Biodegradable plastics tuaj yeem ua biobased lossis fossil roj raws. Cov hom tshiab ntawm cov yas tau tsim nyob rau xyoo tas los no los daws qhov teeb meem ntawm cov yas muaj kuab paug, los ntawm kev sim ua kom luv luv lub sij hawm uas yuav tsum tau degrade lawv, tshwj xeeb tshaj yog nyob rau hauv tej yam ntuj tso. Txawm li cas los xij, tsis yog tag nrho cov yas biodegradable tam sim no tau ua tiav lub hom phiaj no.
Definition of Biodegradable Plastics
Biodegradable plastics yog cov uas tuaj yeem degraded los ntawm microbial nkaus los tsim cov khoom kawg, xws li dej thiab carbon dioxide, nyob rau lub sijhawm tsim nyog. Lub sij hawm xav tau kom decompose tag yog nyob ntawm cov khoom, ib puag ncig tej yam kev mob xws li kub thiab noo noo, thiab qhov chaw ntawm decomposition raws li Biodegradable Products Institute (BPI pg. 2).
Compostable plastics yog cov uas biodegrade sai thiab tig mus rau hauv humus uas tsis kis los ntawm hlau. Tsis yog txhua yam biodegradable plastics yog compostable; tsuas muaj qee leej xwb.
Cov ntaub ntawv yuav tsum ua tau raws li ASTM Specifications D6400 lossis D6868 kom hu ua biodegradable thiab compostable rau hauv av, thiab ua tau raws li ASTM D7081 specifications rau marine ib puag ncig. ASTM yog ib pawg khoom lag luam thoob ntiaj teb.
Biobased Polyster Plastics Uas Biodegrade
Plastics uas tau los ntawm cov nroj tsuag hu ua biobased plastics. Tsis yog tag nrho cov no yog biodegradable; Piv txwv li, muaj biobased PET fwj ua kom ruaj khov. Biobased plastics uas biodegrade yog ua los ntawm ob yam khoom: biomass thiab polysters muab los ntawm cov nroj tsuag. Muaj ob hom biobased polysters: polylactide acid (PLA) thiab polyhydroxyalkanoate (PHA).
Polyhydroxyalkanoate (PHA)
PHA yog tsim los ntawm cov kab mob thiab Genetically Modified Organisms (GMO) cov nroj tsuag, tab sis muaj cov phiaj xwm sim ntau lawm los ntawm cov khoom pov tseg. Polyhydroxybutyrate lossis PHB kuj yog ib hom PHA uas tau siv dav. PHAs kim heev los ua kom tsuas yog muaj tsawg xwb thiaj tsim tau los ntawm cov kab mob.
- Siv:PHAs yog siv los ua zaub mov qhwv, khob, phaj, txheej rau ntawv thiab duab los qhia, thiab 'ntau yam siv kho mob, suav nrog sutures, gauze, thiab coatings rau tshuaj' raws li tsab ntawv ceeb toom los ntawm Center for Industry and Education Collaboration (CIEC report). Nws tuaj yeem hloov pauv feem ntau ntawm cov roj fossil loj raws li cov yas siv tam sim no, xws li PE, PS, PVC, thiab PET cov ntsiab lus ntawm Bio Based Press.
- PHA-blended starch/cellulose plastics: Qee cov khoom yas yog ua los ntawm PHA nkaus xwb, xws li cov ntawv sau hauv lub raj mis dej Bio Based Press. Txawm li cas los xij, txij li kev tsim khoom ntawm PHA yog kim, nws kuj tau sib xyaw nrog cov hmoov txhuv nplej siab thiab cellulose ua kom nws pheej yig dua. Qhov no muaj qhov zoo ntxiv ntawm kev txhim kho tus nqi decomposition raws li Dartmouth Undergraduate Journal of Science (DUJS).
- Biodegradation: Nws tuaj yeem ua tau tag nrho compostable nyob rau hauv ib puag ncig uas nplua nuj nyob rau hauv microbes thiab fungi, tshwj xeeb tshaj yog av. Cov kab mob no rhuav tshem PHA nrog kev pab ntawm enzymes. Lub sij hawm tsim nyog rau degrade nyob ntawm qhov concentration ntawm microbes nyob rau hauv ib puag ncig.
- PHA siv sijhawm ob lub hlis los ua kom puas hauv cov tiaj nraum qaum tsev, raws li Bio Based Press.
- Tus nqi decomposition qeeb qeeb hauv cov dej hiav txwv uas tsawg dua 50% tawg tom qab rau lub hlis ntxiv CalRecycle (pg. 6). PHA dhau qhov kev xeem ASTM D7081 los ntawm kev qhia 30% decomposition hauv rau lub hlis (pg. 7).
