For a long time, various forms of disposable plastic products have been widely used in lives of residents. In recent years, with development of new formats such as e-commerce, express delivery and takeaway, consumption of plastic lunch boxes and plastic packaging has grown rapidly, resulting in new pressures on resources and environment. Accidental release of plastic waste will cause "white pollution", and non-standard disposal of plastic waste poses a risk to environment. So, what do you know about basics of plastic waste management?

01 What is plastic?

Plastic is a kind of high molecular weight organic compounds, which is a general term for thermoplastic molding materials such as filler, plasticizer and dye, and belongs to family of high molecular weight organic polymers.

02 Classification of plastics

According to properties and characteristics of plastic after molding, it can be divided into two types of plastics: thermoplastic and thermoset. A thermoplastic is a chain linear molecular structure that softens when heated and can be replicated many times over. Thermosetting plastics, which have a reticulated molecular structure, deform irrevocably after heat treatment and cannot be reproduced by reprocessing.

03 What are most common plastics in life?

Common materials for plastic products in daily life mainly include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyester (PET). Their uses:

Polyethylene plastics (PE, including HDPE and LDPE) are often used as packaging materials; polypropylene plastic (PP) is often used as packaging materials and return boxes, etc.; polystyrene plastic (PS) is often used as foam pads and fast food boxes, etc.; polyvinyl chloride plastic (PVC) is often used as toys, containers, etc.; polyester plastic (PET) is often used to make beverage bottles, etc.

Plastic everywhere

04 Where does plastic waste go?

Once plastic is discarded, there are four paths: incineration, landfill, recycling, and environmental disposal. A research report published in journal Science Advances by Roland Geyer and Jenna R. Jambek in 2017 indicated that as of 2015, humans have produced 8.3 billion tons of plastic products over past 70 years, of which 6.3 billion tons were thrown out. About 9% was recycled, 12% burned, and 79% landfilled or thrown away.

Plastic is a man-made substance that is difficult to decompose and decomposes very slowly in natural conditions. When it ends up in a landfill, it will take 200 to 400 years to decompose, which will reduce landfill's ability to recycle waste; if they are burned directly, it will cause serious secondary pollution of environment. Burning plastic produces not only large amounts of black smoke, but also dioxins. Even in a professional incineration plant, temperature must be strictly controlled (above 850°C), fly ash must be collected after incineration, and finally solidified and buried. EU 2000 standard to minimize environmental pollution.

The garbage contains a lot of plastic waste, direct burning can easily lead to formation of strong carcinogenic dioxin

If they are released into natural environment, in addition to visual pollution of people, there will be many potential environmental hazards: for example, 1. Impact on agricultural development. The decomposition time of plastic products currently used in my country is usually 200 years. The waste plastic film and plastic bags in agricultural land remain in field for a long time. The waste plastic products are mixed with soil and continuously accumulated, which affect absorption of water and nutrients by crops and hinder development of crops, resulting in reduced crop yields and deterioration of soil environment. 2. Poses a threat to survival of animals. Waste plastic products thrown onto land or into water bodies are swallowed by animals for food, which leads to their death.

The whale died after eating 80 plastic bags (weighing 8 kg)

While plastic waste carries many dangers, it is not "disgusting". Their destructive power is often associated with a low level of processing. Plastics can be recycled to become raw materials for plastics production and materials for generating heat and electricity, turning waste into treasures. This is most ideal way to recycle plastic waste.

05 What are technologies for recycling plastic waste?

First step: classification and collection.

This is first step in plastic waste recycling and provides convenience for later disposal.

Plastic waste from plastic production and recycling process, such as leftovers, inferior products and waste, is uniform, not polluted or aged, and can be collected and recycled separately.

Some plastic waste discharged during circulation can also be recycled separately, such as agricultural PVC film, PE film, PVC cable sheath material, etc.

Most plastic waste is mixed waste, which includes various contaminants, labels, and various composite materials in addition to complex plastic types.

Second stage: crushing and sorting.

When crushing plastic waste, choose right crusher according to its properties, for example, choose single shaft crusher, double shaft crusher or underwater crusher according to its hardness. The degree of crushing varies greatly depending on needs: size 50-100 mm - coarse crushing, size 10-20 mm - fine crushing, and size less than 1 mm - fine crushing.

There are several separation methods, such as electrostatic method, magnetic method, sieving method, wind method, specific gravity method, flotation enrichment method, color separation method, X-ray separation method, near infrared separation method, etc. .

Third step: resource processing.

Plastic waste recycling technologies mainly include following aspects:

1. Direct recycling of mixed plastic waste Mixed plastic waste is mainly polyolefins, not large. 2. Recycling into plastic raw materials Recycling of relatively simple plastic waste collected into plastic raw materials is most widely used recycling technology, mainly used for thermoplastic resins, and recycled plastic raw materials can be used in packaging, construction, agriculture, and raw materials for industrial tableware. Different manufacturers use independently developed technologies in processing process that allow them to endow products with unique properties. 3. Recycling into plastic andProducts Using above-mentioned plastic raw material recycling technology, it is possible to directly mold products from same or different types of plastic waste. As a rule, these are products with thick walls, such as plates or rods. 4. Use of thermal energy: sorting plastic waste from municipal waste and burning it to produce steam or electricity. The technology is relatively mature and incineration kilns include rotary kilns, stationary kilns and vulcanizing kilns; Improvements in secondary combustor and advances in tail gas treatment technology can already turn tail gas emissions from plastic waste incineration into energy recovery. system reaches a very high level. The plastic waste incineration heat and power recovery system must form a large-scale production to obtain economic benefits. 5. The calorific value of waste plastic waste can be 25.08 MJ/kg, which is an ideal fuel and can be turned into solid fuel with uniform heating, but its chlorine content must be controlled below 0.4%. The usual method is to grind waste plastic into a fine powder or micropowder and then turn it into a fuel slurry. If waste plastic does not contain chlorine, fuel can be used in cement kilns, etc. 6. Research is currently underway on thermal decomposition to produce oil, and extracted oil can be used as fuel or raw material. There are two types of thermal decomposition devices: continuous and intermittent. technologies such as hydrolysis are also being explored.

06 What can we do for Mother Earth?

1. Try to reduce use of single-use plastic products such as plastic utensils, plastic bags, etc. These single-use plastic products not only do not contribute to environmental protection, but are also a waste of resources.

2. Please take an active part in sorting waste, put plastic waste in recyclable containers or take it to service stations where two networks are connected. You know? For every ton of plastic waste recycled, 6 tons of oil can be saved and carbon emissions reduced by 3 tons. Also, there is a little reminder I have to tell you: clean, dry and uncontaminated plastic waste can be recycled, but some contaminated and mixed with other waste cannot be recycled! For example, contaminated plastic bags (film), disposable fast food takeaway boxes, contaminated express packaging bags should be disposed of as dry waste.