This study examined the effects of incorporating biochar made at different temperatures into denitrifying bioreactors used to treat agricultural runoff. Five bioreactor configurations were tested: woodchips only, woodchips with separated low-temperature biochar, woodchips with combined low-temperature biochar, woodchips with separated high-temperature biochar, and woodchips with combined high-temperature biochar. Results showed that the bioreactors with biochar thoroughly incorporated into the woodchips had the highest nitrogen reduction. Additionally, the high-temperature biochar gained nitrogen during the experiment while the low-temperature biochar lost nitrogen. The study provides insights into optimizing biochar properties and reactor design to maximize nutrient removal from agricultural run

1. Thermally Treated Biomass for Denitrifying Bioreactors
Michael Smith, Dr. Daniel Ciolkosz, & Dr. Siobhan Fathel
The Pennsylvania State University, Department of Agricultural and
Biological Engineering, State College, PA, 29631
Abstract
Denitrifying bioreactors (DNBRs) provide one solution to the issue of nutrient runoff into environmental systems by harnessing the power of microbial denitrification pathways. Biochar has potential to increase the rate of
denitrification and reduce emissions when incorporated into DNBRs. This project studied two factors on the behavior of added biochar: separation of the biochar vs. incorporation into the woodchips and the treatment temperature of
the biochar. The implications of this project on nutrient recycling into fields are also discussed. Five groups of bioreactors were tested. The treatments are: woodchips, woodchips and separated biochar treated at 420 C (400BC),
woodchips and combined 400BC, woodchips and separated biochar treated at 600 C (600BC), woodchips and combined 600BC. The reactors with biochar thoroughly incorporated into the woodchips displayed the largest total nitrogen
reduction with C420 containing just over 1% of the original nitrogen concentration after 36 hours and W still containing over 80%. A significant difference was also found in the nitrogen content of the biochar before and after the
experiment, with 600BC gaining 0.3% nitrogen content and 420BC losing 0.05%.
Procedure
• Biochar production
– A Lindberg Blue Box Furnace Oven was used with an LCL
heating rate of around 10-15 °C and nitrogen flow of 5 L/min.
– The oven was purged of oxygen for 30 minutes then turned on,
heated to 220 °C and left for 25 minutes.
– The oven was then heated to the target temperature and left for
15-20 minutes. For “420BC”, a target of 420 °C was used. For
“600BC”, a target of 600 °C was used.
• Treatment groups (each receiving influent of 11 mg/L 𝑁𝑂3 − 𝑁)
– Woodchip control [2 L woodchips (WC)]
– S420 [1.6 L WC, 400 mL 420BC separated by a mesh
screen]
– C420 [1.6 L WC, 400 mL]
– S600 [1.6 L WC, 400 mL 600BC separated by a mesh
screen]
– C600 [1.6 L WC, 400 mL 600BC]
• Measurements
– 𝑁𝑂3-N, 𝑁𝑂2-N, 𝑃𝑂4-P levels were taken at 0, 18, and 36 hrs
– 𝑁2𝑂 concentration was taken at 0, 12, 24, and 36 hrs using
GC
– Total N content of biochar was taken before and after
Conclusions
• 600BC likely has higher sorption potential then 420BC.
• Thorough incorporation of biochar into woodchips has a significant
impact on microbial activity, favoring more rapid denitrification.
• Combined bioreactors do not necessarily behave as more “efficient”
emitters even when normalized for greater microbial activity.
References
“Capturing and Recycling Excess Nutrients from Farmland.” Illinois Sustainable Technology Center, University of Illinois
Board of Trustees, July 2019.
Cayuela, M., Sánchez-Monedero, M., Roig, A. et al. “Biochar and denitrification in soils: when, how much and why does
biochar reduce N2O emissions?” Sci Rep 3, 1732 (2013).
