Recycling HDPE Oil Containers

[Kakashi-01]

I am participating in a competition to identify new markets for recycling around 2000 tonnes HDPE oil containers colllected annually. About 80 % of these containers are blowded molded while the remaining are injeciton molded. They previously contained gear oil, hydraulic fluid, and engine oil. The market for recycled HDPE from oil containers is currently limited to applications like new oil containers or plastic lumber, making processors less incentivized to collect them because of the backlog inventory they have.

Currently, the market for recycled HDPE from these containers is limited to applications such as new oil containers or plastic lumber leading to inventory backlogs and making processors less incentivized to collect them.

The recycling process description provided to us is somewhat vague, making it difficult to suggest improvements or assess the processors' capabilities. The process includes:

• Manual removal of contaminants such as metal and non-program plastic containers
• Shredding containers into flakes (<25mm)
• Some processors wash and centrifuge the flakes to remove oil others dont, but label residue (paper and glue) remains a challenge.
• Depending on the end product, flakes may be mixed with other plastics or pelletized, though all processors currently lack pelletizing capabilities

I was considering agricultural pipes as a potential market since they have less stringent requirements (
https://www.sciencedirect.com/science/article/pii/S0959652620341263) and could be a single large customer for the processors, given the collection rates and process losses for the recycled HDPE. However, I'm finding conflicting information some sources suggest processors can blend recycled HDPE with virgin plastic for pipes, while others indicate that its a last-resort material with significant losses in functionality makes it more suitable for the existing markets.

I am also trying to understand how to predict pricing for a new market and what would incentivize a pipe manufacturer to source recycled HDPE instead of purchasing virgin plastic from a supplier producing at much larger production rates, benefitting from economies of scale.

 

[btrueblood]

The oil contamination might not be a good fit for ag pipes (I'm thinking irrigation piping)? But if the wash process was improved, maybe? A lot of the hdpe oil buckets and bottles are screen printed nowadays, so maybe that reduces label residue. Regardless, the chain length of the hdpe gets reduced with each re-melt, so that "loss of functionality" is a constraint regardless of the recycled material source.

 

[Kakashi-01]

The oil contamination might not be a good fit for ag pipes (I'm thinking irrigation piping)? But if the wash process was improved, maybe? A lot of the hdpe oil buckets and bottles are screen printed nowadays, so maybe that reduces label residue. Regardless, the chain length of the hdpe gets reduced with each re-melt, so that "loss of functionality" is a constraint regardless of the recycled material source.

https://patentimages.storage.googleapis.com/7d/e5/1a/c298c20150dd4a/EP3341462B1.pdf
I found a patent that claims >90% cleaning efficiency of contaminated. It involves contacting the contaminated plastic with a physical mixture of two liquid phases: water and an organic phase comprising of acetate ester with the general formula C-COO-R, where R is an alkyl group with 4, 6, or 8 carbon atoms, in a concentration of 8-55 wt%.

If this method is viable at scale it could significantly improve the quality of recycled HDPE expanding its functionality beyond existing markets.

Regarding chain scission during remelting, if degradation is unavoidable, instead of repurposing the flakes using only recycled HDPE, could we blend it with virgin resin in small quantities to retain the key mechanical properties while still benefiting from recycled content?

 

[3DDave]

Patents are worth something when you can buy a working device from the holder of the patent. In this case, the question is how to decontaminate or otherwise deal with the contaminated cleaning agent along with how much cleaning agent is required and determining how contaminated the containers are.

What manufacturers of goods don't like is variability. This process seems likely to add variability. So it needs to be sufficiently less expensive to take that risk, but is also bounded by the way the material is degraded. Suppose you can cut 50% off the price of virgin resin, but you can only use 5% of the material - then you only save 2.5% while adding the systems to ensure that the mix can be no more than 5%.

When you wrote "Currently, the market for recycled HDPE from these containers is limited to applications such as new oil containers or plastic lumber leading to inventory backlogs and making processors less incentivized to collect them." that lack of ability to use more is the reason for the limitation.

While I don't believe this effort would be successful, it is worth creating a financial and process model with which to make a decision. For example - the use of fracking in recovering natural gas and oil is very expensive and is only worth it when other energy producers are unable to keep their prices down. When oil and gas from other sources goes up, the fracking starts. When the prices drop, the fracking stops.


Go to a local garage and ask to collect or otherwise examine containers they have emptied and would just toss out; invert them and let them drain for a week or so to get the majority of remains out of the container. This will give an estimate of how much will need to be cleaned. Weighing the container afterwards will give a ratio from which to extrapolate the amount of cleaner per unit weight of container.

 

[waross]

I would investigate cleaning and re-using the containers.
As a by-product you will get usable amounts of the original contents.
One market for reclaimed product may be s boiler fuel or a boiler fuel blend.
Shipping in barrels implies large commercial users and fairly large quantities.
Large users may be attracted to a reduced price for accepting reclaimed barrels.
The next problem to be solved is;
"How clean is clean enough?"

 

[Kakashi-01]

What manufacturers of goods don't like is variability. This process seems likely to add variability. So it needs to be sufficiently less expensive to take that risk, but is also bounded by the way the material is degraded. Suppose you can cut 50% off the price of virgin resin, but you can only use 5% of the material - then you only save 2.5% while adding the systems to ensure that the mix can be no more than 5%.

I looked into the issue of variability a bit more and found that organizations collect tax money from customers and use it to pay processors, incentivizing them to collect and mechanically recycle plastic. The processors working with these organizations don’t just handle oil containers, they process various types of plastic waste. Through contracts, they sell recycled HDPE flakes or pellets as a substitute for virgin plastic, blending it at different percentages based on price and availability.

Go to a local garage and ask to collect or otherwise examine containers they have emptied and would just toss out; invert them and let them drain for a week or so to get the majority of remains out of the container. This will give an estimate of how much will need to be cleaned. Weighing the container afterwards will give a ratio from which to extrapolate the amount of cleaner per unit weight of container.

I would investigate cleaning and re-using the containers.
As a by-product you will get usable amounts of the original contents.
One market for reclaimed product may be s boiler fuel or a boiler fuel blend.
Shipping in barrels implies large commercial users and fairly large quantities.
Large users may be attracted to a reduced price for accepting reclaimed barrels.
The next problem to be solved is;
"How clean is clean enough?"

As for cleaning, I came across a study showing that shredding the containers releases the remaining motor oil, with an average of 10-13% residual oil per unit. Given that the partnered processors handle a mix of plastic waste, I suspect they may not be focusing on thoroughly cleaning and reusing the oil containers specifically. Instead, their operations seem to be toward broader recycling streams, which might explain why the containers aren’t cleaned and reused directly.