Regeneration is the process of oxidizing the accumulated soot from a filter. To comply with environmental regulations, your John Deere tractor may come with an after-treatment device, which includes a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF). After at least 3,000 hours, your machinery will let you know when the filter needs to be removed and cleaned. But there are two types of regeneration: passive and active. Let’s take a closer look at each, as well as why regeneration is important for your engine.