advantages and disadvantages, re- Chemical Properties of Biochar Materials searchers worldwide are working on Manufactured from Agricultural Products optimizing and evaluating biomass conversion processes to improve Common to the Southeast United States quality and performance of biomass- based production of fuels, chemicals, 1,5 2 3 and biochar. Specific and unique Michael R. Evans , Brian E. Jackson , Michael Popp , properties of each biochar product and Sammy Sadaka4 depended on the properties of the original feedstock material (Altland, 2014) and method of production ADDITIONAL INDEX WORDS. cation exchange capacity, electrical conductivity, employed (Spokas et al., 2012). It growing media, pH, substrates has been reported that the higher SUMMARY. The use of biochar as a soil amendment has fostered much attention in the temperature, the smaller and recent years due to its potential of improving the chemical, physical, and biological more porous the resulting biochar properties of agricultural soils and/or soilless substrates. The objective of this study particles became (Kloss et al., 2012). was to evaluate the chemical properties of feedstocks, common in the southeast These smaller particles tended to United States, and their resulting biochar products (after being torrefied) and have proportionally more surface area determine if the chemical properties were within suitable ranges for growers to use (Shackley et al., 2013) which had the biochar products as root substrate components. Poultry litter biochar produced benefits such as an increased CEC. at 400 C for 2 hours had a higher total phosphorus (P), potassium (K), calcium Due to its high carbon concen- (Ca), magnesium (Mg), sulfur (S), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), sodium (Na), and zinc (Zn) concentration than biochar tration, biochar has the potential to made using the same process with mixed hard wood species, miscanthus (Miscanthus be used in a number of applica- capensis), cotton (Gossypium hirsutum) gin trash, switchgrass (Panicum virgatum), tions including soil conditioning, rice (Oryza sativa) hull, and pine (Pinus sp.) shavings feedstocks. The pH of the as activated carbon or in chemical biochar products ranged from 4.6 for pine shaving biochar to 9.3 for miscanthus manufacturing. The application of biochar. The electrical conductivity (EC) ranged from 0.1 dSÁmL1 for mixed biochar to soils contributed to the L hardwood biochar to 30.3 dSÁm 1 for poultry litter biochar. The cation exchange sequestration of carbon from the capacity (CEC) of the biochar products ranged from a low of 0.09 meq/g for mixed atmosphere, since carbon captured hardwood biochar to a high of 19.0 meq/g for poultry litter biochar. The water- from the environment by the biomass extractable nitrate, P, K, Ca, Mg, sulfate, boron, Cl, Cu, Fe, Mo, Na, and Zn were was shown to be retained in the soil higher in poultry litter biochar than in all of the other types of biochar. The high EC and mineral element concentration of the poultry litter biochar would prevent its (Manya, 2012). Wood contained use in root substrates except in very small amounts. In addition, the high degree of around 50% carbon that increased to variability in chemical properties among all of the biochar products would require 70% to 80% once it was processed to users to know the specific properties of any biochar product they used in a soil or biochar. This carbon could be stored soilless substrate. Modifications to traditional limestone additions and fertility from the atmosphere when applied programs may also need to be tested and monitored to compensate for the biochar to the soil (Winsley, 2007). In addi- pH and mineral nutrient availability. Users should be aware that biochar products tion, the utilization of biochar im- made from different feedstocks can have very different chemical properties even if proved the quality of the soil because the same process was used to manufacture them. of its sorption qualities that helped to retain nutrients and nitrogen (Ippolito iochar is a term that refers to atmosphere (Lehmann and Joseph, et al., 2012). a black carbon-rich material 2009) and is generally considered to The components of horticultural Bthat is produced from or- be similar to charcoal. There are dif- substrates used in commercial green- ganic matter at temperatures lower ferent processes used to make bio- house and nursery operations can be than 700 C in an oxygen-limited char, including pyrolysis, gasification, a major production cost, as most and torrefaction, and these processes customary components are com-
This project was supported by the University of may differ in temperature, residency monly shipped from outside the Arkansas System Division of Agriculture. time, and oxygen availability. Al- United States or manufactured sub- 1Department of Horticulture, University of Arkansas though different processes have their strates are transported significant System Division of Agriculture, 318 Plant Sciences Building, Fayetteville, AR 72701 2Department of Horticultural Science, North Caro- lina State University, 130 Kilgore Hall, Raleigh, NC Units 27695 To convert U.S. To convert SI to 3Department of Agricultural Business and Agricul- to SI, multiply by U.S. unit SI unit U.S., multiply by tural Economics, University of Arkansas System 29.5735 fl oz mL 0.0338 Division of Agriculture, 217 Agriculture Hall, Fayet- teville, AR 72701 3.7854 gal L 0.2642 25.4 inch(es) mm 0.0394 4 Department of Biological and Agricultural Engineering, 1 meq/g molÁkg–1 1 University of Arkansas System Division of Agriculture— 1 mmho/cm dSÁm–1 1 Extension, 2301 South University Avenue, Little Rock, AR 72204 28.3495 oz g 0.0353 28,350 oz mg 3.5274 · 10–5 5 Corresponding author. E-mail: [email protected]. 1 ppm mgÁL–1 1 doi: 10.21273/HORTTECH03481-16 ( F – 32) O 1.8 F C( C · 1.8) + 32
