From the rooftop of Klaus Lackner's seven-storey building on the Arizona State University campus, photovoltaic panels seem to glisten in every direction.
The school claims to have more solar capacity installed than any other university in America - part of a plan to offset the carbon emissions of this institution of more than 80,000 students.
But the odd little box Lackner has come to check might someday take things a big step further. If it works on a larger scale, what's in the box could make the university a negative emitter - more than offsetting the amount of carbon it releases into the air.
Lackner's box is part of a new wave of technology aimed at heading off climate change.