Biochar is a special material produced from heating plant waste without much oxygen. It's strong and doesn't easily break down, so it's useful for trapping carbon. Researchers looked at how biochar is made, how long it sticks around in soil, and how plants and carbon in soil like it. They found that how biochar is made and how well it stays in soil affect how much carbon it can trap. They also studied how effective biochar is at storing carbon and if it makes financial sense. Their work outlined areas needing more study to make biochar more useful in China.