On an average, every household uses 330 bottles and jars each year. If the average household recycled all their glass they would save enough energy to:

2. Recycling Conserves the Environment

Recycling your glass saves raw materials from being quarried and then thrown away in rubbish dumps as used bottles and jars. This saves hundreds of thousands of tones of quarrying each year and conserves the countryside for everyone. It takes 1:2 tones of raw materials to make a tone of glass but only 1 ton of cullet.

3. Recycling Cuts Waste Disposal Costs

By weight, glass makes up about 8% of our rubbish. Glass recycling reduces the cost of collecting and disposing of glass mixed in with our rubbish.

4. Recycling Increases Public Awareness of the Benefit of Minimizing Waste

Everyone can help the environment by recycling their glass. Even a small change in behavior has a measurable benefit.

5. Recycling Creates Jobs

Jobs are created by glass collection schemes and at recycling centers which smash and clean recycled glass.

Greys Paper Recycling Industries Limited, Edmonton has a proposal to manufacture "Pavement Blocks" from waste glass and other waste products. The compositions of raw materials for the manufacturing of "Pavement Blocks" will be 30% waste glass, 20% recycled aggregates, 20% flyash and 30% cement. The technology uses a mechanized molding method for producing paving blocks. The method can replace both the fine and coarse natural aggregates by recycled aggregates in making the paving blocks. Using such a method, the mixed materials are molded under a combined vibrating and compacting action so that the requirement for maintaining a workable mix is not as important as that in normal concretes. Only a minimal amount of water is needed to make the mixture fluid enough to be fed into the molding machine. On the top of the blocks, 5-6 mm thick layer of TiO2 (Titanium Di-oxide) will be applied with a binding agent.

This flow chart clearly explains how the post-consumer glass bottles are processed and recycled as an important ingredient in the production of an environmental friendly "Pavement Blocks" and how the used blocks are recycled and reused:

Chemical Properties of TiO2

Titanium dioxide (TiO2) is naturally occurring compound widely used in toothpaste, sunscreen, paint, plastics, cosmetics, and a host of other products. Its unique capacity to absorb UV light without being consumed in the reaction is a primary reason for its inclusion in products such as sunscreen. The molecule has several different structures: anatase, rutile, and brookiet. Anatase is the preferred molecular form for breaking down air pollutants due to its higher photocatalytic reactivity. More information on Titanium dioxide (TiO2) is attached as Annexure 2.

The Photocatalytic Process

Activated by the energy of UV light, TiO2 interacts with water vapor and oxygen to create hydroxyl radicals and superoxide ions which disperse over the surface of the catalyst and react with other substances. Significantly, these radicals and ions oxidize organic compounds such as nitrogen and sulfur oxides, key ingredients of air pollution. The byproducts of the reaction vary depending on what substances are involved, but they are relatively benign. Nitrogen oxides are broken down into nitrates, while organic compounds are turned into carbon dioxide and water. It is this photocatalytic reaction that destroys the molecules of air pollutants, including nitrogen and sulfur oxides, carbon monoxide, and benzene. In the presence of light and air, titanium dioxide (TiO2) breaks down harmful elements into relatively benign molecules such as calcium carbonate and nitrates.

Photocatalysis involving TiO2 is a rapidly developing area in the field of environmental engineering. To improve the efficiency of this process, research has focused on creating nanosized particles with a different atomic structure than the ordinary pigment used in paint. These nanoparticles, which are approximately seven nanometers wide, offer an optimal surface for the photocatalysis of air pollutants. Research is also being conducted to expand the range of light wavelengths and intensities that stimulate the process, to further its use for both exterior and interior applications. Copy of Nitric oxide removal test of photocatalytic paving blocks prepared by the Hong Kong Polytechnic University is attached as Annexure 3.

Environmental Factors Influencing Photocatalysis

Environmental factors, including light wavelength and intensity, relative humidity, temperature, and wind plays an important role in the effectiveness of the photocatalytic process.

The best photocatalytic results are obtained under higher temperatures and light intensities greater than 300 nm. An increased relative humidity (over 30%) in the atmosphere reduces the adhesion of pollutants to TiO2 surfaces. Therefore, a hot summer day with low relative humidity and no wind would provide optimal conditions for reducing air pollution; appropriately, this type of scenario often coincides with high levels of smog. Other factors such as speed of traffic, concentration of air pollutants, and wind direction also influence the reduction rate of pollutants.

TiO2-based products, already well-appreciated for their self-cleaning and antimicrobial properties, also appear to be useful for reducing harmful airborne pollutants. As with all products introduced into the natural and human environment, a cautious approach must be taken. However a growing number of studies and applications have demonstrated a positive impact on our roads and cities, and perhaps on wider-ranging problems such as global warming and acid rain.

Mechanism of Titanium Di-oxide (TiO2):

When titanium dioxide is exposed to ultraviolet radiation from sunlight, it absorbs the radiation and electron excitation occurs. The following reactions then occur on the surface of the titanium dioxide crystals:

Photolysis of water: H2O ? H+ + OH (hydroxyl radical) + e-

O2 + e- ? O2- (a superoxide ion)

The overall reaction is therefore:

H2O + O2 ? H+ + O2- + OH

The hydroxyl radical is a powerful oxidizing agent and can oxidize nitrogen dioxide to nitrate ions:

NO2 + OH ? H+ + NO3-

The superoxide ion is also able to form nitrate ions from nitrogen monoxide:

NO + O2- ? NO3-

The oxidation of NOx to nitrate ions occurs very slowly under normal atmospheric conditions because of the low concentrations of the reactions. The photochemical oxidation with the aid of titanium dioxide is much faster because of the energy absorbed by the coating on the block and also because the reactants are held together on the surface of the block. The reaction using titanium dioxide shows a greater oxidizing power than most other metal-based catalysts.

1. Ultraviolet radiation is absorbed by the titanium dioxide, which causes the photolysis of water into superoxide ions and hydroxyl radicals.
2. Nitrogen oxides react with the superoxide ions and the hydroxyl radicals to form nitrate ions.
3. The nitrate ions are absorbed into the block and form stable compounds.

After a lengthy research period by the Hong Kong Polytechnic University, Air Pollutant Removal Paving Block has been successfully invented. The results demonstrated that air cleaning agent such as titanium dioxide can be incorporated into the technique of producing concrete paving blocks made with local wastes to remove air pollutants such as nitrous oxides (NOx) by at least 20 %.

Mechanism of Decomposition of Air Pollutants Photocatalytic titanium dioxide is energized by UV and accelerates the decomposition of organic particulates and airborne pollutants such as nitrous oxides (NOx). The catalysed compounds break down into oxygen, water, sulfate, nitrate and other molecules that are not harmful to the environment.

It is also being used to reduce air pollution. In one study, photocatalytic paving decomposed 15 percent of the nitrous oxide released by cars traveling the roadway and was more effective, in this regard, than planting trees on both sides of the roadway.

Benefits of Pavement Blocks: