Fertilizer is essential for modern agriculture, helping crops grow by providing nutrients like nitrogen. However, producing synthetic fertilizers is energy-intensive and contributes to global greenhouse gas emissions—around 2% of the total. As a result, scientists and companies are exploring alternatives, such as using microbes to supply plants with nitrogen naturally. This could reduce the need for chemical fertilizers, which are made through a process called the Haber-Bosch method, where natural gas is used to convert nitrogen from the air into usable compounds like ammonia. One company exploring this approach is Switch Bioworks, which is developing microbes that can fix nitrogen for plants in a more efficient way. The company is currently testing its product in six U.S. states, aiming to bring it to market in two to three years. Initially, it’s targeting corn, the most widely planted crop in the U.S., which covers over 90 million acres in 2026. According to the company’s models, its microbes could eventually replace up to 50% of synthetic fertilizer, but the first version of the product is expected to replace about 25% of what farmers currently use. Plants need nitrogen to grow, but they can’t use the nitrogen in the air directly. Instead, they rely on "fixed" nitrogen—compounds like ammonia that are more reactive and usable. In nature, certain microbes can fix nitrogen, and some plants, like legumes, have symbiotic relationships with these microbes, housing them in root nodules. Synthetic fertilizers mimic this process, but they require significant energy and resources to produce. Microbial fertilizers aim to replace some of this synthetic nitrogen with microbes that can fix nitrogen naturally, but one challenge is that microbes use a lot of energy to produce ammonia, which can slow their growth. Another company in this space is Pivot Bio, which has been using microbial fertilizers on millions of acres of crops since 2011. It offers various products, some of which are applied when seeds are planted, while others are used before the seeds even reach the farm. The company has expanded its offerings to include fertilizers for crops like cotton, wheat, and small grains such as sorghum and barley. Despite these advances, experts say that microbes are unlikely to fully replace synthetic fertilizers anytime soon. Experts like Dan Blaustein-Rejto of the Breakthrough Institute note that while microbial fertilizers can help reduce emissions and nitrogen pollution from farms, they are not a complete replacement for synthetic fertilizers. “There is no clear and plausible vision for replacing it entirely in the foreseeable future,” he says. As a result, other strategies to reduce emissions and pollution from agriculture will remain essential in the coming years.