Almost all chemical energy is dissipated as heat in combustion.
They may seem to have the same final result because of the same overall chemical formula, but they actually have major differences. When talking about burning, you might imagine a blazing forest, the flame rages to dye dark sky a fiery scarlet. In burning wood or gasoline, carbon and hydrogen are stripped directly from the organic material and combined with oxygen to form water and carbon dioxide. Because the potential energy changes dramatically in a very short time, a bright light is emitted and the temperature is blazing. Most of the energy is dissipated as heat and allows the surrounding molecules to gain enough kinetic energy to overcome activation energy. Light energy accounts for only a small portion. The entire process occurs outside the cell and is generally not accessible to water. Thus, at the end of combustion, all energy is released into surrounding space rather than stored in organic matters.
Although oxygen is required for combustion of wood, natural gas and fuels in everyday life, it does not mean that oxygen is necessary. Combustion is essentially a redox reaction where one substance loses electrons and another gains them; the potential energy lost by electrons is converted into light and heat. In some cases, oxygen is replaced by other highly electronegative substances to exhibit the same phenomenon. For example, when hydrogen is ignited in chlorine gas, it emits a pale white glow and a great deal of heat. The product is corrosive and acidic hydrogen chloride (HCl). Here chlorine is oxidant in this process. Magnesium burns in carbon dioxide to produce magnesium oxide (MgO) and carbon (C). Although carbon dioxide is usually considered a gas that inhibits combustion, it contains elemental oxygen that participates in the magnesium combustion as an oxidant.
Aerobic respiration releases energy slowly
Aerobic respiration is the main way that most life on Earth obtains energy. It is a slow controlled biochemical reaction that occurs in living cells. Enzymes lower the activation energy of each step to make respiration easier. Oxygen does not contact with organic matter directly. It only accepts electrons and protons at the end of electron transport chain to form water. The entire process is immersed in an aqueous environment and is broken down into many steps. Before entering the electron transport chain, almost all energy of glucose is distributed in 10 NADH, 2 FADH₂ and 4 ATP (10x220+150x2+36x4=2644 KJ/mol, standard Gibbs free energy of glucose is 2867 KJ/mol). We roughly estimate the average energy released through a respiratory chain complex: 220÷3≈70,150÷3=50. The energy they release is 1-2 times as much as ATP hydrolysis, which is tolerable to organisms. This is a gentle biochemical process without visible light. 40% chemical energy of organic matter is temporarily stored in ATP that is used in almost all life activities. 60% energy becomes heat energy to just offset the heat dissipated from surface.