As consumers demand faster shipping times, carriers scrambling to make next-day deliveries don’t pack trucks as efficiently, meaning delivery trucks make their rounds with extra space in the back. It also means that each package has a higher carbon footprint. But a new shipping carrier called Sendle is designed to make use of that wasted space.

Sendle, an Australian logistics company that launched in the U.S. today, buys the extra room on other carriers’ trucks to make shipments for small businesses. It also buys carbon offsets for each package, making it the first 100% carbon-neutral national delivery service in the country. The company’s use of extra space means that it can offer the service affordably.”It doesn’t have to be a choice between carbon-neutral and saving money,” says Sendle CEO and cofounder James Chin Moody. “You can actually do both.”

The startup, a certified B Corp, grew out of another platform that the founders launched to help people donate old goods. Not finding a shipping service that was reliable and affordable enough, they ended up developing a new option for delivery themselves. It was so popular that they began offering it to others—focusing on sellers with small businesses on Etsy, eBay, and other platforms. Those customers, Moody says, are looking for “the right mix of speed and cost” and don’t necessarily need an option for next-day shipping; Sendle focuses on 2-day and 3-day shipping. In the U.S., the company will first pay for the extra space available on USPS trucks (Amazon recently cut back its use of the postal service, freeing up more room), so the packages will be delivered by your postal carrier. In the future, it could work with other carriers, like UPS and FedEx, as well.

In Australia, it works with a variety of carriers. “We basically said, ‘Look, if we can help you fill your trucks, we can improve your density, which again, improves the efficiency of the system,'” he says. The startup is also working with carriers to help them explore other ways to reduce the carbon footprint of shipping, such as shifting to new types of vehicles. It also helps customers further improve their environmental performance through offering options like a shipping pouch that can be composted in the recipient’s backyard.

By spending money on carbon offsets, Sendle believes that it’s also better prepared for the future. “We’re de-risking our business now,” says Moody. “Sentiment is changing all over the world around climate change. If and when we have a price on carbon, that’s already been factored into our business model. We are de-risked from that perspective, and I think that our merchants are de-risked from that perspective as well.”

Some of the world’s largest shippers are slowly starting to change. Amazon, for example, announced earlier this year that it would make half of its shipments carbon neutral in a little over a decade, and in September, announced plans to buy 100,000 electric delivery trucks. DHL will begin to roll out electric delivery vans in American cities next year. This type of sweeping change is necessary, says Moody. “All commerce is turning into e-commerce in some type of form,” he says. “It’s a megatrend that’s occuring. And it’s so important that the ecommerce industry does start to take responsibility for emissions and for impact.”