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Home , Biosequestration, Carbon sequestration, Primary production

Understanding how and how much dioxide can be fixed by natural ways

Educational material mix for the School Agenda 21, compiled and adapted by Josean Kijera – Ingurugela, Donostia (Basque Country) 1 1.

A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon- containing chemical compound for an undefined time.

The process by which carbon sinks remove (CO2) from the is known as . Awareness of the significance of CO2 sinks has grown since the , where their use as a form of is promoted. There are different strategies used to enhance this generic process.

Figure 1. Natural and anthropogenic interactions in the ´s (Source: The State Department of Environmental Conservation, DEC; http://www.dec.ny.gov/energy/76572.html)

2 2.

Biosequestration is the capture and storage of the atmospheric gas carbon dioxide by biological processes. This can happen by increasing (through some practices like preventing , and ); by enhanced carbon trapping in ; or by the use of algal biosequestration ( bioreactor) to absorb

CO2 emissions from , (oil) or based , transportation... Biosequestration, as a natural process, has occurred in the past, and was responsible for the formation of the extensive coal and oil deposits which are now being Figure 2. Biosequestration of carbon, as CO2 by photosynthesis (Source: International burned for energy. Center for Tropical Agriculture, CIAT; http://dapa.ciat.cgiar.org/carbon- sequestration-one-true-green-revolution/)

3 Biosequestration of carbon by

Some definitions:

• Carbon dioxide: it is a by-product of respiration and substrate for the photosynthetic process; also, a massively produced by hydrocarbon .

• CO2 flux: the transfer of a quantity of CO2 per unit of area and per unit of time.

• Gross (GPP): the total amount of organic material assimilated by plants in an assumed time.

• Net Primary Production (NPP): the total amount of organic material accumulated by plants in a specified time; in other terms:

NPP = Photosynthesis – Respiration.

Carbon biosequestration in plants is the process by which CO2 is removed from the atmosphere and stored as .

4 Carbon biosequestration can be considered at a number of levels. At the level of an discrete plant, the amount of carbon sequestered is this:

CO2 sequestered = Photosynthesis – Respiration

So that, the amount of sequestered carbon is just as to the NPP of the plant.

If carbon biosequestration is considered at level, some more factors have to be accounted. The diagram indicates the mean processes involved in ecosystem carbon sequestration:

- Blue arrow: process that bring carbon into the ecosystem. - Red arrows: processes returning carbon from the ecosystem to the atmosphere.

Figure 3. Carbon biosequestration in by plants (Source: University of Colorado; http://www.colorado.edu/geography/blanken/GEOG%206181%20F all%202003/zarter/html/zarter_cseq.shtml) 5 Temperate and their capacity incorporating carbon dioxide

Temperate forest, vegetation type with a more or less continuous canopy of broad-leaved . Such occur between approximately 25° and 50° latitude in both N and S hemispheres. Near the polar regions they grade into boreal forests, which are dominated by perennial conifers. Mixed forests, containing both deciduous and coniferous trees, occupy transitional areas. Temperate forests can be classified into two main groups: deciduous and evergreen.

Figure 4. Temperate forest areas in the world (Source: Encliclopaedia Britannica; http://global.britannica.com/E Bchecked/topic/586555/tem perate-forest)

6 Deciduous forests are found in regions of the Northern Hemisphere that have moist, warm summers and frosty winters (primarily eastern North America, eastern Asia, and western ). In contrast, evergreen forests grow in areas with mild, nearly frost-free winters. They fall into two subcategories: - Broad-leaved forests. - Sclerophyllous forests. (Sclerophyllous vegetation has small, hard, thick ).

The former grow in regions that have high year-round rainfall; the latter occur in areas with lower and more inconsistent rainfall.

Figure 5 and 6. Temperate forest plants (Source: Encliclopaedia Britannica; http://global.britannica.com/EBchecked/topic/586555/temperate-forest) 7 Temperate forests are vigorous carbon sinks and deforestation in temperate zones has largely stopped. Where demand for land and/or allows, reforestation would enable carbon sequestration and could provide other benefits, as well as higher .

Figure 7. Carbon contained in natural ecosystems (Source: Grida; http://www.grida.no/publications/rr/natural- fix/page/3725.aspx) 8 Terrestrial storage in wild lands and agricultural landscapes

Soils exemplify a small to long-term carbon storage medium, and contain more carbon than all terrestrial vegetation and the atmosphere combined. , like other biomass, accumulates as organic matter in , and is degraded by chemical and biological degradation. More recalcitrant organic carbon , such as cellulose, hemi- cellulose, lignin, aliphatic compounds, waxes and terpenoids, are collectively retained in the .

