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Renewable Resources Research Laboratory
The Renewable Resources Research Laboratory (R3Lab) is a test-bed for the development of innovative technologies and processes for the conversion of biomass into fuels, high-value chemicals, and other products. A consistent theme of the lab's research throughout its history has been the search for new uses for Hawaii's abundant agricultural crops and by-products. Currently the R3Lab is evaluating the suitability of Honolulu’s sewage sludge for the production of biocarbons (i.e., charcoal) using the patented HNEI Flash Carbonization™ Demonstration Reactor. Sewage sludge biocarbons can be used to replace imported coal that is burned to generate electric power in Hawaii. Coal combustion is the primary contributor to climate change that threatens island communities worldwide. Also, sewage sludge charcoal can be used for soil beneficiation and carbon sequestration (i.e., “Terra Preta”). In addition to producing biocarbons for Terra Preta applications and our NSF-sponsored biocarbon fuel cell research, our ongoing work includes the testing of afterburners for heat recovery from the effluent gas of the Flash Carbonization™ Reactor. Earlier in its life the R3Lab engaged in research on conversion of biomass into gaseous fuels (hydrogen), and liquid fuels (ethanol). Reprints of publications are available upon request to Prof. Antal. News Item: the HNEI HEET project is sponsoring Flash Carbonization™ tests of Honolulu’s sewage sludge. The goals of this work are to eliminate smoke emissions from the Flash Carbonization™ Demonstration Reactor by use of a suitable afterburner, to reduce CO emissions sufficiently to satisfy state and EPA regulations, to assess other emissions and the behavior of heavy metals in the sludge during carbonization, and to produce sewage sludge biocarbons for various market studies. Research at the University of Hawaii (UH) has led to the discovery of the Flash Carbonization™ process that quickly and efficiently produces biocarbon (i.e., charcoal) from biomass. This process involves the ignition of a flash fire at elevated pressure in a packed bed of biomass. Because of the elevated pressure, the fire quickly spreads through the bed, triggering the transformation of biomass to biocarbon. Fixed-carbon yields of up to 100% of the theoretical limit have been achieved in as little as 20 or 30 minutes. (By contrast, conventional charcoal-making technologies typically produce charcoal with carbon yields of much less than 80% of the theoretical limit and take from 8 hours to several days.) Feedstocks have included woods (e.g., leucaena, eucalyptus, and oak), agricultural byproducts (e.g., macadamia nutshells, corncobs, and pineapple chop), moist green wastes (e.g., wood sawdust and Christmas tree chips), various invasive species (e.g., strawberry guava), and synthetic materials (e.g., shredded automobile tires). During 2008 we completed studies of the carbonization of raw sewage sludge produced in Honolulu's Ewa sewage sludge treatment plant. We were surprised by the ease with which air-dry sewage sludge can be converted into charcoal. We obtained charcoal yields of about 30% (dry basis) from the sewage sludge. The charcoal contained 45-51% ash and 40% fixed-carbon. These results are described in a recent peer-reviewed, technical, archival-journal paper that can be obtained by request to Prof. Antal. We are now testing a commercial-scale, stand-alone (off-the-grid) Flash Carbonization™ Demonstration Reactor ("Demo Reactor"). The first successful test of the Demo Reactor occurred on 24 November 2006. A canister full of corn cobs was carbonized in less than 30 min. This test proved that the Flash Carbonization™ process can be scaled-up to commercial size. Although considerable progress has been made in the design, fabrication, and operation of an effective atmospheric-pressure, catalytic afterburner, we are now examining the suitability of off-the-shelf, commercially available afterburners for use with the Demo Reactor.
The UH Flash Carbonization™ technology is protected by U.S. Patent No. 6,790,317. The UH has applied for patents on the Flash Carbonization™ process in many other countries. Some of these patents have been granted, and others are pending. The first license was signed in 2003. Kingsford obtained a limited license in 2007. Licenses to practice the Flash Carbonization™ process in the State of Hawaii and many other states are now available. HNEI intends to employ the UH Flash Carbonization™ Demonstration reactor as a showcase facility to both display its capabilities and to refine its operation as a benefit to licensee(s) of the UH patents. All patent licensing activity is handled by Lee Taylor in the UH Office of Technology Transfer and Economic Development (OTTED). Based on prior experience, a potential licensee should take the following steps to develop a relationship with HNEI and OTTED.
