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. Almindelig nedbrydelig plast
Det diskuteres i øjeblikket, at bionedbrydelig plast, som bruger vedvarende biologiske ressourcer, såsom afgrøder, mikroorganismer osv., og nogle bruger fossile ressourcer. Den mest almindeligt anvendte kommercielle bionedbrydelige plast er PHA (polyhydroxyfedtsyreester) og PLA (polymælkesyre), som henholdsvis udsættes for mikroorganismer (afgrødefodring) og majs som hovedråmaterialet.
2, nedbrydelig plastproduktion
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. Traditionel plast, der bruger mindre energi end egenskaber under bionedbrydelig plastproduktion. I produktionsprocessen af bionedbrydelig plast er det generelt 2500-45 millioner koksenergi, og den mest almindelige PLA kræver 44,7 millioner volutenergi. Den traditionelle plast skal forbruge 7300-86 millioner koksenergi pr. kilogram, hvilket er meget højere end bionedbrydeligt plast. Hvis den globale ikke-nedbrydelige plastik erstattes med en bionedbrydelig plast, kan det spare 1-2,2 1019 joule energi hvert år ifølge den globale plastproduktion i 2019. Det tegnede sig for 1,7-3,8 procent af det globale energiforbrug på 5,8 1020 Joule i 2019.
2.3. Med hensyn til produktionsomkostninger er prisen på bionedbrydelig plast nu lidt højere end traditionel plast (mellem 1-2 gange), men i henhold til industriens udviklingshastighed vil prisen fortsætte med at falde i den nærmeste fremtid.
2.4. Produktion af 1 kg biologisk nedbrydelig PLA-plast kræver cirka 2,65 kg majs, at producere 1 kg biologisk nedbrydelig PHA-plast kræver cirka 3,7 kg majs. Ifølge data fra 2019, hvis al traditionel plast erstattes af PLA, forbruges der cirka 975 millioner tons majs hvert år; hvis al traditionel plast udskiftes til PHA, forbruges der ca. 1,36 milliarder tons majs hvert år. Samtidig er den globale majsproduktion i 2018/2019 1,09 milliarder tons, tæt på prisen på erstatningsplast. Desuden vil priserne på majs og andre afgrøder naturligvis stige, hvis der bliver brugt mere majs, eller dyrket jord til at plante råvarer som bionedbrydelig plast, og dermed fortsat true fødevaregarantierne i lavfødevareområdet. Det kan ses, at bionedbrydelig plast er en stor trussel mod den globale fødevareforsyning, og det er svært at fuldt ud alternative traditionel plast, før teknologien er opnået.
2.5. Under råvareplantningsprocessen af biologisk nedbrydelig plast bruges en stor mængde gødning og insekticid, hvor det giftige stof vil trænge ned i vandet, og drikkevandssikkerheden er sikker, dyrelivets sikkerhed og jordbundens sikkerhed.
3, genbrug af nedbrydelig plast
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. Når kreativt nedbrydningsplastik ikke genvindes effektivt, vil de nedbryde en stor mængde drivhusgas-metan i et aerobt miljø.
3.3. Når kreativ nedbrydningsplast ikke genvindes effektivt, efter at den er kommet ind i havmiljøet, reduceres den kraftigt af tilstrækkelige mikroorganismer og ilt og bionedbrydningseffektivitet. Fordi det ikke er muligt at nedbryde i tide, har disse nedbrydelige plastik stadig stor sandsynlighed for at skade de marine organismer, før nedbrydningen er afsluttet.
4 sammenligningsøn af den samlede kulstofemission
På grund af de forskellige råmaterialer er bionedbrydelig plast mindre end traditionel plast i hele livscyklussen. Fordi råmaterialerne i bionedbrydelig plast hovedsageligt er planter, er deres nedbrydning mindre end kuldioxiden i plantevæksten, så kuldioxidemissionerne fra bionedbrydelig plast stammer hovedsageligt fra mekaniske emissioner under produktion og transport. Den traditionelle plast pr. kilogram traditionel plast vil frigive 2,5-3,4 kg kuldioxid i hele sin livscyklus, og bionedbrydelig plast vil frigive 1,8 kg kuldioxid pr. kg biologisk nedbrydelig plast. Hvis traditionel plast erstattes med bionedbrydelig plast, vil verden afhængigt af arten frigive 0-830 millioner tons kuldioxid hvert år (overvej hele produktets livscyklus). Denne ordre er cirka 2,3 procent sammenlignet med cirka 36 milliarder tons kulstofemissioner om året 17.
5 potentiel trussel
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.
