Composting is a well-known method for waste management, but it causes greenhouse gas emissions. Various techniques have been used to reduce emissions and improve the quality of compost, but they resulted in an increased composting time. Keeping in view the above points, the current study aimed to reduce the composting time and gas emissions along with improving the nutritional value of compost using FeSO₄ as an additive to cattle manure and corn straw composting. Seven treatments were established, including control (CK) without FeSO₄ and six levels of FeSO₄ (0.25%, 0.50%, 1%, 2%, 4%, 8%). The results revealed that FeSO₄ reduced the CH₄ (36.1–36.7%), H₂S (10.7–34.5%), N₂O (17.2–48.5%), and NH₃ (18.3–69.0%) emissions compared to CK. In addition, the total N (8.4–40.0%) content in compost products was also improved. The study showed that a higher dose of applied FeSO₄ can significantly reduce emissions, but it reduces the temperature at the start of composting resulting in an increase in the composting time, while the lower dose (0.5–1%) also has the capability to reduce the emissions compared with the control without negatively affecting the temperature rise. The study concludes that using 0.5–1% of FeSO₄ can effectively utilize its inhibitory action of decomposition that mitigates gas emissions and prepares an N-enriched compost.