Haijing Yuan, Zhijun Zhang, Mengya Li, Tim Clough, Nicole Wrage-Mönnig, Shuping Qin, Tida Ge, Hanpeng Liao, Shungui
Zhou. “Biochar's role as an electron shuttle for mediating soil N2O emissions.” Soil Biology and Biochemistry, Volume
133, 2019, Pages 94-96. ISSN 0038-0717.
Ying Yao, Bin Gao, Ming Zhang, Mandu Inyang, Andrew R. Zimmerman. “Effect of biochar amendment on sorption and
leaching of nitrate, ammonium, and phosphate in a sandy soil.” Chemosphere, Volume 89, Issue 11, 2012, Pages 1467-
1471. ISSN 0045-6535.
Acknowledgements
This research was supported by the Penn State Agricultural and Biological Engineering
Department. Dr. Daniel Ciolkosz was the project’s primary supervisor and Dr. Siobhan Fathel
was a co-supervisor. Dr. Lauren McPhillips and Tahiya Tarannum provided assistance for nitrous
oxide measurements and the development of that procedure. Dr. Tyler Groh provided advice for
the procedure. The project was funded by the USDA MASBio grant (2020-68012-31881).
Results
• A large number of 𝑁𝑂3-N values fell
below the minimum detection.
– These values were treated as zeros for analysis.
– Total nitrogen (𝑁𝑂3-N + 𝑁𝑂2-N) had to be used instead of 𝑁𝑂3-N.
– 𝑁𝑂3-N data is entirely missing at the beginning.
• C420 and C600 have highest N
removal and W has the lowest removal.
– Two factor ANOVA test proves significance of results.
• 𝑃𝑂4-P data
– Data not statistically significant, but it seems as though the general
trend is that W exported the most 𝑃𝑂4-P, followed by the 420BC
samples. 600BC seemed to export the least 𝑃𝑂4-P.
• Combined biochar/wood chip treatments do not emit less even when
adjusted for higher denitrification rates. Significance not proven.
• There is a significant difference
between the 420BC and 600BC
treatments
– Confirmed by single factor ANOVA and Tukey’s test
Background
• The negative effects of excessive agricultural nutrient runoff are
well researched.
• DNBRs filled with woodchips have become a promising form of
point-source treatment.
• Biochar has showed potential as an amendment to these systems
to increase nitrate reduction and mitigate 𝑁2𝑂 emissions
• Areas of the DNBR/biochar field are still lacking in robust
research. For instance:
– Finding ways to effectively recycle nutrients to create a “product” stream
– Minimizing and eliminating harmful 𝑁2𝑂 emissions in field scenarios
Liquid Nutrient Concentrations
Nitrous Oxide Emissions
Biochar Nitrogen Content
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
W S420 C420 S600 C600
Percentage
of
initial
total
N
(%)
Treatment
0
10
20
30
40
50
60
70
80
90
100
W S420 C420 S600 C600
N
2
O
accumulation
(ppm)
Treatment
0
1
2
3
4
5
6
7
8
9
W S420 C420 S600 C600
N
2
O
/
Nitrogen
reduced
(ppm
/
mg/L)
Treatment
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
W 420BC 600BC
Change
in
%N
content
Treatment
Significance
• Biochar benefits soil structure
and could facilitate nutrient
recycling.
• Biochar loses much of its
potential for denitrification
many years before woodchips.
• With more research, a two-
chamber technique could
facilitate easy biochar removal.
Figure 1. Percentage of initial nitrogen
concentration (reported as 𝑁𝑂3-N + 𝑁𝑂2-
N) remaining after 36 hours.
Figure 2. Accumulation of 𝑁2𝑂
after 36 hours.
Figure 3. Accumulation of 𝑁2𝑂
divided by nitrogen reduced after
36 hours.
Figure 5. Illinois Prairie Research Institute
depiction of separated chambers:
https://www.istc.illinois.edu/research/pollutants/
agricultural_chemicals/capturing_recycling_exc
ess_nutrients_from_farmland/.
Figure 4. Change in nitrogen content of the
biochar before and after experiment