Welcome to the (delayed) first post of the year. This is a sui generis article a bit more comprehensive than usual.
Polymers, more commonly known as plastics have become indispensable since their explosion in the middle in the 20th century.
Source: Plastics Europe.Here’s the distribution of plastics production in the world.
Packaging and Construction are the sectors that lead plastics consumption.
I am not going to describe the numerous advantages of polymeric materials, on the contrary I will focus on what made plastic infamous, its sustainability issues.
Also, taking into account the name of this blog, most of the examples and comments will be relayed to the packaging industry.
PLASTICS AND SUSTAINABILITY
Plastic environmental issues are basically twofold:
- Their end-of-life problems
- Their non-renewable origin
Since plastics production keeps growing, and Packaging is the main consumer of polymeric materials, let’s see what happens to plastics in general – and plastic packaging in particular – after their end of life.
One third of the plastics produced are destined to single-use packaging applications.
As commented in the first post of this blog, plastics form land-based sources end up in the oceans.
So, what happens to plastic waste? How much is recycled?
Of course,the answer to these questions varies from country to country:
In the U.S. it’s about 12%. Here’s the data for 2017:
Last year U.S. plastic resin producers announced their aim to recycle or recover all plastic packaging by 2040.
When they are not recycled, plastics are incinerated -generating energy in the process – or end up in landfills.
Plastics in landfills may contaminate the waterways, aquifers and limits the landfill areas, and Incineration may release harmful gases, dioxins, HBr, polybrominated diphenyl ethers and other hydrocarbons.
So this is one of the main plastics sustainability and environmental issues, Let’s see the other one.
Plastics Original Sin
If somehow, all plastic waste was managed in the most sustainable way possible, polymeric materials would still have an environmental drawback: they come from fossil fuels, a nonrenewable source.
The environmental effects of burning fossil fuels (mainly oil (petrol), natural gas, and coal) are well known, but oil extraction involves its own environmental problems. Unfortunately, oil is the main feedstock for producing most of the polymers used in Packaging and many other sectors.
So what will happen when we run out of oil?, and when is this going to happen?
The End of Oil
In 2009, an estimated 84 to 85 million barrels was extracted, and just as much was consumed. According to BP current world oil consumption is around 100 million barrels per day, and estimates that number will go up by another 10% before levelling off.
So, how long can this go on pumping fossil fuels out of the ground without exhausting our supplies?
The world has “almost run out of oil” at least five times in the past two centuries. Here are some examples:
- “The world will run out of oil in 10 years.” – U.S. Bureau of Mines (1914).
- “The world will run out of oil in 13 years.” – U.S. Department of the Interior (1939 and 1950).
- “The world will run out of oil and other fossil fuels by 1990.” – Paul Erlich, Limits to Growth (1973).
- “The world will run out of oil in 2030, and other fossil fuels in 2050.” – Paul Erlich, Beyond the Limit (2002).
These analyses did not consider the advances in technology that would make some extraction method possible. Also, the rise in the price of oil has made “unconventional” reservoirs worth extracting.
However, some nations have already reached peak oil. U.S. production peaked in 1971 and has been in decline ever since [source: EIA]. Some analysts and industry officials that believe global oil production would peak before 2030.
And what happens after peak oil? it’s difficult to know, since once oil prices begin to rise, consumption may fall, or unconventional and more expensive production methods could be used. Anyway, at some point we will run out of fossil fuels, or they will become too expensive.
Because of our heavy dependence on crude oil and its many byproducts, a small decrease in oil production can have important economic consequences.
Hoping that any post-oil doomsday scenarios are avoided, and that we have been able to find one or several alternative energy resources to replace fossil fuels, what about polymers?, will we already have alternative ways of obtaining plastics?
Plastics Beyond Oil
The early plastics industry in the 19th century was based on coal conversion chemistry. Even today some countries like China produce plastics from coal. The postwar plastics revolution occurred in the United States following the invention of the Zeigler and Zeigler-Natta catalysts for polyolefin synthesis, and the fluidized bed processes for ethylene oxide production.
Not only are oil and natural gas the feedstock for those reactions but also provide the heat and pressure that drive them cheaply.
So let’s take a look at the existing and in progress alternatives to oil as feedstock for polymers.
Currently, the most viable candidate to replace oil as a source of raw materials for polymer production is natural gas.
Using the new catalyst, ethene for the production of plastics can be obtained from natural gas.
But natural gas is not a renewable resource but another fossil fuel.
In the first one I mentioned that the term bioplastic or biopolymer can characterize two types of polymeric materials:
- Those obtained from a renewable source.
