As the environmental problems caused by plastic waste have received more and more attention, alternative materials such as plastic bags and plastic packaging have been continuously proposed. Among them, bio-based packaging or bags have been mentioned the most, and most of them have been mentioned. It is a degradable material, including polylactic acid. So what is the current application of degradable materials in our country, what impact will it have on our waste management, and how to combine it with waste classification.
Based on the sorting after sharing, we also want to remind readers that if biodegradable materials are still disposable products, they are still thrown away when they are used up, which cannot solve our current disposable plastic waste problem. At the same time, biodegradable materials classify waste. The system has high requirements. If there is no guarantee of waste sorting and industrialized composting plants, the degradable bags and packaging cannot be recycled, or they cannot escape the fate of becoming rubbish. Therefore, for the plastic waste pollution and problems we face, we should work harder from the source control direction and continue to prohibit the application of disposable plastic products.
As the environmental problems caused by plastic waste have received more and more attention, alternative materials such as plastic bags and plastic packaging have been continuously proposed. Among them, bio-based packaging or bags have been mentioned the most, and most of them have been mentioned. It is a degradable material, including polylactic acid. So what is the current application of degradable materials in our country, what impact will it have on our waste management, and how to combine it with waste classification.
We invited manufacturers of polylactic acid that are engaged in biodegradable materials in the "Waste Sorting and Moving Towards Zero Waste" WeChat group to give a detailed explanation of this material. Based on the sorting after sharing, we also want to remind readers that if biodegradable materials are still disposable products, they are still thrown away when they are used up, which cannot solve our current disposable plastic waste problem. At the same time, biodegradable materials classify waste. The system has high requirements. If there is no guarantee of waste sorting and industrialized composting plants, the degradable bags and packaging cannot be recycled, or they cannot escape the fate of becoming rubbish. Therefore, for the plastic waste pollution and problems we face, we should work harder from the source control direction and continue to prohibit the application of disposable plastic products.
The orange part represents the global plastic consumption-500 million tons, of which the European plastic consumption is about 100 million tons, but the global bioplastic production is only a little bit green in the lower right corner of the picture. There are more than 30 varieties of bioplastics. Polylactic acid accounts for only 5% of the global bioplastics, which means that the annual global production capacity of polylactic acid is 200,000 tons. It is just a spark, and it is nowhere in sight to replace this 500 million tons of plastic.
But there is an important policy that changed this pattern. In August 2017, the state promulgated the "Waste Prohibition Order", resulting in short-term disposal of waste plastics in major developed countries in the world. The European Union therefore urgently promulgated a plastics strategy, announcing the ban on the use of single-use non-degradable plastic products before 2022. There are 67 countries in the world that have issued similar policies, which brings huge opportunities for biodegradable materials. Take the polylactic acid industry that I studied as an example. We have done very hard in the previous 15 years, with a production capacity of only 15,000 tons, and there is a surplus of annual production capacity. Due to the "Abolition Ban", the production capacity of biomaterials and the market suddenly exploded.
Polylactic acid is a relatively mature and widely used fully biodegradable compostable plastic. In addition to the biodegradability of this material, there are several different characteristics.
One of the important characteristics is that polylactic acid is a material with higher food contact safety. Its monomer is lactic acid, which is a food additive, and lactic acid exists in yogurt, cosmetics or condiments. Its own safety level is safer than materials made from petroleum monomer. Moreover, polylactic acid was used as a medical material in the 1960s and 1970s for surgical sutures and bone fixation. Later, because of technological breakthroughs and cost reductions, it entered the ranks of civilians.
Secondly, polylactic acid is a bio-based material, which is derived from plants. Among the more commonly used raw materials are corn, cassava and sucrose. Corn, cassava and other crops are extracted into starch, which is fermented into lactic acid, and then chemically polymerized into polylactic acid. It is a relatively clear bio-based raw material.
Thirdly, the low-carbon properties of polylactic acid materials. The so-called low-carbon refers to the concept of relatively low carbon dioxide consumption or emissions. For example, a certain material, in its entire life cycle from production to death, from monomer, polymerization, transportation, storage to use, the total amount of carbon dioxide absorbed and emitted is added up. By comparison, if it is carbon dioxide in plastic materials Those with relatively low total emissions are called low-carbon materials.
