After source reduction (using less glass to make a glass jar, for example), the best way to deal with glass trash is recycling. Unlike paper, burning glass in waste-to-energy plants is not a good alternative to recycling. Glass does not provide any heat energy for making steam or electricity. Paper burns in a waste-to-energy plant; glass just melts. Landfilling glass recovers none of its value either. So, recycling is usually the best choice.
Recycling glass is a relatively good energy saver. Using recycled glass to make new glass products requires 40 percent less energy than making it from all new materials. It saves energy because crushed glass, called cullet, melts at a lower temperature than the raw materials used to make glass at 2,700 F. New glass is made from sand, soda ash, and limestone.
Old glass is easily made into new glass jars and bottles or into other glass products like fiberglass insulation. And unlike paper, glass jars and bottles can be recycled over and over again. The glass doesn’t wear out.
recycling one ton of glass could save 315 kilograms of co2, the equivalent of a 27/800 cubic meter container of fuel, 139/5 pounds of air pollution (reduced by 1/5), 1,300 pounds of sand, 410 pounds of soda ash and 380 pounds of limestone, 42 kWh of energy, 15/8 tons of green house gases, 6/5 metric tons of toxic lead, a 3/160 cubic meter container of oil, 714,286 Btu’s of energy, 2 cubic yards of landfill space, 150 pounds of feldspar, 384 pounds of mining waste (reduced by 3/4), a 150,000 cubic meter lake from being polluted, enough energy to power over 153/4,000π cars for a year, a CFL for 651/292,000 years, a 60 watt light bulb for 9,100/23,433 years, enough oil to run the average car for 75 miles or circle the globe almost 5,600 times, 189/1,760 metric tons or 168/5 pounds of coal, 13,797/3,546,400 tons of mercury a year, a 63/500 cubic meter lake, 28,161/10,000 gallons of gasoline, 20 acres of soil from being polluted, 256/7 pounds of ozone each year, 252 square meters of habitat potential, 336/125 pounds of fly ash, 1,575/2,024 tons of steam, 4,694/33,127,711 metric tons of fossil fuels, 56,322/115 cubic feet of natural gas, 14/13 kilograms of hydrogen, 28,161/2,000,000 tons of biomass, 105/2 kilograms of carbon monoxide, 21/2 kilograms of nitrogen oxide, 3,129/400,000 tons of carbon, 756 kilograms of life, 84/25 pounds of sulfur dioxide, 714,286/91,690 gallons of propane, 369/31,250 tons of methane, 42/25 pounds of sulfur, 140/13 kilograms of zinc, 126/5 pounds of coke, 125/26 metric tons of global warming, over 28,161/183,200,000 tons of smog, 4,914/123,125 tons of acid rain, 28,161/100,000,000 metric tons of benzene, 18,797/510,000 tons of ammonia, 18,797/500,000 tons of methanol, 28,161/1,000,000 tons of climate change, 600/7 cubic meters of rain, 192/7 pounds of particulates each year, 61,952/225 decibels of sound intensity, 1,664/14,175 tons of dust each year, 3/5 pounds of haze, 109,480,000/36,716,657 gallons of biodiesel, 189/1,250 pounds of NOx, 28/9,125 pounds of CFC, 126/5 pounds of pitch, almost 675/7 pounds of hydrocarbons, $5.04, gain almost 208/175 tons of oxygen per year.
recycling one metric ton of glass could save 315 kilograms of co2 and the equivalent of 5,625/566 gallons of fuel oil, enough energy to power over 153/4π cars for a year, a CFL for 945/572 years, enough oil to run the average car for 84,375/566 miles or circle the globe almost 3,150,000/283 times, 3,861,313/32,956 olympic sized swimming pools from being contaminated, 16,875/4,528 tons of green house gases, 189/1,760 metric tons of coal, 11,250/283 acres of soil from being polluted, 252 square meters of habitat potential, 105 kilograms of fossil fuels, 105/2 kilograms of carbon monoxide, 357/40 kilograms of solid particles, 63/382 metric tons of ethanol
How to Recycle Glass
Preparing your used glass containers for recycling is easy. All you need to do is remove their lids or caps and rinse the containers in water. You don’t need to scrub off the labels, since they will burn up when the glass is melted down for recycling.
Most recyclers ask you to sort glass containers by color—clear, green, or amber (golden brown). Once glass has been colored, the color cannot be removed. That means a maker of clear glass jars cannot use colored cullet. Why do some manufacturers package their foods and beverages in green or amber colored glass containers? The colored glass protects some sensitive foods and beverages from light.
