1: Develop pyrolysis processes that enable the commercial production of marketable, partially-deoxygenated pyrolysis oil intermediates. 2: Develop post-pyrolysis technologies that enable the commercial upgrading of pyrolysis oils into marketable fuels and/or chemicals. 3: Develop scalable technologies that enable commercially-viable pyrolysis oil-based products and co-products.
A three-tier developmental approach at the analytical, pilot and field scales will be followed to overcome the scientific, engineering and economic barriers that have challenged production and blending of biomass pyrolysis oils (bio-oil) into hydrocarbon fuels. In doing so three specific thrust areas including catalytic pyrolysis, reactive/co-reactant assisted pyrolysis, and upgrading of pyrolysis oils produced from these processes, already advanced at ARS, will be strengthened. The step-wise approach includes (i) the quest for novel processing strategies that address bio-oil stability issues directly at the farm site; (ii) enabling robust catalytic deoxygenation processes that will allow for effective separation of critical (valuable or detrimental) chemical species present within bio-oils; (iii) production of an intermediate bio-oil product that can support interim markets (e.g. home heating oil) and; (iv) production of hydrocarbons suitable for refining into fuels and for manufacture of specialty chemicals. Additionally, extensive physical and chemical property data will be collected to enable operations from the farm to the refinery. Data will be used to demonstrate compatibility of the liquid hydrocarbon product with petroleum refining unit operations and for economic and environmental assessment of the process life cycle.
Considerable progress was made on all objectives, all of which fall under National Program 306 – Product Quality and Uses, Component 3 - Biorefining. Objective 1: (1) The 60 month milestone to complete demonstration scale experiments on advanced pyrolysis methods was partially completed and reported on in the previous year’s report. Additional demonstration scale experiments for non-catalytic pyrolysis using pyrolysis temperatures (600 °C) and catalytic pyrolysis over HZSM-5 zeolites have been completed during the current reporting period. (2) Additional development work on the role of bio-char in biomass vapor deoxygenation has been completed. At temperatures of 650 °C both switchgrass and rice hull derived bio-char proved capable of catalyzing reactions to deoxygenate bio-oil. Rice hull char was more effective in producing bio-oil with <20 wt% oxygen. (3) Additional work on using bio-char and other carbon based catalysts for non-deoxygenation based bio-oil stabilization has been completed. At 300 °C, use of bio-char in ex situ catalytic pyrolysis provided net hydrogenation of reactive carbon-carbon double bonds. For example, significant decreases in 4-vinylphenol with concurrent increases in 4-ethylphenol were observed with use of bio-char as a catalyst. (4) In research performed in collaboration with the University of Maine funded by a USDA-NIFA Sun Grant, we studied the Ca promoted deoxygenation of switchgrass pyrolysis vapors by co-feeding calcium oxide, hydroxide and formate. The effect is related to catalytic effect of the compounds combined with their ability to change the reactor atmosphere, by releasing water and CO, as well as enhancing CO2 production by conversion to CaCO3. Variables including temperature and Ca-loading rate were studied. Production of bio-oils with about 20 wt% oxygen content and carbon yields greater than 20% were achieved. (5) An on-line distillation column for separation of pyrolysis vapors prior to condensation was designed and assembled for interfacing with our laboratory scale pyrolysis unit. Test experiments with this unit provided a fraction that concentrated levoglucosan to greater than 18 wt%. Furthermore, on-line distillation produced a solid bottoms fraction of 6 wt% of the organic recovery whereas post-production batch distillation converted 45 wt% of the organic bio-oil into intractable solid bottoms. (6) A method was developed to apply diffusion NMR analyses to biomass pyrolysis oils. The method allows for both quantification of various fractions of bio-oils based on MW, while at the same time giving more chemical information about those said fractions via a 1H NMR spectrum. This marks an improvement in the level of characterization of high molecular weight bio-oil components that is possible without fractionation. The common method, gel permeation chromatography (GPC) can only provide average molecular weight estimations without any chemical information. The method was applied to look at differences in various size molecules present in bio-oils produced from switchgrass at different temperatures. Objective 2: (1) We strengthened our processing capabilities for separation of phenolic compounds from advanced pyrolysis bio-oils. Previously, we enhanced separation of higher-value phenol from alkylphenols (from Objective 1), whereby 70% of the phenolic isolate consists of the compound phenol. We have adapted phenolic separations to a continuous flow system. Flowing both bio-oil distillates and sodium hydroxide together results in the parallel and continuous production of isolated phenolics and hydrocarbon streams. The flow system attains the same purity of phenolics from hydrocarbons as in batch experiments. (2) Using the isolated hydrocarbon stream mentioned in item 1, we demonstrated a simple and cost-effective method for desulfurization of bio-oils with elevated levels of sulfur. Distilled fractions of bio-oil hydrocarbons were found to contain sulfur ranging from 400 – 700 ppm. Sulfur characterization revealed the sulfur groups to be labile, so Raney Nickel was used for hydrogenation, which reduced sulfur content to < 15 ppm. (3) Using a rotary tube furnace meant to mimic continuous industrial processes, we conducted experiments on biocoke calcination. Using petroleum coke sourced from collaborators, process conditions were adjusted to allow for continuous production of calcined petcoke before applying it to biocoke. After conducting these baseline tests, we conducted continuous calcination of biocoke/petcoke blends. The product produced