Is There an Alternative Way to Dispose of Expired Reagent Plates?

APPLICATIONS OF USE

Since the reagent plate's invention in 1951, it has become essential in many applications; including clinical diagnostics, molecular biology and cell biology, as well as in food analysis and pharmaceutics. The importance of the reagent plate shouldn’t be understated as recent scientific applications involving high-throughput screening would be seemingly impossible.

Used in a wide variety of applications in healthcare, academia, pharmaceuticals and forensics, these plates are constructed using single-use plastic. Meaning, once used, they’re bagged up and sent to landfill sites or disposed of by incineration - often without energy recovery [1]. These plates when sent to waste contribute to some of the estimated 5.5 million tons of laboratory plastic waste that is generated each year [3]. As plastic pollution is becoming a global problem of increasing concern, it raises the question - could expired reagent plates be disposed of in a more environmentally friendly way?

We discuss whether we can reuse and recycle reagent plates, and explore some of the associated issues.

WHAT ARE REAGENT PLATES MADE FROM?

Reagent plates are manufactured from the recyclable thermoplastic, polypropylene. Polypropylene is well suited as a laboratory plastic due to its characteristics - an affordable, lightweight, durable, material with a versatile temperature range. It’s also sterile, robust and easily mouldable, and in theory is easy to dispose of. They can also be made from Polystyrene and other materilals.

However, polypropylene and other plastics including Polystyrene which were created as a way to preserve the natural world from depletion and over-exploitation, are now causing a great deal of environmental concern. This article focuses on plates manufactured from Polypropylene.

DISPOSING OF REAGENT PLATES

Expired reagent plates from the majority of the UK’s private and public laboratories are disposed of in one of two ways. They are either ‘bagged’ up and sent to landfills, or they’re incinerated. Both of these methods are detrimental to the environment.

LANDFILL

Once buried at a landfill site, plastic products take between 20 and 30 years to biodegrade naturally [4]. During this time the additives used in its production, containing toxins such as lead and cadmium, can gradually percolate through the ground and spread into groundwater. This can have extremely harmful consequences for several bio-systems. Keeping reagent plates out of the ground is a priority.

INCINERATION

Incinerators burn waste, which when done on a massive scale can produce useable energy. When incineration is used as the method of destroying reagent plates, the following issues arise:

● When reagent plates are incinerated they can discharge dioxins and vinyl chloride. Both are associated with harmful effects on humans. Dioxins are highly toxic and can cause cancer, reproductive and developmental problems, damage to the immune system, and can interfere with hormones [5]. Vinyl chloride increases the risk of a rare form of liver cancer (hepatic angiosarcoma), as well as brain and lung cancers, lymphoma, and leukaemia [6].

● Hazardous ash can cause both short-term effects (such as nausea and vomiting) to long-term effects (like kidney damage and cancer).

● Greenhouse gas emissions from incinerators and other sources like diesel and petrol vehicles contribute to respiratory disease.

● Western countries often ship waste to developing countries for incineration, which in some cases is at illegal facilities, where its toxic fumes quickly become a health hazard for residents, leading to everything from skin rashes to cancer [7].

● According to the Department of Environment’s policy, disposal by incineration should be the last resort [8]

THE SCALE OF THE PROBLEM

The NHS alone creates 133,000 tonnes of plastic annually, with only 5% of it being recyclable [2]. Some of this waste can be attributed to the reagent plate. As the NHS announced it's For a Greener NHS [2] it is committed to introducing innovative technology to help lower its carbon footprint by switching from disposable to reusable equipment where possible. Recycling or reusing Polypropylene reagent plates are both options to dispose of plates in a more environmentally friendly way.

