Warming Up To Outdoor Wood Heaters

Outdoor wood appliance manufacturers are feeling the heat of new regulations, but many were already focused on providing cleaner and more efficient systems.
By Katie Fletcher | August 10, 2014

Humans have been burning wood as a primary source of heat for many centuries, and its use has evolved greatly over time. Along with demand for new applications and means of increasing the use of inexpensive and renewable wood heat, environmental concerns have also grown. The wood heat sector has responded by producing cleaner and more efficiently designed units for a multitude of applications, from residential-sized outdoor wood boilers for heating swimming pools to commercial-sized hot air pellet furnaces for heating poultry farms.

Current trends in the small-scale wood heat sector lean toward indoor wood chip and pellet boilers and stoves, but traditional outdoor wood boilers, or hydronic heaters, are still widely used today, despite the units being amongst the most heavily scrutinized appliances in the wood heating sector. This likely spurred the outdoor wood industry to approach the U.S. EPA requesting more regulation, to move away from the wood heat pollution poster child it had become.

The EPA’s New Source Performance Standard for residential wood heaters has been around for years, but proposed changes place pressure on all manufacturers to redesign wood heaters to become cleaner and lower emitting. Many manufacturers are trying to meet the proposed emission standards to keep their businesses open by producing models qualified by EPA’s phase-two voluntary program, which requires no more than 0.32 pounds of fine particles per million Btu of heat with a maximum individual test run of 18.0 grams per hour. These furnaces hope to positively impact preconceived notions about emissions and efficiencies of wood heating, but based on EPA documented efficiencies of the boilers, many still have progress to be made. Non-EPA qualified, traditional outdoor wood furnaces that are purchased before the final rule will be grandfathered in.

The final rule is expected to be announced in 2015, and although the heat is on, some manufacturers seem optimistic about adapting to the changing standards. Northwest Manufacturing Inc. WoodMaster and Central Boiler Inc. are two of the manufacturers working with the EPA to set new testing standards, and have EPA qualified models available for purchasing. Lee Energy Solutions LLC is another manufacturer in the sector creating carbon neutral, commercial pellet furnaces in the U.S. South, for use predominantly at poultry farms and greenhouses.

The environment and customers are meant to benefit from the standards; they may even be warming up the public to the idea of the units as an option for clean, safe and efficient energy. John Ackerly, president of the Alliance for Green Heat and board member of the Biomass Thermal Energy Council, believes the way to move forward is to have restrictions. “These regulations help the industry maintain standard, public support for the technology, and it makes us have a higher priority on clean air,” he says.

Clean air is something outdoor wood and pellet heating systems are turning their focus to. According to studies posted by Central Boiler Inc., there are more than 16 million fireplaces used in homes in the U.S. with reportedly only 200,000 outdoor wood furnaces. Many wood boilers can actually heat a home with less wood burned and far fewer particulate matter (PM) emissions than heating the same home with fireplaces. This is because the number of fireplaces or wood stoves required to heat the home would have comparable emissions to those from a single outdoor wood furnace heating that same home.

When choosing between these indoor and outdoor options, manufacturers say outdoor models work better to uniformly heat the entire home without a mess. “Outdoor is typically designed for home heating to keep the mess and fire hazard outside, and have the option to heat multiple buildings,” says Chuck Gagner, president of Northwest Manufacturing Inc. WoodMaster.

Minidistrict heating is what Gagner is referring to, or the ability to heat multiple buildings. The wood heat sector sees this as one of the best applications of the technology, in which two or more buildings are heated from the same boiler in the yard.

If an outdoor boiler is a desired option, there are a few considerations to take into account; the type of application should be the first. After determining the application, time must be dedicated to understanding details of how to operate the machinery, as well as weighing the pros and cons of each unit. And because of policy changes surrounding the units, what manufacturers are doing to improve the image and efficiency of their products may be something to consider.

