- Fly Ash
Fly ash is a fine powder which is a byproduct from burning pulverized coal in electric generation power plants. Fly ash is a pozzolan, a substance containing aluminous and siliceous material that forms cement in the presence of water. When mixed with lime and water it forms a compound similar to Portland cement. The fly ash produced by coal-fired power plants provide an excellent prime material used in blended cement, mosaic tiles, and hollow blocks among others.
Fly ash can be an expensive replacement for Portland cement in concrete although using it improves strength, segregation, and ease of pumping concrete. The rate of substitution typically specified is 1 to 1 ½ pounds of fly ash to 1 pound of cement. Nonetheless, the amount of fine aggregate should be reduced to accommodate fly ash additional volume.
Fly Ash Applications
Fly ash can be used as prime material in blocks, paving or bricks; however, one the most important applications is PCC pavement. PCC pavements use a large amount of concrete and substituting fly ash provides significant economic benefits. Fly ash has also been used for paving roads and as embankment and mine fills, and it’s gaining acceptance by the Federal government, specifically the Federal Highway Administration.
Fly Ash Drawbacks
Smaller builders and housing contractors are not that familiar with fly ash products which could have different properties depending on where and how it was obtained. For this reason, fly ash applications are encountering resistance from traditional builders due to its tendency to effloresce along with major concerns about freeze/thaw performance.
Other major concerns about using fly ash concrete include:
- Slower strength gain.
- Seasonal limitation.
- Increase in air entraining admixtures.
Fly Ash bricks
Pulverised ash brick (PAB) technology is a process of converting industrial waste materials into quality building materials. At present, the technology is well established in converting thermal power plant waste into quality bricks. PAB technology uses dry ash (fly ash collected from ESP or silos of thermal power plants); filler materials (usually coarse sand or stone crusher dust); and additives (lime, gypsum or cement). The strength of the bricks can be engineered by varying compositions. Equipment used can be manual or mechanised. Mechanised machines deploy hydraulic compaction to produce a variety of bricks and can be operated through electric or diesel power.
The Ministry of Environment and Forests issued directives for proper utilisation of fly ash discharged from coal or lignite-based thermal power plants. The importance for restricting the excavation of top soil for manufacture of bricks and promoting the utilisation of fly ash in the manufacture of building materials and in construction activity was recognised. It was notified that within a radius of 100 km from a coal or lignite-based thermal power plant, all brick making units must compulsorily utilise 25% of fly ash (by weight).
The highlights of the notification was
- Use of fly ash, bottom ash or pond ash in the manufacture of bricks and other construction activities.
- a) Within a radius of 100 km from coal or lignite based thermal power plants, no person shall manufacture clay bricks,
- b) Tiles or blocks (for use in construction activities) without mixing at least 25% of ash with soil on weight basis.
- c) The authority for ensuring the use of specified quantity of ash shall be the concerned Regional Officer of the State Pollution Control Board. In case of non-compliance, the authority (in addition to cancellation of consent order issued to establish the brick kiln) shall move the district administration for cancellation of the mining lease. To enable the authority to verify the actual use of ash, the thermal power plant shall maintain monthly records of ash made available to each brick kiln.
- Availability of fly ash for brick making
- a) Every thermal power plant shall make available ash, for at least ten years without any payment or any other consideration for the purpose of manufacturing ash-based products.
- b) Central and State Government Agencies, State Electricity Boards, NTPC and the management of the thermal power plants shall facilitate in making available land, electricity and water for manufacturing activities and also provide access to the ash lifting area. This will promote and encourage setting up of ash-based production units proximate to the area where ash is generated by the power plant.
- Specifications for use of ash based products
- a) Every construction agency engaged in the construction of buildings within a radius of 100 km from thermal power plants shall use fly ash bricks in construction projects. It shall be the responsibility of the construction agencies (either undertaking the construction or approving the design or both) to ensure compliance.
Environmental Impacts of Concrete
- Making cement results in high levels of CO2 output.
- Cement production is the third ranking producer of anthropogenic (man-made) CO2 in the world after transport and energy generation.
- 4 – 5% of the worldwide total of CO2 emissions is caused by cement production.
