Read the article in Today’s Boiler
By David Bohn
Fueling boilers has become more complicated. Many conventional fuels are now impractical because they can be dirty and expensive, and they are sometimes incompatible with modern environmental regulations. This creates a challenge since changing out an entire boiler system is a massive expense. Is it possible that your current system could work with new, environmentally friendly fuels? The answer is yes, at least when it comes to these groundbreaking new fuel options.
The latest innovations in biofuel technology
Traditional biofuels such as wood chips or pellets, while preferable to non-renewable fossil fuels, have still been found to have a negative environmental impact that can be problematic in many applications. A relatively recent innovation in the sector involves replacing wood chips with a fuel known as “bio-oil” (also referred to as “liquid wood”). While this biofuel is more environmentally friendly, some users found it incompatible and difficult to use at first—but that is now changing. Boilers can be more easily modified to be compatible with liquid wood, and the cost is about one-tenth that of replacing the system.
Created by Ensyn Technologies Inc. out of Ontario Canada, liquid wood is produced using a thermochemical process called pyrolysis, in which wood is burned in excess of 500º C (in the absence of oxygen) and is transformed into a combustible liquid. Because there is no oxygen, the wood does not combust. It first becomes charcoal, and then further decomposes into gas and liquid. It behaves similarly to natural gas or crude oil except that it has much lower carbon emissions.
Liquid wood still has the advantage of being a renewable wood-based resource. The raw wood used to create liquid wood is harvested from tree farms—and more trees can continuously be planted to replace those used for fuel oil. Reducing dependence on fossil fuels and other non-sustainable sources is critical to reducing overall greenhouse gas emissions, and turning the raw wood into liquid wood fuel increases the environmental benefits even further.
An added advantage is that liquid wood is less cumbersome to store than wood chips or pellets. In order to utilize wood chips, the user must address two onerous tasks—turning the bulk wood into chips, and then storing the chips themselves until they are used. There is also the challenge of getting the wood chips or pellets to the burner as they are not often stored in the same location. The logistics involved in managing chipping and storage can lead to significant added costs, as Bates College in Maine discovered.
Bates recently overhauled their campus heating system. They weighed the idea of converting to wood chips, but they found that building a wood chipping plant and storing the wood chips on campus would have cost a startling $10 million upfront. When they realized they could achieve the same environmental benefits by converting to liquid wood instead of wood chips, while only spending $1 million on the conversion, the choice was easy. They implemented liquid wood as their primary heating source and saw their carbon footprint reduced by an astounding 83 percent.
What is Bio Residual™ oil?
One of the newest innovations in environmentally responsible fuel is bio-residual oil (BRO. This renewable energy source has 85 percent lower emissions that typical fossil fuels and has the potential to reduce carbon emissions in the United States by thousands of tons per year.
Made by Renewable Energy Group in Ames, Iowa, Bio Residual™ Oil is the biodiesel equivalent of No. 6 oil. It is made up of all the heavy hydrocarbons left over after the refining of biodiesel, which can be made from diverse biological materials such as agricultural waste, animal fats, and recycled cooking oil. BRO™ is too heavy and viscous to be burned in an engine, so Renewable Energy Group has been working with Preferred Utilities Manufacturing to test the capabilities of BRO as a boiler fuel.
Preferred’s engineers Chuck White and Dan Wallace have now adapted one of their burners to cleanly burn BRO.
Striking the balance between electrical consumption and NOx emissions
Although greenhouse gases are the chief focus of most sustainability goals, they are not the only emissions to consider. Industrial boilers also emit nitrogen oxide (NOx), which is a significant air pollutant and is the key component in smog. These NOx emissions are regulated by the EPA and state agencies, with standards becoming steadily tighter since the 1990s.
Unfortunately, decreasing NOx emissions means upping electrical usage—the lower the NOx, the more electricity required. This can be a source of concern for those looking at low-NOx burners. They face the tough choice of either getting a system with the lowest possible emissions while sacrificing significant electrical efficiency, or else using a higher emissions system (that might become obsolete in a few years if regulations continue to get stricter) in an attempt to save on electricity. This rock-and-a-hard-place dilemma is even tougher in states with high electrical costs such as Connecticut and Hawaii.
The solution lies in the flexibility afforded by a new generation of low-NOx burners with configurable emissions. These systems can be configured to meet current regulations or targets, while operating at the highest electrical efficiency possible. Should regulations ever change, the burner can easily be updated for the new target NOx levels.
The demand for fuels that will have minimal negative environmental impact and not contribute to harmful CO2 emissions is ever-growing for many reasons. Regulation of the industry is likely to continue and become more stringent, “green” methods are becoming more economically desirable, and, perhaps most importantly, manufacturers are actively seeking ways to use renewable resources because they believe it is the responsible thing to do. Innovations like liquid wood and BRO, as well as new configurable low-NOx burners, are helping customers to reach their renewable energy goals in ways that maximize positive results for their bottom line and for the environment.
David Bohn is president and CEO of Preferred Utilities Manufacturing Corporation.