Do First: The Carbon Cycle

After the organisms die, they sink to the seafloor. Over time, layers of shells and sediment are cemented together and turn to rock, storing the carbon in stone. Only 80 percent of carbon-containing rock is currently made this way.

Microbes in the digestive tract (or rumen of animals such as sheep, cattle, or buffalo) decompose and ferment food, producing methane (CH₄) as a by-product.

A process through which bacteria break down organic matter—such as animal manure, wastewater biosolids. The break down releases CO₂ as a gas.