Beneficial uses of fly ash include serving as a raw material in concrete, grout and cement or as a fill material in stabilization projects and road beds. Bottom ash is generally just used as fill or snow control on roads. Around 43% of fly ash in the USA is currently recycled with the largest use by far being the replacement of portland cement.

http://breakingenergy.com/2014/02/18/can-coal-fly-ash-waste-be-put-to-good-use/

I did a work on adsorption of dyes using fly ash and utilizing such spent fly ash for brick manufacture. I compared mechanical properties of raw fly ash and spent fly ash. As an experienced scientist in this field, you may suggest any ideas.

Beneficial uses of fly ash include serving as a raw material in concrete, grout and cement or as a fill material in stabilization projects and road beds. Bottom ash is generally just used as fill or snow control on roads. Around 43% of fly ash in the USA is currently recycled with the largest use by far being the replacement of portland cement.

http://breakingenergy.com/2014/02/18/can-coal-fly-ash-waste-be-put-to-good-use/

Fly ash makes concrete more durable by decreasing its permeability. Fly ash also helps mitigate the heat of cement hydration in large concrete structures like the Wilshire Grand foundation. Environmental benefits include conservation of energy, water and natural resources, as well as significant reductions in greenhouse gas emissions by displacing the manufacturing of cement. http://www.marketwatch.com/story/headwaters-fly-ash-used-in-record-settinglos-angeles-concrete-placement-2014-02-17

About 1% of fly ash is reported to be used in agriculture in India. It is an excellent soil amendment, microbial carrier as well as substrate in composting / vermicomposting. Physico- chemical properties of fly ash improve the soil fertility and crop yield. It is important to remember that-

Always use optimized dosage of fly ash in any crop. The standard dose vary for different crops as well as soils.

Mix fly ash with organic fertilizers in soil.

Use beneficial microorganisms viz. Azotobacter sp., AM fungi etc. to improve the mineralization of fly ash and better absorption of nutrients by plants. Moreover, these microbes reduce toxicity of heavy metals in the plants in case they are present in fly ash or soil.

After field trials for long duration I have obtained significant enhancement in yield as well as quality of onion and grape. As well as application of fly ash with microbes reduced up to 50% chemical fertilizer requirement.

Thanks Dr.Seema Mishra for your R&D effort for utilisation of fly ash.By desilication treatment, the Al2O3/SiO2 molar ratio of coal fly ash could be improved to the range of 1.63–2.0. The desilicated coal fly ash (DSCFA) was enriched in alumina extraction. A processing technology was developed for alumina extraction from the DSCFA with the lime sintering process. Ca/(SiO2+TiO2) molar ratio, and NaO/Al2O3 molar ratio, sintering time, and temperature were the most significant parameters impacting on the aluminum extraction efficiency. The optima aluminum extraction efficiency was obtained under conditions of Ca/(SiO2+TiO2) molar ratio of 2.0, NaO/Al2O3 molar ratio of 0.98, and sintering at 1 200 °C for 60 min. A standard industrial dissolution method was used under conditions of caustic ratio (αk=n(NaO)/n(Al2O3) of 2.0, Al2O3 concentration of 50 g/L, sodium hydroxide concentration(Nk) of 60.78 g/L, Na2CO3 concentration of 10 g/L, temperature of 85 °C, and dissolution duration of 10 min. The final aluminum extraction efficiency was 90%.http://www.sciencedirect.com/science/article/pii/S1003632610600349

It is saying that Fly ash can be used as fertilizer in agriculture sector. Once I attended the workshop of Fly Ash Mission formed by DST, Govt. of India in New Delhi. There few scientists reported the use of fly ash in agriculture. They showed that particular %age of fly ash addition in soil improves the crop yield and the heavy metal content of fly ash did not affect the crop germination and growth. But they failed to answer that how much amount (%age) of fly ash should be added every year as a fertilizer as plants can not take up all the fly ash or/and fly ash can not be degraded itself (as NPK fertilizer degrades).

Sir, would you please comment on the question that how much fly ash can be added to soil every year as fertilizer? Can one estimate the residual fly ash in soil?

Thanks and Regards.

Thanks.Crops grown in quantities of fly ash ranging from 5 to 20 percent of soil weight absorbed toxic metals, according to a study by Indiana State University researchers.Please see details in the link provided.http://www.scientificamerican.com/article/coal-ash-in-soil/

Respected Dr. Sukla,

Thanks for your reply and really a nice answer (link) you provided. Amazing that use of fly ash (1.1%) increased the crop growth by 70% and no groundwater contamination had been observed. Still researchers practising same but they are unanswered that every year how much we can use fly ash every year as they also admit that regular use may cause accumulation of metals in plants that prove harmful to humans.

If you can get any other information regarding this, please let me know. I will be very thankful to you. Regards.