[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

FOOD FOR THOUGHT: Plastic vs. Paper Grocery Bags



Date sent:      	Tue, 16 Feb 1999 12:29:12 -0500 (EST)
From:           	"ctaylor@sa.kevric.com" <ctaylor@kevric.com>
To:             	"'p2tech@great-lakes.net'" <p2tech@great-lakes.net>
Subject:        	Plastic vs. Paper Grocery Bags 
Send reply to:  	"ctaylor@sa.kevric.com" <ctaylor@kevric.com>


Because I thought this might be of interest to a much broader 
audience, I respond to the group. This question comes up again 
and again under many different circumstances, and I am always 
struck by the confusion -- and by the difficulty in conducting a fair 
and convincing life cycle analysis. First (as I'm sure you've already 
heard) the reusable cloth grocery sack is the solution of choice -- 
that is if you can't avoid the grocery store and the sack altogether 
by growing your own food, milking your own cows, making your 
own cheese, etc.

One answer to your question is found in "Pollution Prevention: 
Homework & Design Problems For Engineering Curricula," a 
document prepared by the Ameican Institute of Chemical 
Engineers Center for Waste Reduction Technologies and the 
American Institute for Pollution Prevention. The very first problem 
presented to students is "Paper or Plastic? A Life Cycle Inventory 
Comparing Unbleached Paper Grocery Sacks and Polyethylene 
Grocery Sacks".

The text takes students through mass and energy balances, 
recycle streams, life cycle inventories and introduces them to 
product substitution. There's a nice synopsis of the problem and 
the need to construct a consistent framework for keeping track of 
the flows of material, energy and waste. There are many 
assumptions made, including that a paper sack will hold 2 times 
as much as a polyethylene sack. I would be hard pressed to 
provide the details of the analysis (all 6 pages with tables and 
graphs) but will send to anyone who requests -- when I return to my 
desk March 8.

Franklin Associates, Ltd., 1990, offers the following data:

Air Emissions and Energy Requirements for Polyethylene and 
Paper Grocery Sacks

						Air Emissions		Energy Required
						(oz/sack)			(Btu/sack)

						Paper	Poly		Paper	Poly
Life Cycle Stages

Materials Manuf.		.0516	.0146		905		464
Product Manuf.
Product Use

Raw Mats. Acq.		.0510	.0045		724		185
Product Disposal

Calculating the effect recycling rates has on the equation, it is 
clear that in terms of both energy required and atmospheric 
pollutants, the poly sacks beat out the paper -- except where 
recycle rates top 80%. At 80% and greater, there appears to be no 
significant difference in energy requirements for PE and paper 
sacks. Atmospheric emissions show a similar decline with 
increasing recycle rates. At 0% recycle, total atmospheric 
emissions are 60-70% lower for PE sacks; this difference gradually 
declines to 40% at 100% recycle. Atmospheric emissions of 
particulates, nitrogen oxides and sulfur oxides are all higer for 
paper, but as might be expected, higher levels of hydrocarbon 
emissions are associated with PE sacks.These hydrocarbon 
emissions are likely to qualitatitively different from the hydrocarbon 
emissions generated by paper sack production. It would be difficult 
to assess the respective environmental consequences of the 
hydrocarbon emissions without a much more detailed description 
of the emissions than was available for this study/problem.

Petroleum requirements of PE sacks: 0.052 lb petroleum/sack
					Total for 2 sacks = 0.104 lb petroleum

Petroleum requirements of Paper sacks: 0.008 lb petroleum/sack

Two PE sacks require more than an order of magnitute more 
petroleum than a paper sack!

The quick and dirty? Use a reusable durable sack when you can, 
and then...the choice is yours -- but do reuse the sack if you can 
and recycle it when it's no longer usable. Dispose only as a last 
resort. My personal preference still runs toward the brown paper 
bag when I forget my cloth sack.

Make it a GREAT day and a WONDERFUL week all!



Doug Kievit-Kylar, Pollution Prevention Planner
Vermont Agency of Natural Resources
Environmental Assistance Division
103 South Main Street
Waterbury   VT   05671-0411
phone: (802) 241-3628
FAX: (802) 241-3273
e-mail: Doug.Kievit-Kylar@anrmail.anr.state.vt.us
"Smart people solve problems. Geniuses prevent them."
-- The wisdom of Albert Einstein --