Location: Sustainable Biofuels and Co-products Research
2018 Annual Report
Objectives
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.
Approach
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.
Progress Report
Considerable progress was made on all objectives, all of which fall under National Program 213 –Biorefining, Problem Statement 3.1 and 3.2 of Component 3 of the ARS Biorefining Action Plan, Pyrolysis.
Objective 1: (1) Demonstration scale testing of catalytic fast pyrolysis processes (CFP) of switchgrass over zeolite catalyst (HZSM-5 with silica to alumina ratio of 80) was performed using the combustion reduction integrated pyrolysis system (CRIPS). This included production of several liters of stable highly deoxygenated bio-oil (< 10 wt% oxygen) and successful demonstration of continuous catalyst regeneration via the ARS-patented CRIPS dual fluidized bed design. The valuable data from this system is currently being used for both greenhouse gas emissions life cycle analysis and to complete a technoeconomic analysis for production and utilization at location-produced bio-oil from feedstocks such as switchgrass, equine waste and forest residues. Demonstration of non-catalytic pyrolysis has been completed in previous years. (2) Following up a study reported in the previous year’s report we have studied the effects on producing bio-oils with catalysts of various levels of deactivation on downstream refining processes. Bio-oils with varying oxygen content based on catalyst activity during production were subjected to mild hydrotreating conditions to further stabilize them. Results indicated that bio-oils with oxygen contents of ~25 wt% oxygen may be more efficiently stabilized (with respect to yield from biomass, final oxygen and hydrogen contents and storage behavior) than highly deoxygenated bio-oils (<15 wt% oxygen) or minimally deoxygenated bio-oils (>30 wt% oxygen). (3) We have initiated study on use of moderate temperature (300 degree C) post pyrolysis catalytic process to increase production of alkyl phenols for use as renewable petrochemical replacements. (4) Concerning reactive atmosphere pyrolysis, named tail gas reactive pyrolysis (TGRP), an alternative process to CFP invented in-house, we have completed the study on the role of process parameters including gas flow rates, residence times, reaction atmosphere and temperatures at various points in the system in producing stable, deoxygenated marketable bio-oils. Results indicated that system temperatures in combination with the presence of bio-char build up can have significant effects on deoxygenation rates via TGRP. (5) We have begun experimentation to develop a process that combines TGRP with Ca based catalysts to produce a higher yield of deoxygenated pyrolysis oil with potential to have higher concentrations of potential chemical co-products. This research is being conducted in collaboration with University of Maine via funding form USDA-NIFA SunGrant. (6) In the final months of the FarmBio3 project (a NIFA funded BRDI projected completed in 2017) resource and exegetic life cycle analysis was largely completed on various processes using CRIPS data in collaboration with Drexel University and Swarthmore College.
Objective 2: (1) A life cycle assessment and techno-economic analysis of a pyrolysis-based farm-scale refinery was conducted, using horse manure as the target feedstock (collaborators: Drexel University; Swarthmore College). By utilizing experimental data and process simulations, metrics such as global warming potential and minimum fuel selling price were calculated. It was found that the parallel production and isolation of phenol as a coproduct that could significantly offset both the global warming potential and the energy input of biobased jet fuel, significantly lower than their values for petroleum jet fuel. Biobased jet fuel could be economically competitive with petroleum jet fuel, if coproduct market conditions and fuel conversion were optimal. (2) Continuous distillation of bio-oil produced on the larger-scale mentioned under Objective 1 was successfully demonstrated on flash distillation systems. The yield of distillates varied directly with the bio-oil’s oxygen content. Low oxygen-containing oils produced by catalytic and/or TGRP pyrolysis resulted in distillates with yields as high as 75 – 80 wt%. In contrast, the yields of distillates from traditional bio-oils were extremely low (~6%), which indicates that traditional bio-oils would require upgrading (via catalysis and/or hydrotreatment) before distillation to fractionate the bio-oil into various fractions suitable for addition to gasoline, diesel, jet fuel or specialty chemicals. One process design facilitates separation of aqueous streams, while a second process facilitates accumulation of coke residues within the drum, allowing the process to operate analogously to other refinery processes. Simultaneous production of distillates and coke coproduct (mentioned in #1) was demonstrated to be possible. (3) As