Final answer:
A process that treats solids and produces methane gas is known as anaerobic digestion. This biological procedure occurs in an oxygen-free environment, turning organic waste into renewable energy.
Step-by-step explanation:
A solids treatment process that produces methane gas is called anaerobic digestion. This biological process occurs in a sealed, oxygen-free tank known as an anaerobic digester. Organic matter, such as sewage sludge, animal manure, or food waste, is broken down by microorganisms, and as a result, methane is produced. Methane, a potent greenhouse gas, can be harnessed as a renewable energy source to generate electricity or as fuel for heating. Thus, anaerobic digestion not only helps manage waste but also contributes to the production of clean energy. For instance, landfill gas (biogas), produced primarily from the decomposition of organic waste in landfills, is captured and can be used similarly. Additionally, the treatment of solids in sewage can produce methane through the digestion of sludge, adding to the potential sources of this valuable gas.