Heating Oil Emissions are Cleaner than You Think

Posted by admin on July 27, 2009 at 11:46 am

A recent study, conducted for the heating oil dealers of Maine, had some interesting findings, as reported in a Maine newspaper, The Morning Sentinel.  With pellet stoves gaining popularity in the state – even getting a boost from Maine’s government – threatened heating oil dealers thought a comparison of the relative cleanliness of oil versus pellets might do them some good. It did.

According to the article the study was conducted by David Dixon of Dirigo Environmental Consultants. Dixon is a former air bureau manager at the Maine Department of Environmental Protection.

Dixon compared emissions from existing oil furnaces, older wood stoves and modern pellet stoves. The pellet stoves in the study did better than the older wood stoves, but still released 50 times more particles than the oil furnaces. Dixon found similar patterns for carbon monoxide. Pellet stoves also compared poorly to oil furnaces in terms of air toxics, such as certain organic compounds. Maine has good overall air quality and can handle more wood heat, Dixon said. But because pellet heat is new and fast growing, he said, policy makers should examine the potential impact. “If we’re converting older wood stoves to pellet stoves, I’d go with that,” Dixon said. “But oil furnaces to pellet stoves, that’s a step backwards.”
So, home heating oil comes out looking pretty good when compared to the alternatives. The other big difference today is the equipment.

Thirty years ago, the average heating oil customer used 1,300 gallons of oil per year. Today, that number has been reduced by nearly 50 percent, to 700 gallons per year, thanks to high-efficiency equipment. Less oil being burned means less pollution of any kind, and new burner technology is responsible for the improvement. The new oil burners release near zero levels of smoke and combustion discharge. They produce on average six ounces of particulate emissions (or soot) a year from burning three tons of heating oil.

The home oil burners that are still producing anything significant in terms of air pollution are standard efficiency boilers, probably fifteen or more years old. Many of them are still around, because oil equipment typically has a long life expectancy. These antiquated boilers operate at an efficiency level of about 60% or lower. Since the early 1970s, the industry has been working to improve the efficiency of furnaces and boilers, and since 1992, oil burners have been required to have at least a 78% efficiency rating. The introduction of improved burners with flame-retention heads was the first major step in boosting the efficiency of conventional oil-fired heating equipment. Flame retention heads produce a smaller, more compact flame and increase turbulence in the combustion chamber to improve combustion.

The high-static burner, which has recently come onto the market, has further enhanced the efficiency capability of heating systems. The high static air pressure produced by the burner helps prevent particle buildup.

New “mid-efficiency” oil furnaces convert 80 percent or better of the energy contained in fuel into useful heat, to make the most of the superior performance of these new burners. Super-high efficiency condensing furnaces, now available, cool combustion gases to recover heat that is normally lost as water vapor. These furnaces, which use sidewall ventilation rather than a chimney, operate at close to 100% efficiency.

Diagram of a modern oil-fired furnace. (image: oee.nrcan.gc.ca)

Benefits of a good mid-efficiency furnace are much lower combustion and dilution air requirements, as well as more power to exhaust the combustion products (an advantage in newer, tighter housing), a safety shut-off in case of raft problems, and a more effective venting system.
Mid-efficiency furnaces have an efficiency rating of 83 to 89 percent and use about 30 percent less fuel than an old conventional furnace while producing the same amount of heat.

Whatever kind of oil furnace you have, even if it’s an older one, keeping it clean and properly tuned through regular servicing will maximize its efficiency – annual maintenance results in at least a 13% reduction in fuel consumption according to the EPA – while minimizing unwanted emissions. You should have your system serviced at least annually or at any sign of trouble such as smoke or odors. A new oil burner can have a life expectancy of 30 years or more if it is properly maintained.

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