16 • February 2017 27(1) distances from the production facility with those grown in coconut coir Feedstocks were then transported to to the end user. Interest in using fiber alone (Graber et al., 2010). the bioenergy laboratory at the Rice biochar for horticultural purposes Those authors speculated that the Research and Extension Center, Uni- has increased substantially in recent improved plant growth was a result versity of Arkansas System Division of years due to its potential as a low-cost of the biochar stimulating the benefi- Agriculture (Stuttgart, AR). substrate component. In particular, cial plant growth promoting rhizo- The biochar was produced in biochar products have been shown bacteria populations or due to 1-gal cylindrical metal containers filled to be a potential replacement for hormesis (positive plant growth re- with feedstock samples and placed in perlite in greenhouse substrates sponse to low doses of phytotoxic or a controllable muffle furnace (model (Northup, 2013), because it is light- biocidal chemicals) caused by the 3-1750; Neytech Vulcan, Bloomfield, weight, porous, and thought to have biochar. Red oak (Quercus rubra) CT). Each container was loaded with potential cost-saving benefits over biochar added to peat or peat- 400 g of raw feedstock before tightly perlite. Other reported benefits of vermiculite substrates resulted in an securing the lid allowing only the using biochar products in substrates increased shoot biomass of hybrid evolved volatiles to escape through include the potential of increasing poplar (Populus sp.) cuttings as a re- 3-mm vents on the lid. In this study, CEC (Nemati et al., 2015) and rhizo- sult of increased nutrient concentra- the evolved volatiles were not col- sphere biology (Graber et al., 2010). tions and availability due to the high lected nor quantified. Before placing Numerous researchers have eval- CEC and initial nutrient content of the containers in the furnace, they uated the use of biochar and products the biochar (Headlee et al., 2014). In were purged with nitrogen (N) gas similar to biochar as substrate com- contrast, Northup (2013) reported through one of the 3-mm vents for ponents and have reported mixed re- that the incorporation of hardwood- 10 min to ensure minimal oxidation of sults. Coal cinders were evaluated as produced biochar into the substrate the feedstock. The furnace tempera- components in substrates to enhance resulted in either no effect or decreased ture and the residence time were set at the physical and chemical properties growth of pepper, tomato (Solanum 400 C and 2 h, respectively. The of a pine bark nursery substrate (Neal lycopersicum), cucumber (Cucumis sat- feedstocks were placed into the and Wagner, 1983) and again as ivus), marigold (Tagetes patula), and heated furnace once the desired tem- a component in the growth of azalea petunia (Petunia ·atkinsiana). perature level was achieved. After [Rhododendron obtusum (Wagner and There are conflicting reports on retrieval from the heated furnace, Neal, 1984)]. Coal cinders were the potential for biochar to be used as containers were immediately covered found to contain high concentrations a soilless substrate component. This with aluminum foil to prevent bio- of heavy metals, which limited their could be due to the wide range of char oxidation and were allowed to use in substrates even though plant biomass materials used to produce cool. growth trials proved to be successful biochar, which may alter the proper- The original feedstocks and their with up to 50% (by volume) cinder ties of the final product. Any biochar resulting biochar products were sent incorporation. Regulski (1984) products that are to be used in hor- to a commercial laboratory for analy- reported the use of a gasifier residue ticultural substrates must have chemical sis (MMI Laboratories, Athens, GA). as an amendment in a pine bark sub- properties within acceptable ranges Two types of analyses were conducted strate to have reduced shrinkage, for such use. Therefore, the objective on the feedstocks and biochar prod- compared with the pine bark control, of this study was to evaluate the ucts. The first was a total elemental and provided increased easily avail- chemical properties of feedstocks com- analysis. The feedstocks and biochar able water and water buffering capac- mon to southeast United States and products were dried in an oven at ity for the duration of a 9-month their resulting biochar products and 100 C, ground and acid digested. crop. Holcomb and Walker (1995) determine if the chemical properties The N, P, K, Ca, Mg, S, boron (B), reported the growth of chrysanthe- were within suitable ranges for growers Cu, Fe, Mn, Mo, Na, and Zn con- mum (Chrysanthemum indicum) and to use the biochar products as root centrations were determined using