Polylactide Acid (PLA)
DUJS piav qhia tias PLA yog cov thermoplastic ua los ntawm fermentation los ntawm cov kab mob. PLA yog cov saw ntev ntawm ntau cov lactic acid molecules. Txij li thaum muaj ntau txoj kev pheej yig ntawm kev tsim cov lactic acid, cov no tsuas yog yuav tsum tau polymerized los yog koom nrog. Yog li ntawd, PLA tsis tshua kim dua PHA. Txawm li cas los xij, PLA yog nkig thiab nws daim ntawv thov raug txwv ntau dua li PHA. Cov neeg tsim khoom tau txais ib puag ncig qhov teeb meem no los ntawm kev suav nrog cov tshuaj ntxiv lossis cov polymers.
- Siv: Nws yog tsim rau hauv lub hnab khoom noj, ntim khoom noj, lub raj mis, khob, thiab phaj. Txij li thaum nws decomposes zoo nyob rau hauv lub xub ntiag ntawm acids, nws yog siv nyob rau hauv ib co kev kho mob daim ntawv thov xws li kev kho mob sutures thiab daim hlau, qhov twg nws dissolves tom qab 90 hnub sau ntawv CIEC daim ntawv qhia. Nws kuj tseem siv rau hauv 3-D luam ntawv ntawm cov khoom.
- PLA thiab polymer blends: PHA kuj tuaj yeem sib xyaw nrog polymers los ntawm cov khoom siv txuas ntxiv los txhim kho nws cov khoom zoo raws li DUJS.
- Biodegradation: PLA tsis tuaj yeem muab tso rau hauv lub tiaj nraum qaum tsev vim qhov ntsuas kub thiab dej xav tau tsis muaj nyob hauv qhov chaw no.
- PLA tuaj yeem siv rau 6-12 lub hlis kom degrade hauv av.
- PLA siv sijhawm peb-rau lub hlis los ua kom tsis zoo hauv cov chaw lag luam, sau World Centric.
- Thaum decomposition tshwm sim nyob rau hauv lub xub ntiag ntawm oxygen, cov khoom kawg yog carbon dioxide thiab dej.
- Yog tias PLA degradation tshwm sim hauv qhov chaw pov tseg yam tsis muaj oxygen, nws tsim cov pa roj methane uas yog 20 npaug ntau dua kev puas tsuaj rau ib puag ncig dua li cov ntsiab lus carbon dioxide tawm ntawm American Chemical Society tso tawm (pg. 2).
- PLA tsis tau xeem ASTM D7081 li tsuas yog 3% decomposed nyob rau hauv dej hiav txwv tom qab rau lub hlis raws li CalRecycle (pg. 7).
Vim tias PLA tsis tawg sai sai hauv av lossis dej hiav txwv, qhov no tuaj yeem ua teeb meem thaum littered.
Biomass Raws li Biodegradable Plastics
Biomass raws li plastics yog ua los ntawm cov hmoov txhuv nplej siab thiab cellulose tau los ntawm cov qoob loo residue nrog rau cov ntoo los ntawm cov ntoo.
Cellulose Acetate
Cellulose acetate (CA) yog cov khoom siv hluavtaws uas tau los ntawm cov cellulose uas muaj nyob hauv txhua qhov ntawm cov nroj tsuag. Cellulose yog tam sim no siv los ntawm paj rwb, ntoo, thiab qoob loo pov tseg raws li kev tshawb fawb xyoo 2018. Qhov no tuaj yeem siv los tsim cov khoom yas molded, luam yeeb lim, coatings, yees duab-films thiab lim. Cellophane yog biodegradable zaj duab xis tsim los ntawm cellulose. Muaj kev tshawb fawb tshiab txuas ntxiv mus nrhiav cov yeeb yaj kiab yas tshiab los ntawm cov qoob loo pov tseg thiab cov khoom siv ntoo uas muaj dej resistant thiab biodegradable raws li Phys.org.
Biodegradability: Kev tshawb fawb qhia tias CA degrades thiab raug txo los ntawm 70% ntawm nws qhov hnyav tom qab 18 lub hlis hauv xwm.
Starch
A 2017 tshuaj xyuas cov hmoov txhuv nplej siab tau kho nrog cov cua sov, dej, thiab cov yas los tsim cov thermoplastic. Txhawm rau txhim kho nws lub zog, nws tau ua ke nrog cov fillers ua los ntawm lwm cov ntaub ntawv. Qhov chaw tseem ceeb ntawm cov hmoov txhuv nplej siab yog pobkws, nplej, qos yaj ywm, thiab cassava. Cov yas no yog siv rau hauv ntim, hnab, thiab ua liaj ua teb mulch films, tableware, paj lauj kaub, thiab molded los ua ntim thiab cov khoom siv. Nws tau pom tias yog lwm txoj hauv kev rau polystyrene (PS) raws li Food Packaging Forum. Cov hmoov txhuv nplej siab tau ntxiv rau cov khoom siv biobased thiab cov pa yas ua kom lawv cov ntawv sau biodegradable 2017 Phys report.
Biodegradability: Starch-based plastics tuaj yeem ua compostable lossis tsuas yog biodegradable. Compostable variants xav tau 90 hnub rau degrade nyob rau hauv industrial chaw, thaum lub biodegradable sawv daws yuav xav tau 100 hnub rau 46% degrade thiab mus txog rau ob xyoos kom degrade tag.