Take polylactic acid as an example. From the beginning of corn or cassava planting, to the extraction of glucose, lactic acid fermentation, polylactic acid polymerization, and the processing of polylactic acid products, the total carbon dioxide emission data is that one kilogram of polylactic acid film The amount of carbon dioxide released is about 1.274 kg. For comparison, to make one kilogram of PET material mineral water bottle, 4 kilograms of carbon dioxide will be emitted. The production of one kilogram of PP material shampoo bottle is about 2.5 kilograms.
The last is the degradable composting properties of polylactic acid materials. In a composting environment, it can degrade 100% to produce carbon dioxide and water without polluting the environment. Take the Jiangsu-Zhejiang-Shanghai area as an example. Generally, it can be degraded in two to five years. Other places are different due to factors such as climate. In the laboratory, we have some relatively clear data, such as 0.3 mm thick polylactic acid tablets, which are invisible to the naked eye after six weeks. Of course, not seeing it does not mean that it is degraded. It will not be completely degraded in six weeks, and it will take time.
05
Biodegradation of polylactic acid and its source
This is actually tested according to the national standard GBT20197-2006 definition, classification, labeling and testing methods of biodegradable materials, while the national standard is established with reference to the American ASTMD6400
The method of measuring carbon dioxide is based on ISO14855. In the test, the subsequent release of dioxide is small, and the test error is relatively large. Therefore, it is generally measured for 105 days, if the biodegradation rate exceeds 60%, the experiment can be terminated, and it will be determined what the material belongs to. Of course, it will be compared with natural substances such as lignin. If the two curves are basically the same, and it exceeds 60% at 105 days, it is basically judged to be a real degradable material.
Can only composting be used for the treatment of compostable materials such as polylactic acid? If there is no composting facility, what will the composting facility do? In fact, in addition to composting, compostable materials can be processed in other ways, such as burning. Compared with plastic, the products of complete combustion of polylactic acid are carbon dioxide and water, which will not pollute. It can also be landfilled. Although the degradation rate is relatively slow, at least it will not pollute the groundwater, damage the growth of plants, and waste arable land. Of course, it can be recycled, but the cost of recycling is relatively high.
When talking about polylactic acid materials derived from cassava and corn, many people will ask: human food is used to make polymer materials, will it affect food security? Everyone is very concerned about this issue. Of course, it is right to think this way. If we really have nothing to eat, we must ensure food security in advance. It is impossible to make polymer materials first, right. But from an objective point of view, this worry is unnecessary. I will share a few sets of data with you.
The use of plant starch to produce polylactic acid materials will not affect the food industry. The global corn production is 1 billion tons/year, 80% of which is used for feed and fuel, about 50% of fuel ethanol is burned, and about 30% of feed. Only 10% is used for food, about 100 million tons. Assuming that PLA production is 2 million tons per year, that is, 6 million tons of corn are consumed, accounting for 0.6%. We have a large surplus of grain production, and now China still has 200 million tons of stale grain. In addition to corn, other crops, such as cassava, have an annual global output of 300 million tons. 60% of the output is used in industry and is not human food.
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Application of polylactic acid
The more well-known application of polylactic acid is paper cups. There is a layer of film in the paper cup. Traditional paper cups use PE film. Now, starting from Seattle Starbucks, the United States has replaced the PE film with polylactic acid film, and the lid is basically made of polylactic acid material.
Straws are very hot in 2018. Plastic straws are being used all over the world, and polylactic acid straws can be used here. For example, Starbucks announced that it will stop selling plastic straws before 2020, and China's straw king is making polylactic acid straws. So the compostable material mainly depends on what it is processed with. It is definitely not possible to process it with traditional plastics. It is no problem to process it with kitchen waste, but it can also be processed with paper.
In addition to making disposable products, polylactic acid also makes some other products, such as daily necessities. A relatively well-known brand in China, "Gu's Home", uses polylactic acid to make daily necessities. The daily necessities are not made for degradation, but use polylactic acid. The material has high food safety. At the same time, the polylactic acid material has high strength, it looks like ceramic when knocked, and high gloss, which is much brighter than other plastics. Such polylactic acid products can also be bought casually on the Chinese market. Although they are not biodegradable, they are used for several years and finally discarded. They are definitely much less harmful than traditional plastics.
