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. Uobičajena razgradiva plastika
Trenutno se raspravlja da biorazgradiva plastika, koja koristi obnovljive biološke resurse, kao što su usjevi, mikroorganizmi itd., a neke koriste fosilne resurse. Najčešće korištena komercijalna biorazgradiva plastika je PHA (ester polihidroksi masnih kiselina) i PLA (polimliječna kiselina), koji su podvrgnuti mikroorganizmima (hranjivanjem usjeva) i kukuruzom kao glavnom sirovinom.
2, proizvodnja razgradive plastike
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. Tradicionalna plastika koja troši manje energije od karakteristika tokom procesa proizvodnje biorazgradive plastike. U procesu proizvodnje biorazgradive plastike, to je generalno 2500-45 miliona energije koksa, a najčešći PLA zahtijeva 44,7 miliona voltne energije. Tradicionalna plastika treba da potroši 7300-86 miliona energije koksa po kilogramu, što je mnogo više od biorazgradive plastike. Ako se globalna nerazgradiva plastika zamijeni biorazgradivom plastikom, može se uštedjeti 1-2,2 1019 džula energije svake godine prema globalnoj proizvodnji plastike iz 2019. To je činilo 1,7-3,8 posto globalne potrošnje energije od 5,8 1020 džula u 2019.
2.3. Što se tiče troškova proizvodnje, cijena biorazgradive plastike je sada nešto viša od tradicionalne plastike (između 1-2 puta), ali s obzirom na brzinu razvoja industrije, cijena će nastaviti da pada u bliskoj budućnosti.
2.4. Za proizvodnju 1 kg biorazgradive PLA plastike potrebno je oko 2,65 kilograma kukuruza, a za proizvodnju 1 kg biorazgradive PHA plastike potrebno je oko 3,7 kg kukuruza. Prema podacima iz 2019., ako se sva tradicionalna plastika zamijeni PLA, svake godine se potroši oko 975 miliona tona kukuruza; ako se sva tradicionalna plastika zameni PHA, oko 1,36 milijardi tona kukuruza se potroši svake godine. Istovremeno, globalna proizvodnja kukuruza 2018/2019 iznosi 1,09 milijardi tona, blizu cijene zamjenske plastike. Štaviše, sa više kukuruza, odnosno obrađenog zemljišta koje se koristi za sadnju sirovina kao što je biorazgradiva plastika, cijene kukuruza i drugih usjeva će prirodno rasti, nastavljajući time ugrožavati garancije za hranu u oblasti niske količine hrane. Može se vidjeti da biorazgradiva plastika predstavlja veliku prijetnju globalnoj opskrbi hranom i da je teško u potpunosti alternativna tradicionalna plastika prije nego što se tehnologija postigne.
2.5. Tokom procesa sadnje sirovine biorazgradive plastike koristi se velika količina gnojiva i insekticida, gdje će toksična supstanca prodrijeti u vodu, a sigurnost vode za piće je sigurna, sigurnost divljih životinja i sigurnost tla.
3, recikliranje razgradive plastike
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. Kada se kreativna degradirajuća plastika ne povrati efikasno, ona će razgraditi veliku količinu gasova staklene bašte-metana u aerobnom okruženju.
3.3. Kada se kreativna degradirajuća plastika ne povrati efikasno, nakon ulaska u morsko okruženje, ona je uvelike smanjena dovoljnom količinom mikroorganizama i kiseonika, kao i efikasnošću biorazgradnje. Budući da nije moguće razgraditi na vrijeme, ova razgradiva plastika i dalje ima veliku vjerovatnoću da naškodi morskim organizmima prije nego što se razgradnja završi.
4 comparisin ukupne emisije ugljika
Zbog različitih sirovina, biorazgradiva plastika je manje od tradicionalne plastike u cijelom životnom ciklusu. Budući da su sirovine biorazgradive plastike uglavnom biljke, njihova degradacija je manja od ugljičnog dioksida u rastu biljaka, tako da emisije ugljičnog dioksida biorazgradive plastike uglavnom proizlaze iz mehaničkih emisija tijekom proizvodnje i transporta. Tradicionalna plastika po kilogramu tradicionalne plastike će osloboditi 2,5-3,4 kilograma ugljičnog dioksida u svom potpunom životnom ciklusu, a biorazgradiva plastika će osloboditi 1,8 kg ugljičnog dioksida po kilogramu biorazgradive plastike. Ako se tradicionalna plastika zamijeni biorazgradivom plastikom, ovisno o vrsti, svijet će ispuštati 0-830 milijuna tona ugljičnog dioksida svake godine (uzmite u obzir životni ciklus cijelog proizvoda). Ovaj redoslijed je otprilike 2,3 posto u poređenju sa oko 36 milijardi tona emisija ugljika godišnje17.
5 potencijalna prijetnja
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.