contained the benefits of both biocoke and petcoke: it was low in metallic impurities while simultaneously attaining the required crystalline properties. (4) In collaboration with Penn State University, results from design and modeling of continuous bio-oil distillation were recently published. We elucidated optimal conditions for separation of BTEX compounds (benzene, toluene, ethylbenzene, xylenes) from bio-oils. (5) In collaboration with the University of Tennessee Knoxville and Oak Ridge National Laboratory, we successfully demonstrated the cleanup of pyrolysis aqueous-phase waste products. Using microbial electrolysis, oxygenated compounds in the aqueous phase were converted into hydrogen gas, resulting in water with more than 99.9% purity. (6) As part of a new project with stakeholder Rain Carbon Inc., bio-oil distillate residues were tested for suitability as a substitute for coal tar pitch, a binder used in carbon anodes for aluminum production. Current experiments are ongoing, with the goal to improve the softening temperature of the residues as a binder. (7) In conjunction with ARS scientists, bio-oil-based phenolic compounds were used to synthesized bio-based lubricants with anti-bacterial properties. Yields of the target product were improved, and work on testing the anti-bacterial properties is ongoing. Objective 3: The 60-month milestone was fully completed thanks in part to parallel and synergistic efforts with Interagency grant project ‘Distributed On-Farm Bioenergy, Biofuels and Biochemicals Development and Production via Integrated Catalytic Thermolysis’ (FarmBio3). In this objective, a self-sustained 2 metric ton per day (MTPD) scale combustion reduction integrated pyrolysis unit (CRIPS) that enables commercially-viable pyrolysis oil-based products and co-products successfully developed in prior years was deployed and tested at farm site. Data collected was employed to evaluate the techno-economic, environmental, and social sustainability of distributed farm scale pyrolysis on a life cycle basis including exergetic life cycle in collaboration with Drexel University and Swarthmore College both in Pennsylvania. The economics of the distributed production and use of pyrolysis oil for power generation was assessed using a scenario in Brazil processing eucalyptus feedstock. With a commercial scale CRIPS capacity of 2000 MTPD a breakeven point of electricity generated via the USDA technologies was estimated to be competitive at US$0.34 and US$0.62 per kWh for the single and the distributed scenarios respectively, considering a 10-year payback period. The economics of processing a minimum of 200 MTPD of guayule bagasse to produce biofuels in a biorefinery co-located with a guayule latex processing facility using the developed scalable technologies was also evaluated during this reporting period. An estimated minimum fuel selling price (MFSP) of 1.88 $/L for gasoline, 1.84 $/L for jet fuel and 1.91 $/L for diesel fuel derived from bagasse-derived pyrolysis oils, informed the limitations imposed by economies of scale of the current guayule bagasse availability in the USA. The study suggesting that the gasoline selling price could be lowered to 0.96 $/L with a large integrated facility of 2000 MTPD along with useful coproducts such as premium-quality residual guayule biorefinery coke. To expand on the use of feedstocks important to U.S. agriculture and explore the economics of not only fuels but also chemicals we conducted a techno-economic analysis and life cycle assessment for the coproduction of phenol as a value-added renewable chemical, alongside jet-range fuels from horse manure in a distributed system. The net global warming potential (GWP) and cumulative exergy demand (CExD) of jet fuel produced using the developed scalable technologies were assessed as 10 g of CO2 eq and 0.4 MJ per passenger kilometer distance traveled, respectively. These values being considerably lower than the GWP and CExD of petroleum-based aviation fuel. The social sustainability metrics were computed in collaboration with SUNY-College of environmental Science and Forestry by collecting data from a sample of farmers, stratified by size and type, to understand the barriers, challenges and benefits that farmers perceive in relation to the emergent biofuels industry. The multitude of management practices employed by the biomass industry owners such as guayule bagasse (for the tire industry) and landowners (for the forest industry) inform their perceptions of how biomass energy could be incorporated into their portfolio of products. Interviews reveal that these management practices play a critical role in their willingness to utilize residues for biomass energy.
Boateng, A.A., Schaffer, M.A., Mullen, C.A., Goldberg, N.M. 2019. Mobile demonstration unit for fast- and catalytic pyrolysis: the combustion reduction integrated pyrolysis system (CRIPS). Journal of Analytical & Applied Pyrolysis. 137:185-194. https://doi.org/10.1016/j.jaap.2018.11.024.
Elkasabi, Y.M., Mullen, C.A., Boateng, A.A., Brown, A., Timko, M.T. 2019. Flash distillation of bio-oils for simultaneous production of hydrocarbons and green coke. Industrial and Engineering Chemistry Research. 58:1794-1802. https://doi.org/10.1021/acs.iecr.8b04556.
Raymundo, L.M., Mullen, C.A., Strahan, G.D., Boateng, A.A., Trierweller, J.O. 2019. Deoxygenation of biomass pyrolysis vapors via in situ and ex situ thermal and biochar promoted upgrading. Energy and Fuels. 33:2197-2207. https://doi.org/10.1021/acs.energyfuels.8b03281.
Satinover, S.J., Elkasabi, Y.M., Nunez, A., Rodriguez Jr, M., Borole, A.P. 2019. Microbial electrolysis using aqueous fractions derived via tail-gas recycle pyrolysis of willow and guayule. Bioresource Technology. 274:302-312. https://doi.org/10.1016/j.biortech.2018.11.099.
Mullen, C.A., Boateng, A.A. 2019. Mild hydrotreating of bio-oils with varying oxygen content produced via catalytic fast pyrolysis. Fuel. 245:360-367. https://doi.org/10.1016/j.fuel.2019.02.027.
Gunukula, S., Daigneault, A., Boateng, A.A., Mullen, C.A., DeSisto, W.J., Wheeler, M.C. 2019. Influence of upstream, distributed biomass-densifying technologies on the economics of biofuel production. Fuel. 249:326-333. https://doi.org/10.1016/j.fuel.2019.03.079.