Introducing a one-stop solution for integrating alternative fuels (specifically ammonia, methanol, and hydrogen) into existing marine or heavy-duty engines. Our innovative system integrates with current engines, demanding minimal structural changes. The modular design of the system incorporates fuel supply, combustion control and online monitoring. The design also ensures optimal combustion without any output degradation. Users can flexibly adjust the CO2 reduction range to meet regulatory standards, achieving up to 90% reduction with ammonia and a complete 100% with hydrogen. Remarkably, our solution is priced at merely 10%-20% of a conventional engine of similar capacity.