Grantee Research Project Results

2023 Progress Report: Three- Step Scrubber for Ammonia Removal

EPA Grant Number: SV839356
Title: Three- Step Scrubber for Ammonia Removal
Investigators: Rupiper, Amanda , Barsanti, Kelley , Limon, Gwyndolin , Flores, Alexis , Sanchez-Diaz, Nancy , Iqbal, Usman , Bang, Eric , Orozco, Omar , Chan, Dylon , Martinez, Dianna-Kristina
Institution: University of California - Riverside
EPA Project Officer: Page, Angela
Phase: II
Project Period: March 1, 2018 through February 29, 2020 (Extended to February 28, 2025)
Project Period Covered by this Report: March 1, 2023 through February 29,2024
Project Amount: $40,240
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2017) Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources , Sustainable and Healthy Communities

Objective:

Eight undergraduate students have been at work on this project over the past year resulting in noted progress. Three undergraduate students focused on running lab experiments to create biochar in-house and assess the ammonia absorbency in preparation for a new round of five senior design students who started in January 2023. These three students worked a combined total of 300 hours on the project during the summer and into fall 2023. The outcomes of their work include a SOP for creating biochar from rice husks as well as limited data on the absorbency of various biochar production methods. This data, along with a comprehensive literature review, is being used by a group of 5 students participating in a senior design class to design a full-scale version the 3-phase air scrubber with biochar adsorption column. This group of 5 senior undergraduate students will work on this project from 01/24 through 06/24 to complete a full-scale design and life cycle assessment of the technology compared to conventional air scrubber designs.

Progress Summary:

Biochar Production

We produced 15 batches of rice straw-based biochar under two temperature conditions, 400C and 500C for 60 minutes. The mass yield of the produced biochar under each condition is summarized in Figure 1 and Table 1. The higher temperature conditions resulted in a smaller mass yield of 38.3% on average compared to 45.6% with the lower 400C temperature. 

Pyrolysis Temperature (C)	400	400	400	500	500	500
Sample #	initial	Final (g)	%Yield	initial	Final (g)	%Yield
1	10.001	6.43	64.29	30.806	11.781	38.24
2	30.004	13.304	44.34	30.718	11.541	37.57
3	31.2	13.099	41.98	30.398	11.67	38.39
4	30.18	12.506	41.44	30.72	11.712	38.13
5	30.182	12.614	41.79	30.519	11.861	38.86
6	13.308	5.69	42.76	30.307	11.479	37.88
7	30.116	12.795	42.49	30.474	11.627	38.15
8				30.74	12.01	39.07

Table 1. Biochar % yields under 60 minutes pyrolysis conditions at two temperatures: 400C and 500C.

Figure 1. % yield distributions of biochar produced under 400C and 500C temperatures. Average % yields: 45.6% (400C) and 38.3% (500C).

 

Testing

Our ammonia testing method using HACH reagents was requiring high levels of dilution and resulting in data that was subject to sizable error. For this reason, we switched to using an alternative method for quantifying ammonia, an Ion-Specific Electrode (ISE). Students spent a month figuring out how to use the ISE and how to appropriately calibrate the instrument each week for accurate ammonia estimation. This slowed progress on experimental data collection but will result in more robust data moving forward.

ISE Calibration Curves: Using our new ammonia measurement method, students calibrated the ISE probe using high and low concentrations of ammonia-N to create slopes that could be used to translate voltage readings from the probe into ammonia-N concentrations. The results of this calibration are shown in Figure 1.

Figure 2. Ammonia Ion-specific electrode curves generated from calibration activities.

Ammonia Absorbency Data: To assess the overall capacity for our newly produced biochar to absorb ammonia we conducted a series of jar tests allowing known concentrations of ammonia to sit in a beaker with measured masses of biochar. After a set duration, the biochar was removed, and we measured the ammonia concentration in the beaker. We anticipated there would be a decrease in ammonia concentration indicating that ammonia sorbed to the biochar, but that is not what we found. This result was surprising, and we do not yet have an explanation for what we observed. We plan to spend more time figuring out what is going on – if the problem is with how the biochar is being created or if we are continuing to have ammonia measurement issues. Table 2 summarizes the results of the jar test.

Table 2. Ammonium biochar adsorption jar test results.

