Why do plants get high?

At a young age, we are taught in school that all living organisms are born, grow, reproduce, and die. As simple as that. So naturally, to carry out these vital functions, the metabolism of every living organism must be equipped to provide nutrients and chemicals either by consuming nutrients from the environment (e.g. digesting the delicious bowl of pasta I just devoured to obtain essential amino acids), or by synthesizing chemicals (e.g. producing nonessential amino acids). These molecules resulting from our metabolism are called metabolites. When metabolites are synthesized to support growth, development or reproduction of an organism, they are called primary metabolites.  

(NOTE: to keep things simple, let’s leave the whole dilemma around whether viruses are living organisms or not out of this post.)

You may have already inferred that the classification of these metabolites as “primary” indicates that there are more types of metabolites, which is right! 

Life is complex, and metabolisms are beautiful machineries that do much more than the bare minimum. The metabolic pathways in our cells not only allow us to survive, they allow us to live fully! The biochemical stimuli in our cells tell us our bodies need food, so we get hungry (and often hangry…), and once we’ve had our meal there is more stimuli to make us feel happy about it and sleepy to allow our bodies to digest the nutrients they just got (or as my people would call it, el mal del puerco). 

Many organisms, including bacteria, fungi, plants and animals, produce secondary metabolites. Secondary metabolites satisfy functions that allow us to stay balanced; or in other words, maintain homeostasis. Many of the popular superfoods got this title due to their abundance in particular secondary metabolites, such as antioxidants, flavonoids and other phenolic compounds. 

There is a group of secondary metabolites, however, that have become the center of attention over the past few months: cannabinoids. 

These chemicals are often discussed in the context of their incredible potential as therapeutic drugs, but we don’t hear much about their originally intended purpose. Why did the Cannabis plant start to produce cannabinoids in the first place?  

Photo by Patrick Tomasso on Unsplash

Plants produce secondary metabolites for various reasons, mostly as a response to stress, which is a bit ironic as many people consume Cannabis to deal with stress. Regardless…for plants, stress can come in many forms, such as drought, lack of nutrients, too much sunlight (UV light), and pathogen exposure, to name a few. 

In 2017, Jonathan Gorelick and Nirit Bernstein authored an excellent chapter in the book “Cannabis sativa L.- Botany and Biotechnology”, which summarizes many studies providing evidence to the environmental factors influencing cannabinoid production in the plant. Gorelick and Bernstein discuss studies in the 70’s showing a correlation between high amounts of macronutrients and an increase in THC content in the plant. They also discuss a study in 2012 where THC content increased after exposure to UV light (likely due to an increase in floral material and not necessarily due to an increase in THC synthesis), and three studies between 1977 and 2003 talking about the insecticide and insect deterrent potential of THC, suggesting the role of cannabinoids in plants as a protection against insects. Similarly, they included studies from 1984 and 2009 discussing the antimicrobial role of cannabinoids, which suggests that cannabinoids also play a role in protecting the plant from microbial pathogens; they also discuss studies from the 70’s showing an increase in trichome density in dry conditions, and even a couple of studies from the 80’s discussing that cultivation of hemp in dry environments (a variety known for its lack of THC) produced a significant amount of this cannabinoid.  

This very long and dense paragraph illustrates the following: most studies we have on the matter are more than 10 years old. Of course, I do not claim to have read every single publication out there on the topic, but even if there are more scientific publications that provide evidence to the role of cannabinoids in the plant, they are not easily accessible. 

 Yes, we have some knowledge on the role that cannabinoids play in defense against insects and microbes, as well as UV irradiance. These roles are attributed to the little hairs present in leaves and flowers of many plant species, called trichomes, and I don’t think Cannabis should be any different. However, we do not know many details about these mechanisms. Why are there more than 70 different cannabinoids in the plant? What triggers cannabinoid synthesis in the plant? Does pathogen recognition trigger cannabinoid production? Does the plant synthesize different cannabinoids depending on the particular species of the insect or microbe attacking it? Are there symbiotic associations that stimulate cannabinoid synthesis? 

