RNGPLUS FROM TAILGAS CO2 AND HYDROGEN

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: ACTIVE
• Funding Source: SMALL BUSINESS GRANT
• Reporting Frequency: Annual
• Accession No.: 1028912
• Grant No.: 2022-39539-38588
• Cumulative Award Amt.: $599,424.00
• Proposal No.: 2022-04507
• Project Start Date: Sep 1, 2022
• Project End Date: Aug 31, 2025
• Grant Year: 2022
• Program Code: [8.6]- Rural & Community Development

Recipient Organization
Quantalux, LLC
1005 Lincoln Ave
Ann Arbor,MI 48104

Performing Department
Quantalux LLC

Non Technical Summary
To meet the strong demand for Renewable Natural Gas (RNG) by States and utilities, the team at Quantalux is developing an innovative system to produce more RNG using tail gas produced at existing dairy RNG facilities. By combining tail gas carbon dioxide (CO2) with hydrogen (H2), additional methane can be produced, augmenting overall RNG production A conservative estimate is that the Quantalux RNGplus system will increase overall RNG production by 20%+.Catalytic methanation is well-established for natural gas and coal gas, but RNG tail gas CO2 poses new challenges given unique trace contaminants in biogas. For example, trace amounts of oxygen (present in RNG tail gas) can pose considerable issues for metallic guard beds. In addition, dairy biogas contains hydrogen sulfide (H2S) levels as high as 5000 ppm, with other sulfuric compounds (COS and CS2) present as well. Ultra-high-performance technology is needed to decrease dairy sulfur compounds to a parts-per-billion range. Before delivery, RNGplus must also meet strict gas quality regulations to be injected into existing natural gas pipelines.The Quantalux Phase II project will develop the key gas conditioning modules to support biogas methanation: a guard bed module to remove contaminants and a methanation module to produce RNGplus. Production of RNGplus will result in increased revenue for the facility-owner.

Animal Health Component

25%

Research Effort Categories

Basic

(N/A)

Applied

25%

Developmental

75%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
402	3499	2020	100%

Knowledge Area
402 - Engineering Systems and Equipment;

Subject Of Investigation
3499 - Dairy cattle, general/other;

Field Of Science
2020 - Engineering;

Keywords

biogas

biogenic carbon

carbon dioxide

hydrogen

methanation

tailgas

Goals / Objectives
The primary technical goal is to develop a prototype gas conditioning skid to produce Renewable Natural Gas, aka RNG (99% methane) by combining tail gas carbon dioxide CO2with hydrogen (H2).The Phase II project will seek to meet this goal by answering the following questions:What are the unique trace gases in biogas? Our team will analyze biogas from operational dairy RNG facilities to determine the type and variability of trace gases.How can we eliminate poisoning the methanation catalyst? Because methanation catalysts are highly sensitive to sulfur poisoning, our team will design and test a multi-stage guard bed reactor to remove trace sulfur compoundsHow can we achieve pipeline quality RNG using methanation? The methanation module will be designed to achieve maximum CO2 conversion and minimum H2slip.How can we cost-effectively deliver H2? Since hydrogen production will be a major cost item for any RNGplus system, our team will evaluate PEM-based and emerging electrolysis units to identify best-candidates for full-scale systems.Can we deliver pipeline quality RNGplus using guard beds and methanation modules? Build a prototype methanation unit and testHow can the prototype from Phase II be scaled up to full scale? Our team will use its industrial experience with RNG at dairies to design and detail a full scale RNGplus methanation module.What is the best market to sell RNGplus into? Our team will determine the Carbon Intensity for the RNGplus system based the GREET 3.0 life-cycle models (ANL/US DOE). Based on this CI evaluation, Phase II will develop a Design Pathway package for the Low Carbon Fuel Standard (California Air Resources Board).

