As an environmentally friendly alternative to traditional plastics, whether the production process of biodegradable bags generates wastewater and waste gas has always been a focus of the industry. In fact, the production of biodegradable bags is accompanied by a certain amount of wastewater and waste gas emissions, but the pollution intensity is significantly lower than that of traditional plastic bags. Moreover, through scientific management and control, compliance with emission standards can be achieved, and its environmental advantages remain prominent.
From the perspective of the production process, wastewater generation is mainly concentrated in the raw material pretreatment and equipment cleaning links. The core raw materials of biodegradable bags are mostly polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), or starch-based composite materials. Some raw materials need to undergo drying and cleaning processes before modification and processing, which will produce a small amount of cleaning wastewater. This type of wastewater mainly contains dust attached to the surface of raw materials, a small amount of unreacted monomers, and residual additives, with a low concentration of pollutants. The Chemical Oxygen Demand (COD) is usually 50-150 mg/L, which is much lower than the oily and heavy metal-containing industrial wastewater produced in traditional plastic production. In addition, during the regular cleaning of production equipment, a small amount of detergent-containing wastewater will be generated. If directly discharged, it may cause slight water pollution. However, after pretreatment in a sedimentation tank and treatment by the biofilm method, it can meet the comprehensive wastewater discharge standards.
Waste gas emissions mainly come from the raw material processing and thermoforming stages. During thermal processing such as extrusion and film blowing, biodegradable materials will produce a small amount of Volatile Organic Compounds (VOCs) due to high temperatures. The main components include residual monomers in raw materials, volatile substances from additives, and a small amount of thermal decomposition products. Different from the large amount of toxic waste gas such as benzene series and halogenated hydrocarbons released in traditional plastic bag production, the concentration of VOCs generated by biodegradable bags is extremely low, and most of them are degradable low-carbon organic substances without strong toxicity. In addition, when some manufacturers use natural raw materials such as starch, a small amount of dust will be generated during the drying process. If not collected in a timely manner, it may cause local atmospheric particulate pollution. However, by installing equipment such as bag filters and electrostatic precipitators, the spread of dust can be effectively controlled.
It is worth noting that with the upgrading of environmental protection technologies, enterprises engaged in biodegradable bag production have established a mature pollution control system. In terms of wastewater treatment, most enterprises adopt a combined process of “pretreatment + biochemical treatment”, and the treated wastewater can be recycled or discharged up to standard. For waste gas treatment, sealed production equipment, activated carbon adsorption devices, and UV photolysis purification systems are used to significantly reduce the emissions of VOCs and dust. Some advanced production lines also adopt green production technologies, such as direct synthesis of bio-based raw materials and low-temperature forming processes, to reduce pollutant generation from the source.
Compared with the large amount of highly toxic wastewater and waste gas emissions in traditional plastic bag production, the pollution emissions of biodegradable bags are characterized by “low concentration, easy treatment, and degradability”. With sound environmental governance measures, the emissions of wastewater and waste gas can strictly comply with national environmental protection standards, and the environmental impact throughout the entire life cycle is much lower than that of traditional plastics. Therefore, biodegradable bags are not only an environmentally friendly choice in the end-use stage, but their production process has also achieved environmental friendliness through technological upgrading, making them an important direction for plastic pollution control.