There are so many questions to which answers are not easily available, and in this day and age it should be quite easy to find all sorts of information, so maybe we have not figured them out yet. 

We talk about the need to characterize the pharmacological activity of cannabinoids, which I consider crucial for the success of this emerging industry, but I also believe it is equally important to effectively understand the role of cannabinoids in the context of the plant. If we do not understand why plants need to get high, we might not be getting the full picture. 

The microfactories of whisky and fibres

 When the word “microorganisms” pops up in a conversation it can trigger multiple perceptions. To some, the first thing that comes to mind are diseases. [Salmonella, influenza, Candidiasis...] To others, microorganisms remind them of nutritional yeast, baking, and of course, alcoholic beverages like wine and beer (oh, La vie Boheme).  

There are few others, however, that picture something entirely different when thinking about microorganisms: microfactories. Even though I am a huge (and I mean HUGE) fan of whisky, beer and company, I consider myself in this last group. Microorganisms are incredible. They can adapt to extreme conditions, have survived multiple extinction events, and are even responsible for the change in atmospheric gas composition that allowed for life as we know it on Earth. 

Psychedelic microbes hard at work!

The number of microorganisms studied so far opens the door to the vast capabilities they exhibit. Just in the last decade, the most revolutionary tool in gene editing, the CRISPR/Cas9 system, was developed after studying the adaptive microbial immune system. And it is only the tip of the iceberg. We don’t know what we don’t know, but we know there are hundreds of microbial species we don’t know, you know? 

If microbes were politicians I have no doubt that Saccharomyces cerevisiae would be leading the polls, followed very closely by Lactobacillus acidophilus and some of its lacto-cousins. However, I want to further explore the amazing roles available to microorganisms in our industry. From fermentation in food and beverages, to the production of bioenergy and bioplastics, our industry benefits immensely from microbial machineries. The following list provides some of my very personal favorite examples of how these tiny guys can make a huge impact in our industry. 

Bacterial Cellulose

Lignocellulosic biomass, or plants that produce hard wood, is rich in cellulose, a fiber composed of multiple glucose molecules (a.k.a. polysaccharides). For decades our industry has benefited grandly from these fibers, with paper being the most popular application. Other uses of cellulose include composites, biocompatible materials, and about 80% of the textile fibres produced in the world are based on cellulose or polyester. 

Another advantage of cellulose is that it can be modified through chemical alteration to obtain or improve specific capabilities. For example, cellulose in its natural form can serve as an adsorption material; however, the adsorption capacity of cellulose can be drastically improved with chemical modifications. In fact, cellulose can be a precursor to form activated carbon, the most popular and highly efficient adsorbing material.

Cellulose is great, and we keep on learning new ways to use it. So why bring bacteria in the equation? The extraction and purification of cellulose from plants can be expensive, with large requirements of energy, harsh chemicals, and the use of expensive enzymes. 

Machinery to synthesize cellulose (cellulose synthase operon in technical terms) has been found in the genome of several bacteria. These bacteria synthesize cellulose to facilitate the formation of biofilms, and in cases of pathogenic bacteria, colonization of a host.  Therefore, these bacteria have the capacity to produce cellulose, and then secrete it out of their cell, simplifying the commercial production of cellulose drastically. 

Many reports exist on the efficient use of bacterial cellulose, including biomedical applications, drug delivery, food, cosmetics, and emulsion stabilization, amongst others.

Bioplastics

Similar to the case of bacterial cellulose, some bacteria can naturally synthesize polyhydroxyalkanoates (PHAs) and polyhydroxybutyrates (PHBs). PHA and PHB are amongst the most popular bioplastics as they have similar physical properties than petrochemical plastics, are biodegradable, and biocompatible. 

PHA- and PHB-producing bacteria accumulate these bioplastics in storage granules inside of the cell (in the cytoplasm), and usually they don’t follow a strict diet. In fact, there have been reports of these bacteria thriving in municipal sewage, fish solid waste, food waste, and plant-based waste. So with these bacteria we can literally convert waste into bioplastics!