Biocarbon Fuel Cells The National Science Foundation will sponsor HNEI research aimed at the development of a moderate-temperature aqueous-alkaline/carbonate biocarbon fuel cell. The three-year NSF grant has a start date of September 2008 and will provide support for a graduate student, Professor Michael J. Antal, Jr. (HNEI), Professor Stephen Allen (Hawaii Pacific University), and Dr. Gabor Varhegyi (Hungarian Academy of Sciences). The Summary of the proposal that NSF has funded is below. Thus far, HNEI research on biocarbon fuel cells has resulted in the publication of three archival-journal papers that are available from Professor Antal upon request. Summary Aim. The aim of this proposal is the development of an aqueous-alkaline/carbonate biocarbon fuel cell which performs well (see below) while realizing electrolyte invariance by exploiting electrochemical reactions that are favored at temperatures near 300 °C.Broader impacts. Very large quantities of lignocellulosic residues (e.g., corncobs, coconut shells) accompany the production of bioethanol and biodiesel fuels. These residues can be efficiently and quickly converted into biocarbons. Carbon fuel cells can generate electricity from these biocarbons – as well as from coal, and other fossil carbons – with a theoretical thermodynamic efficiency of 100%. A recent EPRI study indicates that carbon fuel cells have the potential to convert biocarbons into electrical power at a system level efficiency of about 60%, which is over 20% higher than the efficiencies realized by current state-of-the-art integrated gasification combined cycle (IGCC) or advanced pulverized coal power generation systems. Thus the production of biocarbon can complement the production of bioethanol and biodiesel in a biomass refinery that also produces electricity at a very high efficiency. In addition to the primary aim of this proposal (above), other impacts include the training of two BS and two MS students, the involvement of Hawaii Pacific University (HPU) faculty, and the development and inclusion of new electrochemical engineering course material in the UH and HPU curricula. In view of the fact that a college degree in chemical engineering is not offered in the State of Hawaii, these impacts have special significance.Intellectual merit. This proposal is based on the following two hypotheses. 1) At temperatures approaching 300 °C the aqueous-alkaline/carbonate biocarbon fuel cell will offer an open circuit voltage (OCV) of about 1 V and a steady, maximum power density that exceeds 100 mW/cm2. 2) During operation, the composition of the electrolyte will evolve towards an equilibrium mixture of hydroxide and carbonate ions that afterwards will be invariant (i.e., stable).The cathode of this cell resembles that of a Bacon fuel cell, where oxygen in air is reduced to hydroxide ion over a silver catalyst. New thermodynamic analyses presented in this proposal indicate that the cathode should perform well at temperatures approaching 300 °C. Likewise, new thermodynamic analyses indicate that, at these temperatures, both the hydroxide ion and the carbonate ion (formed by the reaction of CO2 with hydroxide ion) should vigorously oxidize the carbon anode and release electrons; thereby generating power at high efficiency. This proposal has three objectives: 1) to characterize the oxidation behavior of anodic charcoal in the aqueous-alkaline/carbonate environment of the fuel cell at temperatures near 300 °C; 2) to characterize the stability of the electrolyte, together with the catalytic effects of differing electrolytes on the anodic and cathodic reactions at temperatures near 300 °C; and 3) to characterize the performance of the biocarbon anode as a working electrode in a setup that includes a counter electrode, and flow of the electrolyte through a heat exchanger bridge to a reference electrode maintained at system pressure, but at a much lower temperature. Previous work at UH detailed the performance of a lower-temperature aqueous-alkaline carbon fuel cell. Operating at 245 °C and 35.8 bar with 0.5 g of corncob charcoal, this cell realized an OCV of 0.57 V and a short circuit current density of 43.6 mA/cm2. A comparison of Temperature Programmed Desorption (TPD) data for the oxidized anode biocarbon with prior work indicated that the temperature of the anode was too low: carbon oxides accumulated on the biocarbon without the steady release of CO2 and active sites needed to sustain oxidation; consequently the OCV of the cell was less than the expected value. New thermogravimetric-mass-spectrometric studies by colleagues in the Hungarian Academy of Sciences substantiate the TPD findings, and show that oxygen chemisorption with an accumulation of carbon oxides on the biocarbon anode should give way to the steady release of CO2 (i.e., steady oxidation) at temperatures approaching 300 °C. These new findings give credence to the first hypothesis of this proposal. High-Yield Activated Carbons from Biomass Activated carbons made from biomass (i.e., coconut shells) charcoal are used to purify water and air. The R3Lab has developed an air oxidation process that produces high-yield activated carbons from biomass charcoal. This work was supported by the National Science Foundation. Hydrogen Production from Biomass A conventional method for hydrogen production from fossil fuels involves the reaction of water with methane (steam reforming of methane) at high temperatures in a catalytic reactor. Research sponsored by the U.S. Department of Energy led to the development of a process by the R3Lab for hydrogen production by the catalytic gasification of biomass in supercritical water (water at high temperature and pressure). This "steam reforming" process produces a gas at high pressure (>22 MPa) that is unusually rich in hydrogen. Unfortunately, research on this topic within HNEI halted after a U.S. Department of Energy economic study projected dismal economics for the process. Biomass Pretreatments for the Production of Ethanol The R3Lab has been a leader in the development of a pretreatment process that employs hot liquid water to render lignocellulosic biomass susceptible to simultaneous saccharification and fermentation for the production of ethanol. This process can also be used to produce microcrystalline cellulose from biomass. The research was supported by the U.S. Department of Agriculture and the Consortium for Plant Biotechnology Research. Contact: Michael J. Antal, Jr.Renewable Resources Research Laboratory |
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