biochar
For my 5th design studio, my team designed a solar reactor from scrap materials as well as a cheap glass vacuum tube. This reactor was specifically designed for and along with students in Ghana. It reached temperatures of 700°F and we successfully used it to create a material known as "biochar." This is a sustainable, carbon-negative fertilizer made from coconut shells, a common waste product from the oil industry in Ghana. Heating the shells in a vacuum turns them to charcoal, instead of having to cut down trees and burn out the trunks like what is traditionally done.