Does your local water treatment plant produce lime sludge as a byproduct of the water treatment process? How is this lime sludge disposed of? Rather than sending this sludge to a landfill, empower your learners to develop a process where farmers can pick up the lime sludge from the water treatment plant for free so it can be used to adjust the pH value of their soil. This project could offer significant savings for your city and local farmers, while turning waste into a product that can help grow new food. Sounds like an impactful project.