poinsettia (Euphorbia pulcherrima)in substrate components. the filtered extract for simultaneous coal gasification slag amended sub- inductively coupled plasma emission strates to be equal to plants grown in Materials and methods spectrometry (Jones, 1977; Munter a peat:perlite control at up to 50% Various agricultural by-products and Grande, 1981). amendment (Bi et al., 2009; Evans common to the southeast United The second test was a deionized et al., 2011). Researchers who con- States were collected and used as water-based saturated media extract ducted a container experiment using feedstocks for the production of bio- using a volume of 1 part feedstock or natural field soil amended with rice char products. The feedstocks in- biochar product and 1.5 part deion- hull biochar demonstrated increased cluded rice hulls, hardwood chips ized water (Warncke, 1988). The plant growth for lettuce (Lactuca composed of a mixture of oak, poplar, solution was then incubated for sativa) and chinese cabbage (Brassica and ash (Fraxinus sp.), softwood 45 min and the solution was extracted chinensis) when compared with plants chips from pine shavings, cotton gin using a vacuum. The pH was deter- growninunamendedsoil(Carteretal., trash, switchgrass, miscanthus grass, mined using a pH meter (Accumet 2013). Pepper (Capsicum annuum) and poultry litter. The feedstocks model AB 15; Fisher Scientific, Pitts- grown in coconut (Cocos nucifera)coir were air dried and ground to particle burgh, PA), and the EC was deter- fiber amended with wood-derived sizes between 10 and 20 mm in di- mined using an EC meter (model biochar was shown to have increased ameter using a Wiley mill (model 4; 441; Corning, Corning, NY). The + plant growth and yields as compared Thomas Scientific, Swedesboro, NJ). ammonium (NH4 ) was determined
• February 2017 27(1) 17 RESEARCH REPORTS by the nitroprusside–salicylate proce- pine shavings to 17,740 mgÁL–1 for shavings had higher concentrations of dure (Wall et al., 1975), and the poultry litter (Table 1). The K con- Fe and Mn than their respective feed- – nitrate (NO3 ) concentration was de- centration of the biochar products stocks. However, the concentration termined using the copperized cad- ranged from 1985 mgÁL–1 for mixed of the other micronutrients varied mium reduction procedure (Keeney hardwoods to 18,391 mgÁL–1 for with no consistent patterns among and Nelson, 1982). The concentra- the poultry litter biochar (Table 1). feedstocks or biochar products or 2– tions of P, K, Ca, Mg, sulfate (SO4 ), The K concentration was higher between a feedstock and its resulting B, Cl, Cu, Fe, Mn, Mo, Na, and Zn in the resulting biochar products than biochar. were determined using the filtered in the respective feedstocks for the WATER-EXTRACTABLE CHEMICAL extract for simultaneous inductively mixed hardwoods, miscanthus, and PROPERTIES. The pH of the feedstocks coupled plasma emission spectrome- pine shavings. However, the K con- ranged from 4.6 for the pine shavings try (Jones, 1977; Munter and Grande, centration was lower in the cotton gin to 8.7 for the poultry litter (Table 3). 1981). The CEC of the biochars and trash biochar than in the cotton gin Poultry litter was the only feedstock original feedstocks were determined trash feedstock. with an alkaline pH. The pH of the according to procedures described by The Ca concentration of the biochar products ranged from 4.6 for Dumroese et al. (2011) and Kloss et al. feedstocks ranged from 1054 mgÁL–1 pine shavings to 9.3 for miscanthus. (2012). for rice hulls to 15,226 mgÁL–1 for ThepHofallofthebiocharprod- There were three independent poultry litter (Table 1). The Ca con- ucts with the exception of chicken litter replications (different production centration of the biochar products and pine shavings was higher than runs) per feedstock and biochar prod- ranged from 2078 mgÁL–1 for rice hull their respective feedstocks. The pH uct. An analysis of variance was con- biochar to 25,203 mgÁL–1 for the of pine shavings biochar was un- ducted to determine if significant poultry litter biochar (Table 1). The changed while the pH of the poultry differences occurred among the dif- Mg concentration of the feedstocks litter biochar was lower than the ferent feedstocks and biochar prod- ranged from 190 mgÁL–1 for mixed poultry litter feedstock. ucts. Where significant differences hardwoods to 4237 mgÁL–1 for poul- Except for poultry litter, miscan- occurred, a least significant difference try litter (Table 1). The Mg concen- thus, and cotton gin trash, the EC of mean separation test was conducted tration of the biochar products the feedstocks ranged from 0.1 to determine significant differences ranged from 340 mgÁL–1 for rice hull dSÁcm–1 for mixed hardwoods to 0.7 between specific means. biochar to 4586 mgÁL–1 for the poul- dSÁm–1 for rice hulls (Table 3). The try litter biochar (Table 1). The Ca poultry litter, miscanthus, and cotton Results and Mg concentration was higher in gin trash feedstocks had higher EC TOTAL ELEMENTAL ANALYSIS. the resulting biochar products than in values of 33.7, 2.2, and 6.0 dSÁm–1, The N concentration of the feed- the respective feedstocks for all of the respectively. Except for poultry litter, stocks ranged from 0.14% for pine biochar products except for rice hulls. the EC of the resulting biochar prod- shavings to 