DESULFURIZATION OF BIODIESEL PRODUCED FROM LOW-QUALITY FEEDSTOCKS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: SMALL BUSINESS GRANT
• Reporting Frequency: Annual
• Accession No.: 1016066
• Grant No.: 2018-33610-28504
• Cumulative Award Amt.: $100,000.00
• Proposal No.: 2018-00478
• Project Start Date: Aug 1, 2018
• Project End Date: Mar 31, 2020
• Grant Year: 2018
• Program Code: [8.8]- Biofuels and Biobased Products

Recipient Organization
ENVIRONMENTAL FUEL RESEARCH, LLC
102 QUAINT RD
MEDIA,PA 19063

Performing Department
(N/A)

Non Technical Summary
As biodiesel production in the USA increases, bottlenecks in feedstock appear likely. Several companies have formed to investigate novel forms of conversion of lower cost feedstocks but all have found the same substantial hurdle, meeting the 15PPM sulfur specification of ASTM D6751. Numerous experiments have shown that low-cost fats, oils and greases may contain 300 - 500PPM sulfur and that no single technology with acceptable operating requirements is available for desulfurization of these feedstocks. After exhaustive experimentation we have discovered two "primary purification" technologies which remove unsaponifiables, color bodies and reduce sulfur to approximately 30 - 50PPM. To further reduce sulfur to below15PPM, we've identified the need for a polishing step or "secondary purification". Six effective adsorbents, each showing sulfur reductions of at least 30%, as well as an effective catalyzed method of removal have been identified as possible candidates for a production system.The goal of this SBIR is simple; to conduct a thorough comparison of two primary purification technologies, to compare six proven adsorbents and to optimize results with catalyzed sulfur reduction. The data will be assembled into a technoeconomic analysis which shows the estimated cost of operating the two stage desulfurization unit. Such a desulfurization unit will allow biodiesel producers to utilize a wider variety of feedstocks and possibly allow producers of these feedstocks to increase their values. It would increase the availability of US produced feedstock and aid in the ability of producers to meet the mandates in the 2007 Energy Independence and Security Act.

Animal Health Component

45%

Research Effort Categories

Basic

10%

Applied

45%

Developmental

45%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
403	5370	2000	100%

Knowledge Area
403 - Waste Disposal, Recycling, and Reuse;

Subject Of Investigation
5370 - Sewage and waste disposal facilities and systems;

Field Of Science
2000 - Chemistry;