There are also applications on 3D printing consumables. The moon lamp shown in the picture is printed with polylactic acid materials. This type of printing is called FDM3D printing. More than 90% of its consumables are polylactic acid materials. Because the polylactic acid material not only has no smell when printed, but also has a sweet scent. In addition, it has good dimensional stability, is not easy to deform, and has a small shrinkage rate. Of course, the model printed out of the polylactic acid material is discarded and can be degraded.
The application of polylactic acid materials can also be used on fibers, making silk scarves, tea packaging, diapers, films, window films and other different uses.
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Global compostable standards and certifications
At present, the relevant standards and certification bodies for composting around the world are probably in this form.
For example, the European Union’s certification standard is EN13432, so there is one certification body in Germany, one in Belgium, and the certification body is AIB VINCOTTE and DIN-CERTCO. These two certification bodies have a certain reputation in the world. If you are engaged in related industries, you can pass his standards to certify. In China, we also have the standard GB/T20197-2006, but unfortunately, we do not have a logo. The American standard DSTMD640, the certification body BPI, and the Japanese standard JIS K 6953. Both in Australia and South Korea, they are not listed here. They all have relevant organizations to certify. In other words, perform experiments in accordance with relevant standards, and apply for certification with the experimental report when the experiment reaches the standard. Only when the certification is passed can the certificate be issued.
The certification fee is quite high, 16,500 euros, more than 100,000 yuan. General small companies are very reluctant to do it, and one of the more well-known ones in the world is in Germany, which is inconvenient for small companies. However, laboratories are not certification bodies. There are laboratories in China. Our National Plastic Products Inspection Center can do it, but many people do not want to believe in laboratories in China.
To conduct an experiment in this kind of laboratory, there are different steps: the first step is to analyze the chemical composition of the sample sent, and to detect what material it is by analyzing the infrared spectrum. For example, the material sent for testing is said to be 100% polylactic acid, but in fact it is mixed with other things, the chemical composition will be known as soon as the analysis. The cost of this analysis is not high, more than 700 euros, about more than 6,000 yuan.
After the chemical composition analysis is over, the second step is the disintegration experiment, which is the process of the material from large pieces to small fragments. This process generally lasts for three months, and the material needs to change from a large piece of 10cm×10cm to a small piece of at least 3mm×3mm before it can be deemed to pass the disintegration test.
Through the disintegration experiment, the third step of biodegradation experiment will be carried out. Take those 3mm small fragments through the action of microorganisms and collect carbon dioxide to analyze its biodegradation rate, that is, the two tables shared with you earlier, test the ratio of the material to cellulose, how much biodegradation rate can be achieved in how many days. The duration of this experiment is about six months.
Finally, even if the biodegradation test is completed and meets the requirements, the material is deemed to be 100% degradable. Still can't issue certificates, and have to pass environmental toxicity tests. The most direct effect of degradation is on the soil. If the degradation leaves harmful substances in the soil, such degradation is meaningless. Therefore, various certification standards around the world also stipulate that the fourth step is called environmental toxicity test, which is to verify whether the biodegradation is harmful to the environment. Carry out plant planting tests, such as two soils with and without compost, and choose ten groups to plant different small green vegetables to see if the growth of the plants is affected. Only when the environmental toxicity test is passed can the certification be obtained. General photo-oxidation degradable plastics and destructive biodegradable plastics absolutely cannot pass the test, so this is more authoritative.
In addition, some bio-based materials cannot be claimed to be bio-based, because bio-based materials can also be detected. The bio-based content test uses the isotope-carbon half-life method to determine the biomass content. The decay of carbon 14 into carbon 12 is generally a decay in 5600 years. If a material passes the test, it is all carbon 12, the result is basically fossil carbon. The test standard for biochar is ASTM D6866 in the United States, and there is also a standard in China. For example, in the measurement of polylactic acid, the report you usually test is 94% or 99% bio-based content. As long as the actual test result meets more than 80% of the bio-based, it is the highest level. Therefore, biobased also has authoritative standards and methods to verify.
