Up In Smoke: Half of the carbon dioxide emitted from a modern cement kiln is the result of the chemical reaction required to create the basic ingredient for cement. Photos: CUCCIAIONI

Up In Smoke: Half of the carbon dioxide emitted from a modern cement kiln is the result of the chemical reaction required to create the basic ingredient for cement.

A large modern kiln uses 2.65 million Btus of energy to produce one ton of “clinker,” the basic chemical ingredients that are combined and ground into Portland cement. Half of that plant’s CO2 emissions comes from the chemical reaction, “and there’s not much you can do to reduce that,” says Steve Regis, senior vice president of corporate services for CalPortland, a Glendora, Calif.-based manufacturer that is Energy Star’s Partner of the Year for Sustained Excellence for 2013.

The laws of thermodynamics are one reason why engineers at MIT, Cambridge University, and Utrecht University believe manufacturers of steel, cement, paper, plastics, and aluminum—which consume half the energy and emit more than half of the carbon dioxide in the manufacturing sector—are hitting a technological wall when it comes to efficient production. If worldwide demand doubles over the next 37 years, as expected, manufacturers could struggle to achieve the United Nations’ goal of 50 percent reduction in CO2 emissions by 2050 (benchmarked against year 2000 levels).

Regis thinks any meaningful measure of a product’s carbon footprint shouldn’t stop at the factory. He favors a life-cycle assessment (LCA) that tracks the product through its supply chain, manufacture, application, and disposal or reuse. Jim Boyer, director of the responsible materials program at The Dovetail Group, a nonprofit design consultant, agrees, noting that while manufacturers may or may not achieve further production efficiencies, LCAs provide a “fairly sophisticated accounting system” for gauging a product’s long-term environmental impact.

Owens Corning, which operates more than 120 plants worldwide, is committed to conducting life-cycle assessments on all of its core products by 2015. Frank O’Brien-Bernini, OC’s chief sustainability officer, sees the “next step” in the LCA continuum in Product Category Rules, where industry and standards officials set consensus parameters for how manufacturers represent their assessments. OC is also working with Harvard University’s School of Public Health on determining a product’s “handprint,” or net positive impact on the environment, user and employee health, and the economy

However, O’Brien-Bernini also sees “plenty of runway for efficiency improvements” at the manufacturing level.

In June, OC will release its sustainability report, tracking its efforts over the past decade. Among the goals it achieved was reducing greenhouse gas emissions from its plants by an average of 25%. For potential future efficiency gains, O’Brien-Bernini points to OC’s roofing plant in Compton, Calif., which recently installed two big fuel cells. A 2.6-megawatt photovoltaic system powers a plant in Delmar, N.Y. The supplier also just launched a program to convert 60% of its inbound and outgoing transportation (based on total miles traveled) to natural gas from diesel, which should cut transportation-related CO2 emissions by 22%.

John Caulfield is a senior editor at Builder.