- Plastic materials that are completely biodegradable and compostable (according to EN 13432 in Europe ASTM D 6400  and ASTM D 6868  in the US, while. Australia and New Zealand refer to the AS 4736  standard).
I will focus on the first type (sometimes called bio- based), since my aim is to comment on the possibilities of replacing fossil fuel based polymers.
Bio- based plastics some issues. I mentioned some of them (mainly for bio-based biodegradable polymers) in post 2. The main one would be that despite claiming a lower carbon footprint than conventional plastics, it can actually be higher due to the energy and materials used in growing the crops.
But supposing these issues could be minimized, or that we will have no choice but to accept them due to oil scarcity, could bio-based plastics replace conventional plastics in the near future? What are the main the main obstacles for this?
1. Production capacity
The global bioplastics production capacity is set to increase from around 2.1 million tonnes in 2018 to 2.6 million tonnes in 2023 according to the results of the European Bioplastics’ annual market data update.
In 2018 the global bioplastics production reached 7.5 million tonnes – just 2% of the production volume of conventional oil-based polymers.
The potential is much higher but, will higher oil prices and favorable legislation help close this huge production difference in time?.
Polymers from renewable resources can be obtained through chemical modification of natural polymers, such as starch, cellulose, or chitin (more on this one further on). They can also be synthesized from biomass (lignin, cellulose, starch, plant oils).
Another option, is to polymerize renewable monomers (obtained by modern biotechnology and biorefinery processes).
Also, by using biological foodstuffs, the obtained polymers could be more biodegradable (which can be a two-edged sword: and cause problems due to shorter shelf-life, and also suring recycling/composting).
One way of assuring the same functionality of current polymers is using the biobased versions of current plastics. Two types of these plastics are especially relevant:
Existing bioPET bottles combine bioPET and recycled PET.
I am not aware of an economically viable, 100% bio-based PET bottle on the market.
Usually, the bio-based content of “green” PET bottles is about 30% such as the famous Coca-Cola’s PlantBottleTM technology.
This is an interesting article about the first bottles with bio-PET.
Several companies are on the race for the first 100% bio-based PET bottle.
Here’s a proposal from 2102:
On February 26, 2019, Plastic News Europe informed about a recently developed conversion process that aims to create 100% bio-based polyethylene terephthalate (PET). The owner of this breakthrough is the company Anellotech, and here’s video about this process:
PEF (polyethylene furanoate)
Competing with bioPET is a 100% bio-based polymer, PEF. For more info on PEF vs bioPEt, please read this article.
PEF has other advantages, such as higher gas barrier properties, better tensile strength, and superior thermal stability are superior gas barrier (10x PET for O2 and 5x for CO2) and better tensile strength, which permits greater light weighting and superior thermal stability without heat-setting (can be hot-filled at about 200-deg F). And it is “sustainable” since it is 100% bio-based molecule.
These several reasons that prevent PEF to replace PET as a packaging material:
- PEF has a time- and energy-intensive production. This relatively costly performance of PEF suffices to overcome the cost-performance of 100% bio-PET for commodity packaging.
- Although a 100% bio-PET molecule does not yet exist (the terephthalic acid (TPA) portion of the molecule is still petroleum-based), it is reasonable to assume that it will be achieved soon; and it will probably be a drop-in molecule, indistinguishable from conventional PET.
- PEF molecule is a contaminant in the current PET stream, so it’s not likely that PEF could be combined with PET.
- Existing PET infrastructure (converting, tooling, recycling) is compatible with bio-PET.
PLA (polylactic acid)
PLA is one of the oldest and more widespread bio-based plastics (second only to thermoplastic starch). It is made from renewable resources such as corn starch or sugar cane.
In the packaging industry, PLA plastics are often used for plastic films and food containers, it is biodegradable and has characteristics similar to PP, PE (usually LDPE), or polystyrene (PS). It uses standard manufacturing equipment, and it’s relatively cost efficient to produce.
I could not find many rigid packaging examples of PLA in the market (only films). Most of what i found is over 10 years old.
One of the advantages of PLA causes some problems: it is compostable, but only in facilities with controlled environments to speed up decomposition. Even in these environments the process can take up to 90 days (more info here). PLA can generate greenhouse gases (methane) in landfills. There are still only a few hundred industrial-grade composting facilities across the United States. Also, PLA must be kept separate when recycled, lest it contaminates the recycling stream.
Other PLA cons are:
- As any other food crop based polymer PLA competes for land with biofuels and food crops. PLA increasing demand could affect the price of corn.
- PLA film life from the time of manufacture to final use can be as little as 6 months, not enough longevity especially for exported products.