Project Methods
The Quantalux team will conduct a number of evaluations before diving into the design and testing portion of the project.The production of biogas from dairy manure is a complex microbiological process involving a consortium of bacteria, archaea and fungi. Our Phase II evaluation is not to determine how different trace gases are produced. Rather, we need to determine the concentration variation of those trace gases that will potentially poison the methanation catalyst. For example, very small concentrations of a gas such as carbonyl sulfafe (COS) would have zero impact on the use of biogas in a generator or a boiler, but may have substantial negative impact on the catalyst material.We will begin the Phase II with an evaluation of the trace gases present in dairy biogas. Biogas will contain methane, carbon dioxide, oxygen, nitrogen, volatile organic compounds (VOCs) and sulfur compounds. Preliminary data from operating dairy digesters shows that the specific chemical makeup of biogas can vary in terms of the type and concentration of sulfur compounds and other trace gases. Our team will gather data from a variety of digesters and then reduce the data to determine gas concentration variability.Next the team will evaluate existing sorber materials to use for gas conditioning. Many commercial products exist for the general problem of sulfur removal, but it is unknown how effective these materials will be for the specific compounds found in dairy biogas. We will work with vendors to evaluate candidate materials, and then conduct a trade study to identify the best option(s).Similarly, many materials are available for methanation catalysts, but are traditionally used for syngas production using other feed gases. Our team will work with vendors to identify candidate materials for the specific gas composition found in dairy biogas. Different materials may be suitable for bulk methanation and trim methanation. Operational conditions for different materials will also be evaluated (temperature, etc)Note that our team will also look at hybrid gas conditioning using biotrickling filters and sorber-based gas conditioning. Because of the catalyst's demanding gas conditioning requirements, a hybrid solution may be needed to remove trace gases to the sub-ppm level.An essential aspect of methanation is the supply of hydrogen, with the goal of using purely green hydrogen. Our team will evaluate the path-to-maturity for various electrolyzer technologies: Alkaline, PEM, SOE and the emerging AEM. Other novel technologies will also be evaluated. Key to this evaluation is to "right-size" the H2 generation technology. For each option, we will sketch out different development paths: scale-up for large scale production, scale to mid-size for targeted production, and even down-scale for something like portable H2 production.This set of evaluations will provide our design team with the necessary technical inputs to select materials and design operational procedures.

Progress 09/01/23 to 08/31/24

Outputs
Target Audience:The goal of this Phase II SBIR is to develop technology to convert biogenic waste carbon dioxide (CO2) from RNG facilities into market-ready Renewable Natural Gas (RNG). Biogenic CO2 is a by-product produced when biogas is upgraded to RNG, and in most cases the CO2 (referred to as "tailgas CO2") is simply vented to the atmosphere. This project will develop technology to combine tailgas CO2 with hydrogen to produce additional RNG that can be injected into a commercial pipeline along with the base RNG produced at the facility. This "bonus" RNG (aka "RNGplus") is nearly identical to natural gas. Markets include the USEPA's Renewable Fuels Standard (RFS) and California's Low Carbon Fuel Standard (LCFS). RNGplus can be considered a carrier for green hydrogen, allowing the energy in hydrogen to be readily transported in existing natural gas pipelines for use in any natural gas appliance or CNG vehicle. Other markets in the carbon transformation market are being evaluated. Changes/Problems:The NIFA SBIR office recently gave Quantalux a No-Cost Extension (NCE) for this project. As discussed with our project sponsor (Dr. K Harris), a change in the tax law in 2022 significantly changed how income from SBIR research projects was taxed. The Tax Cuts and Jobs Act (TCJA) from 2017 made significant changes to how R&D costs were treated. Under Section 174 of the IRS tax code, R&D costs were previously considered an ordinary business expense, which meant that the expenses for subcontracts, equipment, etc. were deductible for tax purposes in the same year as they were incurred ("same-year expensing"). The TCJA provision changed Section 174 and eliminated same-year deductions for R&D expenses. Beginning in 2022, companies were spread out the deductions over 5-year period, which meant that 80% of any contract income would be treated as ordinary income in Year 2 and taxed as such. This applied to large businesses and small SBIR companies alike. Section 174 of the TCJA would have extreme tax consequences for our company (and for other SBIR companies). In fact, we analyzed the implication of Section 174 with our accountant, with the conclusion that the tax burden based on Phase II contract income would leave Quantalux ownership substantially in the red. It is hoped that after the November elections, Section 174 will be changed. The previous work on the project has required minimal draws from the account, omitting equipment purchases or subcontracts that would be treated under Section 174 with deleterious tax consequences. The NCE will allow the project to stay active until these changes are made. Once same-year expensing is returned, the project can move forward in earnest. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?In coming months, our team will focus on trading off the required cost/complexity of sulfur removal with the revenue from given markets. We will also clarify the Carbon Intensity of the tailgas CO2, which drives the value of the gas in the market. Essentially we are taking a market-driven approach to selecting best-use for tailgas CO2.

