Twilight for Gas Guzzling, Polluting Livestock and Styrofoam.

How can I use my car in more environmentally friendly ways? --Brian George, Sterling Heights, MI

The best thing you can do, of course, is to leave your car in the rage and take mass transit. But if you have to drive, start by filling up at night. In hotter temperatures, which typically occur during daylight hours, more gasoline evaporates through the fuel opening, allowing potentially dangerous hydrocarbons to enter the atmosphere. These hydrocarbons combine with nitrogen oxides to form ozone, a major component in smog.

Short of exchanging your car for a bicycle, you can follow some tips from the California Energy Commission (CEC) on using less gas: Keep your tires filled to the correct pressure (this decreases rolling resistance and increases fuel economy); drive the speed limit because gas mileage decreases at faster speeds; keep your vehicle in good working order (dirty parts make engines less efficient). The CEC advises drivers to use flow-through ventilation on hot days (open windows increase air resistance and cut down on fuel efficiency). Also, slow acceleration uses less gas than a speedy start.

Environmental Defense estimates that a properly maintained manual transmission offers a five percent fuel savings over the same car with an automatic. Drive light; fuel economy is reduced by one mile per gallon for every additional 200 pounds of weight. After changing antifreeze and motor oil, take them to your local garage for recycling. Throwing them in the garbage can lead to groundwater pollution. CONTACT: CEC Consumer Energy Center,

[phone], www.consumerener gycenter.org.

How much animal waste and methane gas is produced by livestock in the U.S. meat industry? --David Rietz, Goose Creek, SC

The United States Department of Agriculture (USDA) reports that the U.S. meat industry produces 61 million tons of waste each year, or five tons for every citizen. According to the Environmental Protection Agency, livestock waste has polluted 35,000 miles of rivers in 22 states and has contaminated groundwater in 17 states.

Livestock naturally produce methane as part of their digestive process, belching it while chewing cud and excreting it in their waste. Methane gas is a greenhouse gas that has nearly doubled in accumulation over the past 200 years. Scientists believe that rising concentrations of methane, which absorbs and sends infrared radiation to the Earth, are contributing to global warming. John Robbins, author of The Food Revolution and founder of EarthSave International, says methane is 24 times more potent a greenhouse gas than carbon dioxide. According to the Worldwatch Institute, 15 to 20 percent of global methane emissions come from livestock. CONTACT: USDA, [phone], www.usda.gov; Worldwatch Institute, [phone], www.worldwatch.org.

What is the best way to recycle Styrofoam? --Carol Torchia, Bellevue, WA

There was no recovery system for Styrofoam, or expanded polystyrene (EPS) plastic, before 1988. According to the Alliance of Foam Packaging Recyclers (AFPR), reused or recycled polystyrene rose from 0.8 percent in 1974 to 10.4 percent in 1994, eliminating more than 800,000 tons of it from waste streams and landfills. As of 1999, the Polystyrene Packaging Council (PSPC) reports that more than 345 million pounds of polystyrene packaging have been recycled. Much of this recycled EPS is limited to protective packaging and non-durables like single-use cameras and video cassettes. The PSPC says post-consumer food service packaging (coffee cups, bowls, plastic cutlery) is often too contaminated with food waste to be cost-effectively recycled. But some businesses are switching to more natural, post-consumer biodegradable materials, such as Earthshell's containers.

Many manufacturers of protective packaging, such as Polyfoam Packers, Styrotek and Foam Fabricators, are taking the material back for recycling or reuse. The firms grind up the EPS and remold it into new forms. Both the AFPR and the PSPC provide online resources for curbside, drop-off, recycling and reclamation programs nationwide. The AFPR also provides information on recycling polystyrene food service packaging, durable goods and other plastics.

GrassRoots Recycling Executive Director Bill Sheehan suggests bringing the Styrofoam back to the retailer. "With enough pressure from consumers," he says, "manufacturers will have to develop a recovery system for such materials." CONTACT: AFPR, [phone], www.epspackaging.org; GrassRoots Recycling Network, [phone], www.grrn.org; PSPC, [phone], www.polystyrene.org.

Send your questions about environmental issues, from the personal to the political, to Ask E, P.O. Box 5098, Westport, CT 06881, or by e-mail to [e-mail]. Please keep your questions brief, and type them double-spaced. Include your full name, address and a daytime phone number.