CHEN Jun, a 24-year-old accountant, now takes her own ceramic cup to the office, so she no longer wastes disposable paper cups she kept in her desk.

She makes it a rule to take public transport instead of taxis, if the trip is less than an hour. She turns off her computer instead of leaving it on stand-by if she isn't going to use it for more than an hour. She prefers local products to imported ones because of their smaller carbon footprint for transport - if the quality is about the same.

"Those are all trifles, and I know that there's much to improve. But these small things will help reduce my carbon footprint, maybe it could help the planet."

Leading a low-carbon life is becoming popular among some Chinese young people (though there's hardly a mass movement), following the Copenhagen climate summit.

"Carbon footprint," which used to be an arcane notion, has become a buzzword.

Walk or drive? Climb the stairs or take the elevator? Set the thermostat at 15 or 20 degrees Celsius? Use throwaway chopsticks or take your own?

These are infinitesimal steps but many young Chinese are asking how they can live more environmentally sensitive lives.

Chen admits that she never gave a thought to drinking from disposable paper cups until a friend teased her about being wasteful.

"She was right. How hard is it to wash a ceramic cup?" says Chen, "but thousands of trees can be saved if we quit using paper cups, napkins and assorted paper that we take for granted."

A carbon footprint is the total amount of greenhouse gas emissions caused by an organization, event, product or individual (it can also be wasting and not recycling). The footprint is often expressed as the amount of carbon dioxide and other greenhouse gases emitted.

"Leading a low-carbon life means to reduce the use of non-renewable fossil energy as much as possible; it can cover every aspect of your life," says Li Lin, strategy director of World Wide Fund For Nature (WWF).

Almost all human activities generate greenhouse gas emissions and leave a carbon footprint, according to Lu Linlin, an official of Shanghai Roots and Shoots, a program designed to educate youths about environmental issues and humanitarian values with a special focus on group interaction.

Electricity use is a major cause of emissions because most energy is generated by burning coal. Vehicles fueled by petroleum products are big emitters.

Using paper is responsible for gases too because paper is made by killing trees that turn carbon dioxide into oxygen.

Over-purchasing anything - from clothes to appliances - means contributing to greenhouses cases that occur during production process and transport of everything.

"It is not that you have to give up your modern life to pursue going green," says Lu, "The secret of a low-carbon life just lies in cutting out the unnecessary consumption."

Research by WWF shows that by buying one less garment a year, one can help save around 2.5 kilograms of coal and reduce 6.4 kilograms of carbon dioxide emissions. Hand-washing clothes once a month can help save around 1.4 kilograms of coal, and reduce 3.6 kilograms of carbon dioxide emission.

Using one less plastic (made from petroleum) bag when shopping can help save 0.04 gram of coal and reduce 0.1 gram of carbon dioxide emission.

Multiplying the savings by thousands of people can really make a difference.

"Many people would agree to making a change when they realize that leading a low-carbon life is not that difficult," says Lu Yating, a 21-year-old student at Shanghai Finance University.

Lu volunteers for the Eco-audit Program of Shanghai Roots and Shoots. The program initiated in 2006 provides free environmental audits for company and schools. The companies and schools get scores and suggestions for more environmentally friendly operations.

The big wasters include using one side of paper only, leaving computers on stand-by and never turning the lights out in an office.

Most companies accept suggestions and improve their scores in the next month. Some companies are using video-conferencing instead of some business trips, since flying generates an enormous amount of greenhouse gas.

Volunteers suggest that those who must fly make donations to programs that plant trees, to help make up as trees are great environment helpers. Over its life, a box tree can absorb about 250 kilograms of carbon dioxide, says Lu from Roots and Shoots.

Many Websites provide greenhouse gas emissions calculators so people can see how much is generated in daily activities.

"They can donate trees according to their green-gas emission numbers to make up for what they have produced," says Lu. So far 200,000 trees have been planted in the Inner Mongolia Autonomous Region with donations to Roots and Shoots since the Million Tree Project started in 2007.

The goal is to plant 1 million trees by 2014. Going low-carbon at work

Use energy-efficient lights; only turn on lights where they are needed; turn them off if no one is in the office or area for more than 15 minutes.

Do not use private heaters in the office; close the doors and windows when the air-conditioner is running. Open the curtains in winter to let the sunshine warm the room; close the curtains on cloudy days to reduce heat loss.

Don't throw a lot of toilet paper down the toilet. That wastes water when flushing: use a rubbish bin.

Turn off taps whenever possible.

Take personal cups, bowls and chopsticks rather than using disposable ones.

Set computers at automatically stand-by mode. Turn it off when leaving work station for more than an hour. Pull the plug or turn off the power when leaving work.

Avoid using the printer as much as possible; print on both sides; print in sketch mode if it's not important; Use print preview before printing. Recycle the ink cartridge. Turn the printer off when leaving the office.

Use public transport, cycle or walk as much as possible. Reduce the number of business trips. Use the telephone, e-mail or video-conference when possible.

Calculate greenhouse gas emissions monthly and compensate by donating to a tree-planting project.

Use stairs instead of the elevator if your destination is not more than two floors above.

Keep potted plants inthe office. Living low-carbon at home

Set the goal of 26-28 degrees centigrade in the summer, 16-18 in the winter.

Don't thaw frozen foods in a microwave oven. Let them thaw at room temperature or put them in a cupboard that's supposed to be cool.

Don't store too much food in the refrigerator or leave it running while empty; 80 percent full is most appropriate.

Use good-quality low-foaming detergent to reducethe amount of water usedto rinse.

Clean the electric hot tray of rice cooker frequently. Accumulated dirt reduces efficiency, wasting electricity.

Cover foods with cling-wrap or place in nontoxic plastic container to keep moisture from evaporating.

Use energy-efficient light bulbs.

Use water-saving taps.

Turn off appliances that are not in use; stand-by status wastes energy.

Turn on a 5-watt electricity-saving lamp when watching TV, while turning down the brightness of the TV. Million Tree Project

By donating 25 yuan (US$3.66), individuals and organizations can help fight global warming by ensuring that one more tree is planted in the Inner Mongolia Autonomous Region.

The trees planted in the Million Tree Project help reclaim land suffering from severe desertification and resulting sandstorms in Kulun Banner and Tongliao areas.

The project was started in 2007 by Shanghai Roots and Shoots.

Mostly trees like hybrid poplars are planted as they are hardy, capture a lot of carbon dioxide and don't require much water.

Local people are hired to take care of the trees and volunteers often visit and check on the growth.

A carbon calculator is available on the Website. It shows, among other things, how many trees should be planted for each airline flight.

Take Shanghai?Beijing flight as an example:

Round trip = 2,200 km

2,200 km x 0.1753 kg CO2/km divided by 250 kg CO2/tree = 1.54 trees (~2 trees)

So two trees should be planted for a round trip flight from Shanghai to Beijing. Then Shanghai to Singapore, three trees; Sydney, seven trees; Paris, eight trees; and Chicago 10 trees, etc.

Website: www.mtpchina.org/