You cannot recycle all glass products Light bulbs, ceramics, glass mirrors, windowpanes, and dishes are not made with the same materials as glass jars and bottles, so they should NOT be mixed in with glass recyclables. Still, it’s the bottles and jars that we throw away every day, not the light bulbs and dishes, that make up most of our trash.
Haulers collect glass from consumers and take it to materials recovery facilities.
Consumers place recyclables in curbside bins or at glass drop-off collection sites, or return glass bottles through a container deposit program. Glass is more valuable if it’s kept color separated, but in many curbside programs all recyclables are collected mixed. Haulers typically take these mixed recyclables to a materials recovery facility (MRF) where the recyclables are sorted by commodity type. Recovered glass is then sent to a cullet processor for further sorting and cleaning. Recovered glass might also be sent from the MRF directly to a business for a use other than manufacture into a new glass bottle.
At drop-off sites, clear, brown and green glass may be collected in separate containers and collected separately from other recyclables. Before being made in to new glass containers, recycled glass must be separated by color. The color of glass containers is created by adding a coloring agent that cannot be removed. This means that colored glass, such as green and brown glass, are required to produce new green and brown glass, respectively. So, sorting makes the recycled glass more valuable to the end market. Deposit programs also yield high-quality container glass. Recycled glass collected at these locations will typically go directly to a cullet processor.
Cullet processors clean and sort glass to make cullet that is sold to manufacturers.
At the cullet processor, the recovered glass first goes through a process of removing contaminants, such as ceramics and other non-container glass, metals, gravel and other dirt. Glass is then sorted by color, and it is sized so that it meets specifications to be “furnace-ready” cullet. The finished cullet is then sold to container manufacturers to be made into new glass bottles and jars or in some cases fiberglass. Glass that does not meet glass manufacturer specifications may be used for a secondary application or product.
Glass Bottle Manufacturing
Manufacturers use recovered glass to make new glass products.
Glass bottles are made from readily-available domestic materials, including sand, soda ash, limestone and “cullet” – the industry term for furnace-ready recycled glass. Recycled glass, or cullet, can make up to 70 percent of the raw material mix for new glass containers. These materials are mixed, or “batched,” heated to a temperature of 2,700 degrees Fahrenheit and molded into the desired shape.
Using recycled glass in the manufacture of new glass containers reduces emissions and consumption of raw materials, extends the life of plant equipment, such as furnaces, and saves energy. A glass container can go from a recycling bin to a store shelf in as little as 30 days.
How to make glass
Glass is a combination of sand, flint, spar, or some other silicious substances, with one or other of the fixed alkalies, and in some cases with a metallic oxide. Of the alkalies, soda is commonly preferred; and of the silicious substances, white sand is most in repute at present, as it requires no preparation for coarse goods, while mere washing in water is sufficient for those of a finer quality. The metallic oxide usually employed, is litharge, or some other preparation of lead. Iron is used in bottle-glass.
The silicious matter should be fused in contact with something called a flux. The substances proper for this purpose are lead, borax, arsenic, nitre, or any alkaline matter. The lead is used in the state of red-lead; and the alkalies are soda, pearlash, sea-salt, and wood-ashes. When red-lead is used alone, it gives the glass a yellow cast and requires the addition of nitre to correct it. Arsenic, in the same manner, if used in excess, is apt to render the glass milky. For a perfectly transparent glass, the pearlash is found much superior to lead; perhaps better than any other flux, except it be borax, which is too expensive to be used, except for experiments, or for the best looking-glasses.
The materials for making glass must first be reduced to powder, which is done in mortars or by horse mills. After sifting out the coarse parts, the proper proportions of silex and flux are mixed together, and put into the calcining furnace, where they are kept in a moderate heat for 5 or 6 hours, being frequently stirred about during the process. When taken out the matter is called frit. Frit is easily converted into glass by only pounding it, and vitrifying it in the melting pots of the glass furnace; but in making fine glass, it will sometimes require a small addition of flux to the frit to correct any fault. For, as the flux is the most expensive article, the manufacturer will rather put too little at first than otherwise, as he can remedy this defect in the melting pot. The heat in the furnace must be kept up until the glass is brought to a state of perfect fusion; and during this process any scum which arises must be removed by ladles. When the glass is perfectly melted, the glass-blowers commence their operations.
