‘Shocking’ Discovery: Nanocellulose Can Turn Footsteps into Electricity

Many exciting developments have resulted from the Forest Products Laboratory (FPL) and the University of Wisconsin (UW) working together to find applications for nanocellulose. From computer chips made of wood to aerogels that could clean up oil spills, the technologies researchers dream up are fascinating.

This week, yet another discovery from this FPL/UW collaboration was unveiled: flooring that converts footsteps to usable energy.

The following is a press release from the UW on this newest development in the world of nanocellulose.


Move over, solar: The next big renewable energy source could be at our feet

Flooring can be made from any number of sustainable materials, making it, generally, an eco-friendly feature in homes and businesses alike.

Now, flooring could be even more “green,” thanks to an inexpensive, simple method developed by University of Wisconsin-Madison materials engineers that allows them to convert footsteps into usable electricity.

Associate Professor Xudong Wang holds a prototype of the researchers’ energy harvesting technology, which uses wood pulp and harnesses nanofibers. The technology could be incorporated into flooring and convert footsteps on the flooring into usable electricity. Credit: Stephanie Precourt/UW-Madison

Associate Professor Xudong Wang holds a prototype of the researchers’ energy harvesting technology, which uses wood pulp and harnesses nanofibers. The technology could be incorporated into flooring and convert footsteps on the flooring into usable electricity. Credit: Stephanie Precourt/UW-Madison

Xudong Wang, an associate professor of materials science and engineering at UW-Madison, his graduate student Chunhua Yao, and their collaborators published details of the advance Sept. 24 in the journal Nano Energy.

The method puts to good use a common waste material: wood pulp. The pulp, which is already a common component of flooring, is partly made of cellulose nanofibers. They’re tiny fibers that, when chemically treated, produce an electrical charge when they come into contact with untreated nanofibers.

When the nanofibers are embedded within flooring, they’re able to produce electricity that can be harnessed to power lights or charge batteries. And because wood pulp is a cheap, abundant and renewable waste product of several industries, flooring that incorporates the new technology could be as affordable as conventional materials.

While there are existing similar materials for harnessing footstep energy, they’re costly, nonrecyclable, and impractical at a large scale.

Wang’s research centers around using vibration to generate electricity. For years, he has been testing different materials in an effort to maximize the merits of a technology called a triboelectric nanogenerator (TENG). Triboelectricity is the same phenomenon that produces static electricity on clothing. Chemically treated cellulose nanofibers are a simple, low-cost and effective alternative for harnessing this broadly existing mechanical energy source, Wang says.

The UW-Madison team’s advance is the latest in a green energy research field called “roadside energy harvesting” that could, in some settings, rival solar power — and it doesn’t depend on fair weather. Researchers like Wang who study roadside energy harvesting methods see the ground as holding great renewable energy potential well beyond its limited fossil fuel reserves.

“Roadside energy harvesting requires thinking about the places where there is abundant energy we could be harvesting,” Wang says. “We’ve been working a lot on harvesting energy from human activities. One way is to build something to put on people, and another way is to build something that has constant access to people. The ground is the most-used place.”

Heavy traffic floors in hallways and places like stadiums and malls that incorporate the technology could produce significant amounts of energy, Wang says. Each functional portion inside such flooring has two differently charged materials — including the cellulose nanofibers, and would be a millimeter or less thick. The floor could include several layers of the functional unit for higher energy output.

“So once we put these two materials together, electrons move from one to another based on their different electron affinity,” Wang says.

The electron transfer creates a charge imbalance that naturally wants to right itself but as the electrons return, they pass through an external circuit. The energy that process creates is the end result of TENGs.

Wang says the TENG technology could be easily incorporated into all kinds of flooring once it’s ready for the market. Wang is now optimizing the technology, and he hopes to build an educational prototype in a high-profile spot on the UW-Madison campus where he can demonstrate the concept. He already knows it would be cheap and durable.

“Our initial test in our lab shows that it works for millions of cycles without any problem,” Wang says. “We haven’t converted those numbers into year of life for a floor yet, but I think with appropriate design it can definitely outlast the floor itself.”

