Try this: a "just married" voucher worth 180 euros (234 dollars)... in carbon offsets.

Smaller than a toaster but more meaningful, this piece of paper will compensate for nine tonnes of perilous, climate-damaging carbon dioxide (CO2).

That is the amount of pollution that bride and groom are likely to generate by staging a wedding party with 150 guests and by taking a long-haul return flight for their honeymoon.

The voucher, launched by a French firm, Climat Mundi, is only one of a fast-growing array of products in the market for carbon offsets.

Put simply, carbon offsets are a form of self-imposed tax that more and more green-living people are contemplating, aware that their lifestyle inflicts an environmental cost that is simply not reflected in the price of fossil fuels.

Burning oil, gas and coal releases carbon dioxide (CO2) gas, which causes solar heat to build in the atmosphere.

This greenhouse effect -- global warming -- is driving potentially catastrophic changes in Earth's climate system. Water stress, floods, shrinking snow cover, retreating glaciers and permafrost, more powerful hurricanes and typhoons: all these feature in the expected weather changes of the 21st century.

Carbon offsetting is a practice that dates back about a dozen years and includes among its advocates former US vice president Al Gore, maker of the Oscar-nominated global warming docufilm "An Inconvenient Truth."

It entails compensating for one's own unavoidable CO2 pollution by investing in projects elsewhere that reduce or eliminate those emissions.

For instance, the French government, staging the January 29-February 1 meeting of the UN's Intergovernmental Panel on Climate Change (IPCC), calculated that the meeting would generate 1,150 tonnes in CO2 or its equivalent in other greenhouse gases, mainly from air transport.

To help make this calculation, each of the 500 scientists attending the IPCC talks was asked to fill in a questionnaire, detailing his or her itinerary and the mode of travel.

To ensure that the meeting was "carbon neutral," France reduced 1,150 tonnes of CO2 elsewhere. It is financing high-yield cooking stoves in rural Eritrea, in the Horn of Africa.

These stoves are heated by wood, the traditional fuel in Eritrea, but they are 50-percent more energy-efficient than previous models.

Corporations and individuals who want to ease carbon guilt -- or flourish green credentials -- can buy the offset through an intermediary.

Some intermediaries deal with investments in foreign mega-projects, such as biogas initiatives in China aimed at weaning the world's most populous country from its dependence on coal. Such schemes typically fall under the Clean Development Mechanism (CDM) or Joint Implementation initiative of the UN's Kyoto Protocol.

Other schemes, though, are smaller, local and targeted at the individual.

For example, the CarbonNeutral Company in Britain calculates that driving a car with a petrol engine of between 1.4 and 2.0 litres for around 10,000 kilometers (6,000 miles) a year generates around two tonnes of CO2.

With a purchase of just 14.80 pounds (29.6 dollars), the firm says, you could help plant trees in native forest in Britain that would soak up these emissions -- in effect, making your driving a zero-emissions activity.

The broadening range of offsets innovations is triggering debate about the quality of some schemes.

Earlier this month, the British government launched a consultation about standards and a code of practice as a safeguard against ripoffs or disappointment that could badly damage a promising activity.

"People need to be sure that the way they offset is actually making a difference," said Environment Secretary David Milliband.

Alister Scott, spokesman for the University of Sussex Energy Group, an independent group researching energy projects, said offsets were "well-intentioned" but variable in their effect.

The best schemes were those that built capacity, in other words, they generated further emissions reductions in their own right.

"Simply taking a straight CO2 number and thinking that you are solving the problem is a bit naive," Scott told AFP. "It is not enough, you have to look at the question critically."

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.