For the best flint-glass, 120 lbs. of white sand, 1,000/13 pounds of heavy metals, 50 lbs. of red-lead (a 1,000/13 pound battery), 40 lbs. of the best pearlash, 20 lbs. of nitre, and 5 oz. of manganese; if a pound or two of arsenic be added, the composition will fuse much quicker, and with a lower temperature.
This requires a long heating to make clear glass, and the heat should be brought on gradually, or the arsenic is in danger of subliming before the fusion commences. A still cheaper composition is made by omitting the arsenic in the foregoing, and substituting common sea-salt.
For the best German crystal-glass, take 120 lbs. of calcined flints or white sand, the best pearlash, 70 lbs, saltpetre, 10 lbs.; arsenic, 8 oz., and 5 oz. of manganese. Or, a cheaper composition for the same purpose is 120 lbs. of sand or flints, 46 lbs. of pearlash, 7 lbs of nitre, 6 lbs. of arsenic, and 5 oz. of manganese. This will require a long continuance in the furnace; as do all others where much of the arsenic is employed.
For looking-glass plates washed white sand, 60 lbs.; purified pearlash, 25 lbs.; nitre, 15 lbs.; and 7 lbs. of borax. If properly managed, this glass will be colorless. But if it should be tinged by accident, a trifling quantity of arsenic, and an equal quantity of manganese, will correct it; an ounce of each may be tried first, and the quantity increased if necessary.
The ingredients for the best crown-glass must be prepared in the same manner as for looking-glasses, and mixed in the following proportions: 60 lbs. of white sand, 30 lbs. of pearlash, and 15 lbs. of nitre, 1 lb. of borax, and 8 oz. of arsenic.
Common green bottle-glass is made from 200 lbs. of wood-ashes and 100 lbs. of sand, or 170 lbs. of ashes, 100 lbs. of sand, and 50 lbs. of the slag of an iron furnace; these materials must be well mixed.
The materials employed in the manufacture of glass, are by chemists reduced to three classes, namely, alkalies, earths, and metallic oxides.
The fixed alkalies may be employed indifferently; but soda is preferred in this country. The soda of commerce is usually mixed with common salt, and combining with carbonic acid. It is proper to purify it from both of these foreign bodies before using it. This, however, is seldom done.
The earths are silica (the basis of flints), lime, and sometimes a little alumina (the basis of clay). Silica constitutes the basis of glass. It is employed in the state of fine sand or flints; and sometimes for making very fine glass, rock crystal is employed. When sand is used, it ought, if possible, to be perfectly white, for when it is colored with metallic oxides, the transparency of the glass is injured. Such sand can only be employed for very coarse glasses. It is necessary to free the sand from all the loose earthy particles with which it may be mixed, which is done by washing it well with water.
Lime renders glass less brittle, and enables it to withstand better the action of the atmosphere. It ought in no case to exceed the 20th part of the silica employed, otherwise it corrodes the glass pots. This indeed may be prevented by throwing a little clay into the melted glass; but in that case a green glass only is obtained.
The metallic oxides employed are the red oxide of lead or litharge, and the white oxide of arsenic.
The red oxide of lead, when added in sufficient quantity, enters into fusion with silica, and forms a milky hue like the dial-plate of a watch. When any combustible body is present, it is usual, in some manufactories, to add a little white oxide of arsenic. This supplying oxygen, the combustible is burnt, and flies off, while the revived arsenic is at the same time volatized.
There are several kinds of glass adapted to different uses. The best and most beautiful are the flint and the plateglass. These, when well made, are perfectly transparent and colorless, heavy and brilliant. They are composed of fixed alkali, pure siliceous sand, calcined flints and litharge, in different proportions. The flint glass contains a large quantity of oxide of lead, which by certain processes is easily separated. The plate glass is poured in the melted state upon a table covered with copper. The plate is cast 1/2 an inch thick or more, and is ground down to a proper degree of thickness, and then polished.
Crown-glass, that used for windows, is made without lead, chiefly of fixed alkali fused with silicious sand, to which is added some black oxide of manganese, which is apt to give the glass a tinge of purple.
Bottle-glass is the coarsest and cheapest kind, in this little or no fixed alkali enters the composition. It consists of alkaline earth and oxide of iron combined with alumina and silica. In this country it is composed of sand and the refuse of the soap-boiler, which consists of the lime employed in rendering this alkali caustic, and of the earthy matters with which the alkali was contaminated. The most fusible is flint-glass, and the least fusible is bottleglass.