One of the most important chemical reactions is combustion. It requires three things - a fuel, an oxidant, and a source of ignition.
For a campfire, the fuel is the wood that you are using, the oxidant is the oxygen in the air around us, and the source of ignition is usually a match or lighter.
In the case of an automobile engine, the fuel is now gasoline or some equivalent material, the air provides oxygen, and the source of ignition is a spark plug.
The combustion of every hydrocarbon compound uses oxygen to produce carbon dioxide and water if everything is in perfect balance. If the balance is out a little bit, then the reaction might have too little oxygen and soot is generated directly. Or the reaction might be tweaked to get hydrogen instead of water. But the reaction is pretty much the same.
So what is meant by the term "clean fuels"? Any combustion reaction involving carbon-based compounds result in pretty much the same end product - carbon dioxide.
And by now, there are very few people that don't understand that increasing the carbon dioxide level in our atmosphere is having detrimental effects on the Earth's climate.
Shouldn't a "clean fuel" mean that it produces no carbon dioxide?
One would think that was the definition. Certainly there are fuels that appear to be clean such as hydrogen which when it is combined with oxygen and ignited generates nothing but water as a product. In this case, with no carbon in the fuel, there is no carbon in the products.
However, while hydrogen sounds like the perfect fuel to drive our economy, it has some major drawbacks. It doesn't exist in its gaseous form in our atmosphere. Indeed, very little gaseous hydrogen can be found on the planet at all.
In order to use hydrogen as a fuel, we need to make it from something else. Presently, the largest supplier of hydrogen is the petroleum industry which generates the gas by stripping hydrogen atoms off of hydrocarbons.
Of course, stripping the "hydro" from "hydrocarbons" leaves nothing but the "carbons" and they get burnt with oxygen to provide the energy to drive the process generating carbon dioxide. Our major source of hydrogen yields more carbon dioxide than just burning the hydrocarbon in the first place because of all of the processing that needs to take place.
In order for hydrogen to be a perfectly "clean fuel", the hydrogen needs to be generated electrolytically by breaking down water molecules. This can be done with solar cells or directly by using specific photolytic chemical reactions but the efficiency of these processes is not particularly high.
Further, solar cells are not carbon neutral as they require an awful lot of energy to make and create an awful lot of waste in the process.
Does this all mean that "clean fuel" is an oxymoron? Perhaps. For example, claims that natural gas is a clean fuel are absurd. A kilogram of natural gas produces 2.45 kilograms of carbon dioxide during combustion while generating 10.8 kWh of electricity.
A kilogram of coal, on the other hand, generates 2.93 kilograms of carbon dioxide but only 2.8 kWh of electricity. On a carbon-dioxide-emission basis, natural gas is over 4.5 times as efficient. No question that natural gas is cleaner than coal.
Indeed, it is more efficient and thus cleaner than any other carbon based fuel.
But that doesn't mean that it is a clean fuel. Already policy analysts are pointing out that natural gas is, at best, a stop gap measure in our search for a clean fuel.
The switch that is occurring in the power generation industry from coal to natural gas has lowered our present output of carbon dioxide from electrical generation. As more power plants are converted and more countries employ natural gas, carbon dioxide emissions will decline.
However, other sources of carbon dioxide will make up the slack and the constantly increasing demand for electricity will mean that carbon dioxide levels from electrical generation even with natural gas will soon be on the rise. If the Center for American Progress is to be believed, we only have until 2030 to figure things out if we want a stable climate.
The answer is to find alternative methods for power generation that are not as carbon expensive. B.C.'s hydro-electrical power generation is one example. It generates over 41.6 kWh of electricity per kilogram of carbon dioxide emitted during the lifetime of the dams and reservoirs. Unfortunately, there is a limited capacity for hydro-electric power.
We should be investing in research to find alternative means of running our economy. Devices that use less power and cars that run on alternative fuels would be a good start.
Of course, it takes a lot of political will and foresight to realize that we have backed the wrong horse and need to find another, better one.
