Plastic-eating Bacteria - The Future of Recycling.
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| A win for managing plastic pollution! Cheers to a cleaner environment! |
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| Biological Process of Recycling. |
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| Recycling with Biology. |
What is Bio-based Recycling?
The chemical processes by which plastic waste is degraded and depolymerised into either other useful materials or monomeric units (i.e the basic building blocks of that material) is referred to as Tertiary chemical recycling, bio-based recycling or simply bio recycling.
A shortlist of other relevant, published bio-recycling research includes:
1. The enzyme scientists discovered in 1977 that attacks ester bonds in some aliphatic polyesters and depolymerise the materials.
2. 2016 in Sakai Japan, a team of researchers led by Kenji Miyamoto discover a species of bacteria in soil samples obtained near a bottle recycling company. The strange bacteria can eat through polyethylene terephthalate or PET used in plastic containers by secreting an enzyme that breaks polymer down into chemical pieces. Growing the organism require special care and feeding but with the right tropical temperatures. Drawing inspiration from the name of their city, the bacteria was named Ideonella sakaiensis AKA PETase.
3. Molecular biologist Christopher Johnson and his ‘dream team’ agreed the work rate of the PETase organism was way too slow for deployment in recycling plants and decided to do something about it. What started as an attempt to understand how the PETase digests PET led to an accidental modification to the DNA of the enzyme produced by PETase so much so that in a four-day period, the altered enzyme worked 30% faster than the original PETase.
Christopher believes that these plastic building blocks “restored” from original plastic, can even be used in things such as auto spare parts and turbines. Their discovery was finally announced in April 2018.
4. In 2018 at a plastic waste site, German researchers discovered a strain of bacteria in the soil which has been identified as Pseudomonas putida. The organism obtains its carbon, nitrogen and energy by feeding on the materials applied to polyurethane as protection from corrosion which is also known as polyurethane diol. It attacks the chemical bonds that hold it together.
5. Scientists discovered four organisms in Lake Zurich that chomp on polyurethane.
6. Research from India where a bacteria species in the ocean was found to break down polyvinyl alcohol which is used in waterproofing paper.
7. A fungus whose cutinase eats at PET has also been discovered.
8. Bacteria work faster in heated conditions so one set of researchers is studying some extremophiles from the hot springs at Yellowstone Park.
9. A French company has revealed the discovery of an enzyme that can degrade 8 out of 10 plastic bottles into their monomers within a 10-hour time period, with heating above 70oC.
In the last 60 years, 9 billion tons of plastic have been produced of which, only 12% has been incinerated and 7% recycled. The current model of recycling plastic involves grinding and melting which results in lower-grade, weakly bonded plastic that is 75% less than the original plastic in monetary value. With these plastic-eating organisms, however, the material is returned to its very basic elements like a brand-new material which can be used in stress-resistant, yet lightweight materials like Kevlar, snowboards, and even aircraft and cars.
Are there challenges or concerns about Bio-based Recycling?
As novel as these achievements are, they have their fair share of concerns to be addressed, which all the types of plastic-eating organisms discovered appear to have in common.
The greatest challenge with the currently available bio-recycling organisms is that none of them is fast enough to make a significant yet speedy dent in the 300 million tons of plastic being produced every year. While some organisms may be able to metabolize bits and pieces of the basic building blocks of polyurethane, they are unable to break down the larger polyurethane polymers.
Issues have been raised concerning the possible negative contributions of bio-recycling to climate change. These concerns point to the carbon released during the process which becomes carbon dioxide, a greenhouse gas. Some researchers try to downplay this concern by implying that its contribution is minimal when compared to the gases from other industries; while others acknowledge that it would be wise to solve the problem of plastics without creating another.
Last but not the least, so much is still unclear whether such enzymes are environmentally safe for direct, widespread application. This is especially true in oceans and seas where time and time again, certain “interventions” created side effects that were largely under-estimated at first but eventually turned hazardous in the long run. We would not want to make plastics even more poisonous than they already are, you know!
Gains of Bio-recycling.
1. Methods of bio-recycling are numerous and are dependent on the type of polymer being handled. This allows for a diverse range of options to choose from without putting pressure on a single recycling organism.
2. When developed to optimal functionality levels, microorganisms that digest polymers can help form a more robust recycling system that can turn overabundant waste material into better value-added products while still turning a profit on investment.
