Physical, Chemical and Biological Characterization of Six Biochars Produced for the Remediation of Contaminated Sites

Summary

Biochar is a carbon-rich material used as a soil amendment with the ability to sustainably sequester carbon, improve substrate quality and sorb contaminants. This protocol describes the 17 analytical methods used for the characterization of biochar, which is required prior to large scale implementation of these amendments in the environment.

Abstract

The physical and chemical properties of biochar vary based on feedstock sources and production conditions, making it possible to engineer biochars with specific functions (e.g. carbon sequestration, soil quality improvements, or contaminant sorption). In 2013, the International Biochar Initiative (IBI) made publically available their Standardized Product Definition and Product Testing Guidelines (Version 1.1) which set standards for physical and chemical characteristics for biochar. Six biochars made from three different feedstocks and at two temperatures were analyzed for characteristics related to their use as a soil amendment. The protocol describes analyses of the feedstocks and biochars and includes: cation exchange capacity (CEC), specific surface area (SSA), organic carbon (OC) and moisture percentage, pH, particle size distribution, and proximate and ultimate analysis. Also described in the protocol are the analyses of the feedstocks and biochars for contaminants including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), metals and mercury as well as nutrients (phosphorous, nitrite and nitrate and ammonium as nitrogen). The protocol also includes the biological testing procedures, earthworm avoidance and germination assays. Based on the quality assurance / quality control (QA/QC) results of blanks, duplicates, standards and reference materials, all methods were determined adequate for use with biochar and feedstock materials. All biochars and feedstocks were well within the criterion set by the IBI and there were little differences among biochars, except in the case of the biochar produced from construction waste materials. This biochar (referred to as Old biochar) was determined to have elevated levels of arsenic, chromium, copper, and lead, and failed the earthworm avoidance and germination assays. Based on these results, Old biochar would not be appropriate for use as a soil amendment for carbon sequestration, substrate quality improvements or remediation.

Introduction

Biochar is a carbon-rich by-product produced during the pyrolysis of organic matter ¹. Interest, both publicly and academically, in adding biochar to soils, stems from its ability to improve soil quality and plant growth ^{2, 3}, sustainably sequester carbon ⁴, and sorb harmful contaminants ^{2, 3, 5-7} whilst simultaneously offering alternatives for waste management and energy production by pyrolysis.

Biochars are being produced by numerous companies and organizations worldwide via different pyrolysis systems. Materials used for biochar production include (but are not limited to) woodchips, animal manu....

Protocol

NOTE: Chemical analyses were conducted at the Analytical Services Unit (ASU) in the School of Environmental Studies at Queen’s University (Kingston, ON). The ASU is accredited by the Canadian Association for Laboratory Accreditation (CALA) for specific tests listed in the scope of accreditation. Other analyses, including greenhouse trials, were conducted at The Royal Military College of Canada (Kingston, ON) in the Department of Chemistry and Chemical Engineering.

1. General Considerations

1. To ensure quality assurance and quality control, analyze an analytical blank and an analytical duplicate, a sample duplicate and a stan....

Results

A summary of all results including a comparison to the criteria set by the IBI ¹³ can be found in Tables 1 (summary), 2 (New, High, Low, Third Feedstock and High-2 biochars) and 3 (Old biochar). All biochars and feedstocks used in 2012 and 2013 (Table 2) were well within the criterion set by the IBI and there were little differences among biochars. Old biochar (Table 3), the first biochar submitted for testing, was made from u.......