2.7% for poultry litter The S concentration of the feed- ucts were not significantly different (Table 1). The N concentration of stocks ranged from near 0% for pine from their respective feedstocks. The the biochar products ranged from shavings to 0.37% for poultry litter EC of poultry litter biochar was lower 0.71% for mixed hardwood biochar (Table 1). The S concentration of the than the EC of the poultry litter to 3.57% for the poultry litter bio- biochar products ranged from 0.02% feedstock but higher than all other char. The cotton gin trash biochar for rice hull and pine shaving biochar biochar products. The CEC of the had the second highest N concentra- to 0.56% for the poultry litter biochar feedstocks ranged from 0.08 meq/g tion at 1.37%. In all cases except for (Table 1). The S concentration of the for the mixed hardwoods to 13.2 the rice hulls, the N concentration poultry litter biochar was higher than meq/g for poultry litter (Table 3). was higher in the resulting biochar for the poultry litter feedstock, but Except for poultry litter, the CEC of products than in the respective feed- there was no difference in the S the resulting biochar products were stock. The N concentration of rice concentration of the other feedstocks not significantly different from their hulls and the resulting rice hull bio- and their respective biochar products. respective feedstocks. The CEC of char was not different. For all micronutrients except B, poultry litter biochar was higher than The P concentration of the feed- the poultry litter feedstock and the the CEC of the poultry litter feed- stocks ranged from 2.64 mgÁL–1 for poultry litter biochar had higher con- stock and at 19.0 meq/g, the highest pine shavings and switch grass to 41.7 centrations of micronutrients than all CEC of all products tested was for the mgÁL–1 formixedhardwoods(Table1). of the other feedstocks and their re- poultry litter biochar. + The P concentration of the biochar spective biochar products (Table 2). The NH4 of the feedstocks products ranged from 4.49 mgÁL–1 The B concentration was higher in ranged from a low of 0.2 mgÁL–1 for for switchgrass to 125.9 mgÁL–1 for cotton gin trash biochar than all other the mixed hardwoods to 70.3 mgÁL–1 the mixed hardwoods biochar (Table biochar products. The Cu, Fe, and for the poultry litter (Table 3). Except 1). In all cases except for the switch Mo concentration did not differ be- for poultry litter and cotton gin trash, + grass and rice hulls, the P concentra- tween the poultry litter feed stock and the NH4 concentration of the result- tion was higher in the resulting bio- the resulting poultry litter biochar. ing biochar products was not differ- char product than in their respective However, the poultry litter biochar ent from their respective feedstocks. feedstocks. had higher Mn, Na, and Zn, and For poultry litter and cotton gin The K concentration of the feed- lower B than its feedstock. All of the trash, the resulting biochar products –1 + stocks ranged from 784 mgÁL for other biochar products except pine had lower NH4 concentrations than
18 • February 2017 27(1) Table 1. Total macroelement concentration from various agriculture byproduct feedstocks and their resulting biochar products. Component Statusz N (% wt/wt)y P (mgÁLL1)y K (mgÁLL1) Ca (mgÁLL1) Mg (mgÁLL1) S (% wt/wt) Poultry litter Feedstock 2.70 36.74 17,740 15,226 4,237 0.37 Poultry litter Biochar 3.57 51.08 18,391 25,203 4,586 0.56 Mixed hardwoods Feedstock 0.18 41.72 924 874 190 0.03 Mixed hardwoods Biochar 0.71 125.93 1,985 2,091 457 0.05 Miscanthus Feedstock 0.63 5.27 7,505 2,971 816 0.05 Miscanthus Biochar 1.09 9.01 17,007 6,631 1,844 0.05 Cotton gin trash Feedstock 0.99 21.70 17,546 6,747 1,884 0.09 Cotton gin trash Biochar 1.37 31.45 13,778 12,079 2,667 0.06 Switchgrass Feedstock 0.43 2.64 1,413 2,716 836 0.06 Switchgrass Biochar 0.86 4.49 2,171 6,743 2,041 0.04 Rice hull Feedstock 0.39 4.21 2,270 1,054 228 0.01 Rice hull Biochar 0.46 5.32 2,849 2,078 340 0.02 Pine shavings Feedstock 0.14 2.64 784 1,127 341 0.00 Pine shavings Biochar 0.55 9.56 3,256 4,780 681 0.02 Significance *** *** *** *** *** *** LSD (a = 0.05)x 0.11 3.60 802 1,186 175 0.08 zFeedstocks ground to particle sizes of 10 to 20 mm (0.39 to 0.79 inch) in diameter. Biochar was produced in 1-gal (3.8 L) cylindrical metal containers at 400 C (752.0 F) with a residence time of 2 h. yPercent was on a dry weight basis and mgÁL–1 was determined using 0.5 mg (1.76 · 10–5 oz) of dry mass per 10 mL (0.34 fl oz) of Mehlich 3 extractant solution; N = nitrogen, P = phosphorus, K = potassium, Ca = calcium, Mg = magnesium, S = sulfur; 1 mgÁL–1 = 1 ppm. x Significant differences among means within columns determined using least significant difference (LSD) mean separation test. ***Significant at P > F of 0.001.
