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Viravid Na Nagara¹, Zhiming Zhang¹, Hadeer Saleh¹, �Sameer Neve¹, Rupali Datta², Paul Truong³, Dibyendu Sarkar¹

1 Department of Civil, Environmental, and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ, USA

2 Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA

3 Veticon Consulting, Byron Bay, �New South Wales, Australia

Pollutant Removal Using Vetiver Grass and �Generation of Biofuel and Biochar From Spent Biomass: �A Circular Economy Model

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Zhiming Zhang

(zzhan100@stevens.edu)

Hadeer Saleh

(hsaleh2@stevens.edu)

Sameer Neve

(sneve@stevens.edu)

Rupali Datta

(rupdatta@mtu.edu)

Paul Truong

(p.truong@veticon.com.au)

Dibyendu Sarkar

(dsarkar@stevens.edu)

Viravid Na Nagara

(viravid.n@gmail.com )

Pollutant Removal Using Vetiver Grass and �Generation of Biofuel and Biochar From Spent Biomass: �A Circular Economy Model

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Problems caused by stormwater runoff��

Source: https://twitter.com/jgodynick/status/1044673777341214722

https://patch.com/new-jersey/secaucus/dramatic-photos-secaucus-flooding-tuesday

Visible threat:

Water ponding and flooding

Invisible threat:

Stormwater�pollution

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Problems caused by stormwater runoff��

Invisible threat: Stormwater pollution

Source: https://sigearth.com/stormwater-runoff-a-top-cause-of-water-pollution/

Metals

Nutrients

Total suspended solids

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Problems caused by stormwater runoff��

Invisible threat: Stormwater pollution

Adverse environmental impacts

Affecting reproduction rates and life spans of aquatic species
Disrupting food chains in aquatic systems
Affecting water supplies
Eutrophication

Source: https://www.draper.ut.us/1021/Pollution-Information�https://www.stevens.edu/news/how-stevens-helping-save-oceans-and-lakes-trimming-nutrient-runoff

Visible threat:

Water ponding and flooding

Invisible threat:

Stormwater�pollution

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Vetiver (Chrysopogon zizanioides)

Parameter		Range of tolerance
pH		3.3-12.5
Temperature	Frost	5°F (-15°C)
	Heat	140°F (+60°C)
Drought		15 months
Altitude		2800 m

High tolerance to harsh climatic conditions
High biomass
Massive root system
Can grow hydroponically
High capability of nutrient and metal uptake

Source: http://vetiver.com.vn/vetiver-grass-system/

Floating treatment platform (FTP)

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Objective

To develop a low-cost, efficient, “green” retrofit for stormwater retention ponds to enhance their metal and nutrient removal capacity and to use spent vetiver as feedstock for the generation of bioethanol and biochar to form a circular economy model.

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Experimental design

Reactor: 150-gallon tanks
Permanent pool volume: � 100 gallons
Simulation volume: � 33 gallons over 2 hours
Spiked initial concentrations: � 50 µg/L Cu� 200 µg/L Pb � 180 µg/L Zn� 900 µg/L P� 5.5 mg/L NO₃^-.
Monitoring period:� 28 days for each simulation, 3 simulations in total

Two �non-vegetated FTPs

(control)

Two �vegetated �FTPs

(vetiver)

30 mins

60 mins

90 mins

120 mins

1 �day

2 �days

3 days

6 �days

9�days

12 �days

15�days

18�days

21 days

24 days

28 days

To achieve the objective, a greenhouse study was conducted.

A total of 4 tanks were used to evaluate the removal of stormwater pollutant of FTP with vetiver

The two tanks on the right were retrofitted with vetiver;

and the other two tanks on the left were control, which did not have vetiver.

Each control tanks were covered with a plastic sheet to mimic plant shade.

In actual system, two weather conditions occur in retention ponds.

First is wet conditions, which is during precipitation when inflow and outflow occur.

Second is dry conditions, which is the interval between precipitation.

Therefore, the experiment was designed to mimic wet and dry conditions in the real system.

Three precipitation simulations were performed with an interval of 28 days.

In each storm event simulation, a total volume of 33 gallons of the adjusted pond water was fed to each tank at a constant flowrate across the two-hour period.

On day 28th of each simulation period, the last set of samples were collected. Then, the next simulation started.