Now lets talk about a different type of microorganisms: microalgae. Microalgae are photosynthetic microorganisms, which means they can convert atmospheric CO2 into sugars though photosynthesis. One of the main energy storage reserves microalgae produce is starch, another polysaccharide formed with glucose. Starch accumulates in granules in several compartments of the cell (cytoplasm and chloroplast), and depending on the species starch content can account to most of the cellular weight. Researchers have preformed a direct plasticization of microalgae biomass into starch-based bioplastics. In addition to starch, proteins and other polymers in microalgae biomass have been converted to bioplastics through a process called electrospinning, in which polymers can be manipulated by the use of electric fields. Through the appropriate optimization of these processes, microalgae biomass can be turned into several types of bioplastics, not to mention the immense benefits this biomass offers… but we’ll get to that in another article.

All of these examples illustrate something bigger than microorganisms producing bioplastics: we can turn waste into plastics. In my opinion this a perfect example of how sustainable development can look like in our society. What do you think? 

CO2 Biosequestration

Perhaps you have heard the term ‘carbon sink’, a natural system where large quantities of atmospheric CO2 are stored. Our oceans are important carbon sinks accounting for the sequestration of large amounts of CO2, storing it into sugars, fats, and biomass. There are also physico-chemical means of CO2 sequestration in our marine ecosystems, but we’ll focus on the biological means for the purpose of this article. Microalgae (including their cousins cyanobacteria) are largely responsible for the (bio)sequestration of CO2 in our oceans and lakes. In fact, cyanobacteria (photosynthetic bacteria, a.k.a as blue-green algae) are responsible for the change in gas composition that allowed for life on Earth as we know it. 

These amazing microorganisms are slowly becoming a macroplayer in our industry. Their ability to photosynthesize makes them ideal for the recovery of CO2 from industrial exhausts. Many cement plants are incorporating microalgae ponds to reduce their CO2 emissions and later utilize the biomass to produce biofuels. Not only do they consume CO2 from the atmosphere, which is one of the greenhouse gases of most concern in our society, but they can also get the rest of their nutrients from wastewater. Most wastewater treatment pants include what is called a ‘tertiary treatment’ where nitrogen and phosphorous are removed. Several studies have demonstrated the feasibility of incorporating a microalgae treatment process in a wastewater treatment plant, where nitrogen and phosphorous species are consumed by microalgae instead of using chemicals. 

From bioenergy and bioplastics, to biofertilizers and nutraceuticals, microalgae biomass opens a world of possibilities for the reduction of CO2 emissions, and the conversion of waste streams into products. 

Renewable Natural Gas

Biogas is composed of methane (≈ 50-70%), CO2 (≈ 25-50%), and other constituents (≈ 10%). It is the main product from the anaerobic digestion (in the absence of oxygen) of organic waste by bacteria. The process of anaerobic digestion is a key player for the treatment of many industrial wastes, including wastes from dairy farms, industrial and municipal wastewater, pulp and paper mill wastes, and lignocellulosic biomass.

Biogas in itself can be used to produce energy, but it can be upgraded to biomethane, a.k.a. renewable natural gas, by converting the CO2 in biogas into methane. Renewable natural gas (RNG) can be injected into the existing natural gas pipelines, as both fuels are interchangeable. In Ontario, we can certainly expect to hear more talks about RNG from the new team at Enbridge Gas Inc.

 Yet another way in which microorganisms can turn waste into energy, revealing a little bit of a trend here, wouldn’t you say? 

Biofertilizers: microorganisms in farming 

We have mentioned several examples of how bacteria and microalgae can play important roles turning different types of waste into products like energy and plastics. Now it is the time to talk about fungi. 

As we expand our understanding of agriculture, the importance of microbial communities in soil becomes more evident. There are many microorganisms that form associations with the rots of plants, where the microbe provides nutrients and protection to the plant, and in exchange the plant provides sugars, or photosynthate, to the microbes. It is a very neat relationship that has huge implications on the crop yields at harvest.  