Table 2. Total microelement concentration from various agriculture byproduct feedstocks and their resulting biochar products. Cu Fe Mn Mo Na Zn Component Statusz B (mgÁLL1)y (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) Poultry litter Feedstock 928.6x 419.24 603.67 330.53 2.61 4,822 403.3 Poultry litter Biochar 889.2 415.35 621.72 412.7 2.74 6,966 552.4 Mixed hardwoods Feedstock 147.4 5.47 21.20 12.6 0.09 124 7.57 Mixed hardwoods Biochar 684.3 3.34 45.84 36.6 0.03 154 6.34 Miscanthus Feedstock 66.3 13.10 55.54 44.6 0.56 100 15.15 Miscanthus Biochar 55.5 9.14 86.25 101.9 1.58 108 28.89 Cotton gin trash Feedstock 235.8 5.10 222.78 26.2 0.37 207 10.76 Cotton gin trash Biochar 961.7 15.61 743.11 61.9 0.03 572 25.16 Switchgrass Feedstock 93.9 7.30 71.57 27.9 0.09 129 6.51 Switchgrass Biochar 115.6 4.52 112.12 66.9 0.17 222 12.12 Rice hull Feedstock 182.8 40.47 51.93 127.1 0.26 59 9.29 Rice hull Biochar 147.9 23.15 106.75 240.9 0.32 70 20.32 Pine shavings Feedstock 53.4 3.25 41.78 159.9 0.02 46 11.40 Pine shavings Biochar 107.7 14.63 201.36 88.5 0.00 84 19.96 Significance *** *** *** *** *** *** *** LSD (a = 0.05)x 28.56 18.62 78.96 16.36 0.17 528 24.7 zFeedstocks ground to particle sizes of 10 to 20 mm (0.39 to 0.79 inch) in diameter. Biochar was produced in 1-gal (3.8 L) cylindrical metal containers at 400 C (752.0 F) with a residence time of 2 h. yConcentration was determined using 0.5 mg (1.76 · 10–5 oz) of dry mass per 10 mL (0.34 fl oz) of Mehlich 3 extractant solution; B = boron, Cu = copper, Fe = iron, Mn = manganese, Mo = molybdenum, Na = sodium, Zn = zinc; 1 mgÁL–1 = 1 ppm. x Significant differences among means within columns determined using least significant difference (LSD) mean separation test. ***Significant at P > F of 0.001. their feedstocks. Except for poultry mixed hardwoods to 126 mgÁL–1 for highest P of all the biochar products. – litter, the NO3 ranged from 0.1 to the poultry litter (Table 3). The P There were no other differences in the 0.7 mgÁL–1 in the feedstocks (Table concentration in the biochar made P concentrations between the biochar 3). The poultry litter feedstock con- from poultry litter and pine shavings products and their respective feed- –1 – tained 16.2 mgÁL NO3 . There was was higher than the P concentration stocks. The K of the feedstocks – –1 no difference in NO3 concentrations in the respective feedstocks. In con- ranged from a low of 23 mgÁL for between the feedstocks and their trast, the P in the biochar made from the mixed hardwoods to 4902 mgÁL–1 resulting biochar products. miscanthus was lower than the P in for the poultry litter (Table 3). The K The P of the feedstocks ranged the miscanthus feedstock. The bio- concentration in the biochar made from a low of 0.3 mgÁL–1 for the char made from poultry litter had the from poultry litter was higher than
• February 2017 27(1) 19 RESEARCH REPORTS
Table 3. The pH, electrical conductivity (EC), cation-exchange-capacity (CEC), and water-extractable primary macroelement concentration from various agriculture byproduct feedstocks and their resulting biochar products. D L EC CEC NH4 NO3 Component Statusz pH (dSÁmL1)y (meq/g)y (mgÁLL1)y (mgÁLL1) P (mgÁLL1) K (mgÁLL1) Poultry litter Feedstock 8.7 33.7x 13.2x 70.3x 16.2 126 4,902 Poultry litter Biochar 6.9 30.3 19.0 0.0 16.4 373 5,684 Mixed hardwoods Feedstock 5.3 0.1 0.08 0.2 0.1 0.3 23 Mixed hardwoods Biochar 5.9 0.1 0.09 0.0 0.0 1.2 17 Miscanthus Feedstock 5.4 2.2 1.87 17.6 0.5 67.4 375 Miscanthus Biochar 9.3 1.7 1.09 0.5 0.1 4.4 379 Cotton gin trash Feedstock 5.6 6.0 3.39 74.1 0.7 71.6 939 Cotton gin trash Biochar 7.0 4.7 2.68 20.5 0.8 55.6 763 Switchgrass Feedstock 5.6 0.6 0.54 25.4 0.3 18.3 76 Switchgrass Biochar 7.6 0.2 0.18 0.1 0.1 3.8 25 Rice hull Feedstock 6.0 0.7 0.56 17.3 0.1 33.5 194 Rice hull Biochar 7.2 0.2 0.20 0.3 0.1 6.8 54 Pine shavings Feedstock 4.6 0.3 0.28 0.8 0.1 8.4 33 Pine shavings Biochar 4.6 0.9 0.91 12.2 0.2 60.6 228 Significance *** *** *** *** *** *** *** LSD (a = 0.05)x 0.2 2.5 1.1 30.3 7.8 42.4 343.5 zFeedstocks ground to particle sizes of 10 to 20 mm (0.39 to 0.79 inch) in diameter. Biochar was produced in 1-gal (3.8 L) cylindrical metal containers at 400 C (752.0 F) with a residence time of 2 h. Values determined using a 1:1.5-deionized water saturated media extract method. y + – –1 –1 –1 NH4 = ammonium, NO3 = nitrate, P = phosphorus, K = potassium; 1 dSÁm = 1 mmho/cm, 1 meq/g = 1 molÁkg ,1mgÁL = 1 ppm. x Significant differences among means within columns determined using least significant difference (LSD) mean separation test. ***Significant at P > F of 0.001. the K concentration in the poultry hardwoods to 6005 mgÁL–1 for the from poultry litter had lower concen- litter feedstock, and the poultry litter poultry litter biochar (Table 4). The trations of Cu, Fe, MN, and Mo than 2– biochar had the highest K of the Ca and SO4 in the poultry litter the resulting poultry litter biochar. In biochar products. There were no biochar were higher than the poultry contrast, the poultry litter biochar had other differences in the K concentra- litter feedstock. There were no other higher Na and Zn concentrations that 2– tions of the biochar products and differences in the Ca, Mg, and SO4 the poultry litter feedstock. their respective feedstocks. concentrations of the biochar prod- The Ca of the feedstocks ranged ucts and their respective feedstocks. Discussion from a low of 3.1 mgÁL–1 for the The highest B concentrations Total mineral element concen- mixed hardwoods to 111.4 mgÁL–1 occurred in the poultry litter for both tration varied widely among both the for the miscanthus (Table 4). The the feedstocks and resulting biochar biochar products and their respective Ca in the biochar products ranged products (Table 5). The B concentra- feedstocks. Other researchers have from 7.1 mgÁL–1 for rice hulls to tion was lower in the biochar made also reported