Fossil Roj Based Biodegradable Plastics
Raws li Bioplastics Guide, muaj ob peb yam tshiab fossil roj plastics uas kuj yuav biodegradable. Cov feem ntau yog Polybutylene succinate (PBS), Polycaprolactone (PCL), Polybutyrate adipate terephthalate (PBAT) thiab Polyvinyl cawv (PVOH / PVA).
- PBATyog ib lub polymer uas yog tsim los ntawm fossil roj derivatives thiab yog siv qee zaum ua ke nrog cov hmoov txhuv nplej siab. Kev siv zog los tsim cov polymer no los ntawm cov khoom siv txuas ntxiv. Bioplastics qhia pom tias nws yog qhov hloov pauv rau LDPE thiab HDPE. Nws yog siv los ua cov hnab khib nyiab, qhwv zaj duab xis, ntim khoom pov tseg thiab cov tais diav (khob, tais diav thiab lwm yam). Nws tsis yog tsuas yog biodegradable tab sis kuj compostable.
- PCL yog cov khoom siv hluavtaws siv los ua cov hnab ntim khoom, hauv daim ntawv thov kev kho mob (sutures thiab fibers), raws li txheej txheej, nplaum rau khau thiab tawv, thiab stiffeners rau khau thiab orthopedic splints. Cov yas no tuaj yeem decomposed los ntawm cov poov xab. Ntau tshaj 90% ntawm cov yeeb yaj kiab, thiab 40% ua npuas ncauj ua los ntawm cov khoom no tuaj yeem degraded hauv 15 hnub.
- PBS yog ib qho resin ua los ntawm fossil fuels los yog tseem tuaj yeem ua biobased raws li Succinity (pg. 1, 5). Nws tuaj yeem ua ke nrog lwm cov biobased polymers lossis fibers zoo li jute los txhim kho nws qhov zoo. PBS yog siv los ua cov ntim khoom noj, cov khoom siv, cov ntawv ua liaj ua teb, cov lauj kaub cog, cov khoom siv tu cev zoo li cov ntaub qhwv, thiab cov nuv ntses.
- PVOH yog cov resin uas tuaj yeem siv los ua cov ntim cov yeeb yaj kiab uas tuaj yeem hloov LDPE thiab HDPE. Nws lwm daim ntawv thov tseem ceeb yog cov coatings thiab additives rau daim ntawv thiab board ntau lawm raws li Food Packaging Forum.
Tag nrho plaub fossil roj raws li plastics biodegrade nyob rau hauv peb lub hlis nyob rau hauv industrial composting, nyob rau hauv ib xyoos nyob rau hauv lub tiaj nyom composting thiab nyob rau hauv ib mus rau ob xyoos hauv av / landfills raws li InnProBio (pg. 4).
Recycling thiab Composting
Cov khoom ntawm cov khoom sib txawv ntawm cov khoom siv biodegradable yuav tsum tau khaws cia hauv siab kom kho lawv thaum kawg ntawm lawv lub neej, ceeb toom rau Environmental Protection Agency (EPA).
- EPA piav qhia tias biodegradable plastics yuav tsum tsis txhob muab ntxiv rau hauv cov bins uas rov ua dua cov khoom qub raws li lawv tau ua los ntawm cov khoom sib txawv. Qhov no muaj tseeb rau ob qho tib si biobased thiab fossil roj hom.
- Txawm hais tias cov plastics tau cim tias biodegradable thiab compostable, ntau ntawm lawv tuaj yeem degrade tsuas yog nyob rau hauv tej yam kev mob muaj nyob rau hauv kev lag luam composting chaw; hu rau cov chaw ua haujlwm rov siv dua hauv zos kom paub txog cov nroj tsuag compost ze tshaj plaws. Tsuas muaj 200 qhov chaw zoo li no hauv Asmeskas xyoo 2017, yog li cov chaw zov me nyuam yuav tsum tau nce ntxiv.
- Qhia kom meej tias lub hnab ntim tau hauv tsev los ntawm kev ua raws li cov lus qhia khoom ua ntej muab tso rau hauv cov khib nyiab khib nyiab.
- Kev rov qab los ntawm cov khoom siv biodegradable plastics tsis tuaj yeem ua los ntawm kev rov ua dua tshiab, vim tsis muaj chaw siv.
Kev sib cais, sib sau ua ke, thiab degradation yog tsim nyog los coj kom zoo dua ntawm biobased thiab biodegradable plastics. Nyob rau hauv nws tsis muaj, feem ntau ntawm biodegradable plastics xaus rau hauv landfills.
Yav Tom Ntej ntawm Biodegradable Plastics
Qhov biodegradable ntawm plastics tsis tuaj yeem daws qhov teeb meem ntawm cov pa phem yog tias lawv tsis muab pov tseg kom zoo. Nws tseem yog ib qho tseem ceeb rau cov neeg siv kev coj cwj pwm kom nyob twj ywm rau kev txo qis kev noj lossis rov ua cov yas kom tau txais txiaj ntsig los ntawm kev hloov pauv ntawm cov pa roj fossil roj plastics mus rau biodegradable plastics.
