Research Article pubs.acs.org/journal/ascecg
Hydrothermal Carbonization (HTC) and Pelletization of Two Arid Land Plants Bagasse for Energy Densification M. Toufiq Reza,*,† Xiaokun Yang,† Charles J. Coronella,† Hongfei Lin,† Upul Hathwaik,‡ David Shintani,§ Bishnu P. Neupane,∥ and Glenn C. Miller∥ †
Department of Chemical and Materials Engineering, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States ‡ Bioproducts Research Unit, Western Regional Research Center, USDA-ARS, 800 Buchanan Street, Albany, California 94710, United States § Department of Molecular Biosciences, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States ∥ Department of Natural Resource and Environmental Science, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States S Supporting Information *
ABSTRACT: In this study, bagasse from two arid land plants, grindelia and rabbitbrush, were hydrothermally carbonized (HTC) along with their raw biomass at 200−260 °C for 5 min. Prior to HTC, biocrude was extracted from grindelia (Grindelia squarrosa), whereas rubber was extracted from rabbitbrush (Ericameria nauseosa). Solid hydrochars and HTC process liquids of extracted feedstocks were characterized by ultimate, proximate, fiber, FTIR, higher heating value (HHV), and GC−MS analyses and the results were compared with their corresponding unextracted conditions. Hydrochars were pelletized in a single-press pelletizer and mass and energy densities of the pellets were measured. From the proximate, ultimate, FTIR, and fiber analyses, the bagasse show similar properties of the raw biomass, although the HHV was slightly increased with crude extraction from grindelia and decreased with rubber extraction from rabbitbrush. With the increase of HTC temperature, solid mass yield was decreased up to 44% for grindelia bagasse and 57% for rabbitbrush bagasse. HHV increases for all the feedstocks up to about 26 MJ kg−1, regardless of biomass type, when treated at 260 °C. HTC process liquid becomes acidic in the presence of short-chain organic acids with HTC temperature. KEYWORDS: Hydrothermal carbonization, Gumweed, Rabbitbrush, Bagasse, Hydrochar, Ultimate analysis
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INTRODUCTION
Ericameria nauseosa (rabbitbrush) possesses a number of characteristics that makes it well suited for Nevada and the Great Basin Region. Rabbitbrush produces high quality rubber (MW > 500 000) with yields ranging from 1.5% to 6.5% of shoot dry weight.7 This plant species was being considered as an emergency source of natural rubber during World War II with wild stands estimated to yield greater than 300 million tons of rubber.8 Several studies have been performed to measure the natural variation in rubber content among wild stands of rabbitbrush throughout the Great Basin Region.9,10 These surveys showed that the rubber content varied depending on the specific subspecies of rabbitbrush sampled and on the specific habitat in which the sample was grown. These initial studies suggested that among the different E. nauseosa subspecies, the consimilis variety, which grows prolifically in Northern and Western Nevada, is among the top rubber producers.10 Samples
Grindelia (Grindelia squarrosa) and rabbitbrush (Ericameria nauseosa) are prevalent in the intermountain Western United States on lands that are not generally suitable for food and feed crops, and both plants have potential as resources for biofuel or higher value industrial and consumer products. The use of grindelia, also known as gumweed, as a source of biofuel, has not been extensively studied previously, although it was mentioned 20 years ago as a potential substitute for wood rosin.1 The use of a related specie, Grindelia camporum, received attention in the early 1980s in Arizona for the potential to produce biocrude and chemical feedstocks.2−4 In a previous study, Lemaire (1981) examined several wild plants in Nevada for “biocrude” production, and found that gumweed (Grindelia squarrosa) was the most productive of the common Nevada plants.5 Gumweed contains 12−14% extractable hydrocarbons, of which 55−60% is grindelia acid. Grindelic acid is a 20 carbon carboxylic acid that can potentially be used as a substitute for abiotic acid (rosin) or catalytically converted to a lower molecular weight fuel.6 © XXXX American Chemical Society
Received: September 28, 2015 Revised: December 1, 2015
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DOI: 10.1021/acssuschemeng.5b01176 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
Research Article
ACS Sustainable Chemistry & Engineering
sticky white buds had begun to turn into yellow flowers. The whole plant was cut and allowed to dry in the sun for 4−6 days. It was bundled in the field and stored in a dry shaded area, followed by milling the dried plants in a hammer mill (Colorado Mill Equipment, Canon City, CO) through a 1/8″ screen. The milled plant material was then extracted in a Soxhlet extractor for 4 h in refluxing acetone. The remaining plant material, in this study CEGB, was dried to remove residual acetone. Wild Ericameria nauseosa plants were collected in 2012 from Austin, Nevada. Plants were cut at the ground level and stored on wet ice during harvesting and transported on the same day to University of Nevada, Reno for further experiments. Plant materials that were stored at 4 °C were prepared for the Soxhlet extractor with a commercial grade wood chipper (CH3 11HP, GXI