Not so fast, says a new study by researchers at MIT.
In some cases, the conventional wisdom is indeed correct. But out of 25 case studies on products in eight categories done by a team led by Professor of Mechanical Engineering Timothy Gutowski, there were just as many cases where remanufacturing actually cost more energy as cases where it saved energy. And for the majority of the items, the savings were negligible or the energy balance was too close to call.
Why are the new results so different from what might have been assumed? The MIT team looked at the total energy used over the lifetime of a product — a life-cycle analysis — rather than just the energy used in the manufacturing process itself. In virtually all cases, it costs less money and less energy to make a product from the recycled "core" — the reusable part of the product — than to start from scratch. But the catch is that many of these remanufactured products are less energy efficient, or newer versions are more energy efficient, so the extra energy used over their lifetime cancels out the savings from the manufacturing stage.
A simple and familiar example is retread tires. They do indeed require less energy to make than new tires, but their rolling resistance might turn out to be just a bit higher, which would mean their energy advantage is eaten up by the extra gas used while driving on them.
The study, published in the journal Environmental Science & Technology, is the latest from Gutowski and his students that, as he puts it, "takes what appears to be a simple, straightforward problem and shows that the world is a far more complicated place than people thought." The paper was co-authored by MIT materials science and engineering graduate student Sahil Sahni; Avid Boustani SM '10, a recent graduate from the Department of Mechanical Engineering; and Stephen Graves, the Abraham J. Siegel Professor of Management in the MIT Sloan School of Management. The work was supported by the MIT Energy Initiative and the Singapore-MIT Alliance.
What often turns out to be the case, Gutowski says, is that "new technology shows up that is so much more efficient, from an energy point of view, that you should get rid of the old device" rather than having it fixed or buying a remanufactured version. For example, the efficiency of many new appliances — such as refrigerators and washing machines — are so much improved over older models that, in terms of energy use, a new model is almost always the better choice.
Unfortunately, that is typically not the way people and businesses make their choices. "The decision is always on cost, not energy," Gutowski says. For example, a remanufactured electric motor, in which the metal core is reused but wound with new wires, is typically 0.5 to 1 percent less efficient than a newer motor. "There is still a cost advantage" to the remanufactured motors, he says, "but from an energy point of view, it's the opposite."
Other effects stem from remanufactured products going to different markets than their original destinations. For example, old cell phones can be remanufactured, but the remanufactured phones tend to be sold in developing countries. "If it goes to a different market, it leads to an expansion of the market," Gutowski explains, so the overall level of cell phone usage globally — and the energy needed to power them — ends up increasing.
For some kinds of products, the benefits of remanufacturing are unequivocal. It clearly makes sense to remanufacture anything that consumes an insignificant amount of energy when it is being used, he says — for example, furniture.
Gutowski emphasizes that this research does not necessarily suggest a specific course of action. For any given product, there may be other reasons for preferring the remanufactured version even if it produces a net energy penalty. For example, remanufacturing may reduce the burden on landfills, reduce use and disposal of some toxic materials, or produce needed jobs in a particular area. And the expanded use of cell phones may have important social benefits, such as contributing to the recent wave of revolutions in North Africa and the Middle East. "We're not saying you shouldn't do it," he says — just suggesting that it's worth understanding the decision's effects in their entirety.
"You think you're doing the right thing, it sounds so simple," Gutowski says. But when it comes to understanding the true impact of purchasing decisions on energy use, "things are far more complicated than we expect."
Marta Buczek | EurekAlert!
The importance of biodiversity in forests could increase due to climate change
17.11.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses