Is Glass Packaging Always Greener Than Plastic?
Glass bottles have been making a comeback, especially as a premium product. On a trip to Central Market in Dallas, Assistant Professor Savannah Tang had her first brush with glass-bottled milk from a local farm. Sparking her study’s interest, Tang reveals an analytical way of mapping out when different packaging strategies work for all stakeholders. Her research shows what levers companies—states and countries too—can pull to encourage sustainable packaging, when choosing between glass or eco-friendly plastic.
On a trip to Central Market in Dallas, Savannah Tang had her first brush with glass-bottled milk from a local farm. It sparked a research path that challenged conventional wisdom about sustainable packaging. In new research, Information Technology Assistant Professor Tang of Ë¿¹ÏÊÓƵ Cox reveals an analytical way of mapping out when different packaging strategies work for all stakeholders.
Glass bottles have been making a comeback, especially as a premium product. But, glass bottles carry an environmental burden that many consumers don't consider. Production of glass can generate more greenhouse gas emissions than plastic manufacturing. Glass bottles also require more energy to transport due to their weight, and are more prone to breakage and leakage during shipping. “We derived these parameter regions, or sweet spots, where we can align firms, customers and societal objective,” Tang notes about one of the paper’s messages.
The research acknowledges that while glass is often perceived as the most sustainable option, its true environmental impact depends largely on return and reuse rates. This is influenced by a firm’s deposit-refund programs and sustainability advertising. The end-of-life disposal presents another challenge. In Texas and many other states, single-stream recycling policies combine all recyclables into one bin. "In this case, glass can be more environmentally harmful, complicating the recycling process for other recyclables," Tang explains. Recycling programs need proper sorting and disposal methods to deal with glass.
For glass to truly deliver environmental benefits, one factor is critical: return rates. If customers don't consistently return glass bottles for reuse, the packaging loses its green advantage. The question also arises: how high must return rates be to justify glass's heavier environmental footprint during production and transportation?
A Deeper Dive
The study considers the many tradeoffs of glass versus plastic packaging options and encourages system-level thinking. The authors used data from a regional Texas dairy firm that produces and packages milk in reusable glass containers. Real-world observations on sales, pricing, return rates, and production costs were used to calibrate their model they developed.
Plastic packaging, often perceived negatively, emerges as a nuanced option in Tang's research. While single-use plastic has drawbacks, eco-friendly plastic alternatives can outperform glass in specific scenarios. Plastic's lighter weight means lower transportation emissions. Its end-of-life disposal, while imperfect, is often less environmentally harmful than glass that ends up in landfills or contaminating recycling streams. “What surprised me was that plastic can be environmentally more beneficial in some cases,” Tang surmises.
The challenge with plastic isn't necessarily its environmental performance—it's consumer perception and firm incentives. Most consumers can't distinguish between conventional plastic and eco-plastic alternatives, unless labeled. This creates a disincentive for companies to invest in greener plastic options when customers won't recognize or value the difference.
A Sweet Spot
Tang's research identifies specific combinations of business conditions where packaging choices align the interests of firms, customers, and the environment. Several key factors matter: customer environmental awareness levels; optimal pricing strategies; packaging costs; and for glass, expected return rates.
The Dallas dairy farm case study illustrates this alignment perfectly. The medium-sized farm offered premium milk beverages in glass bottles to environmentally-geared customers. With high return rates for their main products, the glass packaging proved optimal for business profitability, customers’ desires, and the environmental benefits. Tang says that is her “win-win-win scenario.” Conversely, if parameters are outside this region—low return rates or insufficient numbers of environmentally-concerned customers—then glass might actually be worse for the environment than plastic, though it seems "greener."
Tang also considers the effects of greenwashing and greenhushing, downplaying environmental benefits. While consumers often see past greenwashing, downplaying green benefits can leave value off the table for firms and the environment.
Policy and Infrastructure Matter
Local or national policies and infrastructure can influence sustainable packaging choices. For companies choosing packaging strategies, Tang offers guidance. “If pursuing reusable glass, focus on maximizing return rates through appropriate deposit amounts, convenient return logistics, and customer education,” she emphasizes. For those choosing disposable packaging, whether conventional or eco-plastic, pricing remains crucial. Companies using eco-plastic should invest in raising consumer awareness about the environmental benefits, even though additional marketing expense is necessary. "Raising awareness is still important," she explains, “giving customers better incentives to purchase environmentally beneficial products.”
California's Bottle Bill policy demonstrates how policy can shift best practices in favor of reusable packaging. By creating infrastructure and incentives for returns, such legislation makes glass more viable. "When making policies, such as banning plastic, firm's incentives need to be factored in," Tang suggests. Simply banning plastic without building the necessary infrastructure for glass returns can backfire, leading companies to switch to glass without actually improving environmental outcomes. Some regions and countries that banned plastic saw companies switch to glass or other alternatives without meaningful environmental improvement because the support systems for reuse weren't in place.
The glass-versus-plastic debate is more complex than simple intuition suggests. Glass isn't automatically greener, and plastic isn't inherently bad. The environmental impact depends on considering the entire value chain: packaging production methods, transportation distances, consumer behavior, recycling infrastructure, and end-of-life disposal.
The paper “Glass Half Full: Strategic Packaging Decisions and Environmental Outcomes by Savannah (Yanhan) Tang of Ë¿¹ÏÊÓƵ Methodist University’s Cox School of Business, and Neda Mirzaeian of The University of Texas at Dallas, is under review.
Written by Jennifer Warren.