wide variations in min- 339.7 mgÁL–1 for the poultry litter from poultry litter and mixed hard- eral element concentration among biochar. The Ca concentration in the woods than in their respective feed- different biochar products made from biochar made from poultry litter was stocks. However, for all other different feedstocks (Bates, 2010; higher than the Ca concentration in materials the feedstocks and resulting Dumroese et al., 2011). Most re- the poultry litter feedstock. In con- biochar products had similar B con- searchers have reported that total trast, the Ca in the biochar made from centrations. The highest Cl concen- mineral nutrients in biochar products miscanthus was lower than the mis- trations occurred in the poultry litter were higher than in the feedstock canthus feedstock. There were no for both the feedstocks and resulting used to produce the biochar products other differences in the Ca concen- biochar products (Table 5). The Cl (Judd, 2016). This has typically been trations of the biochar products and concentration was higher in the bio- explained in that the process of mak- their respective feedstocks. The Mg of char made from poultry litter than the ing the biochar reduced the product the feedstocks ranged from 1.2 poultry litter feedstock. In contrast, weight and thus the remaining mineral mgÁL–1 for the mixed hardwoods to the biochar made from cotton gin elements made a higher proportion by 64.5 mgÁL–1 for cotton gin trash trash had a lower Cl concentration weight of the resulting biochar prod- (Table 4). The Mg of the biochar than the original cotton gin trash ucts. In most cases, the results of this products ranged from 1.0 mgÁL–1 for feedstock. For all other materials the research were in agreement with these the mixed hardwoods to 321 mgÁL–1 feedstocks and resulting biochar reports. The notable exceptions were for the poultry litter biochar (Table products had similar Cl concentra- that the P in biochar decreased as 2– 4). The SO4 of the feedstocks tions. The poultry litter feedstock compared with the feedstock for cot- ranged from 2 mgÁL–1 for the mixed and the resulting poultry litter bio- ton gin trash and the B decreased in hardwoods and the pine shavings to char had higher Cu, Fe, Mn, Mo, Na, the biochar as compared with the 3632 mgÁL–1 for poultry litter. The and Zn concentrations than any of the feedstock for the poultry litter. Ob- 2– SO4 of the biochar products ranged other feedstocks or resulting biochar servations of high product variability from 3 mgÁL–1 for the mixed products (Table 5). The biochar made and nutrient data fluctuations in
20 • February 2017 27(1) + biochars presented in this work fur- NH4 concentrations of the biochar were unchanged between a feedstock ther illustrate the need for current and products were unchanged or de- and its resulting biochar product. The future researchers and potential man- creased as compared with their re- water-extractable concentrations of ufacturers (product developers) to spective feedstocks. This finding was all other macro- and micronutrients pay caution in the reliability of differ- consistent with previous research increased, decreased, or remained un- ent biochars and the expected or reports and was attributed to the changed depending on the feedstock. + anticipated results of their use. volatilization of NH4 in the Therefore, the concentration of min- When evaluating the water ex- manufacturing process. In contrast eral elements immediately available + – tractable nutrient concentration, the to NH4 , the NO3 concentrations for plant uptake (water extractable) varied widely based on the feed- stock used to make the biochar Table 4. The water-extractable secondary macroelement concentrations from and these findings concurred with various agriculture byproduct feedstocks and their resulting biochar products. those reported by other researchers y Á L1 z Á L1 2L Á L1 Component Status Ca (mg L ) Mg (mg L )SO4 (mg L ) (Altland and Locke, 2012, 2014; x Bates, 2010). Poultry litter Feedstock 85.3 7.6 3,632 With the exception of P, the total Poultry litter Biochar 339.7 321.0 6,005 concentration of all macro- and Mixed hardwoods Feedstock 3.1 1.2 2 micronutrients were higher in the Mixed hardwoods Biochar 7.9 1.0 3 total elemental analysis than the water- Miscanthus Feedstock 111.4 41.9 8 extractable analysis. For the poultry Miscanthus Biochar 14.5 5.9 33 litter and cotton gin trash biochar Cotton gin trash Feedstock 89.2 64.5 335 products, the total P was not higher Cotton gin trash Biochar 69.3 45.1 228 than the water-extractable P. Both Switchgrass Feedstock 27.9 24.3 9 the poultry litter and cotton gin trash Switchgrass Biochar 16.2 4.4 4 were feedstocks that were highly vari- Rice hull Feedstock 3.8 5.6 16 able and composed of several non- Rice hull Biochar 7.1 3.3 4 uniform components (poultry feces, Pine shavings Feedstock 23.0 9.5 2 rice hulls, cotton plant stems, and Pine shavings Biochar 16.6 29.6 4 burrs). The variability in the feedstock Significance *** *** *** a x could have resulted in nonuniform LSD ( = 0.05) 34.6 36.2 828 biochar products and thus resulted zFeedstocks ground to particle sizes of 10 to 20 mm (0.39 to 0.79 inch) in diameter. Biochar was produced in 1-gal (3.8 L) cylindrical metal containers at 400 C (752.0 F) with a residence time of 2 h. Values determined using in the differences in P concentrations a 1:1.5-deionized water saturated media extract method. observed for these two products. y 2– –1 Ca = calcium, Mg = magnesium. SO4 = sulfate; 1 mgÁL = 1 ppm. x Poultry litter biochar had higher Significant differences among means within columns determined using least significant difference (LSD) mean separation test. concentrations of mineral elements ***Significant at P > F of 0.001. than all of the other types of biochar
