Tuesday, September 09, 2014

Plastics to Oil - Hype or Hope?

The Wall Street Journal had a video Q & A with Steve Russell, vice president of the American Chemistry Council regarding efforts to convert plastic waste and other elements of municipal wastestreams to oil. This process, know as Plastics-To-Oil (PTO), is done by anaerobic pyrolysis - heating the plastic up in an oxygen-free atmosphere to temperatures that degrade it to low molecular weight liquids. The technology is not all that new - I discussed it here over 2 years ago. If obviously works best with plain hydrocarbons - polyethylene, polypropylene, EPDM rubber, etc. Heteroatoms such as oxygen from PET, chlorine from PVC, nitrogen from nylons, etc. make it a little more difficult to produce the pure hydrocarbon output so desired by refiners. But in all cases, the lack of sulfur in most plastics ensures that the output is a very sweet crude oil.

The title of the article, "Plastic May Well Be the Next Big Energy Source", however really bothers me. Of all the petroleum that is taken from the ground, 5% of it ends up being plastic. This then means that at most we can reduce our consumption of oil by 5%. And that's assuming 100% efficiency at recovering all the plastic from all wastestreams, and further that this process can be performed without any additional energy inputs.

The current reality is that about 10% of all plastics are recycled. Even aluminum cans, the paragon of recycling efficiency, has a recovery rate of about 60 - 70%. So 100% recovery of plastics is a pipedream. Even 50% recovery is probably too much to ask for. And of course pyrolysis requires energy to heat the plastics to over 400 oC, so that further reduces the net amount of petroleum that can be gained.

So can a 2 - 2.5% reduction in petroleum consumption through PTO be considered the "Next Big Energy Source"? Considering that petroleum consumption fell all of that and more during the Great Recession, I won't call it that.

Hat tip to Chemjobber (Blog and Twitter) for bringing this to my attention.

Previous Years
"blue"September 9, 2014 - Where's the Cheap Plastic We Were Promised?


milkshake said...

the problem is that the hydro-treatment of plastic garbage (at high temp and pressure) produces lots of contaminated waste water which is hard to treat, and it is not easy to control the input with municipal plastic waste to avoid the contamination with problematic plastics. The process works a lot better with chicken offal waste (when it is built right next to a meat packing plant) - it sterilizes nasty bio-waste, produces oil, and the resulting chicken soup waste water is an excellent liquid fertilizer

John said...

Just handwave though issues away like the guy from the ACC did. (No wonder people think chemistry is so hard.)