Life Cycle Analysis of Printer Cartridges: Environmental Impact

Introduction and Study Objectives

Printer cartridges are an important part of everyday life. Every day, consumers purchase them, use them, and eventually replace them. The objective of this study is to examine the life cycle environmental impacts of printer cartridges. This assessment does not examine a particular type of printer cartridge but considers the life cycle of a printer cartridge to be relatively homogeneous, with the exception of remanufactured cartridges. The goal of this study is to understand the environmental impact of printer cartridges at every stage of their product lifecycle.

Functional Unit and System Boundaries

ISO standards dictate that the functional unit of the system should be designed so that the inventory results can be understood on the basis of its function. The functional unit serves the purpose of ensuring that various printer cartridges can be compared on the same quantitative basis (First Environment, Inc., 2004). A functional unit reflects usage of the item rather than the quantity of materials that go into it. In the case of printer cartridges, the functional unit is defined in terms of the function of the system. Because various printer cartridges can print different numbers of pages per individual cartridge, a standard unit must be defined that more clearly allows comparison of different cartridges. The cartridge functions to produce a certain number of usable pages. Therefore, the functional unit for this study is the printing of 100 usable, single-color, single-sided pages.

The cartridge has several stages included in its system boundaries. Those stages are production, distribution, use, and end of life, defined as follows:

1. Production — The production phase is defined as the production of the materials that go into each cartridge and its assembly. Transportation may be needed from suppliers to the manufacturing facility. This includes the extraction of metals and the production of plastics that go into every component of cartridge manufacture.

2. Distribution — Distribution refers to delivery of the finished product to the end user. This includes energy for warehousing and transportation costs.

3. Use — This refers to operation of the cartridge by the end user. Use is defined as the printing requirements — including paper and a printer — needed to print 100 usable pages.

4. End of life — This boundary refers to the fate of the cartridge after the toner in it has been used up.

This study compares a single cycle in the life of the cartridge. Companies are taking different approaches to the problem of toner cartridges. Some offer only brand-new cartridges that have not been recycled, while others have programs for recycling cartridges that can go through multiple use cycles. Different stages of the product lifecycle may require different levels of transportation, which may add carbon expenditures to the process — making the recycling of toner cartridges a potentially larger environmental impact than simply using and disposing of them. This study explores this issue as part of the life cycle assessment.

Inventory Analysis: Materials and Components

There are two different types of cartridges. The first type is the inkjet cartridge, and the second is the xerographic toner cartridge. Both serve the same purpose for the end customer. The xerographic toner uses toner powder, while inkjet cartridges use liquid ink (Nelson, Carney, & Wille-Irmiter, et al., 2011). The following sections explore the inventory for both types.

Components

The life cycle inventory analysis for an inkjet printer cartridge involves only a few materials. Cartridges consist primarily of polyethylene terephthalate (PET), glass-filled polyester, and electronics (Ord & DiCorcia, 2005). Each cartridge also contains ink, though every cartridge company has its own proprietary formula, and this information is not publicly available. As a result, the material flows for these elements cannot be determined for the purposes of this project (Ord & DiCorcia, 2005).

A survey of material safety data sheets for various ink and toner cartridges identified the most common materials and compounds that make up ink and toner, though these will not be identical for every product considered in this study. In general, ink and toner compounds include styrene acrylate copolymer, polymethyl methacrylate (PMMA), iron oxide, amorphous silica, carbon black, paraffin wax, diethylene glycol, and 2-pyrrolidone (Nelson, Carney, & Wille-Irmiter, et al., 2011). These elements have different energy inputs and different byproducts and wastes associated with their production.

The largest component — making up nearly 80% of the mixture used in toner — is styrene acrylate copolymer, a resin manufactured by a chemical processor. Magnetite, the iron oxide used in toner cartridges, also functions as a pigment. Carbon black is used in both toner and ink as a pigment; its manufacture requires the burning of hydrocarbons at extremely high temperatures in order to obtain elemental carbon (Nelson, Carney, & Wille-Irmiter, et al., 2011). Polymethyl methacrylate (PMMA), diethylene glycol, and 2-pyrrolidone are all petroleum products (Ahmadi, Williamson, & Theis, et al., 2003). While many other minor components are used in the manufacture of printer cartridges, there is insufficient scope within this study to address all of them.

The toner cartridge has three main parts: the hopper, which holds the toner powder; the developer unit, which contains an assortment of negatively charged magnetic beads attached to a drum; and the revolving drum, which coats the entire sheet of paper with a positive electric charge. A laser removes the positive charge at the locations where the image is to be printed, leaving behind a negative electrostatic image. Iron oxide, which carries a positive charge, is the key compound in this process. The negatively charged beads pick up the toner from the hopper, and that toner is attracted to the areas where the laser created a negative image. Before the image is printed, it passes through a pair of heated rollers (Nelson, Carney, & Wille-Irmiter, et al., 2011).

Inkjet cartridges work in a slightly different way. The ink is contained in a foil-lined compartment, and the cartridge deposits ink onto the paper through small jets. A silicon chip contains etchings that act as hydraulic jets; these are connected to a metal plate beneath the ink compartment. Electricity passes through the metal plate and superheats the silicon chip, causing a small amount of vaporized ink to be released through the etchings. Images are formed through the use of dots smaller than a human hair (Nelson, Carney, & Wille-Irmiter, et al., 2011).

Packaging

Cartridge packaging must also be included in the materials inventory of a printer cartridge. Packaging includes paperboard, cartons, brochures, and any other material included with the product. The approximate weight of this packaging is 27 g. Many printer cartridges also come in a hybrid plastic/foil pouch that weighs approximately 1 g (Ord & DiCorcia, 2005).

Post-Consumer Waste

Post-consumer waste refers to consumables that the customer must dispose of throughout the lifecycle of the product. These typically include the cartridge's packaging and the cartridge itself. Research found that the laser multifunction printer produces nearly five times as much post-consumer waste as a solid ink multifunction printer (Nelson, Carney, & Wille-Irmiter, et al., 2011).

Conclusion

Printer cartridges contain many chemicals produced through processes that are harmful to the environment. Their manufacture contributes to air pollution, water pollution, electricity consumption, and landfill volume. Companies such as Hewlett-Packard and Lexmark have taken significant steps to reduce these impacts, but the environmental profile of any given cartridge depends on a wide range of factors — including the manufacturer's practices, the transportation involved, and whether the cartridge is new or remanufactured. This study has demonstrated both the scope of environmental concerns associated with printer cartridges and the limitations inherent in conducting a generalized life cycle analysis. More detailed, brand- and model-specific data would be necessary to draw firm conclusions about the comparative environmental impact of different cartridge types and end-of-life strategies.

References

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