turn waste into treasure
Solid waste has distinct temporal and spatial characteristics, and it is a resource placed in the wrong place at the wrong time. If handled properly, waste can be turned into treasure.
According to the British "Times" report, the British Southern Water Treatment Company extracted and manufactured two kinds of gems from sewage sludge, one of which was light dark gray and embedded in a silver ornament similar to agate and pearl; The other one is brown and decorated with a gold pin. The company has held talks with the sales manager of Ratner, a British jewelry company, about selling this gem. In the near future, people will see this beautiful and unique gem in shops.
Facts have proved that with the development of science and technology and the enhancement of people's awareness of environmental protection, garbage and other "three wastes" (waste, waste gas and waste water) are no longer a burden, but a valuable wealth. Countries began to "recycle" it, turning waste into treasure and recovering "available resources" from it, which achieved considerable economic and social benefits.
For example, 1988, the income of the waste recycling industry in the United States is $4.8 billion, and 1989 has increased to $6 billion. China has recovered 250 million tons of renewable resources from various wastes in the past 40 years, with a value of 72 billion yuan.
For a long time, the methods of garbage disposal in various countries are open-air stacking, enclosure, landfill, incineration and biodegradation. According to American experiments, burning 1 ton of garbage can generate about 525 kwh of electricity, reducing the amount of garbage by 75% ~ 90%. Therefore, many developed countries have established many garbage power plants. At present, there are about 160 in the United States, and there are more than 100 under construction or planning. 1990, Japan spent1.4000 yen on garbage disposal. Tokyo plans to reorganize and open the garbage disposal site within three years. At present, there are 1 800 waste incineration plants in Japan, of which only 90 can generate converted energy, and only 4 1 will sell the generated waste energy to power companies.
However, most of these methods are limited by various factors, which will cause secondary pollution in the treatment process. The European Commission estimates that 520 waste incineration plants in 12 member countries emit 25,000 tons of dust, 570 tons of lead, 144 tons of hydrogen oxide, 68 tons of mercury and 3 1 ton of cadmium every year, which seriously pollutes the ecological environment. Therefore, people began to explore the comprehensive utilization of garbage.
Waste materials, such as waste in people's lives and waste produced in the production process, have always been an important cause of environmental pollution, and people regard it as an important burden. In fact, waste materials are a "treasure". As long as they are collected, processed and recycled, they can become social wealth, which not only saves natural resources, but also prevents public hazards.
According to the British weekly New Scientist, researchers at the University of Nottingham found that it takes three times as much energy to make new plastic bags as to recycle them, that is, it takes1/kloc-0.06 billion joules to make new polyethylene plastic bags, while recycling plastic bags with the same weight only consumes 35.3 billion joules of heat. Moreover, manufacturing 1 ton plastic bags produces 4034 kilograms of carbon dioxide, and recycling 1 ton plastic bags only produces 1773 kilograms of carbon dioxide; The water consumption of the former is 143.9 tons, and that of the latter is 16.8 tons, which is 8 times that of the latter. The sulfur dioxide produced by manufacturing 1 ton of new plastic bags is 6 1 kg, and only18kg is recovered; The former produces nitrogen oxides 2 1 kg, while the latter produces 9 kg. Recycling 1 ton plastic bags also saves 1 .8 tons of fuel than manufacturing1ton new plastic bags.
In order to facilitate comprehensive utilization, all countries classify and recycle waste materials. When Swedes take out the garbage, they throw glass bottles into grass-green tin cans. Discarded batteries are thrown into a battery-shaped iron pipe on the roadside; Scrap iron was thrown into a special container; Waste paper is bundled and delivered regularly. In the United States, garbage is divided into recyclable and non-recyclable, and piled up on the side of the road waiting to be taken away; There is a metal can recycling machine in the supermarket. After customers put the empty cans, they can get the receipts and cash them in the designated stores. For example, if they put in 10 empty cans at a time, they can also get a coupon for buying vegetables cheaply.
In Canada, there are several kinds of light blue bullet-shaped plastic pipes in parks and places frequented by tourists, which are used to recycle waste newspapers, cans and glass bottles. There are 26 "recycling centers" in London, England. In some areas, there are garbage bins for recycling waste newspapers, old clothes, glass bottles and tin cans.
Germany has set up garbage bins for recycling plastics, and France has set up garbage bins for recycling glass bottles. From June 1992 to June 10, Musmann Park set up "electronic trash cans" for residents. There is an electronic circuit system next to it. When the cleaner dumps the garbage into the garbage truck, the garbage truck will send out a wireless signal, and the system will "reply", so that the computer on the garbage truck can identify whose property the "treasure chest" belongs to, and print out a withdrawal slip and send it to the residents. Some factories also use these wastes to produce various recycled products.
The Hokkaido Regional Technology Center in Japan extracted a particle from rice straw ash and processed it into a new type of ceramic at high temperature, which can be used to manufacture automobile engines and artificial hearts. Japan also makes 30 million tons of slag into building materials and high-quality cement raw materials through cooling treatment every year, which are used in buildings, sculptures and so on.
Dupont has established an alliance with North American Waste Disposal Company to recycle waste plastics, and has opened waste management centers in Chicago and Philadelphia. Each center recycles 6.5438 million tons of old plastic bottles, and then makes them into park benches and road isolation roadblocks. Browning-Ferris Company of the United States collected 6.5438+0.4 million household wastes, and made them into fibers, which were used to weave warm linings for carpets and bedding.
Western Electric Company, a subsidiary of AT&T Company, handles about 25 trucks of garbage every day, extracting gold from line components, silver from solder, zinc from old telephone exchanges, and making broken plastic into fence posts and flower pots. The recycled products in the United States are dazzling, including fiber products, detergents, artificial wood ... almost everything.
