Bio gas consists of

Biogas is produced by the anaerobic decomposition of organic materials. Its primary component is methane (${\text{CH}}_4$, about $50\text{–}75\%$), followed by carbon dioxide (${\text{CO}}_2$, about $25\text{–}50\%$), and small quantities of hydrogen gas (${\text{H}}_2$), nitrogen, and trace impurities.