Which of the following are biogas? Choose the correct answer from the options given below.

Marsh gas, swamp gas and compost gas are all names for biogas.

Statement 1, marsh gas, is methane-rich gas from decaying matter in marshes.

Statement 2, swamp gas, is the same biogas rising from swamp sediments.

Statement 4, compost gas, is biogas from decomposing compost.

Statement 3, producer gas, is made by gasifying coal or coke, and Statement 5, flue gas, is combustion exhaust, so neither is biogas.

Biogas is mainly methane with carbon dioxide, produced by anaerobic digestion.