Whether they're sent by land, sea or air, packages can yield immeasurable amounts of pollution across the globe. But there are many ways to lessen the environmental impact of shipping freight.

Here are seven relatively simple ideas that experts recommend to help keep the Earth green -- and in some cases keep a little more green in your shipping budget.

1. Opt for recycled content.
There are a variety of certifications designed to ensure that the box you use is environmentally friendly. Because all paper starts with trees, use a box that came from sustainably managed forests by looking for Forestry Stewardship Council (FSC) certified packaging.

In addition to the triangular chasing arrow logo, which tells the percentage of recycled content in the box, Thomas G. Day, the U.S. Postal Service's chief sustainability officer, recommends also looking for Cradle to Cradle, or C2C, certified boxes. This packaging features adhesives and inks that aren't harmful to the environment, as well as recycled content, Day says.

But being green can come at a premium. The postal service's C2C-certified boxes cost about one-third more than uncertified boxes sold by Uline.

Related: 4 Mobile Apps That Make Shipping Simple

2. Use eco-friendly filling material.
Styrofoam -- that old standby used to insulate products against bumps, drops, heat and cold -- can be hazardous to the environment in a number of ways. Not only is the petroleum-based product non-sustainable, its manufacturing process also generates a tremendous amount of waste.

To avoid fuel-based fillers, you can use fibrous blocking materials such as corrugated inserts, says Pat Cooney, vice president of business development for Portland, Ore.-based Paccess, which helps clients improve packaging and materials sourcing. One alternative, EcoCradle Mushroom Packaging, is a bio-material that works as an alternative to foam.

Though prices vary depending on the box, biodegradable filler can be competitive in price with traditional packing peanuts. For instance, a 20-cubic foot bag of organic starch cushioning costs just $2 more than the industrial version.

3. Keep size in mind.
Reducing the size and volume of packaging not only uses fewer materials, it also takes up less space on a plane, boat or truck, thus improving the carbon footprint. More compact packaging also can help a company's bottom line, cutting material costs and increasing speed to market.

Apple, for example, gets praised for its simplistic packaging, but the consumer-electronics company is doing more than just aping the design of its products. "One of their key drivers is that they can get a high number of units into a cubic meter of aircraft space," Cooney says.

4. Find a 'green' shipper.
The U.S. Environmental Protection Agency's SmartWay Program provides data on low-emission transportation companies. SmartWay-certified members are monitored for everything from proper inflation of tires to idling of delivery vehicles. Every Monday afternoon, the government agency releases up-to-date performance rankings for their freight shipping partners.

Related: How Secure Package Delivery Can Raise Customer Satisfaction

5. Schedule a pickup.
Because delivery trucks are already out making their rounds, it can be more eco-friendly to arrange for package pickup than driving to a shipping office yourself, Day says. Major delivery service routes are already optimized to be fuel-efficient, and companies can generally give their parcels to the regular delivery person. The post office picks up packages for free, while FedEx charges $4 per package and UPS offers varying rates.

The postal service's "Skip the Trip" savings calculator can give you a preview of how much money you can save each month on fuel costs by converting to package pickups.

6. Offset your carbon footprint.
Even the greenest shippers still leave an environmental footprint, but offset credits can be purchased to make shipments carbon neutral. Hood River, Ore.-based Green Shipping, for instance, helps companies offset the environmental impact of shipping by adding a few cents to every package -- money that is sent to renewable energy sources. The service also allows participating companies to use Green Shipping branding on their website and shipping materials, and it lists them as sustainable partners on its website.

In addition, packages can be tracked, showing transport details such as vehicle type and transfers, as well as how many pounds of CO2 the shipment generated.

7. Develop a return plan.
As companies ship more goods because of online sales, they also are likely to receive a higher number of returns. It's vital, therefore, to develop a return plan that takes the environment -- not just costs -- into account.

It may be ecologically irresponsible to process a return because of the fuel used and pollution created in sending the product back. On the other hand, if defective goods are destroyed instead of returned, there's a different environmental impact in the disposal process.

For less valuable items, consider sending a new product without requesting the old one back. This eliminates the pollution caused by return shipping. Or if the product is more valuable, accept the merchandise back and refurbish it so as not to waste the material used to make the goods.

"It's not unusual, in any industry, to have double digit return rates," Day says. "That has got to be a part of your green approach."

Related: 10 Ways to Green Your Retail Store