Keywords

animal fat

biodiesel

distillers corn oil

fuel

grease

poultry fat

purification

renewable

Goals / Objectives
Most of the remaining low-cost biodiesel feedstocks have suppressed prices due to their sulfur content being above the 15 PPM requirement for on-road Diesel fuel. These feedstocks include any Fats, Oils or Greases (FOG's) which have been allowed to sit for an extended period in the presence of water. It is believed that proteins are broken down by biological activity and that their sulfur species then bind to the fatty acid portion of the FOG's (Hughes 2017). Degraded FOG's vary widely in composition and frequently contain 50 - 500 PPM sulfur. The overall objective of this project is to systematically evaluate a combination of process steps to develop an economically-viable desulfurization technology that would be applicable for FAME produced from FOG feedstocks. Four specific technical objectives are listed below.Technical Objective 1: Confirm Impurities in FAME from GTW and other waste FOG: The classes of impurities in FAME from waste FOG are variable and not well understood. Classes of impurities include those compounds which either interfere with conversion of the feedstock into fuel or those which could prevent the fuel from meeting ASTM specifications. These impurities include water, soaps, unsaponifiables, solids and sulfur-containing compounds. Our joint research at the USDA labs suggests that FOG's contain sulfur species including epithiols, thiophenes, sulfides, disulfides, and crosslinking sulfides and disulfides (Hughes 2017). We will obtain FOG from poultry fat, tallow, distillers corn oil and other sources that have elevated sulfur content. Techniques used to evaluate sulfur species in GTW-FAME will be implemented with FAME from other FOG sources to confirm similarities and differences in sulfur contaminants that may affect the choice of desulfurization technology.Technical Objective 2: Evaluation of Primary Purification Technologies: Crude biodiesel is a low viscosity liquid which is dark in color and contains impurities that vary based on the feedstock. These impurities include fine particulates, salts, oxidized organic molecules, color bodies, and assorted forms of sulfur. Numerous previous experiments have shown that vacuum distillation is effective at reducing sulfur levels of GTW-FOG from 300 - 500 PPM down to 15 - 50 PPM. This has been demonstrated many times by EFR using different Wiped Film Evaporators (WFE), Rotary Evaporation, Spinning Band and basic "pot" distillation. Distillation is effective at enhancing the color and clarity of the fuel but does not reliably reduce sulfur content to meet fuel specifications; hence distillation is only effective as a "primary" purification method.Recent experiments using nano-filtration with GTW-FAME have shown similar results to distillation; reduction in sulfur to 25 - 100ppm and significant lightening in color and improved clarity. To our knowledge, no biodiesel producer is yet using nano-filtration, there are still many questions regarding both its economics as well as its suitability for biodiesel processing. But considering the intense energy requirements of distillation, nano-filtration is an attractive alternative. Both distillation and nano-filtration are considered "primary" purification technologies that remove a large amount of the contaminants but will not always produce a biofuel that meets specifications. The second technical objective of this project is to optimize distillation and nano-filtration methods for FAME produced from several FOG sources.Technical Objective 3: Comparison of Polishing Agents/Adsorbents: Primary purification reduces the sulfur content of biodiesel from 20-30 times the permissible sulfur content to approximately 1-4 times the permissible levels. The third technical objective of this project is to evaluate a variety of polishing steps for robust and economic reduction of sulfur content to meet the 15 PPM limit. In our prior work, tests of numerous and varied adsorbents have demonstrated six specific adsorbents that can achieve reduction of sulfur to by 30% or greater. Previous experiments have also shown that use of non-polar solvents can enhance the efficiency of adsorbents. This is believed to cause an increase in the difference of the polarity between the liquid FAME solution and the sulfur compounds, providing a stronger driving force for adsorption. Similarly, the affinity of sulfur compounds for the adsorbents can be enhanced by chemical conversion reactions.Technical Objective 4: Techno-Economic Analysis: To evaluate the commercialization potential of the primary purification and polishing technologies from Technical Objectives 2 and 3, techno-economic analysis (TEA) will be used to estimate the cost-per-gallon of finished fuel for each of the technologies. TEA will be applied to a plants with capacities of 100,000, one million, and ten million gallons per year to evaluate scalability of the technologies. Distillation has a high energy intensity but is a well-established technology. Adsorption has been shown to be effective, but can reduce yields and generate a significant amount of waste; the ability to regenerate and reuse adsorbents may be critical to economic effectiveness but will entail additional processing costs. For all of the process options being considered, there are economic tradeoffs that need to be evaluated with respect to uncertainty/variability in the performance of the desulfurization technologies.

