The researchers at Virginia Tech work in environmental science. Many of them also live in central Appalachia. Central Appalachia is mining country. For generations, the area has been mined for coal. More recently, mining companies have been using a technique called mountaintop removal. This means they take layers of rock and mineral off the top of the mountain in order to get access to the coal seams inside. The removed mountaintop, called overburden, is replaced on the ridge and compacted to replicate the original mountain shape. Energy and environmental industry officials call these areas post-mined land Post-mining sites are difficult to reclaim. The resulting soil is highly acidic and infertile The post-mined compacted soil proves more difficult to seed. The soil needs to be loose and open in order for seed to get into the soil. In post-mined land, the ground is too compact. Post-mining sites, therefore, typically look very different from the surrounding area. These sites are more likely to be home to invasive botanical species. Residents and environmental activists complain the landscape is ruined, that the mountain terrain is scarred Even if no new permits for mountaintop removal mines are issued, the problem of how to reclaim the post-mined sites remains. Researchers at Virginia Tech decided to try using biochar to help reforest the post-mining site soil. They got permission to apply a layer of biochar to a post-mining site before it was reseeded and replanted. What the team found was that the biochar worked, but not as well as they had hoped. Soil samples showed the biochar had improved the chemistry of the soil. But not enough biochar had been added to make a serious difference. Researchers learned they would have to seriously up the amount of biochar they applied to the site. The kind of biochar the team used, however, was expensive. It cost about $1,000 a ton. Ten tons per acre, the amount the researchers applied, wasn't enough biochar to make a significant improvement to the soil conditions across the site The research project had a practical constraint. The team was looking for a solution to the problem of post-mining land. If the biochar was going to cost a small fortune, it would not be feasible for local government or nonprofit groups to use in such large amounts