The ash residue is a basic of combustion or incineration of organic matter , and by extension products such as coal , the lignite or various waste burned in incinerators, open air or in fireplaces or stoves.

The volcanic ash , "natural" are deemed fertile for farming.

Composition

The composition of the ash burned varies by product and by its origin.

Wood ash

Ash composition varies depending on many parameters, which are essentially the burned plant species, plant parts (bark, trunk, or twigs for example), soil type, and the period of the year in which these Plants were harvested.

The ashes of wood are generally rich in potash , while those herbs are rich in silica.

Can be considered as non-organic elements which constitute the wood ashes are mostly bases low with 25 to 50% lime ( calcium oxide ^{Ash from incineration}

The ashes and other residues from incineration, and carbocendres (coal ash) from individual facilities or industrial (incinerators, power plants ..) often contain numerous toxic substances (carbonaceous residues, heavy metals and traces of radionuclides .. ) Uses

Fertilizers and Amendment

We used the ashes as fertilizer (for their wealth in minerals and trace elements ) or amendment (a shovelful of ashes per m ² can refill the soil minerals). Wood ashes have great power alkalizing due to their high content of lime and potash. They act quickly on the pH of the soil, but their effect is short lived at that level. For cons, the intake of trace elements contained in the ash can be significantly more durable, as long as the cultures are not too intensive.

They should be incorporated into the soil or compost in spring, according to the needs of your soil and crops that you are going to perform. Some laboratories offer analysis of your soil to determine the amendments to be carried out, in the form of fertilizers , for agricultural lime or ashes.

The ashes can bring many minerals needed for plant growth, but the ashes should not be the only source of soil amendment, since they contain no nitrogen. To achieve the organic in a plot on which ashes were scattered, it is possible to enrich the soil with nitrogen compounds through the burial of organic matter produced by plants legumes such as alfalfa or clover to plant the following year to plant high nitrogen requirements.

Wood ashes are highly soluble and saline. Excessive amounts of salts in the soil inhibits plant growth and often causes the death of microorganisms. Moreover, by their nature very alkaline (like lime), the ashes can significantly alter plant parts with which they have been contacted directly.

To gradually increase the pH from 0.3 to 0.4 units (example: to get the pH from 6.2 to 6.5): 10 kg / 100 m ^2.

To maintain the pH, once the desired value reached 5 kg / 100 m ^2.

In calcareous soil, it is best to avoid or limit intake to a shovelful of ashes to 5 m ^2.

"He who sows potash crop en masse saying goes. Indeed, the potash content of the ash does not promote growth of plants (this is the role of nitrogen ) but makes it quite beneficial to the development of flowers and fruits such as beets , beans , potatoes , cereals particularly intensive potash.

Because of the presence of calcium, it is preferable not to use the ashes on the mountains of acid-loving plants planted in peaty soil or on seed. When in doubt, you can throw it in small doses to compost will enrich it (too high doses devastate the lives bacterial and fungal necessary for the maturation of compost).

Repeated application of large amounts of ash that you do not know fully the origin (kind of burned products used to train them) can also lead to accumulation of toxic elements ( lead , cadmium ) in soil and pollute the assimilation of minerals by plants. It is therefore recommended that this amendment in moderation, especially if you do not know what was burned to give these ashes.

Other use in the garden: when we want away slugs and snails , they spread the ashes in high proportions in areas they frequent. They do not cross this barrier that dries them drool. To be repeated in case of rain.

Detergent

Some ashes were in the past used to make a kind of soap.

Their black and salt content and sometimes slag has long been used against the ice until the salt is readily available.

Public Works

It uses the ashes of burning thermal power plants in the manufacture of concrete or in the treatment of serious , as partial replacement of cement in concrete, with the addition of lime as binder hydraulic bass.

The ash may also be present in animal feed (dry food, seeds for rodents). It is preferable that the rate is less than 10%.

Ash cleaner

Incinerator ash are less polluted than Refioms theoretically going to landfill, but they nevertheless contain heavy metals that were present in the wood waste burned, unburned and various chemicals as pollutants that are formed by recombining at incineration. During episodes of malfunctioning incinerators, ash quality can significantly worsen.

The vapors from crematoria can also be polluted with dioxins, but also by heavy metals that the mercury lost by dental fillings during cremation.

The ashes of coal-fired plants have accumulated large slag heaps since the ^nineteenth century. They were originally to flights of dust and fine particles called "fly ash".

In North America, the storage pool is sometimes performed in order to limit takeoffs, but not without risk to groundwater or surface water in case of embankment failure (and December 22, 2008, the storage pond ash plant Electric Kingston (Tennessee) broke, releasing about 4 million m ³ of mud polluted by the arsenic from mercury , the selenium of lead and radon radioactive) water near the site analyzed by ' EPA contained levels of arsenic (a carcinogen) in excess of 100 times the acceptable level.