part of efforts to produce finished coke coproduct on a larger scale matching that of oil produced in Objective 1, a rotary tube furnace that mimics continuous industrial processes was acquired. The tube furnace provides heat treatment that mimics industrial processes, producing ‘calcined coke’. Using petroleum coke sourced from collaborators, process conditions were adjusted to allow for continuous production of calcined petcoke before applying it to biocoke. Tests and characterization of calcined biocoke with the continuous system are currently underway. (4) Separation of higher-value phenol from alkylphenols produced in objective 1 was improved. Using sequential extraction steps, phenol can be selectively removed from other phenolic compounds, particularly from cresol isomers. The modified extraction procedure can isolate fractions where 70% of phenolics consist of the compound phenol. The procedure also serves as preliminary data for adaptation towards a continuous extraction system. (5) In conjunction with collaborators at the University of Tennessee and Pacific Northwest National Laboratory, methods for converting pyrolysis wastewater organics into higher-value products are being investigated. Results show that the aqueous stream can be cleaned while simultaneously producing platform chemicals.
Objective 3: As part of the related interagency FarmBio3 project previously reported, a design of a 2 metric ton per day (MTPD) mobile, biomass pyrolysis demonstration unit was completed, built, and operated to simulate the rural distributed on-farm model. The pyrolysis unit was based on a dual-bed Combustion Reduction Integrated Pyrolysis System (CRIPS) that mimics a fluid catalytic cracking (FCC) process. The overarching goal of this effort was to produce a mobile, skid-mounted pyrolysis system suitable for on-farm or in-forest operation and demonstrate non-catalytic and catalytic pyrolysis processes that will improve the technological readiness level (TRL) for such a design from current 4/5 (bench scale) to 6/7 (close to commercialization) as well as collect on-farm data for life cycle analysis. For this reporting period, CRIPS modifications needed to achieve design scale for the milestone under Objective 3 were completed including installation of a heat exchanger to utilize excess heat from the combustion reactor to mitigate premature condensation and fouling of tars in process lines.
With these changes, at least 1 MTPD out of the design limit was successfully demonstrated for non-catalytic pyrolysis; beyond which operational difficulties such as pressure fluctuations were encountered. Bio-oil collected at the electrostatic precipitator met ASTM D7544 (specification for pyrolysis liquid biofuel). While the CRIPS bio-oil oxygen content was not as low as that obtained by the ARS bench scale TGRP results, it was typically less than the simple, conventional bench-scale N2 pyrolysis system exhibiting a huge improvement with market potential. Catalytic fast pyrolysis tests were also carried out as described under Objective 1, above.
In order to conveniently evaluate small quantities of various potential catalysts, the design of a small scale process development unit (PDU, named K.2) was previously initiated. The design and fabrication have been completed under this reporting period and the system has been commissioned and fully tested. A larger system at the 10 kg/h scale (named K2) has also been designed and fabricated but not fully tested. The combined effort completes the integration of new and optimum pyrolysis biorefining unit operations systems under the research project. This has facilitated the understanding and allowed data collection needed to begin life cycle assessment of distributed, integrated farm systems including assessment of social sustainability metrics to guide entire project.
Using the CRIPS demonstration data, a process model of a 2000 metric ton per day MTPD eucalyptus Tail Gas Reactive Pyrolysis (TGRP) and electricity generation plant was developed and simulated in Pro/II software for the purpose of evaluating its techno-economic viability in Brazil. Two scenarios were compared based on operational conditions in the country: a single biomass to bio-oil production facility and a distributed/satellite processing that consists of several small Tail Gas Reactive Pyrolysis (TGRP) production facilities with aggregate capacity similar to the single one, both feeding into one centralized electricity generation plant. The selling price at the breakeven point of the electricity generated via TGRP was estimated to be $0.21 and $0.38 per kWh for the single and the distributed scenarios respectively, considering a 10-year payback period. The single capacity pyrolysis and electricity generation facility was found to have better economic benefits over the distributed plants of small sizes but this was due to the current conditions in Brazil as sensitivity analysis show that the economics for the distributed processing could elsewhere.