Project Methods
Work Plan for Technical Objective 1: Confirm Classes of ImpuritiesTask 1.1: Four separate feedstocks will be obtained from collaborators or industrial contacts: (1) Brown Grease, (2) Poultry Grease, (3) Distillers Corn Oil and (4) Rendered Animal Fat. To establish a baseline for evaluation of primary purification, at least three samples of each type of feedstock will be collected for analysis.Task 1.2: At the one liter scale, each feedstock sample will be converted to crude FAME by a similar procedure and purified by two passes through a wiped film evaporator (WFE).Task 1.3: For each of the purified FAME samples, polar fractions will be isolated by a two-step solid phase extraction (SPE) procedure (Hughes 2017). The same standardized procedures for WFE and SPE will be used to produce reliable comparisons between FAME produced from the different feedstocks.Task 1.4: Finally the isolated polar fractions will be analyzed by GC-PFPD and GC-MS at the USDA to determine sulfur-containing contaminants present. For the variety of samples collected in Tasks 1.1 through 1.4, the following tests will be performed to evaluate changes in impurities during conversion and purification:Feedstock grease: Melting point, Total Acid Number, Soap Content, unsaponifiables content, insolubles content, sulfur contentCrude FAME and Washed Crude FAME: Total Acid Number, sulfur contentPurified FAME: Total Acid Number, sulfur content, free and total glycerin (by GC)Polar FAME fractions: sulfur content, GC-PFPD peak areas, GC-MS analysisOther WFE fractions and SPE elutions: sulfur contentIn addition, the masses of all samples will be recorded to enable determination of the mass balances on FAME and impurities throughout the process, which is important for evaluating yields and separation efficiencies.Work Plan for Technical Objective 2: Evaluation of Primary Purification Technologies Primary purification separates the Fatty Acid Methyl Esters (FAME) from the unsaponifiables, glycerides, salts, polymers, and the majority of sulfur containing compounds. Two primary purification technologies have been identified as most effective: distillation and nano-filtration; both reduce sulfur from approximately 300 - 500 PPM to approximately 25 - 100 PPM. For this technical objective, large batches of crude FAME (10 - 50 gallons) will be produced on EFR's pilot process so that a large number of experiments can be performed using crude FAME with the same starting composition. The optimization experimental strategy presented here will be applied to crude FAME from a single feedstock first. Then the most promising primary purification conditions will be applied to crude FAME from other feedstocks to determine if their performance is comparable.Task 2.1: A variety of commercially-available Organic Solvent Nanofiltration (OSN) membranes will be evaluated in a small test cell. The operating conditions for OSN (temperature, pressure, solvent dilutions) will be varied with the goal of achieving reduction in sulfur content to below 50 PPM and obtaining a clear FAME permeate.Task 2.2: OSN membranes that are able to achieve suitable reductions in sulfur content will be evaluated to determine their functional lifetime - i.e. the amount of FAME that can be purified for a given membrane area before the membrane needs to be regenerated or replaced.Task 2.3: Systematic optimization of WFE performance will be achieved by varying the hot-side and cold-side temperatures for both passes of two-pass WFE. Conditions that achieve sulfur content below 50 PPM will be determined along with the trade-off between sulfur content reduction and yield of purified FAME.Task 2.4: The types of sulfur contaminants that are removed by OSN and WFE will be compared by fractionating the purified FAME for GC-PFPD analysis as explained in Tasks 1.3 and 1.4.Despite a similar final sulfur contents, the mechanisms of distillation and nano-filtration differ enough that it is plausible that they remove different species. Distillation, for example, removes both lighter and heavier sulfur species. Depending on chemical characteristics of the membrane, nano-filtration may be more effective at removing sulfur species with similar boiling points to biodiesel. The outcome from these tasks is identification of technically feasible primary purification processes and operating conditions. Data from these tasks will be used in Technical Objective 4 to evaluate the relative economics of primary purification and their commercial potential. FAME produced from the most promising primary purification methods will be used as the starting point for optimization of the polishing methods.Work Plan for Technical Objective 3: Comparison of Polishing Agents/AdsorbentsAfter distillation, the samples will likely be relatively free of unsaponifiables, will be light in color and have sulfur content between 25 - 50 PPM. The work in Technical Objective 3 will seek maximizing desulfurization achieved by adsorbents; in prior work, six adsorbents have been observed to reduce sulfur content by more than 30%.Task 3.1: Optimization of the process conditions will be carried out for a set of promising adsorbents by varying adsorbent loading, varying time and temperature during adsorption, and the addition of solvents enhance the effectiveness of adsorbents.Task 3.2: Regeneration of the most promising adsorbents will be evaluated by washing and heat treatment of adsorbents.Task 3.3: Hydrogenation of FAME using Raney Nickel will be evaluated as an alternative to adsorption.Task 3.4: Several novel reaction technologies will be explored as options to enhance adsorption or as a replacement to adsorption.Task 3.5: Samples from a subset of both highly-effective and moderately-effective polishing methods will be compared by fractionating the purified FAME for GC-PFPD analysis as explained in Tasks 1.3 and 1.4The overall goal of Technical Objectives 2 and 3 is to identify a set of scenarios (including different combinations of primary purification and polishing) that all achieve robust reduction of sulfur content to well below 15 PPM. The commercial potential of these scenarios will be evaluated in Technical Objective 4.Work Plan for Technical Objective 4: Techno-Economic AnalysisIn prior work, EFR has developed a TEA model of a GTW-biodiesel process that included creation of detailed process flow diagrams (PFDs), calculation of mass and energy balances for each of the process units in the PFDs, estimation of the equipment sizes, estimation of utility consumption, estimation of raw material use, estimation of labor requirements, and scaling the individual costs to an overall plant process economics.Task 4.1: The prior TEA model will be used as a basis for developing TEA models of promising primary purification and polishing process scenarios.Task 4.2: The main outcome of the TEA model will be cost estimates (for example in $/gallon of biodiesel produced) of the purification portion of the process.Task 4.3: TEA estimates will be conducted for a variety of scenarios that enables understanding tradeoffs of different process options.

