Scientists explore new ways to remove atmospheric CO2

Decaying plants contribute to global warming by releasing carbon dioxide into the air. Now researchers are converting plant wastes into biochar, a charcoal-like substance that can be used as fertiliser to permanently lock the carbon underground.

These lettuce plots in Minnesota were amended with 20,000 pounds of macadamia-nutshell biochar per acre to evaluate the effect on crop yield, soil fertility and greenhouse gas production from the field. (Photo: Amanda Bidwell, USDA/Agricultural Research Service)

In his 12 February State of the Union address, President Obama singled out climate change as a top priority for his second administration.

"We can choose to believe that Superstorm Sandy, and the most severe drought in decades, and the worst wildfires some states have ever seen were all just a freak coincidence," he said. "Or we can choose to believe in the overwhelming judgment of science – and act before it's too late."

Four years ago, the president addressed rising global temperatures by pledging a 17 per cent cut in carbon dioxide (CO2) and other greenhouse gas emissions in the United States by 2020, and an 80 per cent cut by 2050. The administration has taken a number of steps to meet those goals, such as investing billions of dollars in wind, solar and other carbon-neutral energy technologies.

But reducing CO2 emissions may not be enough to curb global warming, according to Stanford scientists. The solution, they say, could also require developing carbon-negative technologies that remove large amounts of CO2 from the atmosphere. Their findings are summarized in a report by Stanford's Global Climate and Energy Project (GCEP).

"To achieve the targeted cuts, we would need a scenario where, by the middle of the century, the global economy is transitioning from net positive to net negative CO2 emissions," said report co-author Chris Field, a professor of biology and of environmental Earth system science at Stanford. "We need to start thinking about how to implement a negative-emissions energy strategy on a global scale."