Sustainable Pipetting: Tips for Reducing Plastic Usage in the Lab

Written by Tim Dillon, Mettler-Toledo Rainin

Let’s be frank. We are at perfect liberty to continue our current path of negligent consumption, careless pollution, and ecological vandalism, comfortable in the knowledge that Mother Nature will be just fine in the end.

If that statement seems unusual coming from someone whose LinkedIn profile describes himself as a “Sustainability Gladiator,” then allow me to elaborate. Life is tough, resilient, and extremely adaptable. We can shift the balance of nature dramatically from its current setting, and life will adapt just as it has adapted to past extreme climactic swings, several mass extinctions, and an ever-changing atmospheric composition. Life will adapt and thrive no matter what mess we make of the planet.

Modern Humankind, on the other hand, is not so tough, or at least we have no desire to step back into the deadly game of life as played out in nature. We have a quality of life to protect, and we want to improve this quality as generations pass, so our children and grandchildren don’t experience a harsher, more deadly, and less comfortable life than we do.

So, what is the key to looking after our own best interests? The answer is managing our affairs so that we do not force our environment into a new equilibrium, one that will most certainly not afford us the many blessings we have today.

It’s crucial to look at our personal, individual actions and assess them in light of their impact on the status quo. We must look at what we consume, what we waste, and what the costs of our consumption and waste mean.

When it comes to science, cutting-edge knowledge and research are our superpowers – but this cutting-edge science needs high-quality, often disposable consumables. What cutting-edge science does not need is unnecessary consumption, waste, and irreproducible experimental results or to have to perform an experiment twice where once was entirely possible. 

In a nutshell, the most sustainable plastic is the plastic you do not use.

​Tips for Getting a Start on Reducing Plastic

Laboratories produce a lot of waste, which is no secret. Starting with an understanding of what your lab is throwing away is a great place to start. Conducting a waste audit can help you gain an understanding of what you’re throwing away, how you’re throwing it away, and how you can create more sustainable habits. Learn more about conducting a waste audit here.

There are a variety of ways to reduce your plastic consumption in the lab, which include:
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• Contacting your suppliers to let them know a specific product is creating a lot of waste and see if they have any alternatives.
• Asking colleagues if they have greener alternatives they’re using.
• Researching alternative methods using the ACT label database.
• Reducing packaging & shipping – learn more about how to do so here.
• Spreading the word! If you have extra products, get in touch with other organizations – like local community colleges or high schools – that you can partner with so that products don’t go unused.

And this is just a start. If you’re interested in learning more, My Green Lab has a free, online Ambassador Program that will provide you with a quick introduction to lab sustainability and ideas for how sustainable actions can be implemented at your organization.

My particular area of expertise is in reducing the plastic consumption (and waste) associated with pipetting and safeguarding the highest levels of reproducible experimental procedures. Let's dive in here.

It All Starts with One Little Drop

Precision liquid handling is a foundational step in just about every Life Science process, from basic serial dilutions to a multitude of complex assays.

Every time a sample moves from one vessel to another, every time a buffer or reagent is added, a pipette tip is used. Not only is that pipette tip essential, it must be free of contaminants (DNase, RNase, endotoxins, etc.) as well as manufactured to very high specifications relating to form and function so as to facilitate accurate pipetting.

Pipetting is not optional, and high quality single use pipette tips are not optional. Cutting edge science needs these consumables, and until such a time a technology provides an alternative, we should consider pipette tips a “cost of doing essential science.”

However, much of the plastic associated with how those essential pipette tips is optional. Step back and look at the plastic that comes in your pipette tip racks – it can total more than the plastic you use in tips. This means that with proper assessment of the options available to you, a large part of your pipetting plastic can now become optional consumption.

You manage the essential pipette tip plastic and eliminate the optional tip racking plastic.
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It’s not just about reducing your plastic use either – it is important to shift to the right type of plastic, too. If you must use plastic in your tip rack, then think about using a plastic with a lower environmental impact that the usual polypropylene.

​Tips for Sustainable Pipetting

So, how exactly do you use less plastic and still perform at the high standard you require?

Let’s start with the basic principle that the first step to reducing consumption is to avoid unnecessary consumption, i.e., wasted consumption.

Step one is to have good equipment in good working order. We’re going to use the example of precision pipetting. We generally begin with the pipette and then think of the pipette/tip complex. A pipette tip is, after all, simply a disposable extension of the pipette itself.

Ask yourself:
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• Do you periodically validate your pipettes in between scheduled servicing? How often?
• Do you know what the “instrument limit” is for the particular pipette you are using? Have you accounted for any safety factors? For example, is a 20uL pipette okay for 6uL of sample that is not aqueous and at 4°C, given my current process tolerance?
• Do you know what your process tolerance is? I.e., is it 5%, or put another way, is 100uL nominal volume okay to deliver 95uL or 105uL?
• Do you know what the Uncertainty of a Delivered Volume is for the pipette you are using at any given volume? Is the Uncertainty of Delivered Volume greater or less than your process tolerance? 
• Is it okay to use an air displacement pipette for this sample type? I.e., high vapor pressure sample, hot sample, cold sample, viscous sample, etc.?
• Are you aware of the basics of good pipetting practice and how to avoid the common failing of technique that can contribute to over 5% the Uncertainty of Delivered Volume?