Progress 08/01/18 to 03/31/20

Outputs
Target Audience:The primary audience reached by EFR has been biodiesel producers, the secondary audience has been those who operated businesses peripheral to biodiesel production. Peripheral businesses include investors and adsorbent manufacturers. US biodiesel producers operate plants with an average annual capacity of 26.95MM gallons and median capacity of 15MM gallons (Biodiesel Magazine, U.S. Biodiesel Plants). Feedstocks consists primarily of used cooking oil, soybean oil and distillers corn oil. Biodiesel producers tend not to use brown grease / waste greases due to the contaminants they contain which prevents them from meeting required specifications, this is despite an active opportunity and desire to process poultry greases. The primary concern is the ASTM D6751 sulfur specification of <15ppm. These potential feed stocks are significantly less expensive than those currently being used and robust desulfurization technology would enable their use. The technology proposed by Environmental Fuel Research (EFR) purifies biodiesel made from low-cost greases such as brown greases from waste tallow and poultry processing (sometimes called "high FFA grease"). The main focus is the removal of sulfur, which may be as high as 500ppm and must be reduced to 15ppm or lower (as per regulatory requirements). Excluding current low oil prices (as of May 2020) the typical, recent price for yellow grease is $1.80 per gallon and 'virgin' soybean oil is $2.10. Brown greases, for the same period, sell for $0.68 per gallon. Biodiesel producers would like to use the lower-cost greases but no robust technology currently exists for them to reduce sulfur to required levels; the most common method for converting brown grease into biodiesel is by dilution. During Phase I EFR personnel attended two conferences hosted by the National Biodiesel Board (NBB). Networking opportunities were used to promote our desulfurization R&D and learn more about the prospective customer's needs, wants and perceptions. EFR was an exhibitor at NBB's most recent annual conference where we educated the industry as to EFR's research efforts, shared the results of our research and discussed possible commercial applications. Several of the biodiesel producers we discussed adsorptive desulfurization with also expressed an interest for use "just in case". This was a theme that we were presented with several times, often accompanied with stories of unnamed producers attempting to sell (at a tremendous discount) a batch they had produced which did not meet ASTM D6751 sulfur specification. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Mentoring was provided to coop, graduate and undergraduate level part-time assistants. Each were taught about the processing steps in producing biodiesel and given opportunities to perform experiments within their abilities and areas of interest. Experiments were carried out under supervision and results were discussed at regular meetings. How have the results been disseminated to communities of interest?Throughout Phase I, the scope of our research was communicated through collaborators, via conferences and through an interview in the April edition of Biodiesel Magazine. The results of this research include desulfurization strategies that are in the process of being patented, this currently limits the full extent of our research from being publicly disclosed. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Technical Objective 1: Confirm Impurities in FAME from GTW and other waste FOG: Brown greases from tallow, poultry and waste water were obtained through our collaborators and Distillers Corn Oil (DCO) was purchased via a chemical supplier. Tallow from Grease Trap Waste (GTW) was acquired from a large manufacturer of meatballs. The process of extracting the lipids from their GTW was nearly identical to the aggregated GTW received from the Delaware County Water Authority (DELCORA). With heat and the addition of sufficient acid to eliminate any soaps, four layers tend to form; lipids, "light solids", water and "heavy solids" (from top to bottom). Whereas the trap grease samples contained large and fine particulates, poultry brown grease contained only fine particles, which made it more likely to cause stable emulsions in water washing. While particulate in other greases was removed with a 5 micron filter, a portion of poultry grease particulate would remain until filtered to <1 micron. Tallow trap grease and aggregated trap grease both contained two separate layers of solids; heavy solids of approximately 1mm - 2mm in diameter which created the bottom layer and fine solids, which caused an interface between the water and lipid phases. Reducing the PH of the mixture to 5 would reduce the interface layer and increase the yield of lipids. The total particulate mass across samples would average to 11%. During this project, our on-going collaboration with the USDA Eastern Regional Research Center has continued to identify sulfur-containing contaminants in biodiesel and lipid feedstocks. Identification of the difficult-to-remove sulfur contaminants that remain in FAME or FFA after primary purification is difficult because the concentration of individual species is so low. The USDA researchers subjected samples of FAME and FFA after primary purification to a series of additional fractionation techniques to amplify the concentration of the sulfur-containing contaminants. The additional fractionation techniques include solid phase extraction (SPE), distillation (with wiped-film evaporator and spinning band), urea complexation, and esterification. During this project, the USDA researchers were able to confirm that previously-identified sulfur species are present in the samples produced during this project, but no additional sulfur-containing contaminants were identified. Technical Objective 2: Evaluation of Primary Purification Technologies: The goal of this objective is to compare novel purification methods to distillation and catalyzed desulfurization. Much of this data has been included only in the comprehensive final technical report. Distillation had been previously tested using rotary evaporation, wipe film evaporation and spinning band. Results showed Vigruex distillation to produce comparable results, which was used throughout this research project. Distillation was performed at 150 - 190°C and pressure of 0.5 - 1.5mbar. Yield of distillate was 67% of the starting crude FAME (aggregated trap grease FAME) with starting sulfur content of 185 PPM and ending sulfur of 37 PPM. Hydrodesulfurization (HDS) as used by the petrochemical industry for the removal of organosulfur compounds is the most comparable and mature technology. Research showed that Nickel Molybdenum (NiMo) and Cobalt Molybdenum (CoMo) were the catalysts used by oil refineries for HDS of fuel oils. Philadelphia Energy Solutions (PES) was contacted and was generous enough to supply EFR with samples of both catalysts. A high-pressure stirred reactor was connected to a hydrogen supply with a maximum pressure of 1,000psi. (PES) also made available a HDS specialist who initially recommended 500psi for three hours at 150°C. It was also confirmed that the effectiveness of the HDS would be indicated by reduction of hydrogen pressure in the reactor. This was not observed and sulfur content was not reduced. Several more rounds of HDS with both CoMo and NiMo catalysts were attempted with pressures up to 1,000psi but hydrogen consumption nor sulfur content would change significantly. Further communications with the PES engineer indicated that pressures of 4,000 - 8,000psi are commonly required. These operating conditions were deemed to be impractical for biodiesel production. Sulfur content of the crude FAME was 226 PPM. A control sample using no catalyst and 5.86 MPa hydrogen resulted in 175 PPM sulfur. The lowest sulfur levels achieved with HDS catalysts were 123 PPM using CoMo catalyst and 108 PPM using NiMo catalyst. Technical Objective 3: Comparison of Polishing Agents/Adsorbents: The goal of this objective is to compare novel and traditional adsorbents previously identified. Much of this data has been included only in the comprehensive final technical report. The optimization of these adsorbents is the subject of an in-process patent application. Six promising adsorbents were tested for their ability to remove sulfur. Two were identified as being the most effective on all the FAME's tested. These two adsorbents were tested as part of a polarity-based system. Preliminary optimization was performed by exploring variations in the physical characteristics of the adsorbent. Variations of the same material caused as much as a 92% change in desulfurization abilities. Methods to regenerate the adsorbents were also explored; both chemical and thermal methods were researched and effective methods identified. Technical Objective 4: Techno-Economic Analysis: In our prior work, we used standard Chemical Engineering methods of process design and cost analysis, to generate a Process Flow Diagram (PFD) that reflect the major processing steps in purifying crude biodiesel to purified biodiesel that meets the ASTM D6751 specifications. Our prior research has shown that the most difficult specification to achieve reliably is the 15 PPM sulfur specification. The purification process and TEA model was constructed to have flexibility for several alternative purification scenarios using combinations of primary purification and adsorption. Specifically, a variable number of subsequent stages of each of these purification steps was allowed to account for differences in the difficulty of removing impurities from biodiesel produced from different sources of brown grease. In this TEA, the base case scenario is a process that produces 5.3 million gallons per year of approximately 99.9% purity FAME from a feedstock of 7.5 million gallons of crude FAME using one primary purification step and one adsorption step for the purification process. In the base case, the adsorbent is not regenerated. For the base case process that produces 5.3 million gallons of purified FAME per year, the cost of manufacturing (for purification) is $3,764,198/year or $0.787/gal. The largest contributors to manufacturing cost are raw materials (40%) and labor (45%). The TEA model assumes three operators on-site continuously through all shifts to operate the process; the operating labor could potentially be reduced through process automation, process optimization, or by scale-up to a larger process. Further optimization could decrease the cost of adsorbent (and adsorbent disposal) and primary purification systems. Below are two (non-optimized) models for manufacturing costs relating to primary purification and adsorption stages. The model assumes five regeneration stages of adsorbent before disposal. Cost 10MM gal/year 20MM gal/year Fixed Capital Investment $0.041 $0.032 Operation Labor $0.358 $0.180 Raw Materials $0.189 $0.171 Utilities $0.054 $0.054 Waste Treatment $0.012 $0.012 SUM $0.654 $0.449