Table 5. The water-extractable microelement concentration from various agriculture byproduct feedstocks and their resulting biochar products. Cl Cu Fe Mn Mo Na Zn Component Statusz B (mgÁLL1)y (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) (mgÁLL1) Poultry litter Feedstock 5.1x 2,585 54.7 23.1 2.3 2.6 1,426 19.5 Poultry litter Biochar 4.4 3,294 19.3 4.4 1.8 0.8 2,389 3.1 Mixed hardwoods Feedstock 1.9 5.2 0.0 0.0 0.0 0.0 3.1 0.0 Mixed hardwoods Biochar 0.9 4.6 0.0 0.0 0.0 0.0 2.6 0.0 Miscanthus Feedstock 0.2 171 0.0 0.1 2.0 0.0 2.0 0.4 Miscanthus Biochar 0.0 250 0.0 0.0 0.0 0.0 2.6 0.0 Cotton gin trash Feedstock 0.5 593 0.1 0.2 0.2 0.0 14.8 0.5 Cotton gin trash Biochar 0.4 326 0.0 0.2 0.1 0.0 35.6 0.1 Switchgrass Feedstock 0.0 37 0.0 0.1 0.4 0.0 8.7 0.0 Switchgrass Biochar 0.0 7.1 0.0 0.0 0.0 0.0 3.6 0.0 Rice hull Feedstock 0.2 65.4 0.1 0.1 3.3 0.0 5.5 0.1 Rice hull Biochar 0.0 10.7 0.0 0.1 2.3 0.0 3.6 0.0 Pine shavings Feedstock 0.0 4.5 0.0 0.0 4.4 0.0 2.4 0.2 Pine shavings Biochar 0.3 11.5 0.0 0.2 2.4 0.0 5.0 0.3 Significance *** *** *** *** *** *** *** *** LSD (a = 0.05)x 0.4 169 9.0 3.5 0.5 0.5 221 1.0 zFeedstocks ground to particle sizes of 10 to 20 mm in diameter. Biochar was produced in 1-gal (3.8 L) cylindrical metal containers at 400 C (752.0 F) with a residence time of 2 h. Values determined using a 1:1.5-deionized water saturated media extract method. yB = boron, Cl = chloride, Cu = copper, Fe = iron, Mn = manganese, Mo = molybdenum, Na = sodium, Zn = zinc; 1 mgÁL–1 = 1 ppm. x Significant differences among means within columns determined using least significant difference (LSD) mean separation test. ***Significant at P > F of 0.001.
• February 2017 27(1) 21 RESEARCH REPORTS in this study. In fact, poultry litter high EC in poultry litter biochar has the specific nature of the feedstock biochar contained concentrations of been reported in other findings (Song used in its production. The high P, K, Cu, Fe, and Zn that could be and Guo, 2012). The cotton gin trash concentration variability will also re- high enough to cause phytotoxicity biochar also had a higher than rec- quire the end users such as green- or negatively impact crops being ommended EC, but it was at a con- house and nursery crop growers to grown using the product. These con- centration that if it were blended with have knowledge of their suppliers’ centrations of mineral elements other components, the EC could be feedstocks and specific production would require that poultry litter bio- brought to a desirable concentration. processes and routinely test the bio- char be used in small amounts in All other biochar products had EC char products before use. a root substrate. The other types of concentrations within recommended biochar products had varying concen- ranges for root substrates. trations of water-extractable mineral Based on these results, poultry Literature cited elements. In these cases, the concen- litter-based biochar could be prob- trations of P, and K in particular lematic due to their very high nutrient Altland, J.E. 2014. Amending substrates with biochar. Greenhouse Prod. News would potentially be too high for concentration and resulting EC. 2014(Aug):14–21. most greenhouse crops, but if Other researchers have reported sim- blended with other components, the ilar results with manure-based bio- Altland, J.E. and J.C. Locke. 2012. Bio- concentrations of mineral nutrients char products (Hass et al., 2012; char affects macronutrient leaching from would be within recommended Song and Guo, 2012). This could a soilless substrate. HortScience 47:1136– ranges for most greenhouse crops. introduce management issues and 1140. One point to mention regarding the limit the use of manure-based biochar Bates, A. 2010. The biochar solution: high nutrient concentrations of sub- products. The high carbon feedstock carbon farming and climate change. New strate components (biochars in this biochar products had much lower Society Publ., Gabriola Island, BC, case) at 100% is that those nutrient nutrient concentrations and if Canada. amounts may or may not suggest the blended with other components Bi, G., W.B. Evans, and G.B. Fain. 2009. concentration that would be plant- could likely be useable as substrate Use of pulp mill ash as a substrate com- available once amended in a substrate components easier than some of the ponent for greenhouse production of as a component percentage. Proper- materials with very high chemical marigold. HortScience 44:183–187. ties (physical or chemical) of compo- properties (EC, pH, etc.). However, Carter, S., S. Shackley, S. Sohi, T.B. Suy, nents do not always yield summation even within this group of biochars and S. Haefele. 