08
Q&A
Question: Without composting conditions, waste polylactic acid products (under the natural conditions in Jiangsu, Zhejiang and Shanghai) will take 2-3 years to completely decompose into CO2 and water. What did it degrade into before? What are the intermediate products of incomplete degradation? Why not pollute the environment?
Answer: In the absence of composting, polylactic acid will first age, disintegrate and become fragments like traditional (petroleum-based) plastics. Subsequently, the long-chain polylactic acid of high molecular weight becomes low-molecular short-chain polylactic acid, and gradually becomes monomeric lactic acid. Lactic acid is a kind of microbial food, which can be digested by microorganisms in nature (turned into carbon dioxide and water), so the intermediate product is polylactic acid fragments-short-chain polylactic acid-monomeric lactic acid. There is no pollution to the environment.
Question: Is China's (polylactic acid plastic) output currently significant in the world? Can it be replaced? In the report just now, the output of 2 million tons was used to prove that it has little impact on food security, but compared to the amount of plastic to be replaced, 2 million tons seems far from enough?
Answer: China's polylactic acid production is very small now. Probably, the total output of the country is only 30,000 tons. It is absolutely impossible to replace (all) plastics. Plastic is 500 million tons. In comparison, the 2 million tons just mentioned is a small number. Of course, we cannot replace all the plastics in the world with one material. The world's most used plastics are PE and polyethylene, with 90 million tons. Therefore, it is impossible to replace all plastics with polylactic acid materials. It can only replace part of petroleum-based plastics, which helps to a certain extent. If you want to replace plastic, the only way is to use less and produce less, rather than find substitutes.
Question: Does the chemical polymerization step of polylactic acid need high temperature, high pressure and catalyst? What catalyst?
Answer: First of all, the polymerization process must be high temperature, high pressure, and catalyst. But what kind of catalyst? Your question is beyond the scope. This is a trade secret. I can't tell you, or I don't know. But at least, this is something that can stand the test. Otherwise, there is no mature technical route. If this material is made and the device is installed, it is just a pile of scrap iron. This catalyst is a catalyst that can withstand environmental, safety, and legal tests. I think this is a major premise, otherwise no company would risk investing hundreds of millions to make something problematic.
Question: The intermediate product of incomplete degradation of polylactic acid is lactic acid. What does incomplete combustion produce?
Answer: Of course, incomplete combustion means carbon monoxide and water. This is the same as burning paper and wood. Incomplete combustion may generate carbon monoxide.
Question: Are there any experimental data on the time and conditions for the partial degradation of polylactic acid to lactic acid? This data is also very important. For composting, you only need to care about the conditions and time for degradation to lactic acid, right?
Answer: This question is very good. The degradation of polylactic acid into lactic acid is actually not called degradation called hydrolysis. Hydrolysis means that the polymer chain of polylactic acid breaks into monomers under the action of temperature and water. This is actually a process of disintegration and hydrolysis. This process requires water, and the higher the temperature, the better. You will degrade from polylactic acid to lactic acid. The higher the temperature, the better, and it is best to boil it at 100 degrees faster. Then, the composting environment is generally 58 degrees. In this composting experiment, in fact (mainly) is the process of disintegration and hydrolysis, which is the process of polymer chain scission, and the process of polylactic acid into monomeric lactic acid.
Question: How do you define "true degradation"? What is the essential difference between true and false "degradation"?
Answer: What about real degradation? I think if you want to define it, that is, first of all, it needs to change from this macromolecule to a low molecule, and from an organic substance to an inorganic substance. This is real degradation. Then pseudo-degradation only changes from a high polymer to an oligomer. After the degradation, the organic matter is still organic, and the polymer is still polymer. In other words, if you convert artificial synthetics into natural substances, it can be said to be real degradation. If you degrade synthetic substances and the products are still synthetic substances, then you are not called real degradation.
Question: The two steps of the material certification analysis experiment and the environmental hazard experiment will be shut down (make the above "true and false degradation" judgment)?
Answer: Yes, for the harm to the environment, I will need an environmental toxicity test, and I will check this well. It is to simulate nature and you need to use soil. Are you just planting plants, right? Actually, I also have this environmental toxicity test report here, but it involves more professional knowledge. If you need it, I can share a part with you. In short, it is the certified laboratories, they will take your soil and do it again like a farmer. It's good to grow small cabbage, and plant a little. During this process, observe the impact on the environment and plants every day.