 
All of this is before we even start to think about the pipette tip and the obvious plastic consumption associated with the tip and its racking system!

• Are you using a tip of sufficiently good and uniform fit for your pipette?

 
Differences in pipette insertion into the tip will cause a difference in the pipette/tip complex air column and fundamentally affect the physics of operation for an air-displacement pipette. In brief, a tip that seats the pipette deeper will shorten the air column, and a tip that is overly tight and seats the pipette less deep with lengthen the air column. This affects the relationship between the pipette piston stroke and the force it can exert to draw liquid up into the tip. This is why the current ISO 8655 stipulates that pipettes MUST be calibrated with their manufacturer’s tips.

• Is the tip manufactured to sufficient quality to allow a fine-walled and supple tip collar to facilitate a good seal with the pipette? Thick brittle tips are prone to poor sealing and loss of negative pressure during sample aspiration. The negative pressure generated by the withdrawal of the piston is what draws your sample into the tip.
• Is the tip perfectly clear? Opaque polypropylene is opaque because of micro-scratches on the mould – this leads to surface irregularities on the inside of the tip, increasing the area of tip in contact with the sample, resulting in greater sample adhesion on the tip’s inner wall. 
• Is your tip of sufficient cleanliness and purity? Do you risk introducing contaminants like RNase, DNase, or nucleotides into your sample, or do you risk adding extractables or leachates from tips made from lower-grade materials?

 
These types of considerations should be evaluated before you choose a pipette/tip complex, as all can contribute to the risk of experimental re-runs, irreproducible data, or poor data quality.

Reducing plastic usage

Now we can start to look at what I’m sure you assumed would be the first port of call when thinking about sustainable Pipetting: the amount and type of plastic you are consuming with your pipette tips.

Can you use less plastic? The answer is yes. Refill systems use up to 85% less plastic than the equivalent number of racks of tips. But sometimes, you cannot use a refill system. What if you need filter tips?
The most common material for pipette tip racks is polypropylene. This is far from ideal for several reasons.

Polypropylene (PP) cannot be recycled to produce a product of the same intrinsic mechanical properties as the original product(7). This is because the Molar Mass Distribution of the recyclate is different from the original raw material. This means that even if your PP is recycled, you will never stop the flow of virgin fossil fuel into the product cycle. Your recycled PP must be “downcycled,” and virgin material is needed to make a replacement product. That virgin material represents oil that should stay under the surface of the earth, as well as a whole chain of embedded energy in its extraction, processing, and transport(1,2,3).

That is all assuming your PP is recycled. PP is a Grade 5 polymer(4,5), it requires a high-energy (400F) specialist system to process. It is not widely recycled and has little value in the aftermarket due to the downcycling aspect. Therefore, you have a separate recycling collection for PP in the lab, and as such it will not be recycled in a regular mixed recycling stream. (Click here for further reading about Plastic Resin classifications.)

Here is where sustainable alternatives come into play. PET, on the other hand, is a Grade 1 polymer, meaning it is easy to recycle and can be processed in a general mixed recycling stream. It also requires a lower energy process, 200F in this case(6).

Recycled PET produces a recyclate of very similar characteristics to the virgin material, meaning that, when you recycle PET, you ARE stopping new plastic and new oil from entering the product cycle.

PET is in higher demand in the recycling aftermarket and will be recovered from a general mixed recycling stream. Because it is lighter, it demands less energy to transport and process at end of life.

Rainin has invented the TerraRack, a PET-based rack that uses 50% less plastic in the rack, is half the weight, and produces empty racks that nest inside each other reducing waste volume by up to 80%. TerraRack is a hinged rack that contains BioClean Ultra sterile filter and sterile non-filter tips, so you have options, even with the most demanding of quality requirements. You can find TerraRack in the ACT Database here.

Coming soon will be a Rainin racked tip that removes 100% of the plastic from the rack and lid, substituting a Home Compostable material for the ubiquitous plastic. It is not universally available yet, but we are looking for sustainability-minded pipettors to help us make less plastic the new normal.
 
If you would like to learn more about how you can remove up to 85% of the plastic from your pipetting processes and at the same time shift your plastic consumption to a grade of plastic that is practically (and not just theoretically) recyclable, I am happy to elaborate and expand on the subject. I can be reached at Tim.Dillon@MT.com, or look for me on LinkedIn.

1. Plastic Processing: Upcycling, Recycling, Downcycling and more – Earth5R
2.  The Reasons Why Some Plastic Can't Be Recycled - Better Meets Reality
3. What Plastics Can & Cannot Be Recycled? - Better Meets Reality
4. Can You Recycle Number 5 Plastics? - Earth911
5. Recycling Lab Plastics Poster | METTLER TOLEDO (mt.com)
6. Recycling of Polyethylene Terephthalate (PET or PETE) (azocleantech.com)
7. Recycling of Polypropylene (PP) (azoclea0ntech.com)