Add a company | Add a product | Add a blog

Search

Carbon offset

Posted August 31st, 2007 by Rachel

Carbon offsetting is the act of mitigating ("offsetting") greenhouse gas emissions. A well-known example is the planting of trees to compensate for the greenhouse gas emissions from personal air travel.

The idea of paying for emission-reductions elsewhere instead of reducing by own actions is also known from the closely related concept of emissions trading. However, in contrast to emissions trading, which is regulated by a strict formal and legal framework, carbon offsets generally refer to voluntary acts by individuals or companies that are commonly arranged by commercial or not-for-profit carbon-offset providers.

A wide variety of offset methods are in use — while tree planting has initially been a mainstay of carbon offsetting, renewable energy and energy conservation offsets have now become increasingly popular, and purchase and withdrawal of emissions trading credits is also seen.

Carbon offsetting as part of a "carbon neutral" lifestyle has gained some appeal and momentum mainly among consumers in western countries who have become aware and concerned about the potentially negative effects of energy-demanding lifestyles and economies on the environment. The Kyoto Protocol has sanctioned official offsets for governments and private companies to earn carbon credits which can be traded on a marketplace. This has contributed to the increasing popularity of voluntary offsets among private individuals and also companies. Offsets may be cheaper or more convenient alternatives to reducing one's own fossil-fuel consumption. However, some critics object to carbon offsets, and many have questioned the benefits of certain types of offsets (such as tree planting), and other projects.

Types of offset

Tree Planting

Tree planting includes not only re-creating natural forests (reforestation) and avoiding deforestation, but also monoculture tree farming on plantations for logging, biodiesel production, or other commercial purposes. The term "reforestation" is nevertheless often applied in this context to monoculture tree farming as well as re-creating natural forests. There is also afforestation, which can produce higher carbon sequestration rates because it means establishing forests particularly on land not previously forested, for example on agricultural lands where baseline carbon levels are comparatively low.

Many forestry offset projects have been conceived and/or conducted in ways that are vulnerable to criticism, drawing their net benefits into question. Significant concern also arises over the permanence of carbon storage in trees and forests, as potential future clearing of the forest would return the stored carbon to the atmosphere.

In July, 2007, Vatican City accepted an offer that will make it the only carbon neutral state for the year, due to the donation of the Vatican Climate Forest in Hungary. The forest is to be sized to offset the year's carbon dioxide emissions.

Climate impacts

Trees sequester carbon through photosynthesis, converting carbon dioxide and water into oxygen and plant matter. Hence, forests that grow in area or density will reduce atmospheric CO2 levels. (Carbon is released if a tree or its lumber burns, but as long as the forest is able to grow back, the net result is carbon neutral.) In their 2001 assessment, the IPCC estimated the potential of biological mitigation options (mainly tree planting) is on the order of 100 Gigatonnes of Carbon (cumulative) by 2050, equivalent to about 10% to 20% of projected fossil fuel emissions during that period.

However, the global cooling effect of forests from sequestration is not the only factor to be considered. For example, the planting of new forests may initially release some of the terrain's existing carbon stores into the atmosphere. Specifically, the conversion of peat bogs into oil palm plantations has made Indonesia the world's third largest producer of greenhouse gases. Compared to less vegetated lands, forests affect climate in three main ways:

* cooling Earth by functioning as carbon sinks
* cooling Earth by adding water vapor, a greenhouse gas, to the atmosphere and thereby increasing cloudiness
* warming Earth by absorbing a high percentage of sunlight due to the low reflectivity of forest's dark surfaces. This warming effect, or reduced albedo, is large where evergreen forests (very low reflectivity) shade snow cover (very high reflectivity).

Most tree planting offset strategies to date have taken only the first effect into account. A study published in December 2005 combined all these effects and found that tropical forestation has a large net cooling effect, because of increased cloudiness and because of high tropical growth and sequestration rates. Trees grow three times faster in the tropics than in temperate zones; each tree in the rainy tropics removes about 22 kilograms (50 pounds) of carbon dioxide from the atmosphere each year. However, this study found little to no net global cooling from tree planting in temperate climates, where warming due to sunlight absorption by trees counteracts the global cooling effect of carbon sequestration. Furthermore, this study confirmed earlier findings that reforestation of colder regions—where long periods of snow cover, evergreen trees, and slow seqestration rates prevail—probably results in global warming.

"To plant forests outside of the tropics to mitigate climate change is a waste of time", said Ken Caldeira, a study co-author from the Carnegie Institution. "To prevent climate change, we need to transform our energy system. It is only by transforming our energy system and preserving natural habitat, such as forests, that we can maintain a healthy environment. To prevent climate change, we must focus on effective strategies and not just ‘feel-good’ strategies."

His premise that grassland reflects more sun, keeping temperatures lower is only applicable in arid regions, however. A well watered lawn for example is as green as a tree but absorbs far less CO2. Deciduous trees also have the advantage of providing shade in the summer and sunlight in the winter.

