Shifting our dependence from fossil fuels to carbon-neutral sources is a gradual process. Co-combustion of biomass in existing coal-fired power plants is an attractive option to increase the share of renewable fuels in the energy market. Designing equipment for these blends requires knowledge of pyrolysis and combustion characteristics to maximize energy output, reduce emissions and optimize fuel ratios. The objectives of this research are to: obtain thermal evolution profiles (kinetics and devolatilized compounds) of region-specific coal-biomass blends and probe the effect of heating rate, particle size, and coal to biomass blend ratios on pyrolysis and combustion behavior. A systematic study on locally available second generation feedstocks (agricultural wastes - woods, wheat and corn stalks, and local manufacturing wastes - cocoa shells, barley, hops, fruit pits) blended with coal used by regional power plants will provide knowledge for the incorporation of locally-sourced organic refuse into power generation, and a broader understanding of optimizing such blends for energy generation. The proposed work aims to bridge the gap between fossil fuel dependency and a green energy future while expanding opportunities for students from underrepresented groups to ensure our future engineering workforce is as diverse as the population it serves. Intellectual Merit: Given infrastructure already in place for coal, the most likely avenue in the immediate future for biomass utilization is as a blended feedstock in coal-fired power plants. Coal-biomass blending has the potential to limit the overall cost of fuel for a power plant, assuming the costs to process the biomass (transportation, drying, milling, etc.) are lower than the coal while lowering the carbon footprint of energy production. This proposal explores the thermodynamics and kinetics behind coal-biomass blend combustion to maximize process efficiency, while simultaneously monitoring devolatilized compounds to ensure the co-combustion of biomass and coal represents an improvement in the emissions profile. The knowledge garnered from this work is immediately applicable to state air resource permitting agencies, and directly addresses the EPA's debate over the next three years on how to regulate biomass emissions. The proposed work also provides fundamental data on the behavior of U.S.-specific biomass-coal blends to assist in the transition from fossil fuels to alternative energy sources; the design of an effective thermochemical conversion unit requires knowledge of the chemical composition, thermal behavior, and reactivity of the fuel in question. Broader Impacts: Altering our workforce to more accurately mirror the composition of our society is a gradual process, requiring strong mentors and role models. If we are broadly inclusive -seeking out contributions from all perspectives - we can solve issues surrounding energy and the environment for future generations. The potential benefits of the proposed project to society are twofold: first, by investigating the blending of biomass with coal we can potentially lower greenhouse gas emissions while maintaining current energy production. Second, by actively seeking students (graduate and undergraduate) from traditionally underrepresented groups, we better leverage our human capital to facilitate a diverse, competitive and globally engaged workforce. As many UNH students choose to remain in New England after graduation, a project that specifically addresses local energy needs prepares them to understand regional issues when competing on the job market. To engage the public and industry, the students and PI will present findings from this research at academic conferences and in peer-reviewed publications, and in technical reports to assist in policy-making and industrial energy production schemes. As part of her Broadening Participation Plan, the PI proposes to implement a seminar series called "Engaging Your Future" to the science and engineering community at UNH to work with students on overcoming challenges they face as underrepresented groups, building a resume, and identifying career opportunities. As a woman with a disability, the PI is in a unique position to mentor students from traditionally underrepresented groups through building a research agenda with direct applicability today?s challenges in energy and the environment.
Bringing our society to a carbon-neutral, clean-energy future is an evolutionary process that must combine scientific advances with available infrastructure to overcome economic, policy, and technological barriers. Second-generation biomass feedstocks, comprised of agricultural waste and organic byproducts, may be blended with other solid fuels or utilized as separate fuel streams. However, given current infrastructure perhaps the most viable means of increasing the use of biomass in electricity generation is as a blended feedstock in coal-fired boilers. Much of the work on the chemical reactions behind coal-biomass blending to date originates outside of the United States on biomass sources not cultivable in the U.S. and on non-domestic coals. This hampers efforts to design processes and retrofit boilers for domestic coal-biomass co-firing. Intellectual Merit: This is a broad, systematic study of thermochemical conversion reaction rates, energy requirements, and chemical reaction products as a function of temperature and coal-biomass blend composition. The study queries the kinetics of blends of three coals used in New England, and three locally available biomasses (feed corn stover, brewer’s spent grain, and cocoa shells). No matter the specific coal and biomass chosen, the peak mass loss rate for each pure fuel and blend was within 50°C of each other, though the rate of decomposition is a function of the blend composition. That is, at lower temperatures the biomass is more reactive and has a higher mass loss rate; as the percent of biomass in the blend decreases, so does the rate of reaction. However, such a trend does not exist for the activation energy required to initiate the reaction. Evidence of reaction synergism between the fuels in blends suggests that the biomass promotes reactions within the coal particles, making thermal decomposition easier at lower temperatures. However, because most biomass has a lower heating value than most coals, there is a balance to be struck when blending these fuels between energy lost to initiate the reaction and energy gained upon combustion. A new model to evaluate this activation energy was proposed, enabling a continuous look at how the energy changes as a function of fuel decomposition. Broader Impacts: The work done and outreach performed as a part of this grant impacted the STEM workforce in many ways. First, eight undergraduate and two graduate students, nine of them from under-represented groups, participated in this project and have gone on to continue research or pursue industrial careers in STEM. The PI brought professional development programming to two universities (first as a faculty member at University of New Hampshire, now at Boston University) to encourage science and engineering students to complete their degrees, learn the soft skills needed to succeed, and leverage their experiences in a diverse workforce. Through outreach with a start-up company and local electric utilities, the PI is translating her reaction kinetics model to an industrial scale to yield a renewable energy source that is efficient and cost-effective. Finally, this project has led to collaborations with faculty and graduate students in the social sciences to determine ways to translate this research to the public by learning how to frame messages about the importance of renewable energy to different stakeholders, and how scientists could be a mediating voice in this highly political debate.