Figure 8. Terrestrial storage of carbon in soils (Source: Big Sky Carbon; http://www.bigskyco2.org/whatisit/ter restrial)

9

Current agricultural practices lead to carbon loss from soils. It has been suggested that improved farming practices could return the soils to being a carbon sink. Present wide- reaching practices of are greatly reducing many ' performance as carbon sinks. Some studies shows that regenerative agriculture could sequester up to 40 % of current CO2 emissions. So that, agricultural carbon sequestration has the potential to mitigate global warming. When using biologically based regenerative practices, this powerful advantage can be accomplished with no reduction in yields or farmer profits. Organically managed soils can convert carbon dioxide from a greenhouse gas into a food- producing asset.

Figure 9. Regenerative agriculture. Figure 10. Agriculture and . 10 Enhancing natural sequestration in forest

Forests are carbon stores, and they are carbon dioxide sinks when they are increasing in density or area. For example, in Canada's boreal forests around the 80 % of the is stored in the soils like deceased organic matter. An important and large in time study about African, Asian, and South American tropical forests shows that tropical forests absorb about 18 % of all CO2 from by fossil fuels. Tropical reforestation is a good practice mitigating global warming until all available land has been reforested with mature forests. Truly mature tropical forests sequester no net carbon. In the equilibrium state, growth equals decay; in this situation, tropical soils do not accumulate humus as temperate forests do.

Figure 11. Temperate forest of Montenegro. (Source: Wikipedia, Old-growth forest; http://en.wikipedia.org/wiki/Old- growth_forest)

11 The IPCC concluded that:

A sustainable strategy aimed at maintaining or increasing forest carbon stocks, while producing an annual sustained yield of timber fiber or energy from the forest, will generate the largest sustained mitigation benefit.

Sustainable management practices promotes forests growing at a higher rate over a potentially longer period of time, providing net sequestration benefits in addition to those of unmanaged forests.

Global Potential for Carbon Sequestration (Source: Wikispaces, ; http://climatechange.wikispaces.com /Carbon+Sequestering)

12 expectancy of forests varies throughout the world, influenced by , site conditions and natural patterns. In some forests, carbon may be stored for centuries, while in other forests carbon is released with frequent stand replacing fires.

Figure 12. Timber, and Figure 13. forest in fired (Source: Wikipedia, ; http://en.wikipedia.org/wiki/Wildfire)

Forests that are harvested prior to stand replacing events allow for the retention of carbon in manufactured forest products such as lumber. However, only a portion of the carbon removed from logged forests ends up as durable goods and buildings. The remainder ends up as by-products such as pulp, paper and pallets, which often end with incineration (resulting in carbon release into the atmosphere) at the end of their lifecycle.

13 Biosequestration by reforestation

Sequestration of CO2 trough reforestation is the replanting of trees, often on marginal crop and pasture lands, to incorporate carbon from atmospheric CO2 into biomass. For a good practice, previously retained carbon must not return to the atmosphere from burning or rotting when the trees die. To this end, the trees must grow in perpetuity or the from them must itself be sequestered, e.g., via , bio-energy with carbon storage (BECS) or . Short of growth in perpetuity, however, reforestation with long-lived trees (>100 years) will sequester carbon for a more graduated release, minimizing impact during the expected carbon crisis of the 21st century.

Figure 14. Biosequestration by reforestation. Reforested land. IDEASGALORE: http://affleap.com/reforestation-helps-ease- global-warming-due-to-ecological-imbalance/

14 Carbon sequestration in urban tress

Cities occupy 2 % of the soil of the planet; however, they are responsible for 80 % of the anthropogenic .

In the biogeochemical carbon cycle, led by CO2, mediate decisively living beings, especially those able to perform photosynthesis in both terrestrial and inland and water.

6 CO2 + 6 H2O + Sunligth → C6 H12 O6 + 6 O2

It should be clear that the

best CO2 gas is that which is not generated. Therefore, it must be insisted on the crucial importance of energy efficiency and the deployment of . Figure 15. Photosynthesis.

15 Under the Kyoto Protocol, generation of forest carbon sinks is projected in emerging countries but, unquestionably, is much more valuable to promote them in our own environment, as villages and tows, with those notorious benefits:

- CO2 sequestration and fixation. - Increase the quality of landscapes. - Maintenance of biodiversity. - Improved water balance. - of extreme phenomena.

