The "degradable plastic" defined by the national standard is not a good way to solve the problem of plastic grunge. Although the environmental impact of biodegradable plastics is less than non-degradable plastic, it still leads to many environmental issues, so it can only see it as a substitute for alleviating plastic problems, rather than a solution of plastic problems. Although we can have expectations for technology development, in accordance with the current level of science and technology, only reduce consumption can minimize the impact of plastic products on the environment. To completely compare biological degradation plastics and traditional plastics, we may wish to disassemble the lifecycle of plastics.
1. Plastik mudah terurai biasa
Pada masa ini dibincangkan bahawa plastik terbiodegradasi, yang menggunakan sumber biologi boleh diperbaharui, seperti tanaman, mikroorganisma, dll., dan beberapa menggunakan sumber fosil. Plastik terbiodegradasi komersial yang paling biasa digunakan ialah PHA (ester asid lemak polihidroksi) dan PLA (asid polilaktik), yang masing-masing tertakluk kepada mikroorganisma (makanan melalui tanaman) dan jagung sebagai bahan mentah utama.
2, pengeluaran plastik terdegradasi
2.. Since the current source of biodegradable plastic raw materials is crops (corn, sugar cane, etc.), rather than fossil fuels, so from raw materials, biodegradable plastics can save approximately half of fossil fuel than traditional plastics. If the world's traditional plastics are replaced by biodegradable plastics, it can save approximately 3.49 million barrel fuels per day, accounting for about 4 percent fossil fuel consumption in the world.
2.2. Plastik tradisional yang menggunakan tenaga kurang daripada ciri semasa proses pengeluaran plastik terbiodegradasi. Dalam proses pengeluaran plastik terbiodegradasi, ia biasanya 2500-45 juta tenaga kok, dan PLA yang paling biasa memerlukan 44.7 juta tenaga volut. Plastik tradisional perlu menggunakan 7300-86 juta tenaga kok setiap kilogram, yang jauh lebih tinggi daripada plastik terbiodegradasi. Jika plastik tidak terurai global digantikan dengan plastik terbiodegradasi, ia boleh menjimatkan tenaga 1-2.2 1019 joule setiap tahun mengikut pengeluaran plastik global 2019. Ia menyumbang 1.7-3.8 peratus daripada penggunaan tenaga global sebanyak 5.8 1020 Joule pada 2019.
2.3. Dari segi kos pengeluaran, harga plastik biodegradasi kini lebih tinggi sedikit daripada plastik tradisional (antara 1-2 kali ganda), tetapi mengikut kelajuan pembangunan industri, harga akan terus menurun dalam masa terdekat.
2.4. Pengeluaran 1 kg plastik PLA terbiodegradasi memerlukan kira-kira 2.65 kilogram jagung, menghasilkan 1 kg plastik PHA terbiodegradasi memerlukan kira-kira 3.7 kg jagung. Menurut data 2019, jika semua plastik tradisional digantikan kepada PLA, kira-kira 975 juta tan jagung digunakan setiap tahun; jika semua plastik tradisional digantikan kepada PHA, kira-kira 1.36 bilion tan jagung digunakan setiap tahun. Pada masa yang sama, pengeluaran jagung global 2018/2019 ialah 1.09 bilion tan, hampir dengan kos penggantian plastik. Lebih-lebih lagi, dengan lebih banyak jagung, atau tanah yang ditanam digunakan untuk menanam bahan mentah seperti plastik biodegradasi, harga jagung dan tanaman lain secara semula jadi akan meningkat, sekali gus terus mengancam jaminan makanan di kawasan makanan rendah. Dapat dilihat bahawa plastik terbiodegradasi adalah ancaman utama kepada bekalan makanan global, dan sukar untuk plastik tradisional alternatif sepenuhnya sebelum teknologi itu dicapai.
2.5. Semasa proses penanaman bahan mentah plastik biodegradasi, sejumlah besar baja dan racun serangga digunakan, di mana bahan toksik akan menembusi ke dalam air, dan keselamatan air minuman adalah selamat, keselamatan hidupan liar, dan keselamatan tanah.
