Plastic Bins, UV, CO, and Failure
Poor Choice
Better Choice!
Plastic Bins, UV, CO, and Failure. This blog discusses which plastic bins you can rely on on an urban farm, and which ones you must not use. It all comes down to sunlight, pollution, and chemistry, folks.
“[PP} also degrades back into small microplastics and ends up in your soil and water. It is a de-facto pollutant.”
Understand Chemistry and Plastic
Polypropylene Molecule - the chemical strcture is open and airy — and weak.
Behold, the power and the weakness of the thermoplastic Polypropylene
Polypropylene (PP) is an amazing thermoplastic (heat and mechanical-recyclable polymer). It is incredibly useful, plentiful, and can be molded into virtually any shape. It can also be created in any color. Clear polypropylene storage is very popular.
When we first started working here at Mezzacello Urban Farm we invested heavily in clear PP storage bins. Having lived only in apartments, Clear plastic bins seemed to be a no-brainer. They were sturdy, stackable, inexpensive, and clear.
It seemed like a great idea to use clear bins on an urban farm. We needed to store a wide variety of tools and supplies and clear bins let us visually keep track. It is not and here is why.
The Clear Cons of PP
Clear PP is not UV resistant (sunlight will weaken and destroy it)
Clear PP is easily eroded by CO2 and CO (Carbon Monoxide)
Think about touching a weather-exposed clear bin and it just breaks
An urban farm is virtually encased in CO pollution from traffic
Clear PP becomes VERY brittle when exposed to freeze/thaw temps and water
Yes, It’s nice because you can see in, but soon you will be looking in through holes and cracks
Why PP Resin?
The difference basic chemistry makes
It’s helpful if you think about Polypropylene as flour and it’s Resin as a robust batter.
Basic Polypropylene (PP) is a fine powder that is mixed together, heated, and extruded into any shape. The size of the PP pellets varies, but generally clear PP is made of small, fine granules to impart that clear structure to the finished plastic. This is its weakness on an urban farm.
Like flour and water the shape you get will be fine, but also flimsy. There is nothing in the fine silt structure of clear PP to give the plastic any resistance or structural strength, and so, just like baked cookies, if it is not stored well, it will become stale and brittle.
Using clear PP on an urban farm guarantees you one year of use max and almost NO waterproof ability. It also degrades back into small microplastics and ends up in your soil and water. It is a de-facto pollutant.
Polypropylene Resin (PPR) is also flour, but the flour is cast in pellets and mixed with stabilizers and UV resistant chemicals that create a batter - akin to cake. It still has many of the weaknesses of PP, but the resin DOES impart UV-resistance, structural heft, and CO Pollution degradation resistance, and improved weakness to freeze/thaw and water.
My favorite Bin to use
These PPR Industrial strength black stackable totes are amazing. But even they have limitations. We should discuss their pros and cons here.
PROS
Durable and UV and CO resistant
Stackable and Strong
PPR Lids are also strong and lockable
The PPR bins are endlessly reusable
I have used them for water storage, equipment storage, and even chick brooders
PPR Bins are moderately water tight
PPR Bins come in a wide variety of sizes, but not colors
PPR Bins last considerably longer when in shade and out of direct water
We leverage steel carports at Mezzacello just for this purpose
CONS
Lids are NOT completely water tight
They can be configured water tight with a shower curtain draped over the box and beneath the lid
Interior of the black box will heat up in direct sun and destroy electronics and batteries inside
The PPR bins hold up well, but will eventually degrade if left exposed for years
You MUST label them otherwise, they are literally blackboxes
Final Notes
Stacked PP Resin bins with a weaker PP cousin on top - and indoors only
These black PPR bins are the workhorses of my urban farm and educational outreach. They easily fit atop rolling movers dollies and become mobile storage bays. The photo above is of a series of four stacked PPR bins with one waeker PP bin sat on top. My goal is to find a way to 3D print a door with a watertight clear window.
