That depends on what is being decomposed.
Water and carbon dioxide are given off.
Carbon dioxide
Carbon dioxide
Energy is released during a decomposition reaction.
Methane gas is released, as well as carbon dioxide, during decomposition.
A substance breaks down into two or more simpler substances during a decomposition reaction.
Carbon Dioxide
hydrolysis
a compound partitions into its components
ethylene
Organic matter is converted into animal and microbial tissue during decomposition. This matter can be then used to fertilize the soil.
Oxygen will be given off