Today's consumers have options when it comes to buying green — from organic, sustainable, secondhand and recyclable products to companies that offer carbon credits and eco-friendly shipping options. Though hybrid trucks haven't hit a chord with the typical American family, many U.S. businesses have taken notice. Since 2002, diesel-gas hybrids, electric vehicles and now hydraulic hybrid trucks have worked to reduce harmful tailpipe emissions as part of private delivery fleets.

Doing well by doing good

Walmart looks to save $10,000 per truck every year with its new hybrid tractor-trailer designed by Eaton Corp. and Peterbilt. UPS expects a fuel savings of 176,000 gallons of fuel each year now that it's added 200 new hybrid delivery trucks to its fleet. Carbon emissions may or may not present a business expense in the future, but even without these costs figured in, commercial vehicles recoup their investment within just a few years.

Rachel Beckhardt, program manager for the Environmental Defense Fund, pinpoints the gains hybrids offer business and environment. With 250,000 new diesels hitting the roads every year in the United States, and with hybrids improving fuel efficiency by up to 50 percent, making the switch is common sense, she says.

Clearing the air

According to the EDF, medium and heavy-duty trucks account for 6 percent of carbon dioxide emissions. Delivery trucks idling in traffic burn unnecessary fuel and kick extra emissions into the air. These particles have been tied to respiratory problems like asthma, heart conditions, cancer, and even lower IQ scores in children.

Hybrid trucks cut emissions by switching to electric motors at low speeds, and shutting down during idling. Coca-Cola's New York hybrid fleet has cut emissions by 32 percent. Electric vehicles used for short hauls can cut emissions to zero. Beckhardt says hybrids cut soot given off by trucks by 96 percent.

Today's hybrids

Most large hybrid trucks fall into two categories: diesel-electric and hydraulic hybrids. Diesel-electric trucks use a diesel engine in combination with an electric motor. Electric power takes over during idling or low speeds, and is charged by the diesel engine and during breaking.

In 2006, Eaton Hydraulics paired with the U.S. Environmental Protection Agency to create a hydraulic hybrid delivery truck for UPS. James Van der Ven, assistant professor and head of the Mechanical Energy and Power Systems lab at Massachusetts' Worcestor Polytechnic Institute, says HHVs have benefits over electric hybrids.

"The hybrid system can be responsible for the high power transient requirements, such as accelerating from a stop, passing maneuvers or aggressive braking," Van der Ven says. In addition, hydraulic components cost less, last longer and don't present the same environmental risks once they've run their course.

Making a difference

The Climate Group, an organization that works with businesses and government to improve their environmental practices, looks to legislation to encourage hybrid development. In particular, it argues that holding companies financially accountable for their carbon emissions would make the switch to hybrids impossible for companies to ignore.

Other groups, such as the EDF, still believe the average consumer can make an impact. "Ask your local delivery person if their fleet has hybrids," EDF's Beckhardt recommends.

Tomorrow's hybrids rely on advanced battery packs and high-density hydraulic systems. These greater improvements in fuel efficiency could help lead companies toward better choices, and eventually this new technology will filter down to mainstream passenger vehicles.