Accomplishments
1. Construction and operation of a mobile demonstration scale biomass pyrolysis system. A major drawback in processing biomass into biofuels is the high cost of transporting the low density biomass feedstocks such as switchgrass, corn stover, and wood chips. Various economic models favor distributed processing where the fuel intermediate is produced at the biomass source and the intermediate is transported to a centralized processing for upgrading. Pyrolysis of biomass to produce bio-oil as an intermediate process would be amenable to deploy at the farm or forest site. A mobile pyrolysis system, based on an ARS-patented design, the Combustion-Reduction Integrated Pyrolysis System (CRIPS), was constructed at Wyndmoor, Pennsylvania, to address this knowledge gap. CRIPS was successfully demonstrated for fast pyrolysis at feed rates near 1 metric ton of biomass per day; beyond which operational difficulties such as pressure fluctuations were encountered. Bio-oil collected in fractions met ASTM D7544 (specification for pyrolysis liquid biofuel).
Review Publications
Pighinelli, A.L., Schaffer, M.A., Boateng, A.A. 2018. Utilization of eucalyptus for bioelectricity production in brazil via fast pyrolysis: a techno-economic analysis. Renewable Energy. 119:590-597.
Mullen, C.A., Dorado, C., Boateng, A.A. 2018. Catalytic co-pyrolysis of switchgrass and polyethylene over HZSM-5: catalyst deactivation and coke formation. Journal of Analytical and Applied Pyrolysis. 129:195-203.
Sabaini, P.S., Boateng, A.A., Schaffer, M.A., Mullen, C.A., Elkasabi, Y.M., McMahan, C.M., Macken, N. 2018. Techno-economic analysis of guayule (parthenium argentatum) pyrolysis biorefining: production of biofuels from guayule bagasse via tail-gas reactive pyrolysis. Industrial Crops and Products. 112:82-89.
Tarves, P.C., Serapiglia, M., Mullen, C.A., Boateng, A.A., Volk, T.A. 2017. Effects of hot water extraction pretreatment on pyrolysis of shrub willow. Biomass and Bioenergy. 107:299-304.
Choi, Y., Elkasabi, Y.M., Tarves, P.C., Mullen, C.A., Boateng, A.A. 2018. Co-cracking of bio-oil distillate bottoms with vacuum gas oil for enhanced production of light compounds. Journal of Analytical and Applied Pyrolysis. 132:65-71.
Mullen, C.A., Tarves, P.C., Raymundo, L.M., Schultz, E.L., Boateng, A.A., Trierweller, J.O. 2018. Fluidized bed catalytic pyrolysis of eucalyptus over hzsm-5: effect of acid density and gallium modification on catalyst deactivation. Energy and Fuels. 32:1771-1778.
Sorunmu, Y., Billen, P., Elkasabi, Y.M., Mullen, C.A., Macken, N., Boateng, A.A., Spatari, S. 2017. Fuels and chemicals from equine-waste-derived tail gas reactive pyrolysis oil: technoeconomic analysis, environmental and exergetic life cycle assessment. ACS Sustainable Chemistry & Engineering. 5:8804-8814.
Elkasabi, Y.M., Liu, Q., Choi, Y., Strahan, G.D., Boateng, A.A., Regalbuto, J.R. 2017. Bio-oil hydrodeoxygenation catalysts produced using strong electrostatic adsorption. Fuel. 207:510-521.
Clark, S.C., Ryals, R.A., Miller, D., Mullen, C.A., Pan, D., Zondlo, M.A., Boateng, A.A., Hastings, M.G. 2017. Effluent gas flux characterization during pyrolysis of chicken manure. ACS Sustainable Chemistry & Engineering. 5:7568-7575.
