Making Bioplastic (PLA)
From Earth to Pellet: Comparing Resource Requirements between PLA, PP, PET and EPS Products
Download the .pdf here.
Benchmark: How does PLA compare against its PP, PET and Styrofoam counterparts?
How much resources go into making one pound of each of these materials?
Table 1: From Earth to Resin (Comparison) – Resources (inputs) required to produce one pound of materials.1
Table 2: From Earth to Resin (Comparison) – PLA values are set at 100% for benchmarking.
PLA requires the least amount of energy to produce.
PP requires 25% more, PET requires 38% more and Styrofoam requires 51% more.
PLA releases the least amount of carbon dioxide during production.
PP releases 6.3 times more, Styrofoam releases 9.26 times more and PET releases over 10 times more.
PLA requires more water to produce than PP and PET, but less than Styrofoam.
PP requires 38% less, PET requires 10% less but Styrofoam requires 2.48 times more.
Annual Consumption: What are the consequences of choosing each of these products after one year?
Assumption: Let's assume that the average person uses 5 disposable items per day for one year and that the average household uses 29.19 kWh of energy per day.2
- If he chooses to use only PLA items - in one year, he will have consumed 252.88 kWh of energy, released 9.24 pounds of CO2 and used 283.67 gallons of water. 252.88 kWh is enough energy to power one household for 8.66 days.
- If he chooses to use only PP items - in one year, he will have consumed 316.52 kWh of energy, released 58.17 pounds of CO2 and used 176.57 gallons of water. 316.52 kWh is enough energy to power one household for 10.84 days.
- If he chooses to use only PET items - in one year, he will have consumed 348.15 kWh of energy, released 95.81 pounds of CO2 and used 254.69 gallons of water. 348.15 kWh is enough energy to power one household for 11.93 days.
- If he chooses to use only Styrofoam items (which weighs much less than PLA and plastic items) - in one year, he will have consumed 191.11 kWh of energy, released 95.81 pounds of CO2 and used 254.59 gallons of water. Since the average household uses 29.19 kWh of energy per day, this would be enough energy to power a household for 6.55 days.
Comparisons: What difference would it make to choose PLA?
Choosing PLA corn-starch products over PP and PET plastics will:
Choosing PLA corn-starch products over Styrofoam will:
1Ervin, Vink. NatureWorks. “The eco-profiles for current and near-future NatureWorks polylactide (PLA) production.” 1 November 2007. <-http://delivery.sheridan.com/index.php?ID=GEN_114998_EP->
PlasticsEurope. “Eco-profiles of the European Plastics Industry: Polypropylene (PP).” March 2005. <-http://www.lca.plasticseurope.org/download/pp.zip->
PlasticsEurope. “Eco-profiles of the European Plastics Industry: Polyethylene Terephthalate (PET) (Amorphous grade).” March 2005. <-http://www.lca.plasticseurope.org/download/peta.zip->
PlasticsEurope. “Eco-profiles of the European Plastics Industry: Polystyrene (Expandable) (EPS).” June 2006. <-http://www.lca.plasticseurope.org/download/eps.zip->
2Energy Information Administration (EIA). “U.S. Household Electricity Report.” 14 July. 2005. <-http://www.eia.doe.gov/emeu/reps/enduse/er01_us.html->.
“Electricity consumption by 107 million U.S. households in 2001 totaled 1,140 billion kWh” (1,140 billion kWh / 107 million U.S. households = 10,656 kWh per year, per household; or 29.19 kWh per day per household.)
3Energy Information Administration (EIA). “Urban Forestry: Carbon Sequestration Workbook.” 2005. U.S. Department of Energy, Energy Information Administration. <-ftp://ftp.eia.doe.gov/pub/oiaf/1605/cdrom/excel/urbfor05.xls->.
Based on “Sequestration in Data Year 2005 for All Trees Planted to Date,” we averaged sequestering rates for all tree types (Hardwoods or Conifers), growth rates (Slow, Medium, Fast) and tree ages (1-14) to get 7.381111 lbs per tree each year.
PP: 48.93 lbs of CO2 / 7.381111 lbs of CO2 per tree = 6.63 trees
PET: 86.57 lbs of CO2 / 7.381111 lbs of CO2 per tree =11.73 trees
EPS: 33.53 lbs of CO2 / 7.381111 lbs of CO2 per tree = 4.54 trees
4 Environmental Protection Agency (EPA). “Emission Facts: Greenhouse Gas Emissions from a Typical Passenger Vehicle” 04 February. 2005. <-http://www.epa.gov/otaq/climate/420f05004.htm->
“A gallon of gasoline is assumed to produce 8.8 kilograms (or 19.4 pounds) of CO2.”
“MOBILE calculates values of 23.9 miles per gallon (mpg) for passenger cars”
Thus, for each 23.9 miles driven, 19.4 pounds of CO2 is released.
PP: (23.9 x 48.93) / 19.4 = 60.28 miles not driven
PET: (23.9 x 86.57) / 19.4 = 106.65 miles not driven
EPS: (23.9 x 33.53) / 19.4 = 41.31 miles not driven
5 Environmental Protection Agency (EPA). “Exercise 3: The Superior Car Wash” 22 February. 2006. <-http://www.epa.gov/nps/nps_edu/stopx2.htm->
“It takes… 35 gallons to fill a normal bathtub.”
EPS: (211.93) / 35 = 6.06 bathtubs