Adenosine triphosphate (ATP) is a complex organic chemical that is involved in energy transfer within cells.

Anaerobic digestion is a biochemical process that breaks down organic matter in the absence of oxygen, producing biogas and digestate.

Bacteria are single-celled microorganisms that have a wide range of shapes and sizes.

Biomass is a renewable source of energy derived from organic materials, such as plants, animal waste, and wood.

Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi in mycoremediation, and plants in phytoremediation), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluents etc.

The Wikipedia page for "Cell (biology)" provides an extensive overview of the fundamental unit of life - the cell.

Enzymes are macromolecular biological catalysts that accelerate chemical reactions.