- CO2 is produced at two points during cement production:
- the first is as a byproduct of burning of fossil fuels, primarily coal, to generate the heat necessary to drive the cement-making process.
- the second from the thermal decomposition of calcium carbonate in the process of producing cement clinker.
- Production of one tonne of cement results in 780 kg of CO2.
- Of the total CO2 output, 30% derives from the use of energy and 70% results from decarbonation.
An indicator species is an organism whose presence, absence or abundance reflects a specific environmental condition. Indicator species can signal a change in the biological condition of a particular ecosystem, and thus may be used as a proxy to diagnose the health of an ecosystem. For example, plants or lichens sensitive to heavy metals or acids in precipitation may be indicators of air pollution. Indicator species can also reflect a unique set of environmental qualities or characteristics found in a specific place, such as a unique microclimate. However, care must be exercised in using indicator species.
Indicator species are an appealing research and monitoring tool. A conservation practitioner can use an indicator species as a surrogate for overall biodiversity, monitoring the outcomes of management practices by measuring the rise or fall of the population of the indicator species. River otters have been used as indicators of healthy, clean river systems. In the humid mountain forests of Mexico, many peaks harbor a distinct species of arboreal lizard. The health of these unique tree-dwelling lizard populations is used an indicator of the health and biodiversity of the natural communities in the region. Similarly, maidenhair ferns are known to grow in rich northern hardwoods throughout New England, but a subspecies of maidenhairs that are found only in sites with serpentine mineral soil is an indicator of a specific substrate.
Indicator species are a useful management tool, and can help us delineate an ecoregion, indicate the status of an environmental condition, find a disease outbreak, or monitor pollution or climate change. In one sense, they can be used as an “early warning system” by biologists and conservation managers. Indicator species must also be accompanied by a thorough study of what is being indicated, what is really correlated, and how this one species fits into the rest of ecosystem.
Photochemical smog is a major contributor to air pollution. The word “smog” was originally coined as a mixture of “smoke” and “fog” and was historically used to describe air pollution produced from the burning of coal, which released smoke and sulfur dioxide. While air pollution caused by burning coal has become less common, the combustion of fossil fuels continues to affect air quality.
Both the primary and secondary pollutants in photochemical smog are highly reactive. These oxidizing compounds have been linked to a variety of negative health outcomes; ozone, for example, is known to irritate the lungs. Smog is a particular health danger in some of the world’s sunniest and most populated cities, which are typically sunny, and the sun reacts with the chemicals produced by cars and other industrial processes. Smog can also affect areas of the country that are sunny less frequently, such as New York City. In fact, most major cities have problems with smog and air pollution.
Environmental Concerns of PET Bottles
Plastic bottles contain Bisphenol A (BPA), the chemical used to make the plastic hard and clear. BPA is an endocrine disruptor which has been proven to be hazardous to human health. It has been strongly linked to a host of health problems including certain types of cancer, neurological difficulties, early puberty in girls, reduced fertility in women, premature labour, and defects in newborn babies – to name a few examples.
BPA enters the human body through exposure to plastics such as bottled drinks and cleaning products. It has been found in significant amounts in at-risk groups such as pregnant women’s placentas and growing foetuses. A study conducted last year found that 96% of women in the U.S have BPA in their bodies.
Bottled drinks also contain phthalates, which are commonly used in the U.S. to make plastics such as polyvinyl chloride (PVC) more flexible. Phthalates are also endocrine-disrupting chemicals that have been linked to a wide range of developmental and reproductive effects, including reduced sperm count, testicular abnormality and tumors, and gender development issues. The fact is that phthalate concentration increases the longer a plastic water bottle is stored, or the fact that a bottled drink that is exposed to heat causes accelerated leaching of harmful plastic chemicals into the drink.
In addition to the negative impacts of BPA and phthalates on human health there are also growing concerns regarding carcinogens and microbial contaminants that have been found in test samples of bottled water. Bottling plants also cause problems for the humans who live near them. Water extraction surrounding bottling plants involved millions of gallons of water to make the bottles. This often leads to local water shortages that affects nearby residents, especially farmers who need to provide food for the surrounding neighborhoods.