3, kitar semula plastik boleh degradasi
3.1. Because the production of biodegradable plastics is too small, there is still lack of systematic, large-scale recovery methods. To give a simple example, when the garbage classification is proposed in Shanghai, many people need to shake the kitchen waste garbage when they are throwing garbage, and it is easy to stain your hands. So creating a creative wetting garbage bag, people want to throw the biodegradable garbage bag and wet garbage into wet trash. However, the garbage treatment department quickly sounded, indicating that although "degradable garbage bag" will most degrade, but it still has indiscriminated, even toxic and harmful ingredients, will affect the treatment of wet rubbish. Also, such garbage bag degradation speed is much slower than the kitchen waste, and cannot be treated synchronously. It can only be treated as dry waste incineration. Although biodegradable plastics can be degraded by biodegradation, it does not mean that they will ultimately break the recovery treatment, which is degraded.
3.2. Apabila plastik penguraian kreatif tidak dipulihkan dengan berkesan, ia akan mengurai sejumlah besar gas rumah hijau-metana dalam persekitaran aerobik.
3.3. Apabila plastik degradasi kreatif tidak dipulihkan dengan berkesan, selepas memasuki persekitaran marin, ia dikurangkan dengan banyak oleh mikroorganisma dan oksigen yang mencukupi, dan kecekapan biodegradasi. Kerana tidak mungkin terurai dalam masa, plastik terurai ini masih mempunyai kebarangkalian besar untuk membahayakan organisma marin sebelum degradasi selesai.
4 perbandingananak kepada pelepasan karbon keseluruhan
Kerana bahan mentah yang berbeza, plastik biodegradasi adalah kurang daripada plastik tradisional dalam keseluruhan kitaran hayat. Oleh kerana bahan mentah plastik biodegradasi kebanyakannya adalah tumbuhan, degradasinya adalah kurang daripada karbon dioksida dalam pertumbuhan tumbuhan, jadi pelepasan karbon dioksida plastik biodegradasi terutamanya berasal daripada pelepasan mekanikal semasa pengeluaran dan pengangkutan. Plastik tradisional bagi setiap kilogram plastik tradisional akan membebaskan 2.5-3.4 kilogram karbon dioksida dalam kitaran hayatnya yang lengkap, dan plastik terbiodegradasi akan membebaskan 1.8 kg karbon dioksida setiap kilogram plastik terbiodegradasi. Jika plastik tradisional digantikan dengan plastik terbiodegradasi, bergantung kepada spesies, dunia akan mengeluarkan 0-830 juta tan karbon dioksida setiap tahun (pertimbangkan kitaran hayat keseluruhan produk). Pesanan ini adalah kira-kira 2.3 peratus berbanding kira-kira 36 bilion tan pelepasan karbon setiap tahun 17.
5 potensi ancaman
When the environmental impact of degradable plastic (oil consumption, carbon emissions, energy consumption, agricultural pollution, etc.) still exists, and that degradable plastics will still cause environmental issues. If we are in this time, due to mistakes, it is harmless, and a large amount of "degradable" plastic product is used, the overall environmental impact (the impact of unit plastic products plastic products) may It will be greater than the era of traditional plastics. Not to mention the definition of degradation of plastics, it is still blurred. When it is "degradable plastic", "only needs a long time to degrade in the ideal environment", the environmental hazard Only increasing.
In summary, if you use a biodegradable plastic to replace the traditional plastic, 4 percent fossil fuel can be saved, reducing 2.3 percent carbon emissions worldwide, saving 2 percent of the world's energy consumption. Even if we use biodegradable plastics to replace all disposable plastics (approximately half of global plastics production), it can reach half of the results. At the same time, at the same time, replacement of disposable plastic products to degrade plastics can consume more than half of corn production, and cause risk from methane, pesticides, fertilizers, can't degrade in time. Therefore, it is necessary to emphasize that "degradable" does not explain that this plastic product can be simply harmless, which will still trigger a series of energy consumption, carbon emissions, food shortages, and so on. According to the current level of technology, "degradable plastic" is a way to slow the problem, it is not a way to solve the problem, and it is impossible to use degradable plastic products due to the word "degradable". If we all completely abandon the use of disposable products, it will not cause pollution and consumption of those fuel, energy, carbon emissions, etc., etc. Therefore, under the existing technological conditions, the use of conventional plastics is replaced with degradable / stacui plastics, and the use of a disposable plastic article is better.