It would be impossible to talk about every single example of these plant-microbe interactions in this article, so I want to focus to one of my favorite ones: arbuscular mycorrhizal fungi (AMF). AMF is a diverse group of fungi, and it has been found that more than 80% of land plant species. Through this mutualistic association AMF can take inaccessible forms of nitrogen and phosphorous from the soil and turn them into forms that are accessible for the plant, which has earned AMF the title of biofertilizers. This becomes of increasing importance as our finite resources of phosphorous could be depleted soon if we don’t do anything about it. Additionally, AMF can help maintain a healthy soil aggregation and support the plant during drought stress conditions. How is this relevant in our industry? Let’s take my absolute favorite vegetable as an example; AMF has increased tomato yields by about 25%... That is 25% more pizza! I mean, not really, but you get my point. 

AMF’s potential, however, extends beyond crop yields. These microorganisms also play a significant role in phytoremediation, the use of plants to remediate a contaminated site, and there is evidence showing that AMF can enhance the production of biomolecules in plants, such as vitexin with its many pharmacological effects.

Photo by Michael Schiffer on Unsplash

Here we have explored only five examples of diverse roles that microorganisms can play in our industry. It is my hope that this article provides a little bit of context as to what microorganisms are capable of, and perhaps with a little imagination we will reach a sustainable future were microfactories lead the way. 

The gender gap in Cannabis metabolism

Photo by Tim Mossholder on Unsplash

Early in April, I attended the Cannabis Innovation Summit organized by the Toronto Cannabis and Cannabinoid Research Consortium (TC3), where researchers from universities, hospitals, government and industry shared their findings and expressed the importance of strengthening research focused in cannabis products and the endocannabinoid system. 

Many interesting topics were discussed, such as the effect of endocannabinoids in the motor ganglia of patients with Parkinson’s disease, and an intriguing discussion regarding the impact of cannabis use in brain development. Did you know that there is not enough evidence to determine that cannabis consumption will not have an impact in brain development in young adults under 29 years old? There is still too much to learn!

One of the arguments repeated by several scientists was that there is not enough high-quality scientific literature to support analytical methodologies, including cannabinoid extraction techniques, purification and analysis. In fact, some of the panelists shared stories where products labeled as CBD oil where in fact close to 100% THC. 

Another concern shared by several panelists is how little we know about the effect of each of the components in the cannabis plant, reminding us that each substance, be it a cannabinoid or terpene, may act as an active pharmaceutical ingredient. When we think about it that way, consuming oils with several terpenes and cannabinoids is somewhat like taking several pills without fully knowing what they do.     

These basic issues in quality control could pose a huge impediment in the development of the cannabis industry in Canada, and the lack of scientific evidence around the molecular mechanisms in which cannabinoids interact with the endocannabinoid system (and perhaps other receptors and pathways) is a big challenge to responsibly consume cannabis products. 

It is not my intention to be alarming or sound fatalist here; it is a matter of making educated decisions to make the most of these compounds. This brings me to an interesting fact I learned in this summit: the molecular mechanisms of the endocannabinoid system are not the same between females and males. Even though behavioral responses in adults that consume cannabis are similar, the mechanisms that take place at a molecular level are not the same amongst female and male consumers. I find this fascinating and so I decided to dig deeper to get a better idea on what the literature says about the differences in mechanistic effects of cannabinoids amongst females and males. 

If you are not familiar with the endocannabinoid system, I suggest you read this first. 

Photo by holdentrils on Pixabay

The following program contains material that might be too nerdy. Reader discretion is advised. 

Endocanbinoid receptors and reproduction

When I think about biochemical differences between females and males I immediately think of the reproductive system. The balance of sex hormones, such as testosterone, estrogen and progesterone, is quite different between both sexes, and obviously there is a huge difference between sperms and eggs. That is why I was so interested to learn about the effect the endocannabinoid system has in reproduction.

