Wood hasn't gotten much attention as a renewable energy source for some time. Yet, Focus on Energy (wifocusonenergy.com) set a goal for this fiscal year to increase non-residential wood burning. Why the new interest?

Fuel costs. We've had companies say they'd be out of business if it weren't for wood. They couldn't stay profitable with the current cost of natural gas.

We should back up a minute. Are we talking about burning wood for heat or for electricity?

We're talking primarily about wood for heat -- heat for commercial and industrial use. For example, Superior Kilns dries green hardwood before fashioning it into standard and custom-size boards, annually producing 5,600 tons of shavings and saw dust. An electronically controlled feed auger sends the wood waste to a 230 HP steel fire tube Burnham boiler that supplies low pressure steam (15 psi) to the kilns to continue the drying process.

The Barron Area School District, as another example, has a commercial/industrial automated boiler control system that runs three steam boilers, one Swede Stoker wood-chip boiler, and two back-up gas boilers. These boilers heat the Barron High School, Barron Woodland Elementary School, the Barron Hospital and Medical Center, and Maple Crofts Senior Rest Home - all of which are located in the northern village of Barron, where the January temperature averaged 13 degrees Fahrenheit last winter.

Both of those operations save money compared to other fuel options?

That's always the key question. At first, Superior Kilns was concerned about the higher initial cost of a wood-fired system as opposed to a comparable natural gas system. After considering the energy requirements and other operating costs, the company calculated the payback period to be about three years. The King Coal Furnace and other system components would save approximately $186,000 a year compared with the natural gas costs to produce 275,000 therms. (In total, the kilns require 540,000 therms a year.) A $35,000 Implementation Grant from Focus on Energy in 2004 cut the payback time.

The Barron school district had to shut down its existing wood-fueled boiler a couple of winters ago and rely solely on natural gas to heat the boiler. The cost of heat from the natural gas boiler was double that of the previous year when they used the wood boiler.

A $15,000 Implementation Grant from Focus on Energy helped offset some of the costs for the $70,000 project.

Those are impressive savings. It sounds like any commercial or business operation should look at wood as an option.

It's well worth looking into, but an operation probably should generate its own wood supply. That helped make the system ideal for Superior Kilns.

When the operation produces its own supply, quality assurance is not as much of an issue. The company knows where the wood comes from; it can be cut or ground to a standard size; and, it has often already been kiln dried to lower moisture content.

A business could buy the wood, but the price of wood or wood pellets may increase at a rate parallel to that of natural gas. Additionally the wood may come from decentralized sources, and quality could be an issue.

Even with these considerations, the market for wood as fuel could get bigger, growing significantly each year as natural gas prices continue to increase.

What happened to the option of using wood and other wastes to co-fire electricity generation plants?

Wood still works, but coal is so much simpler -- from sourcing to having a higher energy content than wood. That's why our economy switched from wood to coal in the first place.

Switchgrass, another possible biomass product for co-firing with coal, has some issues too, primarily in the area of materials handling.

Tires can be a waste source for electricity generation. They burn well, as we saw with that huge fire in Jefferson County in July. Unfortunately, the fuel market generally demands that the steel belting from the tires be removed, which requires additional equipment and energy for processing. Processors, therefore, must handle larger numbers of tires to justify the cost of the additional equipment, thereby limiting the number of tire recycling companies. Even with those issues, probably 90% of the old tires in the United States go into fuel markets.

What kind of response do you get from UWGB students to renewable energy -- whether it's wood, wind, solar, or whatever?

At UWGB I teach nine different courses in a two-year cycle of offerings in the undergraduate program in Environmental Science and Policy, so I see a lot of different students.

In my Energy and Society course, most of the students are non-scientists, engineers, and I try to poke and prod them a bit so they see that renewable energy can potentially be an option.

In the upper level and graduate courses, I'm trying to bridge the gap between environmental perspectives and those usually associated with business and industry.

For both groups of students, this might be the only opportunity to give them an awareness of renewable energy, so connecting with them is important because these students are going to be the decision-makers in the future.

I hope that these students leave UWGB with a solid understanding that we can have a stronger economy and better environment at the same time.

John Katers is an Associate Professor of Natural and Applied Sciences (Engineering) at the University of Wisconsin - Green Bay (UWGB) and consultant to Focus on Energy and STS Consultants, covering the business and technology of burning wood for energy.

Katers teaches courses on industrial pollution control, waste management/resource recovery, pollution prevention, resource management strategies, and solar and alternate energy systems.

His research interests include water and wastewater treatment, waste management, recycling and renewable energy.

Prior to joining the faculty at UWGB, Katers spent four years working for the University of Wisconsin-Extension Solid and Hazardous Waste Education Center (SHWEC) as an Industrial Recycling Specialist and is currently an adjunct faculty member of SHWEC.

He also serves as a Senior Consultant at STS Consultants, LTD., primarily working with the thermal renewable program within Focus on Energy.

Katers received a doctorate in Civil and Environmental Engineering from Marquette University, a master's degree in Environmental Science and Policy, and a bachelor's degree in Environmental Science and Business Administration both from UWGB.