Standardized Analytical Methods for Biomass Fuel Characterization
As the U.S. power industry prepares to comply with potential regulations for greenhouse gas (GHG) emissions, many are considering biomass fuels as an option to reduce carbon dioxide (CO2) or to meet renewable fuel mandates. In some circumstances, biomass is considered a carbon-neutral fuel, and the industry would be eligible for CO2 credits on the basis of displacement of CO2 emissions associated with fossil fuel-based electricity. Another advantage of incorporating biomass as a fuel source for electric utilities is that it has the potential to reduce the overall emission of hazardous air pollutants from power plants.
This renewed interest in biomass as a fuel source has led to the need for proper characterization. The U.S. lacks consistency regarding the use of testing methods for biomass when combustion and fuel quality parameters are evaluated, however. Many laboratories are relying on methods that have been developed and validated for fossil fuels, which may not be suitable for biomass fuels.
Biomass materials vary greatly in composition, and the concentrations of some constituents are well outside the range of what is typically found in fossil fuels. Concentrations of sulfur and trace metals are usually much lower in biomass fuels than in fossil fuels; however, some minor and major constituents such as phosphorus and potassium can be an order of magnitude higher. Many European countries have been utilizing biomass as a fuel for decades and have utilized test methods developed by the European Committee for Standardization (CEN), which has a technical committee (CEN/TC 335) solely dedicated to solid biofuels.
The U.S. must collaborate with European and international standards organizations to help establish the use of the most appropriate test methods for biomass. By establishing consistent, reliable methods for biomass characterization, the biomass industry will be able to compare fuel quality results among different fuels analyzed by different laboratories and have confidence that the results can be accurately compared.
As part of a current project sponsored by the U.S. DOE-Center for Biomass Utilization Program, the North Dakota Industrial Commission Renewable Energy Program, Metso Power, and the Electric Power Research Institute, the Energy & Environmental Research Center is reviewing biomass test methods from national, European and other international standards organizations. The International Organization for Standardization (ISO) now has a solid biofuels technical committee, ISO/TC 238, which is working to publish biomass standards that are similar to the European CEN standards. The EERC is involved with this committee and is working with other research and industry participants who share the same interest in establishing standardized test methods for biomass characterization.
After a thorough review of the test methods deemed most appropriate for biomass characterization, this project will apply these methods to determine fuel combustion characteristics for a variety of biomass feedstocks produced in the U.S. The fuels currently enumerated for evaluation include switchgrass, corn stover, wheat straw and a variety of different woody biomass materials. Other fuels may be added as appropriate. The testing parameters will include those that are typically determined when fossil fuels are evaluated, such as moisture and ash content, heating value, volatiles, carbon, hydrogen, nitrogen, oxygen, sulfur, halogens, major ash chemistry, and a full suite of minor and trace elements.
In addition to th
e aforementioned test parameters, the fuels will also be evaluated for potential slagging and fouling behavior in a utility boiler by performing computer simulations to predict the properties of ash in a boiler that might signify potential heat-transfer issues. Various biomass/coal blends will be examined.
As a result of this work, standardized test methods will be established, implemented, and promoted for use throughout the U.S. biomass industry to provide the industry additional confidence when comparing fuels.
Author: Carolyn Nyberg
Manager, EERC Analytical Research Laboratory