A mini-review authored by Italian researchers highlights the important role of the endocannabinoid system in reproduction, particularly related to sperm production and functions, providing examples of studies in both humans and other animals. For example, studies show that THC and the endocannabinoid AEA (anandamide) inhibit acrosome reaction (necessary to fertilize the egg) on sea urchin sperm, which was also observed on boar using the AEA analog methanandamide. Similarly, AEA inhibits sperm motility in humans and frogs (maybe there is a connection between princes and frogs after all…)

These effects result from the binding of the mentioned molecules to the CB1 receptor. For a moment I thought that activation of this receptor has a negative effect on sperm, but studies working with mutant mice lacking the CB1 receptor (Cnr1 null mutant) show that in the absence of this receptor these rodents have poor chromatin quality; in other words, the DNA in their sperm is not packed properly. So it is likely that CB1 plays an important role in formation of sperms, and there seems to be a delicate balance between the time of activation by the endocannabinoid AEA and the positive or negative effects in sperm production and function. 

There is also evidence showing that the endocannabinoid system and sex hormones like testosterone, estrogen and progesterone, regulate each other. The mini-review mentions a couple of studies that demonstrate a correlation between cannabis consumption and a decrease in testosterone levels in the plasma of men, which also correlates to an inhibitory effect on sexual behavior. Similarly, a study in mice showed that production of the enzyme that degrades AEA (FAAH; fatty acid amide hydrolase), is controlled by the sex hormones estrogen and progesterone during pregnancy, suggesting that high amounts of AEA are required to modify the endometrium during pregnancy.

However, a study looking at AEA levels of pregnant women explores this topic further. Levels of AEA in the bloodstream of pregnant women decreased 50% from the first to the second trimester, and remained unchanged from the second to the third trimester. Interestingly, levels of AEA increased 370% during labor (compared to the third trimester levels), and there was a direct relationship between AEA levels and the duration of contractions, suggesting that this endocannabinoid plays a role in preparing the body for birth. The authors recommend that “…the current exploration of the use of exocannabinoids for pain relief in labor be delayed”, as in vitro stimulation of the CB1 and CB2 receptors resulted in the relaxation of myometrial strips (involved in contractions), and a correlation between high levels of AEA and miscarriages has been reported. 

Although the relationship between the endocannabinoid system and reproductive mechanisms is not completely elucidated, these studies suggest an important interaction between the two, highlighting the importance of timing and concentration in which these cannabinoids interact with the endocannabinoid system.

Differences in brain development

One of the topics that I consider fundamental for the responsible consumption of cannabis is the potential effect cannabinoids can have in brain development. However, I never considered that this would be different between young females and males.

A study published in Neuropsychopharmacology looked at the effects of chronic THC consumption in adolescent rats. The authors exposed adolescent rats to THC and observed their behavior in adulthood as well as changes in the development of the cannabinoid receptors. Interestingly, CB1 receptor levels in the brains of adult female rats exposed to THC decreased in the amygdala (a part of the brain responsible for processing emotions), ventral tegmental area, and nucleus accumbens (both involved in reward mechanisms), whereas the decrease in CB1 receptor levels in male rats was observed only in the amygdala and hippocampal formation (part of the brain associated with memory). There were also differences in the behavioral effects, as female rats exhibited alterations in the emotional circuit, leading to depressive behaviours, whereas changes in the behavior of male rats were reflected as an altered sensitivity to rewarding stimuli. 

Photo by vaun0815 on Unsplash

 A similar study showed that activation the CB2 receptor plays an important role in cell proliferation of the medial amygdala, which modulates behavioral sex differences at several ages. The authors suggested that activation of the CB2 receptor reduces cell proliferation in the medial amygdala; in other words, when the endocannabinoid 2-AG binds to the CB2 receptor, CB2 is activated and stops cell proliferation in the medial amygdala of neonatal female rats. The endocannabinoid 2-AG is found in about 40% higher amounts in neonatal male rats, and the enzyme responsible for the degradation of the endocannabinoid 2-AG (MAGL; monoacylglycerol lipase), is found in about 50% higher amounts in female young rats than male. To put it simply, male rats have much higher amounts of 2-AG, while female rats purposefully degrade this endocannabinoid. This increase in 2-AG availability in male rats suggests that “CB2 signaling is maximally activated”, which may explain why young males have lower cell proliferation than females. To further support this theory, newborn female rats were exposed to a cannabinoid receptor agonist that mimics the effects of 2-AG, and the authors observed “masculinization of juvenile behavior”. The effects on brain development after exposing newborn rats to high amounts of THC were so big that it caused very apparent changes in behavior… but only in females.  