2013. The impact of results in a blended substrate. This is made from agricultural byproducts biochar application on soil properties a key point to be aware of regarding common in the southern United and plant growth of pot grown lettuce the effect of substrate components States, many of the chemical proper- (Lactuca sativa) and cabbage (Brassica and amendments before and after ties such as EC, pH, and the primary chinensis). Agronomy 3:404–418. blending/mixing. and secondary macronutrients varied Dumroese, R.K., J. Heiskanen, K. Previous researchers have considerably and would need to be Englund, and A. Tervahauta. 2011. Pel- reported that the feedstock had a sig- considered when designing and man- leted biochar: Chemical and physical nificant impact of the pH of the aging a root substrate. properties show potential use as a sub- resulting biochar product (Fornes Researchers have noted that it is strate in container nurseries. Biomass et al., 2015; Hass et al., 2012; inappropriate to refer to composts as Bioenergy 35:2018–2027. Mukherjee et al., 2011; Nemati single entities and to make recom- Evans, W.B., G. Bi, and G.B. Fain. 2011. et al., 2015; Spokas et al., 2012). In mendations that composts can be Addition of pulp mill ash raises pH, fact, the pH of biochar products in used in substrates is inappropriate modifies physical properties, and alters this research ranged from 4.6 to 9.3. due to the high degree of variability young tomato plant growth and mineral This wide range in pH values could that occurs in composts depending nutrition in a peat-based substrate. J. Plant require growers to make adjustments upon the compost feedstock and the Nutr. 34:1894–1903. in their substrate components or in composting process (Rosen et al., Fornes, F., R.M. Belda, and A. Lidon. their limestone amendment program 1993; Sterrett, 2000; Taylor and 2015. Analysis of two biochars and one to compensate for the differences in Jackson, 2014). The results of this hydrochar from different feedstock: Focus pH and the effect that the different research emphasize that the same set on environmental, nutritional and biochar products would have on the issue occurs with biochar products. horticultural considerations. J. Clean. Prod. root substrates. It is not known Even when made using the same pro- 86:40–48. (reported in the literature) what the cess, the biochar products had very Graber, E.R., Y.M. Harel, M. Kolton, effect of biochar is on the pH of different chemical properties depend- E.Cytryn,A.Silber,D.R.David,L. horticultural substrates when amended ing on the feedstock. Therefore, bio- Tsechansky, M. Borenshtein, and Y. Elad. as a substrate component. char should not be referred to as 2010. Biochar impact on development Similar to the mineral element a single entity and, blanket recom- and productivity of pepper and tomato concentration, the EC of the biochar mendations for the use and perfor- grown in fertigated soilless media. Plant products varied widely. The EC was mance of biochar products as root Soil 337:481–496. very high for poultry litter biochar, substrates components cannot be Hass, A., J.M. Gonzales, I.M. Lima, H. thus making it potentially unsuitable made without specific information W. Godwin, J.J. Halvorson, and D.G. for use in a root substrate unless used regarding all variables related not only Boyer. 2012. Chicken manure biochar in only very limited amounts. The to the methods of production but also as liming and nutrient source for acid
22 • February 2017 27(1) Appalachian soil. J. Environ. Qual. 41:1096– Mukherjee, A., A.R. Zimmerman, and W. Song, W. and M. Guo. 2012. Quality 1106. Harris. 2011. Surface chemistry variations variations of poultry litter biochar among a series of laboratory-produced generated at different pyrolysis tempera- Headlee, W.L., C.E. Brewer, and R.B. biochars. Geoderma 163:247–255. tures. J. Anal. Appl. Pyrolysis 94:138–145. Hall. 2014. Biochar as a substitute for vermiculite in potting mix for hybrid Munter, R.S. and R.A. Grande. 1981. Spokas, K.A., K.B. Cantrell, J.M. Novak, popular. BioEnergy Res. 7:120–131. Plant tissue and soil extract analysis by D.W. Archer, J.A. Ippolito, H.P. Collins, ICP-atomic emission spectrometry, p. A.A. Boateng, I.M. Lima, M.C. Lamb, Holcomb, E.J. and P.N. Walker. 1995. 653–672. In: R.M. Barnes (ed.). De- A.J. McAloon, R.D. Lentz, and K.A. Chrysanthemum and poinsettia growth in velopments in atomic plasma spec- Nichols. 2012. Biochar: A synthesis of coal gasification slag amended media. trochemical analysis. Heyden and Sons, its agronomic impact beyond carbon se- Commun. Soil Sci. Anal. 26:2497–2510. London, UK. questration. J. Environ. Qual. 41:973– 989. Ippolito, J.A., D.A. Laird, and W.J. Neal, J.C. and D.F. Wagner. 1983. Busscher. 2012. Environmental benefits of Physical and chemical properties of coal Sterrett, S.B. 2000. Composts as horti- biochar. J. Environ. Qual. 41:967–972. cinders as a container media component. cultural substrates for vegetable transplant Jones, J.B., Jr. 1977. Elemental analysis HortScience 18:693–695. production, p. 227–240. In: P.J. Stofella and B.A. Kahn (eds.). Compost utiliza- of soil extracts and plant tissue ash by Nemati, M.R., F. Simard, J.P. Fortin, and plasma emission spectroscopy. Commun. tion in horticultural cropping systems. J. Beaudoin. 2015. Potential use of bio- CRC Press, Boca Raton, FL. Soil Sci. Plant Anal. 8:345–365. char in growing media. 4 Oct. 2016. Judd, L.A. 2016. Physical and chemical
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