Currently, solar energy provides less than 1 percent of the world's total energy, but it has the potential to provide much, much more.
Engineers are working on ways to capture and store excess carbon dioxide to prevent global warming.
Human-engineered fusion has been demonstrated on a small scale. The challenge is to scale up the process to commercial proportions, in an efficient, economical, and environmentally benign way.
Engineers can help restore balance to the nitrogen cycle with better fertilization technologies and by capturing and recycling waste.