Potential Applications

The type of application and surrounding conditions will help determine whether the desired benefits are attainable. Ultimately, outdoor furnaces should be considered as a replacement when wanting heat for an entire building. “An outdoor wood furnace is a good choice for replacing fossil fuel energy when the goal is to replace the entire heat load with wood-fired energy that can be thermostatically controlled heat for entire homes and other applications,” says Rodney Tollefson, vice president of Central Boiler Inc.

Outdoor wood heating has primarily been applied in rural, colder climates where end users can source their own wood. Central Boiler’s main applications are for home and domestic water heating. “Other applications are resorts, lodges, swimming pools, greenhouses, brooder barns, dairy farm water heating, warehouses, small businesses, aquaculture and snow melt,” Tollefson says.

Often, use of these units derives from identifying the need for it personally. Suppliers to the industry are no exception. “I had a need, personally, for an outdoor furnace, and living and working on the farm with access to equipment, I just built my own furnace,” Gagner says. “I built the first furnace and then started the company and partnered with my brothers.”

Warmer climates have also been brought into the sector looking for an alternative. “We were agricultural guys looking for an option held hostage by propane,” says Wes Cumbie, Lee Energy Solutions vice president of sales and marketing.

Operation Details

The use of biomass such as wood chips and pellets is one way to loosen dependence on fossil fuels and foreign oils. “Wood pellets are much more stable on a cost per million Btu basis, probably the most stable fuel, whereas propane and fuel oil are the most volatile fuel sources,” Gagner explains.

Although a stable fuel source, people in the wood heat sector stress that the treatment of the fuel will determine the success and amount of smoke of the wood heating system. According to Cumbie, Lee Energy’s dry heat furnace, “when running at 100 percent burn rate, a cigarette puts off more smoke.” One reason for the disparity in smoke is how the unit functions. In a nut shell, the company’s furnaces heat air, and then a blower motor moves the warmed air through a duct system. A boiler heats water, which then flows through a network of pipes in a building or home. When it comes to boilers, successful fueling of the system boils down to the end user. One of the keys is to use dry, seasoned wood. “Seasoned wood is by far cleaner, more efficient, uses less fuel and is less corrosive,” says Jeremy Hanson, Northwest Manufacturing Inc. WoodMaster commercial sales representative.

 “If you want to get the most out of your wood, you should be cutting and seasoning it a year before you burn it,” Tollefson adds. “It will reduce your wood consumption by 20 to 30 percent; when you have unseasoned wood about 50 percent of the weight is water.”

Users also “need to be absolutely confident that whatever boiler they choose it’s properly sized,” says Charlie Niebling, chair of BTEC and consultant with Innovative Natural Resource Solutions LLC. Properly sizing the unit will ensure even heat throughout the home, as well as achieving the highest efficiencies possible. When properly sized, many wood heating systems burn for 12 hours before they need to be reloaded.

Efficiencies range based on the model of the furnace. Manufacturers will agree that some of the older models lack in efficiency, but the EPA phase-two qualified models are demonstrating efficiencies with higher heating value's (HHV) in the upper 70's. Central Boiler's E-Classic 1450 EPA qualified boiler is 78 percent HHV. WoodMaster has similar ranges with their EPA qualified gasification models. The big focus for these manufacturers is to continue to develop lower emitting and higher efficiency models.

Lee Energy also demonstrated comparable efficiency at 80 to 82 percent with the unit capability of 66 pounds of pellets an hour, at 540,000 to 550,000 Btu. The combustion of WoodMaster and Central Boiler furnaces were more difficult to estimate with the wide range of units. “Normally, the heaters we sell are for heat loads of 50,000 to 350,000 Btu per hour for residential applications,” Tollefson says.

Beyond the sizing of the furnace, the installation of the unit is important to ensure efficiency. “The furnace is usually installed 30 feet or more from the building or buildings being heated,” Tollefson says.