Impacts
What was accomplished under these goals? Removing trace amounts of sulfur from tailgas CO2 is a key technical challenge in this project. Trace amounts of hydrogen sulfide (H2S) and other sulfur compounds such as Carbonyl Sulfide (COS) and Carbon Disulfide (CS2) will quickly poison the methanation catalyst, reducing its efficiency until it stops functioning. Technology is required to remove virtually all sulfur compounds prior to contact with the catalyst. In the initial stages of the project, Quantalux first evaluated the constituent gases in a typical membrane-type gas separation system at an RNG facility. In other words: How much sulfur is contained in a typical tailgas sample? We obtained data on gas samples from an optional biogas upgrade skid to identify all sulfur compounds and their concentrations. Sampling was provided by Intertek. The upgrade skid was located at a dairy-RNG system located De Saegher Energy in Middleton, Michigan. (Quantalux has agreements with De Saegher Energy to test and evaluate the tailgas from that facility.) Hydrogen sulfide was in the range of 3000 ppm (parts per million) and other sulfur compounds were also quantified. This data gives us the baseline we need to size the sulfur removal system. Our team also evaluated the allowable sulfur levels for a methanation catalyst. We found that catalysts can tolerate no more than 5-10 parts per billion (PPB) of hydrogen sulfide and are also especially sensitive to trace amounts of COS and CS2. A number of sorbent materials are used in the oil/gas industry to remove sulfur from "sour gas" (natural gas with sulfur compounds). The outstanding question is whether these commercial sorbents can remove sulfur to the point where it no longer poses a threat to the longevity of the catalysts and. Options for sorbent based sulfur removal were discussed in previous reports, and our team will work to expand on this question in the coming months. We also evaluated other emerging sulfur removal technologies such as Thermocrinis, a naturally occurring hyper-thermophilic bacterium (1). Thermocrinis grows by oxidization of hydrogen, thiosulfates and elemental sulfur, and may also metabolize CO2 as well. Operational temperature is 82 to 88°C, which could be readily achievable in a commercial sulfur removal system. We corresponded with Professor Eric Boyd from Montana State University regarding his research in thermoacidophiles (both aerobic and autotrophic) that can use sulfides as electron donors. Candidate sulfides include hydrogen sulfide (H2S) as well as COS and CS2. His lab has current projects and students working to grow cultures to accelerate hydrogen sulfide oxidation. Professor Boyd's research is still lab-stage, but both parties have interest since the need to remove sulfur is a very viable commercial outlet for his team's research. Our team also began the process of determining the Carbon Intensity (CI) score of the RNGplus process. The CI score is a critical data point since revenue from the LCFS program is directly proportional to the CI score. (The better the score, the more revenue per MMBtu of RNG.) The RNGplus project would be considered a Design Pathway to RNG production, so would require a modification of the GREET 4.0 R&D model developed by Argonne National Labs. We were connected to Dr. Tuhin Poddar at Argonne, who provided detailed guidance for how to modify the GREET 4.0 model. Based on our discussion with Dr. Poddar, it is clear that creating a CI score using the R&D GREET model is not a trivial job and requires intimate knowledge of carbon balance for each step of the production process. Ideally, we will hire a graduate student at the University of Michigan in the fall with experience in carbon modeling. Initial discussions with the Center for Sustainability indicate that carbon modeling is an important part of their research effort.