Jar Test	Initial N Con. (mg/L)	Volume (L)	Biochar Mass (g)	Time (Min)	pH	Ending ISE Measurement (mV)	Con. Final (mg/L)	% Change
1	10	0.5	1	60	5	-34.9	53.44	434%
2	10	0.5	1	60	5	-43	68.36	584%
3	10	0.5	1	60	6	-60.2	100.04	900%
4	10	0.5	1	60	6	-47.1	75.91	659%
5	100	0.5	1	60	5	-105.7	183.83	84%
6	100	0.5	1	60	5	-104.1	180.88	81%
7	100	0.5	1	60	6	-104.2	181.07	81%
8	100	0.5	1	60	6	-103.9	180.52	81%

To confirm the removal of ammonia from solution using our produced biochar we reverted to a simpler pH-based method while calibrating our ammonia probe. While we are calibrating and refining our ammonia analysis methodology, we performed an indicator method using pH as a measure of ammonia concentration. Using biochar from two batches produced at 500C for 60 minutes we set up a jar test with two sets of controls: two beakers with ammonia chloride only (5g NH4+) , two beakers with biochar only (5g biochar), and two beakers with ammonia and biochar (5g NH4+, 5g biochar). We measured the pH of each beaker and found that our ammonia only solutions yielded reduced pH of on average 4.88, biochar only of 11.06, and the liquid phase in the beakers with both biochar and ammonia a pH of 7.4. When biochar was removed from beakers 5 and 6, the pH maintained a neutral 7.56 suggesting that the removal of the biochar removed the ammonia with it. The experimental setup and data table can be found in Figure 3 and Table 3.

Figure 3. Illustration of pH jar test using two controls (beakers 1-4) and two experimental set ups (beakers 5&6) with biochar produced at 500C from rice-straw feedstock.

	NH4Cl Only	NH4Cl Only	Biochar Only	Biochar Only	NH4Cl + Biochar	NH4Cl + Biochar
Beaker	1	2	3	4	5	6
Initial	4.9	4.85	11.04	11.08	7.42	7.45
24 hr Average	4.93	4.87	11.07	11.08	7.46	7.47
Filtered (biochar removed)	-				7.47	7.47

Table 3. PH measurements from the jar test illustrated in Figure 3. PH was measured initially and over a 24-hour period (every 2 hours). At the end of the period biochar was removed via vacuum filtration through a glass filter paper.

Scale Up Assessment

Scale up of our design for full scale testing was based on a mass balance projection of a large-scale farm. The mass balance is based on literature values assuming 3000 cows per housing unit, an emissions rates of 59 g/cow-day, a housing unit volume of 793,000 m3, and ventilation rate of 30 ACH (1,2) The full mass balance will be detailed in our final design report and is summarized in Figure 4.

Figure 4. Full-Scale ammonia mass balance in our cattle housing unit assuming steady state, ventilation rates of 30 ACH, housing volume of 793,000m3, 3000 cows, and livestock emissions rates of 59 g/cow-day.

Based on observed efficiencies of our lab scale design we predict the ammonia concentrations at various points in our design to be as shown in Table 4. These concentrations are based on a generation and ventilation rate of ammonia of 0.0146 g/s from the livestock housing unit to our 3-phase air scrubber design. This assumption is based off the mass balanced outlined in Figure 4.  

Location:	Post Air Scrubber	Post Biochar Column	Post Air Stripper
Removal Efficiency (%)	90	83	98
Ammonia Concentration (mg/L)	55.31	9.4	0.188

Table 4. Predicted removal efficiency and ammonia concentrations in our scaled up design.

Initial Economic Assessment

We are in the early stages of our economic assessment as the assessment will vary according to our testing and final design. Students have pulled together rough equipment estimates based on projected design components and will refine these estimates in the coming year.

Future Activities:

We plan to wrap up our research on this project by focusing on scale up of the technology and estimating an accurate life cycle assessment of this system at full-scale including an economic assessment and design parameters. The following outlines the proposed milestones for the upcoming year. We plan to finalize and write up our life cycle analysis and data collection for publication and send a group of senior students to showcase our findings at the P3 conference in the spring. 

Journal Articles:

No journal articles submitted with this report: View all 3 publications for this project

Progress and Final Reports:

Original Abstract

2018 Progress Report

2019 Progress Report

2020 Progress Report

2021 Progress Report

2022 Progress Report

Final

P3 Phase I:

Three-Phase Ammonia Air Scrubber Recycles Water  | 2017 Progress Report  | Final Report