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Apparently China has been processing about half the world's waste until this year, and most of that waste is transported over the ocean in large container ships. Recycling plastic uses less energy and fossil fuels than producing virgin plastic, so some amount of fossil fuel is saved by recycling. But moving large ships across the ocean burns a lot of fuel, so some fossil fuel is used to support the recycling process.

From an energy/fuel use perspective, are the benefits of recycling plastic offset by the need to transport it part way around the world? (I understand there is also value in avoiding accumulation of solid waste, but that's not what I'm asking about here.)

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    Assuming that Chinese businesses were paying for the waste plastic, this would indicate it was cheaper than producing virgin plastic from raw crude, regardless of transportation and processing costs. If, however, the exporting countries were somehow subsidizing the waste plastic, it's hard to say. – LShaver May 2 '18 at 14:04
  • Great question!! China does lots of our ewaste, things like lead, and irridium found in cellphone antenna, and then sells it back the US as cheap plastic junk. Mardi Gras beads are a great example of this. Link to an article by the Smithsonian – flummingbird May 16 '18 at 21:24
  • A recent research article on China's import ban: "The Chinese import ban and its impact on global plastic waste trade". – LShaver Jun 20 '18 at 19:36
  • Add to all that the fact that we are keeping it out of the landfills. That is the main reason I recycle. But the savings of energy is just icing on the cake for me. – Tim Jernigan Mar 19 at 15:54
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tl;dr: No, shipping plastic waste to China for recycling does not offset the benefits, as it reduces the net energy savings by 3% or less.

Polyethylene, The most common plastic

According to Wikipedia, polyethylene is the most common type of plastic. There are three main categories of polyethylene (also from Wikipedia):

  • PET (polyethylene terephthalate), used in polyester fibers, drink bottles, tote bags, furniture, etc.
  • HDPE (High-density polyethylene), used in bottles, playground equipment, plastic lumber, etc.
  • LDPE (Low-density polyethylene), used in plastic bags, six pack rings, tubing, etc.

Oil and gas for PE production

PE is made from ethylene, which can be produced from either natural gas or crude oil. Since ethylene production also generates other useful products, the amount of oil or gas specifically used to produce PE is a bit tricky to track down. However based on the global production of ethylene, PE production uses less than 3% of global crude oil production, and less than 4% of global natural gas production.

Energy savings from PE recycling

More significant, and easier to track, is the amount of energy used in PE production.

A 2003 life cycle assessment from the University of Naples found that recycling of PE takes from 40 to 55 MJ per kg, while production from raw materials requires 77 to 80 MJ per kg. The difference is a savings of 22 to 40 megajoules (MJ) per kg (roughly 6 to 11 kWh/kg). This study is specific to Italy, and unfortunately the details are behind a paywall.

In 2010 the American Chemistry Council (ACC), the Association of Postconsumer Plastic Recyclers (APR), the National Association for PET Container Resources (NAPCOR), and the PET Resin Association (PETRA) funded a life cycle analysis of PET and HDPE recycling. The study is available here: "Life Cycle Inventory of 100% Postconsumer HDPE and PET Recycled Resin from Postconsumer Containers and Packaging".

The report provides the following data on energy use of recycled vs "virgin" plastic production. These figures are for the U.S., and include the energy used to collect, transport, and process the plastic after its first use.

  • Raw HDPE takes 35.8 MMBtu per 1,000 lbs (23 kWh/kg), while recycled HDPE requires 3.87 to 4.24 MMBtu per 1,000 lbs (2.5 to 2.7 kWh/kg), depending on whether collection is allocated by weight or volume. This is a savings of roughly 20 kWh/kg.
  • Raw PET takes 31.9 MMBtu per 1,000 lbs (20.6 kWh/kg), while recycled PET requires 5.18 to 5.45 MMBtu per 1,000 lbs (3.3 to 3.5 kWh/kg). This is a savings of roughly 17 kWh/kg.

Shipping across the Pacific

Assuming an average speed of 15 knots, energy usage is between 0.004 and 0.008 kWh per nautical mile per tonne (kWh/n.m./DWT) for larger classes of ships (source).

Depending on the ports and route, shipping from the US to China involves a journey of 6,000 to 11,000 nautical miles.

Thus shipping plastic from the U.S. to China will require from 24 to 88 kWh/tonne.

Comparison

Energy savings from recycling:   6,000 to 20,000 kWh/tonne

The specific energy savings from PE recycling depends on the type of PE and the allocation method used (whether by weight or volume).

Energy consumption for shipping:    24 to     88 kWh/tonne

This value depends on the vessel, speed, and route between the U.S. and China.

  • In the worst-case scenario (including shipping the plastic back to the U.S.), shipping plastic for recycling reduces the energy savings by 2.9% .
  • In the best case scenario, savings are reduced by 0.12%.

Conclusion

Recycling plastic saves so much energy (a good thing!) and shipping things across the ocean uses so little energy (also a good thing!), that shipping our dirty plastic to China for recycling isn't actually terrible.

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