Comprehensive utilization of "three wastes" to recover "waste" has become an important means for many enterprises to improve economic benefits and strengthen environmental protection. Many enterprises make comprehensive use of it through comprehensive processing; Recycling, processing, separation and reuse; Inter-factory cooperation, hook exchange; Through deep processing and thorough utilization, some metals and minerals can no longer be discharged into rivers and wasted, but can become valuable by-products.
Only when people no longer regard rivers as sewage ditches for arbitrary use and get rid of the viewpoint that substances are only used for consumption, will industrial production follow the objective law of "utilization-decomposition-storage-reuse" and human beings can truly establish the viewpoint of comprehensive utilization.
For example, Germany is recovering useful sulfuric acid from the acidic solution of steel production, vinegar for sale from canned industrial waste, and chemicals from the waste liquid of paper industry for reuse, thus reducing the emissions of modern paper mills by 90%. A company in Brisbane, Australia, firstly sucked iron-containing metals from garbage with magnets, and then mixed 1 ton of ordinary domestic garbage, 1 ton of clay and 300 liters of water (or sewage) to make a mixture, which was ground, extruded into small balls similar to glass marbles, baked and cooled at a high temperature of 1200℃ to make light building materials, and added to cement.
American scientists use genetic engineering technology to cultivate bacteria and process cellulose in garbage into alcohol, which can be used as fuel after distillation and purification. A Japanese research institute uses synthetic zeolite catalyst to efficiently produce fuel oil from waste plastics, and this technology has been patented in Japan. Another research institute uses enzyme fermentation and membrane separation technology to produce ethanol with a concentration of about 50% from low-concentration starch industrial wastewater.
It is worth noting that many governments have enacted relevant laws, which stipulate preferential policies such as tax reduction and exemption and credit provision for waste materials recycling. On September 30th, California issued a law, 1989, requiring its cities and counties to extensively recycle the useful resources in garbage and reduce the amount of garbage by 25% within five years. Toronto, Canada stipulates that from 199 1, four daily newspapers in the city must use at least 50% recycled paper, otherwise their automatic retail newspaper boxes on the street will be banned. The city can recycle 3750 tons of old newspapers every month. For every 1 ton of old newspapers recycled, 19 trees can be cut down less. This means that it only recycles old newspapers and can cut down 855,000 fewer trees every year.
Practice has proved that using waste as resources to produce products is often less investment and shorter payback period than developing minerals and biological resources to produce the same products, and can eliminate pollution and improve the environment.
The American magazine Happiness pointed out: "There is gold in the garbage!" More and more attention has been paid by entrepreneurs. A new industry centered on waste utilization is emerging all over the world and has begun to become a huge torrent of environmental protection in the world.
For a long time, most solid wastes have been dumped into the sea or buried in situ. These methods have left many hidden dangers to the environment. In addition to simple physical methods such as pulverization and classification, chemical and biological treatment technologies are now widely used. These new methods can reduce pollution and recycle some resources.
It is an effective technology to recycle solid waste by chemical transformation of solid waste. Calcination, roasting, sintering, solvent leaching, thermal decomposition and incineration are all chemical treatment technologies.
(1) calcination: calcination is a process of removing carbon dioxide and bound water from materials at a suitable high temperature. Physical and chemical changes such as dehydration, decomposition and combination will occur during calcination. For example, calcium carbonate residue is calcined, and then quicklime is calcined.
(2) Roasting: Roasting is a process of heating a substance to a certain temperature (lower than its melting point) under suitable conditions to make it undergo physical and chemical changes. According to the main chemical reactions in the roasting process and the physical state after roasting, it can be divided into sintering roasting, magnetization roasting, oxidation roasting, medium temperature chlorination roasting and high temperature chlorination roasting.
(3) Sintering: Sintering is a process that powders or granular substances are heated to a certain temperature lower than the melting point of the main components, so that the particles are bonded into blocks or aggregates, and the compactness and mechanical strength are improved. In order to better sinter, a certain amount of flux, such as limestone and soda ash, is added. , usually added to materials.
(4) Solvent leaching: one or more useful metals in solid materials are dissolved in a liquid solvent to extract the useful metals from the solution. This chemical process is called solvent leaching. According to different leaching agents, leaching methods can be divided into water leaching, acid leaching, alkali leaching, salt leaching and cyanide leaching. Solvent leaching is widely used to recover useful elements from solid waste, such as leaching metals such as chromium, copper, nickel and manganese from solid waste with hydrochloric acid, and leaching crystallized aluminum trichloride and titanium dioxide from coal gangue.
(5) Thermal decomposition (or thermal cracking): Thermal decomposition is a process of cutting off large molecular weight organic matter by using thermal energy and transforming it into low molecular weight substances with less carbon content. Applying thermal decomposition technology to treat organic solid waste is a new field of thermal decomposition technology. Through thermal decomposition, fuel oil and gas can be directly recovered from organic waste at a certain temperature. Organic wastes suitable for thermal decomposition include waste plastics (except chlorine), waste rubber, waste tires, waste oil sludge and waste organic sludge.
(6) Incineration: Incineration is a high-temperature heat treatment technology, that is, a certain amount of excess air reacts with the treated waste in the incinerator, and harmful poisons in the waste are destroyed by oxidation and pyrolysis at high temperature. This treatment can completely oxidize the waste into non-toxic substances. Incineration technology is a treatment technology that can realize harmless, reduction and resource utilization of waste at the same time.
Incineration can treat municipal solid waste, general industrial waste and hazardous waste, but it needs to add a lot of fuel when treating waste with little combustible organic components. Generally speaking, garbage with low calorific value is not suitable for incineration; Garbage with calorific value greater than 5000 kJ/g belongs to high calorific value garbage and is suitable for incineration to recover its heat energy.