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Biomass Gasification Systems in the Combined Heat and Power Market  by Wayne T. Bonhag, P.E., P.P.    With the present high costs of both electrical and thermal energy, the use of biomass (wood chips, pellets, and other sustainable green fuels) is an excellent choice especially when coupled with a combined heat and power (CHP) application. The reason that this is an exceptional choice for those facilities in the Northeast part of the United States and Canada is that there is an abundance of wood chips and sustainable fuel. The gasification process is extremely clean so that air emissions are minimal, electrical and thermal delivery is localized to the need therefore minimizing transmission losses, and the use of a single fuel to provide both the electric power and the thermal requirement significantly increases the efficiency of the overall plant. What is a true biomass gasification system? A true biomass gasification system is designed to convert a fuel such as coal, coke, and wood fuel into a combustible gas which is termed "producer gas." This clean producer gas may be used for a fuel in engines, gas turbines, boilers, generators, and many other applications. In fuel firing devices such as boilers which have burners, this fuel will not need to be cleaned and cooled since the hotter gas will enhance the firing of the boilers. In fuel firing devices such as engines and turbines, this producer gas will be further cleaned and cooled so the engine and turbine continues to perform over a long period of time in the manner in which they were designed. From a historic perspective, gasifiers have been in the world for hundreds of years. They come in all sizes from small coal or coke-fired units which have been used in automobiles to much larger fixed-site units that are used to produce both electrical power and thermal energy. They become more viable based on need, thermal-electric balance, fuel cost and avoided energy cost. A gasifier unit like a linear hearth gasifier is now on the open market in New Zealand, Europe, Asia, and in the United States. This technology is the product of many years of commercial gasifier design and fabrication experience by a number of firms. In order for a unit to be cost effective and applicable to a project, it must be fabricated by skilled craftsman, using the highest quality materials available; it must be durable, properly controlled automatically, and be reliable. The single item that makes this technology a gasification unit instead of a combustor is that the control of oxygen to the fire box is controlled so that pyrolysis occurs instead of oxidation. There is no excess air present as there would be in a combustor unit approach. This technology, then, promotes a cleaner operation with much lower emissions and ash from wood chip fuel. This also means that a gasification unit has the capability to develop more energy from the same amount of raw fuel, thus providing a fuel savings on the front end of the system. The entire system of fuel storage, fuel handling, wood moisture preparation chamber, gasifier, cleaner, cooler, and delivery piping to the device is what makes up a total gasification system. In the properly designed system, this is designed for totally automatic operation with all the run modes and safety shut downs. Depending on the sensitivity of the installation, some degree of redundancy is required to assure that the system continues to operate during maintenance shut downs and emergency shutdowns. The combination of a good quality biomass gasifier with a true combined heat and power (CHP) application will provide optimum energy production at a facility. This melding of technologies allows the maximum amount of energy to be obtained from the fuel stock and delivered to the site in either electrical power or thermal energy. A properly designed facility to do this will achieve the result that the owner is anticipating for the benefit of the firm and with the proper socioeconomic attributes. In studies that we have completed on a number of biomass CHP projects, we have determined that utilizing gasification in the process is a major cost savings to the operating cost from fuel resources alone when compared to other t3pes of wood chip systems because of the reduced fuel requirement. When comparing this technology to natural gas, propane, and fuel oil, biomass gasification provides an excellent solution. In fact in many analyses that we have completed on various sized projects, we have found a simple payback between four (4) and six (6) years. In order to implement a gasification project one needs the following: A host site with a good balance of thermal and electric energy consumption. An adequate source of biomass fuel at a reasonable cost. Presently the cost per million BTU of wood chips is in the range of $2.00 to $2.75 per million BTU, depending on quality and location. This biomass fuel cost is significantly less than conventional fuel costs. A knowledgeable engineering resource to properly design the systems and subsystems. A resource for financing of the installation. The gasification technology being available in a commercially proven, readily available product. This applies to both systems and subsystems. The ability to operate the gasification plant and all the axillaries. Thankfully, for all of us within the Northeast region, we are at a juncture in the energy marketplace right now where all six (6) of the above items have come together and are available to the interested owner. It is up to the properly educated owner/operator to bring this technology into being at his facility in order to begin to gather the energy savings from using sustainable, green, biomass gasification systems. It will take some demonstration or pilot project to raise the level of interest in this technology in our area. However, once that demonstration or pilot is done, owners will be interested in jumping on board with the biomass gasification technology. In our opinion, using biomass gasification is the right thing to do, right now. For additional information, please contact Wayne T. Bonhag, P.E., P.P., LEED AP, the principal of Bonhag Associates, PLLC, an innovative consulting engineering firm located in Lebanon, New Hampshire. Mr. Bonhag has designed a number of varied award winning sustainable buildings and gasification CHP projects for clients throughout the United States for residential, commercial, industrial, educational and hospital-healthcare both in new construction and renovation of existing facilities and is a member of the USEPA CHP Partnership Mr. Bonhag is a second generation Mechanical, Electrical and Energy engineer having worked for such firms as Exxon Corporation, DuPont, Bristol Myers-Squibb and locally, Vermont Gas Systems, Fujiflim, and Dartmouth College among others. Mr. Bonhag can be reached at wbonhag@bonhagassociates.com or at 603-448-5180.

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