REUSING REAGENT PLATES

96 Well Plates can in theory be reused, but there are a number of factors that mean this is often isn’t viable. These are:

● Washing them for use again is extremely time consuming

● There is a cost associated to cleaning them, particularly with the solvents

● If dyes have been used, the organic solvents required to remove the dyes may dissolve the plate

● All solvents and detergents used in the cleaning process need to be fully removed

● The plate needs to be washed immediately after use

To make a plate possible to reuse, the plates need to be indistinguishable from the original product after the cleaning process. There are other complications to consider as well, such as if the plates have been treated to enhance protein binding, the washing procedure may also alter the binding properties. The plate would no longer be the same as the original.

If your laboratory wishes to reuse reagent plates, automated plate washers such as this one may be a viable option.

RECYCLING REAGENT PLATES

There are five steps involved in the recycling of plates The first three steps are the same as recycling other materials but the last two are critical.

● Collection

● Sorting

● Cleaning

● Reprocessing by melting - the collected polypropylene is fed into an extruder and melted at 4,640 °F (2,400 °C) and pelleted

● Producing new products from recycled PP

CHALLENGES AND OPPORTUNITES IN RECYCLING REAGENT PLATES

Recycling reagent plates takes much less energy than creating new products from fossil fuels [4], which makes it promising choice. However, there are a number of obstacles that have to be taken into consideration.

POLYPROPYLENE IS POORLY RECYCLED

Whilst polypropylene can be recycled, until recently it has been one of the least recycled products worldwide (in the USA it’s thought to be recycled at a rate below 1 per cent for post-consumer recovery [9]). There are two key reasons for this:

● Separation - There are 12 different types of plastics and it is very difficult to tell the difference between different types making it difficult to separate and recycle them. Whilst new camera technology has been developed by Vestforbrænding, Dansk Affaldsminimering Aps, and PLASTIX that can tell the difference between the plastics [12], it is not commonly used so plastic needs to be sorted manually at the source or by inaccurate near-infrared technology.

● Property Changes - The polymer loses its strength and flexibility through successive recycling episodes. The bonds between the hydrogen and carbon in the compound become weaker, affecting the quality of the material [4].

However, there is some cause for optimism. Proctor & Gamble in partnership with PureCycle Technologies is building a PP recycling plant in Lawrence County, Ohio that will create recycled polypropylene with a "virgin-like" quality. [10]

LABORATORY PLASTICS ARE EXCLUDED FROM RECYCLING SCHEMES

Despite laboratory plates usually being made from a recyclable material, it’s a common misconception that all laboratory materials are contaminated. This assumption means that reagent plates, like all plastics in healthcare and laboratories around the world, have been automatically excluded from recycling schemes, even where some are not contaminated. Some education in this area may be helpful to combat this.

As well as this, novel solutions are being presented by the companies that manufacture labware and universities are setting up recycling programs.

The Thermal Compaction Group have developed solutions allowing hospitals and independent labs to recycle plastics on site. They can segregate plastics at the source and turn the polypropylene into solid briquettes that can be sent for recycling [11].

Universities have developed in-house decontamination methods and negotiated with polypropylene recycling plants to collect the decontaminated plastic. The used plastic is then pelleted in a machine and used for a variety of other products.

IN SUMMARY

Reagent plates are an everday lab consumable contributing to the estimated 5.5 million tons of laboratory plastic waste generated by some 20,500 research institutions worldwide in 2014 [3], 133,000 tonnes of this annual waste comes from the NHS and only 5% of it is recyclable [2].

Expired reagent plates which have historically been excluded from recycling schemes are contributing to this waste and the environmental damage caused by single-use plastics.

There are challenges that are needed to be overcome in recycling reagent plates and other lab plasticware which can end up taking less energy to recycle compared to creating new products.

Reusing or recycling 96 well plates are both environmentally friendly ways of dealing with used and expired plates. However, there are difficulties associated with both the recycling of polypropylene and the acceptance of used plastic from research and NHS laboratories as well as reusing plates.

Efforts to improve the washing and recycling, as well as the recycling and acceptance of laboratory waste, are ongoing. New technologies are being developed and implemented in the hope that we can dispose of reagent plates in a more environmentally friendly way.

There are some barriers that still need to be challenged in this area and some further research and education by laboratories and industries working in this area.