 Based on these studies, stimulating the endocannabinoids system could have different effects in several areas of the brain of females compared to males, and even changes in behavior have been observed. So, when exploring the possibility of using cannabinoids to treat a medical condition, would it be as efficient amongst both sexes? Or rather, would it be safe for both? 

Addressing the gender gap in the molecular mechanisms of cannabinoids

 Even though the CB1 and CB2 receptors are found through out the brains in both sexes, activation of these receptors by either endo- or exocannabinoids impacts different areas of the brain amongst females and males. The studies discussed in this article are just a few examples of differences in the effects cannabinoids can have on brain development of both sexes, and how different the changes in behavior can be.  

 The cannabis plant has shown to produce promising active pharmacological ingredients to treat many diseases, which I personally find very encouraging, but evidence like the very few studies mentioned in this article should not be ignored. Gvien that the lack of effects in one sex could be masking the effects on the other sex when analyzing the data, any treatment targeting the endocannabinoid system should be carefully investigated to assess potential differences in responses amongst female and male patients. 

Going back to the lack of information on the individual cannabis substances mentioned at the beginning of this article… If we want to fully understand how to make the most of these substances, researchers should consider the sex of their subjects as an important parameter for their observations. As the few studies discussed here suggest: there is no gender equality in the molecular mechanisms involved with cannabinoids. 

Fake news in SR&ED

Is there more “Fake News” surrounding the SR&ED Program than the American Media, according to Trump? You decide… Here are just a few things we regularly hear when talking to people about the SR&ED program. 

Photo by AbsolutVision on Unsplash

We can’t make SR&ED submissions because… 

• We’re not creating something new and unique.  Fake news.  

• We’re pre-revenue.  Fake news.  

• We’re not profitable.  Fake news.  

• We’re foreign-owed.  Fake news.  

• We don’t have scientists or do research.  Fake news.  

• We only use sub-contractors.  Fake news.  

• We can’t claim software development.  Fake news. 

• We already completed our project.  Fake news. 

• We’re not yet complete our project.  Fake news.  

• We were told by someone else that this didn’t qualify.  Might be fake news. 

We are happy to offer free consultation and dispel all these myths! 

And the plastics lived happily ever after… A fairy tale gone wrong

Photo by Ayotunde Oguntoyinbo on Unsplash

Plastic pollution is a reality we can no longer ignore. From plastic containers to microplastic particles, plastic waste is rapidly accumulating in our environments, where they can remain for hundreds of years. The rate at which we are consuming and disposing plastics is equivalent to dumping a garbage truck full of plastic waste into the ocean every minute.   

To reduce the amounts of plastic waste, single-use plastics will be banned in the European Parliament by 2021. In Canada, major cities like Montreal and Vancouver have already taken action against single-use plastics, and the conversation has already started in Toronto too.  

As promising as these regulations are for the reduction of plastic waste, the success of this motion will require the involvement of every resident. In April of last year the federal government launched a consultation where Canadians could “…share their views on the topic ‘Moving Canada Toward Zero Plastic Waste.’” The consultation received 1,900 comments and 12,000 campaign letters, which is by no means an extensive pool of participation. Nonetheless, it produced a series of potential solutions and certainly got the conversation going. 

The three R’s: Reduce, Reuse, Recycle 

One of the comments resulting from this consultation touched on how there is plenty of information available for recycling, but not so much in terms of reducing and reusing plastics. This statement is alarming considering that, according to the Canadian Council of Ministers of the Environment (CCME), Canada only recycles about 10% of plastics.  

Sadly, this low percentage of recycled plastics is not exclusive to Canada. According to a study published in 2017 in the journal of Science Advances, it is estimated that only 9% of the plastic waste generated by 2015 has been recycled (out of which only 10% is recycled multiple times), 12% has been incinerated, and 79% has been sent to landfills. Further, the authors estimate that only 30% of plastics produced between 1950 and 2015 are in use.  

It is not clear why recycling rates are so low, but Plastics for Change provides an interesting list of examples that make it much easier to use virgin material as opposed to recycled plastics in developing countries.  