Figure 16. Kyoto Protocol.

16 In towns, urban trees, along with shrubs and herbaceous parks, are continually working to improve persons quality of life. A park is a main sink for CO2; it can say that woodland is a very complex alive device which is based on clean energy, and which promote the stabilization of the atmosphere of cities in terms, too, of levels of CO2 and O2; very significantly, in turn, these trees retain other contaminants (Pb and other heavy metals).

Figure 17. Urban park (Source: Wikipedia; Park; http://en.wikipedia.org/wiki/Park)

17 Urban forests can sequester between 3.5 and 35 t of carbon per hectare per year, compared to maximum costs about 25 € per tree for purchase and maintenance. The optimal sequestration depends on several factors:

- Number of trees per hectare of land. - The species composition, biodiversity. - The age of the individuals. - Own environmental factors of the area. The amount of carbon sequestering a tree is related to its size: the larger the tree, the greater binding capacity.

Each time a tree is got down without alternative, we are supplying to the atmosphere many potential kilograms of

CO2. Figure 18. Urban park (Source: Wikipedia, Urban park; http://en.wikipedia.org/wiki/Jefferson_Memorial_Fore st#mediaviewer/File:Jcf-tuliptree_trail_6-2.JPG) 18 Natural sequestration in

At present, oceans are CO2 sinks. They represent the largest active carbon sink on Earth, absorbing more than a quarter of the CO2 that humans place into the air. On longer timescales they can be both sources and sinks (during ice ages, CO2 levels decrease to ~180 ppmv, and much of this is believed to be stored in the oceans.

As ice ages end, CO2 is released from the oceans and CO2 levels during previous interglacials have been around ~280 ppmv. This role as a sink for CO2 is driven by two processes, the and the . The former is primarily a function of differential

CO2 solubility in and the thermohaline circulation, while the latter is the sum of a series of biological processes that transport carbon (in organic and inorganic forms) from the surface euphotic zone to the ocean's interior. A small fraction of the organic carbon transported by the biological pump to the seafloor is buried in anoxic conditions under sediments and ultimately forms fossil fuels such as oil and natural gas. At the present time, approximately one third of human Figure 19. Bio and physical pumps of CO2 generated emissions are estimated to be entering the (Source: Wikipedia, Carbon Sink; ocean. http://en.wikipedia.org/wiki/Carbon_sink) 19 The , a part of a complex and global solution

One of the most promising new ideas to reduce atmospheric CO2 and limit global climate change is to do so by conserving mangroves, grasses (as Posidonia oceanica) and salt marsh grasses. Such coastal vegetation, dubbed “blue carbon”, sequesters carbon far more effectively (up to 100 times faster) and more permanently than terrestrial forests. Carbon is stored in peat below coastal vegetation as they accrete vertically. Because the sediment under these habitats is normally anoxic, organic carbon is not broken down and released by microbes.

Figure 20. Posidonia oceanica sea botton land in the . (Source: Wikipedia, Posicodia oceanica; http://en.wikipedia.org/wiki/Posidonia_oceanica#mediaviewer/ File:Posidonia_2_Alberto_Romeo.jpg)

Coastal vegetation sequesters carbon for thousands of years in contrast to forest, where soils can become carbon-saturated relatively quickly. Therefore, carbon offsets based on the protection and restoration of coastal vegetation could be far more cost effective than current approaches focused on trees. Furthermore, there would be enormous ad-on benefits to fisheries, tourism and in limiting coastal erosion from the conservation of blue carbon. 20 In Figure 21, it can see all the organic rich sediment that gets accumulated in the mangrove roots as the forest accretes vertically. This makes mangrove forests highly effective at capturing and storing carbon emitted into the atmosphere by humans. However, when mangrove forests are destroyed for development, vast amounts of carbon is released, intensifying global climate change.

Figure 21. Mangrove roots have high capacity accumulating organic carbon (Source: The Blue Carbon Project; http://www.thebluecarbonproject.com/the-problem-2/)

21 Figure 22. Carbon sequestration capacity in costal vegetation and terrestrial forest (Source: The Bule Carbon Projet; http://www.thebluecarbonproject.com/the-problem-2/)

22 3. Artificial sequestration possibilities of carbon dioxide

To restore the carbon balance, scientists are exploring ways to artificially carry out carbon sequestration. These artificial processes usually seek to capture the carbon dioxide gas at the point of production and then have the gas stored in the following forms.

