ASH MAINTENANCE

Use of fly ash in Forestry Plantations & Land Reclamation:

An overview

Photomicrograph made with a Scanning Electron Microscope (SEM): Fly ash particles at 2,000x magnification

At present about 120 coal based thermal power stations in India are producing about 220 million tones of fly ash annually.

It is estimated that fly ash generation may increase to about 500 million tones by 2021-22 and 1000 mt by 31-32

Disposal of such a huge quantity of fly ash poses challenging problems of land use and environmental pollution (50000 ha ash pond).

• More and more fly ash will be produced annually at the rate of 2 tonnes of fly ash per minute at a modern 660 MW capacity generating unit.

Parameters Fly ash Natural Soil

pH 6.0 - 10.0 4.5 – 14.0Specific gravity 1.45 - 2.25 2.55 – 2.75

Bulk density (g/cc) 0.85 - 1.2 1.30 – 1.80

Grain size distribution silt to Silty loam

Varies with soil type

Porosity (%) 45 – 55 20 – 60 Water holding capacity (%)

25 – 40 10 – 45

Electrical conductivity (dS/m)

0.15 – 1.10 variable

Parameters Fly ash Natural SoilSiO2 35 - 65 40 – 65Al2O3 25 - 45 10 – 40TiO2 0.4 -1.8 0.20 – 2.00Fe2O3 0.5 - 6.0 1.00 – 4.00MnO 0.1 - 0.5 0.02 – 0.10MgO 0.01 - 0.5 0.20 – 3.00CaO 0.2 - 8.0 0.50 – 7.00K2O 0.04 - 0.9 0.40 – 0.20Na2O 0.07 - 0.43 0.20 – 3.00L.O.I. 0.2 – 8.0 5 – 16Organic carbon 0.02- 0.20 0.35 - 0.85

Chemical properties of common fly ash and natural soil (%)

Improves soil texture and reduces bulk density. Improves permeability and water holding capacity Improves Improvisation and reduces crust

formation. Enhances root proliferation. Conserves plant nutrients and water. Reduces pest incidence. Provides macro (K, P, Ca, Mg, S) and micro (Fe, Zn,

Cu, Mn, Mo, B) nutrients Part substitution of gypsum (up to about 75% with

fly ash as a substitute for reclamation of in sodic – saline soils

Enhance plant productivity and crop yield

To demonstrate fly ash use in forestry sector especially for raising of nursery, forestry application and restoration of forests, IMMT, Bhubaneswar and OSFDC has demonstrated a project during 2009-2011 at Angul and Talcher forest circle under Forest Dept. of Orissa.

Towards this, pond ash and soil mixtures 0%, 33%, 67% and 100% on v/v basis were filled in 2 kg black polythene bags and trusted quality seeds have sown during Feb.-March, 2009 at Angul and IMMT, Bhubaneswar.

PLANTATION AT RANI PARK, TALCHER

1. Barabati in Sukinda Range:

Plant species- Teak (Approx. 80,000 )

Forest Nursery-In other demonstration at Sukinda nursery approx. 60,000 teak saplings were planted with 50% pond ash (v/v) with soil in poly tubes along with 20,000 control saplings (without ash).

2. Kiajhara in Tamka Range:

Plant species- Teak, Acacia, Radha Chura, Chhattiyan, Karanj, Sissoo, Anwala and Bamboo (Approx. 30,000 )

Treatment details- 0, 25% and 50%(v/v) of fly ash in pits.

*mean of 20 replications

Plant species

July 2009 (Initial height* in cm) Sept. 2013 (Now height* in cm)

Control (No Fly Ash)

25% FA 50% FA Control (No Fly Ash)

25% FA 50% FA

Teak 39.0 38.5 39.5 218.5 228.0 294.0

Acacia 39.5 39.0 37.0 232.0 230.5 241.0

Radha chura

37.5 38.0 38.0 230.0 241.0 266.0

Chhattiyan 37.0 39.5 39.5 268.0 274.0 264.0

Karanj 36.0 35.0 36.5 240.0 284.5 295.0

Shisham 39.0 40.0 39.0 247.5 256.0 274.0

Anwala 40.5 38.5 37.5 222.0 232.4 271.0

*mean of 20 replications

Plant species

July 2009 (Initial girth* in cm) Sept. 2013 (Now girth* in cm)

