What's the difference between just WOOD and COAL?

Question

Why is that burning coal can release more energy that just burning mere dry wood?

is it because hydrocarbons are formed only after exposure to heat, pressure and bacterial activities for millions of years?

What's the difference in the chemical composition of wood and coal?

Thanks!

Answer 1

All I can say, is that a kilogram of coal will produce more heat energy, then a kilogram of wood, it is just a physical fact. Wood does not contain as much chemical energy as coal.

Wood is composed mostly of cellulose fibers, and resinous "lignin", with small amounts of silica and calcium phosphate (ash). Cellulose is made up of very long chains of glucose sugars (C6H12O6)

Coal is mostly "amorphous carbon" with fractions of various large, hydrocarbon solids, known as "bitumen", or "coal tar", and, again, small to moderate amounts of ash.

Wood burns in two steps; first, the heat from nearby flames causes "pyrolysis", converting the wood into charcoal, and producing flammable hydrocarbon gases. It is the burning of the gaseous byproducts of pyrolysis, which gives the bright, visible flame of a wood fire (and produces enough heat to keep the pyrolysis going.) Secondly, the charcoal itself begins to burn, as glowing embers, producing only a faint, reddish blue flame.

The process of pyrolysis tends to consume much of the heat produced by combustion, further reducing the net amount of chemical energy released by burning wood.

Answer 2

Have you ever seen or held a lump of coal? Coal is essentially the carbon remainder of wood from millions upon millions of years ago. It is denser than wood, and the reaction does not involve the oxidation of the hydrogen in wood to water, which is less efficient per gram of oxygen in generating heat.

Answer 3

wood contains cellulose, lignin and a host of other complicated biopolymers whereas coal is composed mainly of carbon along with other elements such as sulfur.