What does anaerobic digestion of sewage sludge help produce?

Anaerobic digestion of sewage sludge is a biological process that breaks down organic matter in the absence of oxygen. During this process, microorganisms decompose the organic materials present in sewage sludge, which results in the production of biogas, primarily composed of methane and carbon dioxide. This biogas can be captured and used as a renewable energy source for heating, electricity generation, or as a vehicle fuel.

Additionally, anaerobic digestion reduces the mass of the sludge itself. This reduction is beneficial because it means there is less material to handle, transport, and dispose of, making the process more efficient and environmentally friendly. The decreased volume of sludge also lessens the impact on disposal sites and helps conserve resources.

The other choices do not accurately reflect the primary outcomes of anaerobic digestion. While clean water is a product of sewage treatment, it is not directly produced from the anaerobic digestion process alone. More sludge is not a desirable result; rather, the goal is to reduce its quantity. Lastly, heavy metals are often found in sewage sludge but are not produced through anaerobic digestion; in fact, the process can help stabilize certain pollutants rather than create new recyclable materials.