Costs

While the benefits of tree-planting are subject to debate, the costs are low compared to many other mitigation options. The IPCC has concluded that "The mitigation costs through forestry can be quite modest (US$0.1–US$20 / metric ton carbon dioxide) in some tropical developing countries.... The costs of biological mitigation, therefore, are low compared to those of many other alternative measures". The cost effectiveness of tropical reforestation is due not only to growth rate, but also to farmers from tropical developing countries who voluntarily plant and nurture tree species which can improve the productivity of their lands. As little as US$90 will plant 900 trees, enough to annually remove as much carbon dioxide as is annually generated by the fossil-fuel usage of an average United States resident.

Types of trees planted

An eucalyptus plantationThe type of tree planted may have great influence on the environmental outcomes. Planting the wrong kind of trees, such as monocultures of eucalyptus where they are not native species, can devastate the lands of the local people. However, it is often much more profitable to outside interests to plant non-native fast-growing trees, such as eucalyptus or pine (e.g., Pinus radiata or Pinus caribaea), even though the environmental and biodiversity benefits of such monoculture plantations are not comparable to native forest, and such offset projects are frequently objects of controversy (see below).

To promote the growth of native ecosystems, many environmentalists advocate only indigenous trees be planted. A practical solution is to plant tough, fast-growing native tree species which begin rebuilding the land. Planting non-invasive trees that assist in the natural return of indigenous species is called "assisted natural regeneration." There are many such species that can be planted, of which about 12 are in widespread use, such as Leucaena leucocephala.

Avoided deforestation

Some offsets aim at carbon benefits from avoided deforestation. It may involve training developing-world communities in the production, sale, and use of fuel-efficient stoves. As almost half of the world's people burn wood (or fiber or dung) for their cooking and heating needs, fuel-efficient cook stoves can reduce fuel wood consumption by 30 to 50%, though the warming of the earth due to decreases in particulate matter (i.e. smoke) from such fuel-efficient stoves has not been addressed.

Renewable energy and energy conservation

Renewable energy offsets commonly include wind power, solar power, and biofuel. Some of these offsets are used to reduce the cost-differential between renewable and conventional energy production. Others operate in developing countries, such as training local communities to produce biodiesel from jatropha oil.

Some offset providers sell in multiple markets, such as the Te Apiti Wind Farm in New Zealand, a project certified to the privately operated CDM Gold Standard which supplies offsets to the Dutch Government, British bank HSBC, and private citizens.

Methane Collection & Combustion

Some offset projects consist of combusting or containing methane generated by farm animals or landfills. Methane has a Global warming potential (GWP) 23 times that of CO2; when combusted, each molecule of methane is converted to one molecule of CO2, thus reducing the global warming effect by 96%. Methane can also be contained using an anaerobic digester, and used to produce electricity or heat.

Links with emission trading schemes

Carbon offsets can also be linked with official emission trading schemes, such as the European Union Emission Trading Scheme and the voluntary Chicago Climate Exchange. By purchasing emission allowances and subsequently withdrawing the allowances from the markets, a reduction of allowable emissions is forced (assuming the trading scheme works as intended). In the case of the European Union Emission Trading Scheme it is widely believed that allowable emissions (during the first phase of the system) exceed physical emissions, in which case there is no physical effect in doing so. EU emission allowances sell for 0.13Euro per metric ton of CO2, As of June 2007. EU emission allowances for the 2008-2012 second phase sell for between 21 and 24Euro per metric ton CO2 As of July 2007. The Chicago Climate Exchange tons trade for about $3.25 per metric ton of CO2, also as of July 2007.

Other

A UK offset provider set up a carbon offsetting scheme which set up a secondary market for treadle pumps in developing countries. These pumps are used by farmers, using human power, in place of diesel pumps. However, given that treadle pumps are best suited to pumping shallow water, while diesel pumps are usually used to pump water from deep boreholes, it is not clear that the treadle pumps are actually achieving real emissions reductions. Other companies have explored and rejected treadle pumps as a viable carbon offsetting approach due to these concerns.

Accounting for and verifying reductions

Due to their indirect nature, many types of offset are difficult to verify. Some providers obtain independent certification that their offsets are accurately measured, to distance themselves from potentially fraudulent competitors. The credibility of the various certification providers is often questioned. Certified offsets may be purchased from commercial or non-profit organizations for US$1–30 per tonne of CO2, due to constant fluctuations with the current market price. Annual carbon dioxide emissions in developed countries range from 6 to 23 tons per capita.

Accounting systems differ on what constitutes a valid offset for voluntary reduction systems and for mandatory reduction systems. Formal standards for quantification of offsets are not in place; differences of opinion between emitters, regulators, environmentalists, and project developers have yet to be resolved.

Accounting of offsets may address the following basic areas:

Baseline - What emissions would occur in the absence of a proposed project?
Additionality - Would the project occur anyway without the investment raised by selling carbon offset credits?
Redundancy - Are the reductions already required by some other law or regulation?
Permanence - Are some benefits of the reductions reversible? (for example, trees may be harvested to burn the wood; many trees, in geological terms, have relatively short life spans, making them unsuitable for long-term carbon sequestration; and does growing trees for fuel wood decrease the need for fossil fuel?) If woodlands are increasing in area or density, then carbon is being sequestered. After roughly 50 years, newly planted forests will reach maturity and remove carbon dioxide more slowly.
Carbon leakage - Does implementing the project cause higher emissions outside the project boundary?

keywords: