Synthetic nitrogen fertilizer is key to increasing yields in some regions, but its overuse is a major source of emissions and environmental degradation. Fertilizer use varies significantly across regions: application rates in Africa are approximately one seventh of those in South Asia and one tenth of the rate in East Asia (FAO, 2020). Fertilizer underuse in Africa limits productivity, while heavy use of synthetic fertilizers in Asia leads to adverse environmental effects and high fiscal costs from subsidies (Holden, 2019; Garg and Saxena, 2023). Globally, the production and use of synthetic fertilizer generate between 2 and 5 percent of global carbon dioxide emissions (Gao and Serrenho, 2023).

Microbial fertilizers use bacteria to facilitate the absorption and availability of nutrients necessary for plant and soil health, primarily through biological nitrogen fixation. These fertilizers do not replace synthetic options but can lower the amount required for optimal plant and soil health. There have been previous successes in their development and use, such as Rhizobium inoculants for soybean production in Brazil. Developed by the Brazilian Agricultural Research Corporation (Embrapa) in the 1990s, Rhizobium inoculants are now used on around 100 million acres of soybeans and can increase yields in several leguminous crops while promoting soil nutrient cycling (Schütz et al., 2018; Adediran et al., 2018; Adjei-Nsiah, 2018; Belete et al., 2019; Ronner et al., 2016; van Heerwaarden et al., 2018; Wolde-meskel et al., 2018).

New technologies aim to reduce the need for synthetic fertilizer in other crops. For example, Pivot Bio’s ProveN40 enhances biological nitrogen fixation in maize and is used on about 10 million acres of corn in the United States. However, results from field trials have been mixed, and independent studies frequently report limited or variable yield benefits (Franzen et al., 2023; Beck’s Hybrids, 2023; Giller et al., 2024).

Using microbial fertilizers instead of synthetic fertilizers could reduce emissions from fertilizer production by up to 98 percent relative to synthetic fertilizer (Havens, 2022). Each ton of synthetic fertilizer replaced by microbial nitrogen fixation would be worth between USD 1,820 and USD 2,530 using USD 190 as the social cost of carbon (U.S. EPA, 2022), generating billions in potential social benefits (Bomfim et al., 2021). More research is needed to understand the most appropriate crops, soils, and agroecological contexts for microbial fertilizers (Chekanai et al., 2018). Because these fertilizers rely on live microorganisms, appropriate storage, transport, and environmental conditions during application are important to preserve their effectiveness (Berninger et al., 2018; Pirttilä et al., 2021; Fadiji et al., 2024). Greater funding could support testing and adaptation across different countries and crop varieties and help transition the technology to scale.