3. These natural processes of breaking down plastic is less energy consuming than chemical recycling.
4. Some bio recycling processes do not require solvents or sorting as in current conventional methods.
3. Molecular biologist Christopher Johnson and his ‘dream team’ agreed the work rate of the PETase organism was way too slow for deployment in recycling plants and decided to do something about it. What started as an attempt to understand how the PETase digests PET led to an accidental modification to the DNA of the enzyme produced by PETase so much so that in a four-day period, the altered enzyme worked 30% faster than the original PETase.
Christopher believes that these plastic building blocks “restored” from original plastic, can even be used in things such as auto spare parts and turbines. Their discovery was finally announced in April 2018.
4. In 2018 at a plastic waste site, German researchers discovered a strain of bacteria in the soil which has been identified as Pseudomonas putida. The organism obtains its carbon, nitrogen and energy by feeding on the materials applied to polyurethane as protection from corrosion which is also known as polyurethane diol. It attacks the chemical bonds that hold it together.
5. Scientists discovered four organisms in Lake Zurich that chomp on polyurethane.
6. Research from India where a bacteria species in the ocean was found to break down polyvinyl alcohol which is used in waterproofing paper.
7. A fungus whose cutinase eats at PET has also been discovered.
8. Bacteria work faster in heated conditions so one set of researchers is studying some extremophiles from the hot springs at Yellowstone Park.
9. A French company has revealed the discovery of an enzyme that can degrade 8 out of 10 plastic bottles into their monomers within a 10-hour time period, with heating above 70oC.
In the last 60 years, 9 billion tons of plastic have been produced of which, only 12% has been incinerated and 7% recycled. The current model of recycling plastic involves grinding and melting which results in lower-grade, weakly bonded plastic that is 75% less than the original plastic in monetary value. With these plastic-eating organisms, however, the material is returned to its very basic elements like a brand-new material which can be used in stress-resistant, yet lightweight materials like Kevlar, snowboards, and even aircraft and cars.
Are there challenges or concerns about Bio-based Recycling?
As novel as these achievements are, they have their fair share of concerns to be addressed, which all the types of plastic-eating organisms discovered appear to have in common.
The greatest challenge with the currently available bio-recycling organisms is that none of them is fast enough to make a significant yet speedy dent in the 300 million tons of plastic being produced every year. While some organisms may be able to metabolize bits and pieces of the basic building blocks of polyurethane, they are unable to break down the larger polyurethane polymers.
Issues have been raised concerning the possible negative contributions of bio-recycling to climate change. These concerns point to the carbon released during the process which becomes carbon dioxide, a greenhouse gas. Some researchers try to downplay this concern by implying that its contribution is minimal when compared to the gases from other industries; while others acknowledge that it would be wise to solve the problem of plastics without creating another.
Last but not the least, so much is still unclear whether such enzymes are environmentally safe for direct, widespread application. This is especially true in oceans and seas where time and time again, certain “interventions” created side effects that were largely under-estimated at first but eventually turned hazardous in the long run. We would not want to make plastics even more poisonous than they already are, you know!
Gains of Bio-recycling.
1. Methods of bio-recycling are numerous and are dependent on the type of polymer being handled. This allows for a diverse range of options to choose from without putting pressure on a single recycling organism.
2. When developed to optimal functionality levels, microorganisms that digest polymers can help form a more robust recycling system that can turn overabundant waste material into better value-added products while still turning a profit on investment.
3. These natural processes of breaking down plastic is less energy consuming than chemical recycling.
4. Some bio recycling processes do not require solvents or sorting as in current conventional methods.
5. One beautiful thing about these plastic-eating organisms is that the end-product of all that chomping process (i.e. the virgin monomers recovered) can be polymerised and recycled multiple times without a loss in quality!6. The combination of approaches i.e. the linking of several plastic-eating enzymes with those that degrade natural fibres, has the potential to create better and faster enzymes that will speed up the timeline for commercial application, which will greatly improve the economics of recycling.
7. Coloured plastics are not let out. Bio recycling can remove the dye from these materials (this is impossible in current recycling methods), and make it transparent.
Plastic pollution problems are real and already upon us as a planet. Current bio recycling options may have their drawbacks and limitations, but they remain viable options in the pursuit to reclaim our environment. The PET industry has had 40years to garner tons of experience in plastics; bio recycling should be allowed more time and latitude to catch up.
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