What’s All the Buzz About Pyrolysis for Recycling Plastic?
There’s been a lot of talk about pyrolysis being the solution to the plastics recycling problem. Is this method the solution that some experts believe it will be? What is all the buzz about?
There are Problems With Plastics Recycling
Before you even get into the purpose of pyrolysis, you have to look at the current problems with plastic recycling. The biggest problem is that you have to collect and sort the plastics. As districts switched to zero-sort, it left sorting up to the recycling facilities. People don’t often recycle properly.
One district may take all plastics, while another may only take #1 and #2. Mixed plastics like #7 are rarely accepted, but people may put them in their recycling bins anyway. That can contaminate a batch of plastics, so workers have to be very careful to remove items that can’t be recycled in that district.
Another issue that happens regularly is items that are too small to be recycled being put in the bin anyway. Bottle caps are a common problem. People will leave their bottle caps on soda bottles or water bottles when they put them in the recycling, and those caps aren’t the same type of plastic and cannot be recycled.
Existing methods for recycling include:
Mechanical Recycling – Separating plastics, shredding them into smaller particles, melting them down, and using them to make new products.
Chemical Recycling – Using chemical reactions to reduce the plastics’ polymers into monomers for new products.
Pyrolysis is meant to eliminate the process of separating the different plastics. It’s meant to help boost plastics recycling, as right now things aren’t great. The U.S. government reported that about 8.7% of plastics were recycled. Worse, Beyond Plastics and Last Beach Cleanup believe it was down to 5% in 2021.
Now that China no longer accepts U.S. recyclables, recyclable rates have declined. Plastic items that aren’t recycled end up in landfills where it takes hundreds of years for them to decompose. It’s a problem.
Pyrolysis is a method where plastics are heated in equipment that lacks any oxygen. There’s no oxygen, so nothing combusts, though some people claim that the use of heat still counts as incineration. The plastics break down and create a product similar to crude oil that can be used as a gas or liquid fuel or as chemical feedstock for new plastics. The product does have some impurities like chlorine, nitrogen, oxygenates, and sulfur that are removed from the pyrolysis oil.
With mechanical recycling processes, the breakdown of plastic during processing weakens the strength of the plastic over time. Pyrolysis restores the plastic without affecting the quality.
Steps to pyrolysis:
- Plastics are dried and ground into pieces to create biomass for treatment.
- They enter a pyrolyzer where they’re exposed to heat in an oxygen-free environment.
- The biomass is separated, and condensation goes to a bio-oil storage tank or is a synthetic gas that powers a furnace for heat and electricity.
- Sand goes to a sand furnace, and char goes to storage where it will become a soil additive.
Here’s one of the reasons pyrolysis is getting a lot of buzz. Mixed plastics pyrolysis is possible. Plants that are incorporating this method do not have to separate plastics first. Again, impurities have to be removed. Sulzer created a multi-stage process for breaking down mixed plastics.
- Quenching – Rapidly cools the plastics during the pyrolysis process to create condensation that stops the process to allow for the next steps.
- Hydrotreating – Impurities are removed using hydrotreating, which removes all heteroatoms while saturating olefins.
- Fractionation – The pyrolysis oil is now purified and has to be fractionated to recover diesel and naphtha.
- BTX Recovery – This technology is specific to Sulzer Chemtech’s process and is able to recover benzene, toluene, and xylene to be reused in the petrochemical industry.
- Wax and Oil Recovery – Finally, pyrolysis oils are processed to recover the oil and wax for reuse in other areas.
Quantafuel in Denmark partnered with Sulzer Chemtech in a plastics recycling facility. It’s estimated that the plant will be able to process 60 tonnes of unrecyclable plastics each day, generating 48 tonnes of hydrocarbons to create chemicals and fuel.
Reduce Your Dependency on Plastics
It’s hard to avoid all plastics at home and work, but you can take steps to reduce your dependency on plastic. When you do have to purchase plastic items, look for items made from recycled plastic.
Here are some products that help you reduce the number of plastics you purchase.
- Stainless steel sandwich containers: Don’t use plastic sandwich bags, get a stainless steel sandwich container that you can wash out and reuse.
- Reusable produce bags: Purchase mesh bags for your produce. Instead of taking a plastic produce bag at the store, use your mesh bags and wash them in between shopping trips.
- Refillable water bottle – Buy a refillable water bottle. Fill it at your home before you go to school or work. Stainless steel and aluminum water bottles are easy to find in stores.
- Glass storage containers – With glass storage containers, only the lids are made of plastic. It lowers the amount of plastic you’re using. If the lid becomes warped or wears out, contact the company to learn how to acquire replacement lids.
- Canvas shopping bags – Purchase a number of canvas shopping bags to bring to the grocery store when you do your shopping. You won’t have to take plastic or paper bags from the cashier.
When you’re shopping, look at the items that you can purchase that are made from recycled plastic. Some clothing designers are using a woven thread spun from plastic bottles. There are shoes that are made from ocean plastics. You’ll also find decorative rugs made from recycled plastic. Support a circular economy by seeking items made from recycled materials.
Reuse what you can. Those bald tires sitting in your garage may not be safe to drive on, but spray paint them a fun color, stack them up, fill them with potting soil, and plant some flowers. They’re eye-catching, add curb appeal, and eliminate the need for planter pots.
Finally, make sure you recycle plastics properly. Even if you can’t recycle a specific plastic in your bins, your local district may be able to recycle plastics if you bring them to the facility. Save the plastic planter pots that you get from garden centers and ask them if they’d like them back or ask others in your community if they can use them. Styrofoam egg cartons are handy for people raising chickens in their backyards.
When you have packagings like bubble wrap, air pillows, padded mailers, and plastic bags from bread, produce, etc., save them in a clear plastic bag. Bring that bag with you during your shopping trip. Most grocery stores have plastic film recycling bins in the entry or near the bottle return. The amount of plastic you’re keeping out of the landfill builds up quickly when you take these steps. Find the nearest plastics recycling facility by visiting Recycle Nation.