Discussion

All of the methods listed in the protocol have been carefully validated and extensively used for soils. As biochar characterization is still in its infancy, the effectiveness of these methods for the carbon-rich substrate was largely unknown. Hence, although these methods themselves are not novel, their application to routinely characterize biochar is. In terms of quality assurance/ quality control, there were no issues among any of the methods with respect to the blanks being below detection limits or the recoveries bei.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Biochar	Burt's Greenhouses		All six biochars were produced at Burt's Greenhouses via BlueFlame Boiler system
NaOAc	Fisher Scientific	E124-4	Dissolving 136.08 g of NaOAC.3H2O in 750 ml distilled, deionized water (DDI water)
Acetic Acid	Fisher Scientific	A38-212
Sodium Hydroxide	Fisher Scientific	SS284-1
Isopropanol	Fisher Scientific	A416P4	80% IPA: 800 ml IPA with 200 ml DDI water.
NH4Cl	Fisher Scientific	A649500	Dissolving 5.35 g NH4Cl into 1 L DDI water.
Alumminum Drying Pan	Fisher Scientific	08-732-110
Drying Oven	Fisher Scientific	508N0024	200 °C for 2 hr.
Desiccator	Fisher Scientific	08-595A
Balance	Mettler	1113032410
Saturating Solution	Fisher Scientific	06-664-25
Vortex	Barnstead/Thermolyne	871000536389
Centrifuge	International Equipment Company	24372808	3,000 x g for 5 min.
Rinsing Solution	Fisher Scientific (Ricca Chemistry Company)	06-664-24
Conductivity Meter	WESCAN	88298
Replacing Solution	Fisher Scientific	06-664-24
ICP-AES	Varian	EL00053841
ASAP 2000 Surface Area Analyser	Cavlon	885	Degassing at 120 °C for a minimum of 2 hr.
Muffle Furnace	Fisher Scientific	806N0024	Heat for 16 hr covering at 420 °C.
pH Meter	Fisher Scientific	1230185263
Sieve	Fisher Scientific	2288926	4.7 mm sieve being at the top.
Sieve Skaker	Meinzer II	0414-02	Shake for 10 min.
Sodium Sulphate	VWR	EM-SX0761-5
Ottawa Sand	Fisher Scientific	S23-3
Soxhlet Apparatus	Fisher Scientific (Pyrex)	09-557A	4 hr at 4–6 cycles/hr.
DCBP	Suprlco Analytical	48318
Dichloromethane	Sigma Aldrich	40042-40855-U
6890 Plus Gas Chromatograph Micro 63 Ni ECD	Agilent	US00034778
Helium	AlphaGaz	SPG-NIT1AL50SMART
Nitrogen	AlphaGaz	SPG-HEL1AL50SMART
Mortor and Pestle	Fisher Scientific (CoorsTeh)	12-948G
Nitric Acid	Fisher Scientific	351288212
No. 40 Filter Paper	Fisher Scientific (Whatman)	09-845A
Quartz/Nickel weigh boats	Fisher Scientific	11-474-210
DMA-80	ATS Scientific	5090264
98–99% Formic Acid	Sigma Aldrich	33015-1L	1 L volumetric filled to 750 ml with DDI water add 20 ml formic acid and fill to volume with DDI water.
Sonicator	Fisher Sientific	15338284
Rotating Shaker	New Brunswick Scientific (Innova 2100)	14-278-108	1 hr at 200 rpm.
No. 42 Filter Paper	Fisher Scientific (Whatman)	09-855A
WhirlPacks	Fisher Scientific	R55048
Potassium Dihydrogen Orthophospahte	Fisher Scientific	181525
2 M KCl	Fisher Scientific	P282100
Plastic Vials	Fisher Scientific	03-337-20
Ammonium Chloride	Fisher Scientific	PX05115	Allow to warm up to room temperature
Colour Reagent	Fisher Scientific	361028260	Allow to warm up to room temperature
Colorimeter	Fisher Scientific	13-642-400	Turn on to let the lamp warm up and run for 5 min.
ASEAL Auto Analyzer 2	SEAL	4723A12068
Liquified Phenol	Fisher Scientific	MPX05115	Alkaline Phenol: Measure 87 ml of liquefied phenol into 1-L volumetric filled 2/3 with DDI water. Add 34 g NaOH, make up to volume with DDI water.
NaOH	Fisher Scientific	S318-3
Commercial Bleach	Retail Store		Hypochlorite Solution: Using 100-ml graduated cylinder measure 31.5 ml of commercial bleach and fill to 100 ml with DDI water.
NaOH Pellets	Fisher Scientific	S320-1
Disodium EDTA	Sigma Aldrich	E5124
Sodium Hyprchlorite	Fisher Scientific	SS290-1
Triton (10%)	Fisher Scientific	BP151-100
Sodium Nitroprusside	Fisher Scientific	S350-100
Ammonium Salts	Fisher Scientific	A637-10
Phenoxide	Fisher Scientific	AC388611000
Eisenia Fetida	The Worm Factory
Spade	Retail Store
Bucket	Retail Store
Potting Soil	Retail Store
Avoidance Wheel	Environment Canada		Constructed by a modified design from Environment Canada’s Acute Avoidance Test.
Alumminum Foil	Fisher Scientific	01-213-100
Petri Dishes	Fisher Scientific	08-757-11	8.5 cm in diameter.
Pumpkin Seeds	Ontario Seed Company (OSC)	2055
Alfalpha Seeds	Ontario Seed Company (OSC)	6675
Centrifuge Tubes (30 ml)	Fisher Scientific	22-038-906
Beakers (50 ml)	Fisher Scientific (Pyrex)	02-540G	Oven dry at 105 °C.
Beakers (30 ml)	Fisher Scientific (Pyrex)	20-540C
Erlenmeyer Flasks (125 ml)	Fisher Scientific (Pyrex)	S76106C
Volumetric Flask (100 ml)	Fisher Scientific (Pyrex)	10-211C
Estuarine Sediment	National Insititute of Standards	1546A	Standard Reference Material
Bleach	Clorox Ultra (5–10% sodium hypochlorite)