Can Stored Carbon Escape Over Time?

Written By Teacher: Elizabeth Ward

My name is Elizabeth Ward. I am a former Early Childhood, Elementary, and English as a Foreign Language educator. I have taught third grade Science and Social Studies as well as Kindergarten in both urban and rural Oklahoma public schools. I taught online EFL to students of all ages in China for four years. I also have experience in curriculum development and content design for teachers in the physical and digital classroom. As a former teacher I have a passion for supporting teachers and making their jobs easier. I currently live in the greater Houston area with my husband and four dogs. 

Storing carbon dioxide underground after capture is a promising climate solution, but questions remain about the risk of leakage over time. The effectiveness of storage depends on geological conditions, monitoring technologies, and proper site management. Exploring this topic allows students to consider both the potential and limitations of carbon capture as a long-term strategy for reducing emissions. Explore the concept of carbon capture with your students using this video or this lesson plan.

Written By: MIT Environmental Solutions Initiative

The MIT Climate Change Engagement Program, a part of MIT Climate HQ, provides the public with nonpartisan, easy-to-understand, and scientifically-grounded information on climate change and its solutions.

Setting up a large-scale “carbon capture and storage” system to stow our planet-warming carbon dioxide (CO2) emissions safely underground is a major challenge of engineering, policy and economics. But keeping the CO2 underground once it’s injected is relatively simple—you just need to inject it carefully and put it in the right place, says Bradford Hager, Associate Director at MIT’s Earth Resources Laboratory. Storing carbon will require detailed geologic tests before sites can get up and running, and careful monitoring once it’s stored, but scientists can borrow “fairly standard techniques” to conduct those tests, Hager says.

CO2 can be injected into a few different types of underground formations, including saline aquifers, which are deposits of briny water, or past oil and gas formations. Geologists look for a particular sequence of different rock types to hold CO2 in place. The lower rock layer needs to be porous, like sandstone or limestone, allowing injection and capture of CO2 in the rock’s “pore spaces.” Above, there must be a non-porous “cap rock” that will seal in the carbon dioxide and keep it from escaping. CO2 also needs to be injected more than 3,000 feet below the surface. This ensures the CO2 will stay at the high temperatures and pressures needed to keep it in a fluid form, which makes it very dense and causes it to take up less space underground. It also places it deeper than deposits of groundwater used for drinking.