Remember in the California gold rush, when the people who made the most money were those who provided the miners with both the dry goods and the wet goods which the miners needed and craved? Most of the miners themselves went bankrupt.

Let that be a lesson to you. ;-)