Figure 23. Carbon artificial capture.

Figure 24. Emissions from .

23 Ocean artificial sequestration:

Scientists are exploring the possibility of sequestering carbon artificially into the oceans.

• One approach is to infuse liquefied carbon dioxide into the deep ocean. The liquid carbon dioxide is infused into a hollow or trench on the seabed, where it would stay as Figure 25. Sequestration in deep ocean (Source: The Resilient Earth; a submarine lake. Based on model studies, http://theresilientearth.com/?q=content/why- carbon dioxide injected at depths of 1500 m carbon-sequestration-wont-work) or more, with careful site selection, could be stored up for several hundred years.

• Another approach is to increase the natural

oceanic uptake of CO2 via microscopic plants called . The theory is to increase biological of these plants, enabling the phytoplankton near the

sea surface to take in more CO2, as such Figure 26. Ocean fertilization. Geo-engineering removing the gas from the atmosphere. And in in the Context of (Source: Geonengineering; the process, oxygen could be produced. http://geoengineering2012.wordpress.com/tag /solar-radiation-management/) 24 Geological carbon artificial sequestration: in this method, the carbon dioxide from power plant exhausts is collected, compressed and pumped into underground chambers, for example old oil reservoirs, and coal seams that are no longer mined.

Figure 27. Geological and sequestration options (Source: Carbon Dioxide Sequestration Project; http://www.sciencebuzz.org/buzz_tags/carbon_se questration)

Mineral carbon artificial sequestration: carbon dioxide is introduced into areas rich in magnesium or calcium. The carbon dioxide will react with those elements to form calcium () and ().

25 For carbon to be sequestered artificially (i.e. not using natural processes of the carbon cycle) it must first be captured, or it must be meaningfully delayed or prevented from being re-released into the atmosphere (by combustion, decay, etc.) from an existing carbon-rich material, by being incorporated into an enduring usage (such as in construction). Thereafter it can be passively stored or remain productively utilized over time in a variety of ways.

Figure 28. Working on pipes carrying liquid carbon dioxide in a power plant in Werder near Berlin (Source: ; http://www.theguardian.com/enviro nment/2010/jun/09/carbon- capture-storage-test-france)

26 If sequestration in wood material, upon harvesting, wood (as a carbon-rich material) can be immediately burned or otherwise serve as a fuel, returning its carbon to the atmosphere, or it can be incorporated into construction on a range of other durable products, thus sequestering its carbon over years or even centuries.

One ton of dry wood is equivalent to 1.8 tons of carbon dioxide. Indeed, a very carefully designed and durable, energy-efficient and energy-capturing building has the potential to sequester (in its carbon-rich construction materials), as much as more carbon than was released by the acquisition and incorporation of all its materials and than will be released by building-function "energy- imports" during the structure's (potentially multi-century) existence. Such a structure might be termed "carbon neutral" or even "carbon negative".

Building construction and operation (electricity usage, Figure 29. Sequestration in wood heating, etc.) are estimated to contribute nearly half of material. the annual human-caused carbon additions to the atmosphere. 27 It must be said that there are main uncertainties and fears about the impact of these approaches on marine and land and the ecological balance of sensitive deep ocean environments. Above all, there are also uncertainties regarding its effectiveness in the long-term storage of carbon dioxide.

Also, artificial carbon sequestration is costly, energy intensive, comparatively untested. At this point, research on the possible dangers of disposing carbon dioxide in such manners is inadequate.

Hence, it may be better if we work on restoring the carbon balance in natural ways, such as through reforestation, reducing our carbon footprint by conserving energy and switching to renewable sources of energy rather than relying on fossil fuels. And we need to do so now, while there is still Figure 30. Artificial carbon storage testing technics (Source: Scottish time Carbon Capture and Storage; SCCS; http://www.sccs.org.uk/education-and-training/downloads) 28 4. Sources http://en.wikipedia.org/wiki/Carbon_sink http://en.wikipedia.org/wiki/Biosequestration http://www.grida.no/publications/rr/natural-fix/page/3725.aspx http://global.britannica.com/EBchecked/topic/586555/temperate-forest http://www.colorado.edu/geography/blanken http://www.all-recycling-facts.com/carbon-sequestering.html http://www.thebluecarbonproject.com/the-problem-2/ http://bluecarbonportal.org/ http://en.wikipedia.org/wiki/Seagrass http://en.wikipedia.org/wiki/Posidonia_oceanica http://www.sccs.org.uk/ 29