Perhaps the easiest way in which we as consumers can contribute to the reduction of plastic waste is to use less plastic. Sounds quite obvious, but when we actively look into how to consume less plastic it is shocking how much we’ve grown accustomed to using plastic products. Fortunately, there is plenty of information online about how we can limit our consumption of plastics to have a positive impact in our society, such as this example I really like.

Photo by Paweł Czerwiński on Unsplash

Recirculate… the fourth R?

 When talking about plastics, we should be careful of lumping all plastics in the same category. Synthetic plastics, those derived from petroleum, are the most widely available types of plastics. Amongst these you are probably familiar with polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET) and polyurethane (PUR).  

One should keep in mind that we have now started to integrate bioplastics and biodegradable plastics in our industry. Bioplastics are made with polymers derived from renewable materials, such as polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB) and starch blends. Biodegradable plastics, on the other hand, can be either synthetic or bio-based, but can be degraded by microorganisms and enzymes.  

The rate of degradation in biodegradable plastics, however, occurs at a very slow rate. It would be unreasonable to assume that plastic degradation could keep up with plastic consumption rates. Additionally, researchers from the University of Basel suggest that microplastic particles derived from biodegradable plastics provoke similar digestive constraints on freshwater invertebrates. So whether you are using synthetic, bio- or biodegradable plastics, the use of plastics should be avoided where possible. 

Over the last decade, there have been several studies aimed to discover microorganisms and enzymes capable of degrading plastics that are considered non-biodegradable. A review published in 2017 provides a recollection of research efforts with the purpose of identifying enzymes that contribute to the biodegradation of recalcitrant plastics for the recovery of chemical feedstocks. Some examples include cutinases that hydrolase ester bonds in PET; hydroquinone peroxidase for the degradation of PS; and laccases, manganese peroxidase, and lignin peroxidase, for the degradation of PE.

 It is important not to confuse bioplastics with biodegradable plastics; while some biodegradable plastics are bioplastics, not all bioplastics are biodegradable (e.g. bio-based PET and PE). This becomes particularly important when recycling systems are in place. If biodegradable plastic is mixed in the recycling bin, it could ruin the entire batch.

Re-refining plastics 

The quality that makes plastics so useful in our industry, durability, is the same reason why we are having such a worrying problem with plastic waste in the first place. The only way to destroy plastics is by burning them, which produces large quantities of CO2, along with many toxic gases. A study comparing two plastic treatment options in The Netherlands, incineration and recycling, concluded that, even though the incineration of plastic waste generates energy, it is not enough to offset the large amounts of CO2 released in the atmosphere.

 However, advances in thermochemical processes make it possible to have more control over the emissions and products obtained. Pyrolysis is a thermochemical treatment in which degradation occurs at temperatures between 500˚C and 900˚C in total absence of oxygen. Pyrolysis produces a liquid product (pyrolysis oil), a gaseous product (syngas), and a solid product (char), and the composition of products is highly dependent on the feedstock used.

 A study from the University of Surrey looked at the conversion of plastic waste into a diesel-like oil through pyrolysis. The authors of the study used a mix of waste products as a feedstock, including styrene butadiene, polyester, PE and PP, and showed that the pyrolysis oil produced could potentially be used in diesel engines, although more work is needed to optimize performance.

 Similar conclusions were discussed in another study, where half of the energy required by the pyrolysis reactor was provided by a sola photovoltaic system. In this study the authors looked at PS, PE and PP independently, and showed that PS had a yield of 90% pyrolysis oil, PE had a yield of 51% syngas, and PP had a yield of 65% syngas.

 Even though thermochemical treatments like pyrolysis are not developed to a point were it is realistic to convert all the plastic waste we have in a responsible way, the technology is getting better and better. We just need to stop making it worse for now.   

As in most issues affecting our environment, the solution to plastic pollution requires that we take action from many angles. By consuming fewer plastic products, recycling our waste properly, and sourcing biodegradable alternatives to plastic, we can stop throwing more plastic waste to our environment. However, this has to be an active choice by individuals, governments, and our industry.