From January to March, Chang backpacked alone through rural Latin America. She climbed volcanic cliffs in Peru and scaled 1,200-foot canyons in Mexico. In Guatemala, she taught chemistry to middle schoolers and installed ventilated “eco-stoves,” which improve respiratory health over traditional open-fire cooking.

In the Peruvian Amazon, she joined Harvard Professor Joost Vlassak as a teaching assistant for his course on sustainability challenges. Together with Professor Carlos Rios from Peru’s University of Engineering and Technology, they took undergraduate students deep into the rainforest to talk to informal miners, who extract gold from the Amazon river’s basin toxic methods toxic to their soil and health, helping them to find safer methods.

“If we’re going to help invent solutions for folks in the developing world,” Chang said, “we have to understand a little bit about what life is like there and not just assume we know what the problems are.”

On mid-March, the COVID-19 pandemic forced Chang to cut her trip short, and she flew home to shelter in place.

Soon, whether in person or virtually, she will begin her Department of Energy ARPA-E Fellowship. There she will develop sustainable technologies for industries that collectively account for one-third of global energy use — concrete, steel, aluminum, pulp and paper, plastics and chemicals.

“For example,” Chang said, “if we could develop a technology eliminating the carbon footprint of steelmaking, we would save over 5 percent of global CO2 emissions. If steelmaking were a country, its emissions would rank fourth in the world, just below India and above Russia.

“In spite of my naive sustainability fanaticism as a kid,” Chang continued, “today I don’t proselytize or chastise or advocate for everyone with the privilege of a career choice to adopt sustainability as their pet cause. My vision for the world is one where we lower our carbon footprint not through ground-up, individual actions, but by creating systems that make sustainability automatic, so that people can go about their lives and do the jobs they are called to do — doctoring, lawyering, homemaking — without needing to add sustainability to their list of worries.”

Unlike Captain Planet, Chang no longer tries to save the world one small act at a time; instead, she’s helping to build a world that no longer needs saving.