Lee Energy’s commercial pellet furnaces are typically set on concrete pads outside the structure to be heated. “We will set our heater on that pad and then right next to the heater will be a 15 to 20 ton storage bin that pellets go into in bulk, and they are automatically loaded through an auger feed system,” Cumbie explains. A customized collapsible duct system is also installed.

The outdoor hydronic heater is designed to work with any existing heating system. Water-to-air or water-to-water heat exchangers or direct circulation conveys the heat into the structure's forced-air furnace, radiant baseboard or radiant floor heating system. This allows for normal thermostatic temperature control.

While it is important for customers to know the basic set up of their desired wood heating system, what many direct their attention to are the major benefits and drawbacks.

Pros and Cons

The main drawbacks to wood-burning systems result from maintenance and user error.  Ash buildup needs removal every week or so, depending on how much wood is being burned. Lee Energy’s BIO pellet furnace needs cleaning just about every day if burning hard. Beyond general ash removal, some are deterred from the labor of manually loading many of the outdoor furnaces once or twice a day.

The biggest drawback comes with the customer’s capacity of misusing the technology. “It is very difficult to control how people choose to use the equipment, namely what they choose to burn,” Hanson says. “If they are burning wet wood or nonbiomass materials, emissions are a concern.”

Although there are setbacks to the technology, there are benefits as well. “The No. 1 is fuel savings, significant fuel savings,” Hanson says.

The prices of Central Boiler and WoodMaster units are comparable. “The units themselves run from about $5,500 for residential on up to about $12,000,” Tollefson says. “You are going to have anywhere between $1,000 to $4,000 in labor and parts involved in installing them.”

New models are on the higher end of the price range because of the lower emissions and higher efficiencies they can demonstrate compared to older models. Commercial sizes run higher. “The typical layout of what a customer buys for turnkey ducting, manufacturing, installation, brings the unit to around $17,000 to $21,000 depending on where you are,” Cumbie says.

Many units last for 20-plus years, with fuel savings offsetting the purchase price and installation of the units usually within the first three years. “After that, it is in effect generating money compared to fossil fuels,” Tollefson says. “We find more than 50 percent of the people that own our furnaces cut their own wood, which results in eliminating their heating costs. If purchasing wood, normally, they save 80 percent of the heating cost.”

In addition, some insurance companies prefer outdoor wood burning furnaces over indoor wood stoves because all combustion is removed from the home or building. This removes the fire hazard and carbon monoxide risk.

Beyond keeping a thicker wallet, the environment can be both a draw and push back for potential users. Wood is a renewable resource, conserving fossil fuels for the future and reducing greenhouse gas emissions. However, even the new models can smoke and do emit, although lower, some PM.

Rectifying an Image

Innovation and collaboration with the EPA is at the forefront of the change in image. Some manufacturers have worked closely with the EPA in helping to set performance standards. WoodMaster’s gasification models and Central Boiler’s E-Classic models both are qualified under EPA’s voluntary phase-two program standards, and are working to meet the drafted NSPS. “There has also been an effort to educate consumers of proper installation and operating practices when using outdoor wood furnaces for the best performance,” Tollefson says.

This education comes from many groups in the wood heat sector. “BTEC, Pellet Fuels Institute, Heating the Northeast, and Heating the Midwest do a great job of educating the general public and raising awareness of the benefits of heating with biomass,” Hanson says. Best burn practices have been developed in conjunction with EPA, Hearth, Patio and Barbecue Association and manufacturers, he added.

Although the heat is on for manufacturers to produce cleaner, more efficient units, it seems that the resulting innovation will ultimately warm customers and the general public to the prospect of outdoor wood heat, and spur advancement throughout the entire sector. “I give a lot of credit to manufacturers, they’ve come a long way and have worked very hard to improve the efficiency, combustion and performance.” Niebling says.

Author: Katie Fletcher
Staff Writer, Biomass Magazine