In France, in the years 1990 to 2000, incinerators and thirty coal-fired power plants still in service (about 4% of the country's electricity by 19 coal plants in 2009) produced a large amount of ash. These dumps are theoretically followed by DRIRE (1996 circular on coal ash), now included in DREAL , and by the ADEME (for orphan sites, or certain aspects of air pollution).
On 5 April 2000, the Independent National Clearinghouse on Waste (CNIID) has warned about a report by the Department of the Environment in 1997 recognizing contamination of incinerator ash by the dioxins.
In 2009, a study by J. Bonnemain ^, for the Nuclear Safety Authority ( ASN , which reiterates that the ash deposits (often forgotten or scattered as building and construction materials) often contain not only dioxins but also of thorium or of the uranium radioactive that were concentrated in the ash, which have become mobile and bioavailable as released from coal combustion process. Bonnemain J. believes that these deposits should be secured, monitored, or confined, while many have been scattered and some are still visited by practitioners of motocross of ATVs , by hikers, mushroom pickers or hunters (the game may then be contaminated). The study also points out that the deposits unprotected takeoffs result in environmental contamination and runoff. The bioturbation by burrowing animals (rabbits, moles, and small mammals, earthworms or even birds that can dig their burrows: Example: Swallows ( Riparia riparia digs its nest in a gallery of about 60 cm deep in the micro-sand cliffs), a colony of swallows had settled into the slag heap of the old coal plant to EDF Pont sur-Sambre , on the banks of the Sambre and a wetland. These plants are often located along a canal or river, which facilitates water pollution by fly ash or ash runoff.
For French law, these deposits are "related facilities" power plants, and should be a simple statement. They are managed (or should be) by the operator of the power plant, even after shutdown). The Ministry of Ecology acknowledges that "the monitoring radiation , including water quality surrounding a radiologically is the missing link "for the environmental assessment and monitoring of the impacts of coal ash.

In France, the Minister of Ecology in 2009 called Prefects to implement control measures around the sites of radioactive waste, including waste dumps to "enhanced natural radioactivity" (ash, phosphogypsum .. .). This initial survey will guide the state policy regarding the risks associated with coal ash which in 2009 were still produced by hundreds of thousands of tonnes annually, with 19 coal plants (15 for EDF and 4 for the SNET ) that France needs to offset that nuclear power can provide peak. Much of the French deposits has been sold or offered for construction ( excavation / backfill trenches or road improvements, including in the cement or concrete , or as fill material for various road and rail ( TGV Est example ). Bonnemains J., author of a study done for the DSC considers necessary a better control of coal ash, which he says requires "the creation of an external structure for producers to monitor longitudinal contradictory ".

Since the early 1980s, incinerator ash or slag from thermal power supply sometimes heated controversy, particularly because of their contents of heavy metals and dioxins. According to Greenpeace , a commercial incinerator, standards, medium-sized burns 32,000 tons of waste, some of which inevitably contain lead , the cadmium , the arsenic from mercury and chromium , emitting (circa 2000) 92 tons of metals in the air per year and producing about 304 tons / year of ash and effluents.

Also in France, where incineration has been developed, a circular of May 1994 prohibits the use "within 30 m of a watercourse, but the ash since then generally considered" recoverable "in road work elsewhere or in cement. The decree also imposing no special precautions for construction equipment. The layer of bitumen is expected to reduce the risk of leaching , but many roads are flooded or periodically in contact with the ceiling of the aquifer. The CNIID For example, criticized the incinerator Tronville have provided large amounts of ash from municipal waste and hospital in a "pilot site" which has contaminated forest roads. In Britain , the incinerator Pluzunet offered his ashes to farmers to make fertilizer. According to ORDIF - Observatoire Regional Waste Ile-de-France region has produced hundreds of thousands of tons of ash, much of which has been "recycled" in the bottom layer of road. Some incinerators like Sete then had huge dumps of ash, part of which flew in the wind or is washed out by rain. EDF has estimated 2006 production of 400 000 to 800 000 t / year of ash (excluding those of the National Electricity Company and thermal (SNET), which operates four plants still load up in France) and remains 9 million tonnes of stock from the former French coal power plants. Many industries ( stationery , cement , glass ) have also previously used the generalization of gas and coal produces large amount of ash released into the environment or stored in old landfills internal unsupervised. BRGM in 2000 concluded that "with the exception of bottom ash from waste incineration, the available data on the detailed characterization of residues

Cultures and religions

In countries where the cremation of dead bodies is practiced various rituals involve the ashes of the dead, which in some tribes were for example parts eaten by the family. Coat the hair or skin with ashes as a sign of mourning or to other regions seems to have been a common ritual. Catholics are still the Ash Wednesday.

References

See also

Related articles

Bibliography

• Report "The coal ash and phosphogypsum" , Robin Hood / Nuclear Safety Authority, January 2009
• Introductory summary of the report "The coal ash and phosphogypsum" 'on the ASN website (accessed 2009 11 03)

External Links

• Incineration, Environment and Health, Greenpeace
• Health impacts of waste management, by ADEME
• List of incinerators in operation by ADEME

• Chemistry portal
• Portal environment and sustainable development

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