Parents are putting their babies’ dirty diapers in the mailbox — for the sake of the environment. Subscription-based baby-care company Dyper, which introduced their biodegrade bamboo diaper in 2018, has partnered with waste-management company TerraCycle to launch ReDyper, a mail-in diaper-composting service for all Dyper customers. Just store your baby’s soiled Dyper diapers until there’s enough to fill up the provided box — specially designed per the United Nations’ hazmat standards — then download and print a mailing label from their website and ship your crap, so to speak, to TerraCycle. Then, it’s off to various centralized composting facilities across the country.   It may sound like nasty business, but the alternative is much worse, says Dyper president Bruce Miller, who called diaper waste statistics “staggering,” as more than 20 billion diapers fill landfills in the US each year.   “I think this has been the Holy Grail for a lot of disposable diaper companies,” Miller tells The Post. “But no one at this point really has closed the loop” by commercializing the diaper-composting process.   Made primarily from bamboo and free of chlorine, perfumes, phthalates, polyvinyl chloride (PVC) and other unsustainable or potentially harmful materials, Dyper’s content manager Taylor Shearer tells The Post their diapers are “already technically compostable” — at least, for the customers who can manage the time- and space-consuming chore, or have access to a local composting facility. Their website also advises homesteaders to avoid composting diapers filled with fecal matter, to prevent the spread of bacteria and other pathogens.   Shearer explains that the new service is aimed at “customers that live in the cities [and] large apartment buildings that don’t have that access,” as well as those who hope to process baby’s poo, too.   Once TerraCycle receives the ReDyper box, the waste is routed to various regional composting operations, though Miller assures it will never be used to fertilize the food on your plate.   “The diapers [go] toward highway infrastructure vegetation,” he says. “If you see wildflowers growing in the median … that’s really where a majority of our composted product goes.”   Dyper’s diaper-delivery subscription starts at $68 per month and promises enough diapers depending on your baby’s size, between 100 and 260 pairs per week. An additional monthly cost of $39 is added for those opting in to ReDyper.   “We believe [the cost is] going to come down dramatically as we get more and more scaled,” Miller says. Still, he thinks their “passionate” customers are eager for it.   When it comes to minimizing human impact on the planet, says Miller, “people just want it to be easy.”