- Commercial composters use microbes to break down the organic materials. If large quantities of PLA were present, the lactic acid present would be wetter and more acidic. These means more oxygen for the microbes, forcing the composting facility in turn to need yet more oxygen for the breakdown. Anaerobic digesters would solve this problem.
- Some of PLA’s barrier properties are not as high compared to conventional plastics.
Polymers from Bioethanol
Ethylene is one of the most important chemical intermediates produced by steam cracking of petroleum liquids and natural gases. Catalytic dehydration of bio-based ethanol, or bioethanol is an alternative route for production of ethylene, which reduces the greenhouse gas emissions and dependency on limited fossil fuels.
In 2014 Tetra Pak announced the launch of the industry’s first carton made entirely from plant based, renewable packaging materials. The new Tetra Rex® used Braskem’s bio-based HDPE (for caps) and LDPE (for film) caps, both derived from sugar cane.
To avoid competing for lamd with food crops, a potential source of fermentable sugars for bioethanol production is biomass (usually agricultural waste) in the form of lignocellulosic or starch‐based materials, bagasse form sugarcane or any other viable organic waste (from food, municipal solid waste, and paper waste).
One of the most innovative alternative to the use of oil as feedstock for chemical reactions is using, renewable electricity to split the molecules of abundant substances – such as CO2, water, oxygen (O2), and nitrogen (N2) into reactive fragments. Then, more renewable electricity would help stitch those chemical pieces together to create the new molecules.
Opus 12 a company from Berkeley, has designed a washing machine–size device that uses electricity to convert water and CO2 from the air into fuels and other molecules, with no need for oil. Siemens, provides the large-scale electrolyzers that use electricity to split water into O2 and hydrogen (H2), which can serve as a fuel or chemical feedstock. Even oil companies such as Shell and Chevron are looking for ways to turn renewable power into fuels.
There are ambitious projects not only to replace fossil fuels as the feedstock for plastics but also as an energy source.
Biomass (food and wood processing waste, agricultural waste, animal manure and human sewage) can be transformed into carbon monoxide and hydrogen (syngas), by liquefaction and gasification, biomass‐to‐liquid (BtL) based on the Fischer–Tropsch process to creating an important feedstock for chemicals.
Bio-oil is a product of fast pyrolysis or liquefaction of biomass. Bio-oil can be the feedstock for high-performance biopolymers and bioresins using – for instance -lignocellulosic biomass.
Here are some papers to dig further into bio-oils: one about sustainable products from bio-oils, another on paper bio-oil production from biomass, and an ongoing project to obtain bio-oil from wastewater algae.
This article on Macromolecular Chemistry and Physics mentions using solar power in biological photosynthesis to convert greenhouse gas carbon dioxide and water into biomass, which is used to obtain biofuels, power, and bio-based polymers. Using thermal or biological degradation, water and CO2 are recovered.
Of course, it’s still early to confirm the viability and sustainability of these projects on a large scale. The same article does not paint a completely pretty picture.
Even the partial substitution of fossil oil and gas for biomass would require intensified farming of energy crops in competition with food production. Farmers could choose to grow higher value‐ energy crops than food.
So, the future will tell if project to produce biofuels and bio-feedstocks from biomass, CO2, and other waste products.
Other alternative materials
Let’s mention some curious alternatives from conventional plastics.
Researchers at Cornell University have developed a plastic that uses carbon dioxide and limonene as ingredients, with similar properties to polystyrene. Limonene makes up 95% of the oil from orange peel.
Liquid wood is a new thermoplastic obtained from wood.
Here’s an example of edible packaging from seaweed.
Oil from Plastics
I also wanted to show- if briefly – some projects in the ‘opposite direction’, converting plastic waste into oil.
Pyrolysis again seem to be the process involve to hjeta the plastic waste over heated to over 400 °C and turned into gas which is later condensed, resulting in the production and collection of oil.
Several companies are using pyrolysis to turn plastic waste into oil, for instance PyrOil, OMV Group‘s ReOil project (see video below), Neste (who targets to develop chemical recycling capacity to process more than one million tons of plastic waste annually by 2030), and Kurata Systems (from used industrial oil, plastic wastes, vegetable oil, and refinery and biomass residues), among others.
It seems that fossil fuel plastics are not going to disappear overnight. Although sustainability is becoming a priority, conventional plastics will not be replaced until the alternatives are economically viable.
On the other hand, the side-effects or some “green” alternatives has to be taken into account before carrying out large scale replacement of existing technologies and materials.
Anyway, the more options we could count on when fossil fuels become expensive as feedstock or energy source, the sooner we will make a painless transition to more sustainable technologies..
January 2020, Bruno Rey – The Packaging Blog –