For generations, synthetic fertilizer has fed billions, but the nitrogen it leaves behind in waterways has become a slow-moving crisis with no easy remedy — until now. Chemists at the University of Michigan, studying how living plants naturally bind and process nitrates, have engineered an iron catalyst that mimics that biological wisdom, converting stubborn nitrate pollution into nitric oxide or ammonia using nothing more than heat or light. The work, published in Nature Chemistry, does not yet clean a single river, but it establishes that the transformation is chemically possible — and in sc