Control (No Fly Ash)

25% FA 50% FA Control (No Fly Ash)

25% FA 50% FA

Teak 3.0 3.2 3.4 27.5 35.5 42.0

Acacia 2.4 2.5 2.4 17.5 18.0 17.5

Radha chura

3.5 3.0 3.5 35.5 42.5 46.5

Chhattiyan 3.8 3.5 3.6 28.5 32.5 36.0

Karanj 3.5 3.0 3.2 27.0 22.5 26.0

Shisham 2.6 2.5 2.8 28.5 33.0 39.5

Anwala 2.0 2.5 2.4 21.0 27.5 29.5

Cost of transportation of ash to farmers’ fields Lack of awareness on its beneficial use Need to strengthen extension work for fly ash

use in agriculture/forestry Need to increase awareness among

agricultural/forest official in the extension area Need to increase awareness among agricultural

scientists at large and to take up location specific projects

Need to increase policy support to facilitate & promote use of fly ash in this sector

Fly Ash For Degraded Waste

Lands

Degradation type Arable land M ha

Open forest (<40% canopy) M ha

Water erosion (>10 t/ha/yr)  73.27  9.30

Wind erosion (Aeolian)  12.40  -

Chemical degradation  17.45  7.23

Physical degradation  1.07  -

Total  104.19  16.53

Grand total 120.72

Due to its physical and chemical properties resembling field soils, Fly ash has potential to reclaim such areas

Thousand of hac. of wastelands due to strip mining of coal have been effectively reclaimed and stabilized using fly ash at Neyveli, MCL, Talcher, CSTPS, Chandrapur etc.

The microecology and chemistry of soil Physical properties as WHC, BD,

structure Soil texture, aeration, percolation,

water retention capacity of soil Enhances nutrient status by its macro

and micro nutrients (Ca, Mg, Fe, Zn, Mo, S, Se) readily available to crops / vegetation

It’s a potential growth improver and serves as a good fertilizer

It is observed that at all levels of application, fly ash and lime were comparable and significantly increased the pH and availability and uptake of phosphorus, sulphur and exchangeable potassium.

Laboratory studies have shown that alkaline fly ash was chemically equivalent to approximately 20 % of reagent grade CaCO3 in reducing soil pH and supplying Ca to the plants.

Addition of large quantity of slightly acidic fly ash may not alter the pH appreciably but can still increase the available Ca 2+ and Mg 2+. The neutralizing ability of fly ash also depends on its source and extent to which it is weathered.

Role of fly ash in ameliorating the bulk density and consequently the water holding capacity / drainage appears to have a major role in showing the positive ameliorative effects. It may have a major role in the post gypsum treatment level to improve the physical structure which results in higher crop yield right in the first year and there after.

In such a situation fly ash use is also expected to reduce fluoride contamination in the ground water as it is an effective adsorbent of fluoride. Thus, an important environmental problem can be also addressed through fly ash application.

Fly ash has been used for the neutralization of acidic mine spoils and restoration of nutrient balance in alkaline wastelands.

The quantity of fly ash required to reclaim such areas depends upon the pH of fly ash, state of weathering and pH of the land to be reclaimed.

Fly ash acts as alternative to lime for reclaiming the acidic mine spoils. Efficacy of fly ash for treating acidic coal mine spoils was evidenced by the results of a pot culture experiment using Sudan grass (Sorghum sudanens) and Oats (Avena sativa) as indicator crops.

Fly ash can be safely applied in agriculture/ forestry sectors and wasteland management as soil modifier/ conditioner and as a source of liming agent/ essential plant nutrient on sustainable basis.

Crops grown on fly ash amended soil safe for human consumption.

The OB dumps/ abandoned ash ponds successfully reclaimed through plantation of suitable species and various amendments.

Need for more awareness on beneficial use of fly ash.

• Fly ash application in red and black soils resulted in decrease in the bulk density measured three years after application in field.•Fly ash application upto 100 t/ha in red and black soils of the experiment did not show any perceptible change in the radioactivity levels.• Concentrations of heavy metals, did not cross their toxicity limits on application of fly ash; Pb, mercury was below the detection limit • FA significantly affected the green forage yield of sorghum and cowpea in both the soil types. The increase in forage yield due to fly ash use was more pronounced at 50t/ha.

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