The Wisconsin Alumni Research Foundation holds the patent to the technology. Other authors on the paper include Zhiyong Cai of the Forest Products Laboratory and UW-Madison graduate students Alberto Hernandez and Yanhao Yu. The Forest Products Laboratory and National Science Foundation provided funding for the research.

—Will Cushman


Wood for Energy Focus of May “Update”

fpmuupdateThe latest Update from the Forest Products Laboratory’s Forest Products Marketing Unit (FPMU) is now available!

The May 2016 Update focuses on wood for heat and power. The Update reveals the winners of the National Wood Stove Competition and outlines the accomplishments of 21 state wood energy teams. It also includes exciting news about a new tribal sawmill operation that runs on biomass, as well as a calendar of upcoming classes, events, and workshops.

If you would like to receive the FPMU Update via email, send a message to asarnecki@fs.fed.us to be added to the distribution list.

Inside View House Teaches Energy-Efficient Construction Practices

The following is a press release from APA – The Engineered Wood Association:

A new home under construction in suburban Chicago has become a learning tool for builders, architects, and code officials to experience and observe how efficient framing practices can conserve energy, speed construction, and reduce utility bills. The Inside View Project, a demonstration house by Beechen & Dill Homes, provides a hands-on look at straightforward energy-efficient construction techniques that can be easily replicated in nearly any house around the country.

The Inside View Project provides a look at energy-efficient construction techniques. (Photo courtesy of APA.)

The Inside View Project provides a look at energy-efficient construction techniques. (Photo courtesy of APA.)

Co-sponsored by the USDA Forest Service, Forest Products Laboratory and APA – The Engineered Wood Association, the Inside View home features advanced framing practices such as 24-inch on-center spacing and corners and headers that provide more space for cavity insulation. The robust floor system also features 24-inch on-center spacing, allowing for ductwork runs while eliminating about one-third of the required joists and subsequently requiring one-third less labor and adhesive. Higher-series, deeper 14-inch I-joists allowed the builder to avoid double joists and, in combination with an upgraded 7/8-inch OSB subfloor, resulted in a stiff floor system despite the wider spacing.

“We’re always striving to be on the cutting edge. We were the first in the area to build energy-efficient homes and to guarantee energy bills; now it’s industry standard,” said Ed Kubiak, director of construction for Beechen & Dill. “With prices going up and labor harder to find, techniques such as these that reduce energy use while making more efficient use of materials and allowing for more efficient construction are the direction the industry needs to be going.”

Beechen & Dill opened up the Inside View house to building pros during a series of open houses July 28 and 30. Visitors had the opportunity to tour the house under construction, with walls and floors left exposed for easy access to viewing and learning about these framing techniques.

“It’s good to be in a house that’s not dry-walled, yet, to be able to see and learn more about the techniques that they’ve been talking about,” said Karen James, community development director for the Village of Shorewood, who attended with several code officials from the nearby town.

“It was a great idea to do this, especially to this extent,” said architect Bruce Obora of Chicago-based Obora & Associates, noting that his firm has designed one home using some advanced framing techniques but is continuing to research the methods in anticipation of additional projects in the future.

The Inside View home, located at 15328 S. Oak Run Ct. in Lockport, is one of 16 houses in the final phase of Beechen & Dill’s Creekside Estates development. The two-story, 2,880-square-foot house includes four bedrooms and two-and-a-half baths, along with a two-story family room, full basement, and three-car garage. As part of a partnership with the Environments for Living program, all of Beechen & Dill’s homes carry an energy bill guarantee, assuring potential buyers of long-term operational costs.

“Energy-efficient 2×6 framing can reap significant monetary savings for homeowners throughout the life of their home, while also helping the builder save on installation time and save costs in meeting the energy code. It’s a win-win,” said Tom Kositzky, director of field services for APA. “What’s more, these techniques are not difficult to implement or understand; once designers, builders, and code officials get familiar with the practices, they can easily become a regular part of their routine.”

“Education is key to furthering the adoption of energy-efficient building techniques. The Inside View Project gives us an excellent learning lab where Beechen & Dill can share ideas and techniques with other design/build professionals in the Chicago area,” added Mike Ritter, assistant director of the USDA Forest Service, Forest Products Laboratory.

For more details on the project, visit http://www.apawood.org/insideview.