Publications

Progress 09/01/22 to 08/31/23

Outputs
Target Audience:The target audience for RNGplus technology consists of two main groups: A) Existing Renewable Natural Gas (RNG) facilities sited at dairy farms, swine facilities, landfills or wastewater treatment plants. Tailgas from these facilities contains biogenic carbon dioxide (CO2), and can be combined with hydrogen to form additional RNG. B) Utilities and companies seeking to acquire renewable fuels to replace natural gas. A strong feature of existing RNG production is the fact that RNG is injected into existing natural gas pipelines for delivery to the customer. Most utilities in the US have set goals to decrease carbon emissions from their pipelines, and RNGplus can be part of achieving that goal. Commerical companies that use natural gas also have reduced-carbon goals and participate in voluntary RNG purchase programs to achieve these goals. Changes/Problems:Technical progress in this Phase II was slowed due to uncertainty in how income from the Phase II SBIR to Quantalux would be taxed. In 2022, a change in the tax law ( Section 174) requires that research expenditures (like SBIR awards) must now apply deductions over five years rather than in a single year. If this provision holds, all SBIR companies will face an extremely large tax liability starting in 2022. The PI (Mr. Tesar) discussed this with Dr Keith Harris at USDA/NIFA (Program Director) and he agreed that this will be a potential issue for Quantalux and other Phase II awardees. It is anticipated that Congress will seek to change this provision, but the timing in unclear. Our team will continue to press our elected representatives to support a change in this tax provision. What opportunities for training and professional development has the project provided?The evaluation and testing of various sorber materials were performed by a team of students at Michigan State University. This activity was part of their Senior Design class in the Fall/Winter semester for the Department of Bioenergy and Agricultural Engineering (BAE). Students learned how to: construct design matrices, gather/evaluate technical data,andwrite up technical results in a professional manner. The students also needed to physically gather gas samples at a local RNG facility (EDL landfill) and test using a gas chromatograph (GC). Data from the GC was reduced to eliminate spurious signals and included in the reporting. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, our team will need to finalize the guard bed material and complete the design of the guard beds and methanation catalysts. A key requirement is that the guard bed completely elimate sulfur species such as H2S, COS and CS2 from tailgas. Catalyst manufacturers have indicated that sulfur removal to a low parts-per-billion range is required. The team will also determine how to best produce hydrogen (H2) for the methantion process. This includes production of the gas plus the identifcation of materials and procedures how to safely handle H2 Tailgas samples will be gathered from the De Saegher Energy RNG facility (north of Lansing MI). This sample produces RNG from dairy manure. Dairy RNG is the largest and has the most potential for profitable RNGplus production. The team will develop a bench scale model to test and evaluate performance using tailgas gathered from an operational RNG facility. A full scale design package will be created based on the results of the bench scale model by scaling lab gas flows to production gas flows. Finally, our team will survey different markets (utilities, voluntary RNG, state programs) to identify eventual customers.

Impacts
What was accomplished under these goals? During this reporting period, our team: 1. Identified candidate materials to eliminate sulfur that may poison methanation catalysts. Selected best candidate 2. Tested candidate materials in the labortary to assess performance using tailgas from landfill RNG facility. 3. Developed a mass flow model of tailgas interacting with sorber materials and mixing with hydrogen. 4. Developed modifications to the H2 Tier 1 model for Carbon Intentity so as to use an approved model for calculations

Publications