They feature a selective catalytic reduction system that reduces the level of nitrogen oxide (one of the most threatening air pollutants) in the exhaust gas from the engine by up to 97 percent.
Moreover, the ballast water taken on board is treated with ultraviolet light in order to sanitize it. This will prevent the ships from carrying invasive species around the world in their tanks. Also, the wastewater or the "black" water from the vessel comes into contact with bacteria that turns it into clean water. Thus, the water resulting can then be safely discharged into the ocean.
But the HMS Tamar and Spey are not the only ones that embraced the green. The HMS Glasgow, the first City-class Type 26 frigate, also went green. It not only shares the latest tech with the "dazzling" duo, but it also has its hull wrapped in anti-fouling. This means that no chemicals are used to keep vegetation from growing onto the vessel.
Inside, Glasgow is illuminated by LEDs. That helps with energy consumption. They also last longer when compared to fluorescent lights. The refrigerators used for keeping the product fresh are cooled with gases that are less likely to contribute to global warming.
Finally, Glasgow features a Sonar 2117 system that identifies the risk caused by the vessel's operation to marine life.