Publications

Progress 08/01/18 to 07/31/19

Outputs
Target Audience:Biodiesel producers are our primary target audience. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?At present, we have contacted a patent attorney and until our intelectual property is sufficiently protected we have provided only a brief overview to potentially interested customers. Publications will not be considered until adequate protections are in place. What do you plan to do during the next reporting period to accomplish the goals?Over the next quarter we will continue exploring primary purification for desulfurization and optimizing conditions. Additional adsorbents will be tested on our four selected feedstocks and their effectiveness evaluated. Regeneration of adsorbents will continue to be critical to our research and will be a focal point over the next quarter.

Impacts
What was accomplished under these goals? Technical Objective 1: Confirm Impurities in Different Feedstocks FOG (Fats, Oils, Greases), brown grease from tallow and poultry grease were obtained through our collaborators and distillers corn oil was purchased via a chemical supplier. Sourcing these feedstocks would often require navigating through large companies who are not accustomed to preparing small quantities for research. This was the case with tallow and poultry greases, one was not received until late November and the other was received while writing this report. Tallow from Grease Trap Waste (GTW) was acquired from a large manufacturer of meatballs. The process of extracting the lipids from their GTW was nearly identical to the aggregated GTW received from a regional waste water treatment facility. With heat and the addition of sufficient acid to eliminate any soaps, four layers tend to form; lipids, "light solids", water and "heavy solids". The light solids typically form a partial interface with the lipids and are the most problematic because they are not easily separated by filtration. The primary differences measured between the lipid feedstocks is color bodies, sulfur content and TAN. Poultry brown grease also contained fine particles, which seemed to cause it more likely to emulsify during washes. These emulsifications were stable and tended to be some of the more difficult ones to separate. Technical Objective 2: Primary purification Novel methods of purification have been tested on three of our four selected "low value" feedstocks and have proven effective at removal of most color bodies and significantly reducing sulfur content. Crude FAME from brown grease is typically dark in color (brown or black) and contains 200 - 500ppm sulfur. The systems explored reliably yield an output stream of yellow esters with sulfur content of 30 - 60ppm. This technology is being evaluated to find if it's a suitable replacement for distillation. Technical Objective 3: Comparison of Polishing: Numerous adsorbent have been tested under various conditions. One particular combination was found to be effective at reducing sulfur to less than 10ppm. This combination can be used at room temperature and at atmospheric pressure with residence time of one hour. Dose of adsorbent is dependent on the quantity of sulfur present in the material to be treated as well as the desired level of desulfurization. This area of research has been very promising and we are presently in the process of preparing to patent these findings. Technical Objective 4: Techno-Economic Analysis: Techno-economic models based on current experimental data includes costs for equipment, consumables, power and disposal of used adsorbent. Based on this information we estimate primary and secondary purification (combined) to cost $0.53 per gallon of biodiesel (plus licensing fees), with the finished product having a light yellow color and sulfur content below 15ppm. Optimization is likely to reduce cost of materials. The spread between yellow grease and brown grease is approximately $1.20 per gallon.

Publications