Wood Energy and the Environment

Forest Products Laboratory retiree John Zerbe has told us about the many ways that wood is used as a form of energy, but how does its use affect the environment? The Forest Service has chosen climate change as one of its top areas of concern; therefore, this question is of great interest. Zerbe breaks the matter down for the reader.

This old stove is quaint, but not the best for the environment. Photo by Victor Grigas via Wikimedia Commons

This old stove is quaint, but not the best for the environment. Photo by Victor Grigas via Wikimedia Commons

Carbon Dioxide

The increasing accumulation of carbon dioxide and other greenhouse gases in the atmosphere is generally considered to be a threat to future stability of the earth’s climate.

There can be no doubt that our vast use of fossil fuels is the major contributor to increased atmospheric carbon. The renewability of wood and other biomass fuels makes them a desirable alternative to fossil fuels to prevent or retard increasing retention of carbon dioxide emissions. When new trees are grown to replace the wood that was the source of the fuel, carbon is constantly used and regenerated in the growth cycle. The carbon that is emitted to the atmosphere is absorbed by photosynthesis in new growth.


Sulfur emissions to the atmosphere are undesirable because they can precipitate and cause harmful acidic conditions in soil and water. Wood contains little sulfur, but some coal and some oil contain substantially more. Therefore, sulfur emissions from wood are more easily controlled than those from their fossil fuel counterparts.

Oxides of Nitrogen

Oxides of nitrogen emissions tend to be lower with wood fuel than with fossil fuels. On the other hand, forest fires are a major source of nitrous oxide (a greenhouse gas) in the atmosphere. Higher oxides of nitrogen emissions usually accompany combustion at higher temperatures. New technology stoves designed to be more efficient have higher oxides of nitrogen emissions than conventional stoves.


Emission of particulates is the most common cause for concern in meeting environmental requirements with the burning of wood fuel. In the United States in some municipalities and under some atmospheric conditions, particularly air inversions, there are periods when wood burning in fireplaces and stoves is not permitted. Catalytic stoves can help in attaining lower emission rates. Inefficient stoves, such as outdoor wood boilers, which more and more places are banning, have been correlated to increases in asthma and other breathing difficulties.

Altogether, with increasingly sophisticated technology in wood stoves, fireplaces, and furnaces, wood is a more benign source of energy than fossil fuels as well as being renewable. FPL’s Mark Knaebe states that, “Burning wood efficiently can actually be better than letting it rot in the woods because a significant amount of methane is produced during decay.”

Wood Pellets: Today's Choice for Wood Energy

In his overview of wood as fuel and a source of energy from the Encyclopedia of Forest Sciences, Forest Products Laboratory retiree John Zerbe reviews chips and sawdust, shavings, manufactured fireplace logs, and briquettes as sources of wood energy, but here at FPL, we know that wood pellets are the most popular alternative to cordwood for heating.


Zerbe and FPL Natural Resources Specialist Mark Knaebe state that wood pellets are becoming increasingly popular. Pellets are made from processed, ground, debarked logs held together with a binder. When pellets are made from clean wood with little bark, the ash content is low.

Pellets are sold at retail outlets in 40-pound sacks, which handle and store easily. The consumer can purchase pellets in bulk, including in one-ton bags, which can be replenished by a truck delivery. Knaebe says, “Bulk pellets are just like with oil heat: the truck will come and fill your container, and your thermostat tells an auger to feed your boiler or furnace. The pellets should be kept dry to prevent disintegration and to avoid risk of mold and decay.”

“In very large piles of pellets,” warns Knaebe, “you will get a fire about 3 weeks after the pile gets wet because of spontaneous combustion and the high insulating properties of a big pile. This can be prevented with blowers or making smaller piles, never more than 10 feet deep.”

Sometimes pellets for cooking are made from woods with special flavors that can be used in barbecuing, directly or with charcoal or gas, for conveying this flavoring to meat or poultry. Excellent pellet grills are available now. However, the most common use of pellet fuel is for heating with modern and convenient pellet stoves. Some of these stoves have automatic ignition, feed, and control systems. To be EPA certified, they must be 78% efficient. To determine the efficiency of your fuel, you can download FPL’s popular Fuel Value and Power Calculator.