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Experimental design

1

2

3

4

5

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Results – Pollutant Removal

NO₃^-

P

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Results – Pollutant Removal

Cu

Pb

Zn

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Results – Pollutant Removal

EDS spectrum of the sediment

keV

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Results – Pollutant Distribution in Vetiver

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Results – Plant growth and chlorophyll content

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Results – Physicochemical characteristics of vetiver biochar

Parameter	Value
Yield	51.28%
BET Surface Area	171.6 m²/g
pH	9.78 ± 0.13
Electric Conductivity	184.5 ± 21.3 µS/cm
Ash Content	23.6%
Cation Exchange Capacity	98 cmol/kg
Bulk Density	0.57 gm/ml
C	69.87 %
H	2.824 %
O	1.720 %
N	19.37 %
H/C	0.04
O/C	0.025
N/C	0.28
Liming Value	3.06 % CaCO₃

Biochar production:

The roots of the spent vetiver were washed clean, air dried, and ground before pyrolysis at 500℃ held for 60 mins.

Circular Economy

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Results – Physicochemical characteristics of vetiver bioethanol

Parameter	Test method	Value
Cellulose	Yang et al., 2006	32.86 %
Hemicellulose	Yang et al., 2006	34.03 %
Lignin	Yang et al., 2006	14.69 %
Extractives	Yang et al., 2006	9.87 %
Bioethanol Yield	Zabed et al., 2016	16.58 g/L �(236.89 mg/g)
Ethanol Content	ASTM D 5501	98.86 %
Density at 25°C	ASTM D 4052	0.77 g/mL
Calorific Value	ASTM D 2014-96	31.36 MJ/kg
Viscosity	ASTM D 88-94	1.02 cSt
Sulfur content	ASTM D 3177-89	0.03 wt %
Water content	ASTM D 95-70	1.01 %
Research Octane Number	ASTM D 2699	107

Bioethanol production:

The bioethanol was generated from the shoots of the spent vetiver via multiple steps, including

1) preparation of biomass, �2) dilute acid-alkali pretreatment, �3) enzymatic hydrolysis, �4) bioethanol fermentation, and �5) distillation.

Yang, H., Yan, R., Chen, H., Zheng, C., Lee, D.H., Liang, D.T., 2006. In-depth investigation of biomass pyrolysis based on three major components: hemicellulose, cellulose and lignin. Energy & Fuels 20, 388–393.

Zabed, H., Sahu, J.N., Boyce, A.N., Faruq, G., 2016. Fuel ethanol production from lignocellulosic biomass: an overview on feedstocks and technological approaches. Renew. Sustain. energy Rev. 66, 751–774.

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Results – Potential metal residues in biochar and bioethanol

Metal leaching potential from biochar:

Synthetic precipitation leaching procedure (SPLP) (USEPA, 1994)
Toxicity characteristic leaching procedure (TCLP) (USEPA, 1992)

^a SPLP criterion: Higher of the health-based leachate criterion or aqueous practical quantitation levels (NJDEP, 2013)�^b TCLP criterion: maximum concentrations of contaminants for the toxic characteristics from Title 40 CFR 261.24 - Toxicity characteristic�^c NR: Not regulated

Metal contents in bioethanol:

No metals were found in bioethanol.

USEPA, 1994. Method 1312: Synthetic precipitation leaching procedure

USEPA, 1992. Method 1311: Toxicity characteristic leaching procedure

NJDEP, 2013. Development of site-specific impact to ground water soil remediation standards using the synthetic precipitation leaching procedure.

To evaluate if biochar can bioethanol can be utilized safely without the contamination of metals. The resultant products were analyzed for metals.

Biochar was subjected to synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) to evaluate metal leaching potential from biochar. Both SPLP and TCLP are used to characterize the quality of leachates from samples and determine whether a material is considered hazardous. SPLP simulates the rainfall conditions, while TCLP simulates the landfilling conditions. The TCLP analysis can identify the toxic materials, and The RCRA (Resource Conservation and Recovery Act) requires organizations working in the waste management industry to perform this test on their hazardous waste. The results of RCRA 8 metals are listed in this slide. They are arsenic, barium, cadmium, chromium, lead, mercury, selenium and silver. This research show that the leaching concentrations all were well below the regulatory limits. And no metals were found in bioethanol.

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Summary

Floating treatment platform with vetiver is an effective retrofit for stormwater retention ponds to remove nutrients and metals.�
The majority of P was translocated from the below-ground tissues to the above-ground tissues, while the majority of the removed metals (Cu, Pb, and Zn) were localized in the vetiver root.

No visible plant stress symptoms was observed.

The yield and quality of biochar and bioethanol �generated from the spent vetiver biomass were desirable.

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Thank you !

Acknowledgement:

This work was supported by United States Environmental Protection Agency/New Jersey Department of Environmental Protection and National Oceanic and Atmospheric Administration/New Jersey Sea Grant Consortium.

We thank Paul Truong for presenting our research in ICV-7.