A 'Bionic Leaf' Could Help Feed The World

 

In the second half of the 20th century, the mass use of fertilizer was part of an agricultural boom called the "green revolution" that was largely credited with averting a global food crisis. Now, the challenge of feeding the world looms again as the population continues to balloon. To help spur the next agricultural revolution, researchers have invented a "bionic" leaf that uses bacteria, sunlight, water and air to make fertilizer in the very soil where crops are grown.

 

The team will present the work today at the 253rd National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features more than 14,000 presentations on a wide range of science topics.

 

"When you have a large centralized process and a massive infrastructure, you can easily make and deliver fertilizer," Daniel Nocera, Ph.D., says. "But if I said that now you've got to do it in a village in India onsite with dirty water -- forget it. Poorer countries in the emerging world don't always have the resources to do this. We should be thinking of a distributed system because that's where it's really needed."

 

The first "green revolution" in the 1960s saw the increased use of fertilizer on new varieties of rice and wheat, which helped double agricultural production. Although the transformation resulted in some serious environmental damage, it potentially saved millions of lives, particularly in Asia, according to the United Nations (U.N.) Food and Agriculture Organization. But the world's population continues to grow and is expected to swell by more than 2 billion people by 2050, with much of this growth occurring in some of the poorest countries, according to the U.N. Providing food for everyone will require a multi-pronged approach, but experts generally agree that one of the tactics will have to involve boosting crop yields to avoid clearing even more land for farming.

 

To contribute to the next green revolution, Nocera, who is at Harvard University, is building on the work he's most famous for -- the artificial leaf -- to make fertilizer. The artificial leaf is a device that, when exposed to sunlight, mimics a natural leaf by splitting water into hydrogen and oxygen. This led to the development of a bionic leaf that pairs the water-splitting catalyst with the bacteria Ralstonia eutropha, which consumes hydrogen and takes carbon dioxide out of the air to make liquid fuel. Last June, Nocera's team reported switching the device's nickel-molybdenum-zinc catalyst, which was poisonous to the microbes, with a bacteria-friendly alloy of cobalt and phosphorus. The new system provided biomass and liquid fuel yields that greatly exceeded that from natural photosynthesis.