Question: Teacher Wu, why is the word "degradable" being used in current Chinese laws and regulations? How is this different from European and American ones?
Answer: GB/T 20197-2006 Definition, classification, labeling and degradation performance requirements of degradable plastics.
"Degradable" is actually a common name, not a professional term. For this term, China’s national standard actually has regulations, and there are regulations in GB/T2019-7. The term "degradable" is not used in Europe and America. Just now we mentioned that the law in California states that you cannot use the term "degradable", you must use the term "compostable". In China ("degradable") is actually a common name established by everyone. Many nouns in China have some common names. In China, this regulation is indeed a big problem. To be honest, you see, if you just make a takeaway lunch box with a little degradable material in the PP material, it can be called "degradable". The main reason is that China does not have this certification system and there is no certification mark. So, everyone has abused this term, or to put it ugly, the term ("degradable") is badly used. So why do our group friends feel disgusted when they hear "degradable". To be honest, I am very disgusted, but what can you do? Our industry is immature and our supervision is immature. Then you can only do your own thing gradually, right? We promote real biodegradable materials and compostable materials. At present, from a market perspective, (being a real biodegradable compostable material company) can only serve European and American customers, and the European and American markets (because the market is well regulated). Including our PLA, more than 80% are (sold to European and American customers). We just do some durable goods in China.
Liwen: In English, "degradable" and "compostable" are two different concepts.
Wu: Biodegradable and compostable.
Zhang Bo: These are two different concepts, but compostable here in Chinese translates to "compostable" in a bit less meaning.
Question: The cost of making mulch is still too high, right? It would be great if it could be made into a degraded chain like PET, a disposable container, and then made of mulch. Just compost directly.
Answer: When making the mulch, the petroleum-based biodegradable material PBAT is used. PLA cannot be used as a mulch. The cost of mulch made of PBAT is three times that of ordinary PE mulch. Therefore, although China has 2 million tons of mulch film to be replaced, although our focus interviews have been revealing that in the cotton fields of Xinjiang Construction Corps, there are 40 kg of mulch film remaining in one cubic meter of land. There is still no good solution under cost pressure.
Question: Since polylactic acid material is strong and sturdy, why can't the appliances made with it be recycled and reused? Or "return to the furnace" to re-polymerize to produce recycled polylactic acid materials, but use them in large quantities in disposable appliances?
Answer: It can be reused, but because the amount is relatively small and the recycling process requires dehumidification and drying or chain extension, the cost is relatively high
Question: What is the current state of our country’s biodegradable market and how is the supervision done? Is the market counterfeit serious?
Answer: At present, Jilin Province, Hainan Province and Jiangsu Province of China are promoting the market of biodegradable materials. Hainan has just passed legislation in the past few days. Products promoted through local legislation are difficult to counterfeit due to strict supervision, but due to the high cost, the dosage is not enough. Large, and there is still no special specification for the post-disposal process. Jilin Province began to completely ban the use of disposable non-degradable plastic products on January 1, 2015. The market capacity of local disposable plastic products is 20,000 tons, but after one year of plastic ban, the use of disposable biodegradable products is only 4000 Ton.
Liwen: Without certification, no supervision, no waste sorting and composting site, our degradable materials may be a huge mess.
Liman: The question is which administrative department should be in charge or a third-party agency.
Wu: Actually, we are very clear about this question. Why is there no supervision now, because now in our China Bioplastics Industry Association, 450 and 60 of the 500 member companies are made of semi-degradable materials. So the whole association is made up of a group of wrong people. You said, how to push this standard? This industry association, they themselves felt that the name was not right, and their words were not right. Originally, they wanted to introduce a fully degradable, certification mark like the European Union. But if you launch it, 80% of the companies do not meet this standard, and 80% of the companies in this industry association do not meet this standard. If you launch it to beat yourself, they dare not do it, because those industry association fees are all paid by these companies. . Therefore, the current failure to regulate bioplastics in China is actually due to the fact that the production capacity of the real biodegradable industry is insufficient, not much. If there are more, industry supervision can naturally go up.