international, Clayton, NC) and were further ground by a hammer mill (AT Ferrell Company Inc., Bluffton, IN). A commercial Soxhlet extractor (Eden Laboratories LLC, Columbus, OH) was used to extract resin and rubber from 3 kg of finely ground material with 25 L of pentane/acetone azeotrope (79:21) by weight.25 The azeotrope solution was collected, filtered, and concentrated using a BUCHI Rotavapor R-220 (BUCHI Corporation, New Castle, DE) rotary evaporator according to manufacturer’s instructions and the rubber was precipitated using 1 volume of acetone.26 The RERB was removed from the Soxhlet extractor and dried in a fume hood and stored until further experiments. The feedstock’s size was reduced to 5 ± 3 mm by a commercial food grinder. Moisture content of the feedstock was 7 ± 2 wt %. The biomass was dried at 105 °C in an oven overnight and stored in a zip-lock bag prior to hydrothermal carbonization. Hydrothermal Carbonization (HTC). In the HTC experiment, around 8 g of dry feedstock was weighed and transferred into a 100 mL Parr reactor (reactor series 4524, Moline, IL). Around 40 mL of deionized water was weighed (maintain 1:5 biomass-to-water-ratio) and poured into the reactor. HTC at three different temperatures (200, 230, and 260 °C) was carried out in this study, and the reaction time was only 5 min. The reaction temperature was controlled by a PID temperature controller (4520 series, Moline, IL) with accuracy around ±2 K. The reactor pressure was not controlled but rather monitored during HTC reactions, and generally corresponded quite closely with vapor pressure of pure water. At the end of the reaction period, the heater was turned off and the reactor cooled down rapidly in an ice−water bath. It took 5−10 min to cool down from 260 to 25 °C (about 1 min from 260 to 180 °C), and the pressure droped from 4 to 4.5 to 0.2−0.5 MPa. The gaseous product was vented in the hood; hydrochar, the solid product of HTC, was filtered using vacuum filtration with Whatman 3 filter paper for 5 min. The process liquid was stored in a 4 °C refrigerator for GC−MS analysis. Solid hydrochar was dried in a heating oven at 105 °C overnight. Dried hydrochar was placed into a zip-lock bag and stored for further physicochemical analyses. Each individual experiment was carried out at least three times, and the solid products and process liquors were examined individually. The mass balance of HTC reactions was performed following a previous study.27 Hydrochars were named as H-T-x, where H stands for hydrochar, T for the HTC temperature, and x for feedstock type, respectively. Characterization of Solid Hydrochar. The elemental composition of the oil product were assessed using a Euro EA3000 CHNS-O analyzer (Eurovector) in order to identify the carbon, hydrogen, nitrogen, sulfur, and oxygen contents. Ash was determined by treating dry samples at 550 °C for 5 h according to ASTM D-1205 method. A PerkinElmer Spectrum 2000 ATR-FTIR (Waltham, MA) with midand far-IR capabilities was used on the raw and hydrothermally treated biomass. IR spectra of all solid samples were recorded at 30 °C using ATR-FTIR. All samples were dried and milled into fine powder for homogenization prior to FTIR. Only 5−10 mg of dry powdered sample was placed in the FTIR for this analysis and pressed against the instrument’s diamond surface with its metal rod. All spectra were obtained using 64 scans for the background (air) and 64 scans for the samples, which were scanned from 500 to 4000 cm−1. A modified van-Soest method using the ANKOM A200 filter bag technique (FBT) was used to determine the contents of hemicellulose, cellulose, pseudolignin, and aqueous soluble compounds in solid samples.28 The details of the experimental procedure can be found elsewhere.29
of E. nauseosa ssp. consimilis collected from alkali flats located near Gerlach, Nevada had rubber contents ranging from 4.71% to 6.57%.10 Current practice for extraction of resins and rubbers from both grindelia and rabbitbrush is the use of volatile organic solvents in a Soxhlet extractor or other large volume extraction systems. Typical solvents are acetone, methanol, and/or low polarity solvents such as hexane. This process is effective, but leaves behind a large amount of bagasse. Cultivated gumweed contains 12−14% extractable hydrocarbons, whereas rabbitbrush contains 1.5−6.5% extractable rubber on a dry plant weight basis, which means about 86−98% of the plant materials remains in the solid residue after solvent extraction. To enable commercial development of gumweed-based fuel industry, and rabbitbrush-based rubber industry, suitable use of enormous amount of solid residue (bagasse) must be identified. The residual biomass residue, here referred as crude extracted gumweed bagasse (CEGB) and rubber extracted rabbitbrush bagasse (RERB) are rich in fibers such as hemicellulose, cellulose, and lignin, which have significant value. CEGB and RERB usually contaminated during solvent extraction and hence are not suitable for feed/food consumption by animals/humans. Direct combustion of CEGB and RERB is inefficient, as the residues are often found as “wet” form and require more energy to drive the residual moisture away. Hydrothermal carbonization (HTC) is a thermochemical pretreatment process where biomass is treated with hot compressed subcritical water (200−260 °C) for 5 min−8 h.11−13 HTC is a unique process that takes any wet waste biomass and converts into a homogenized, friable, hydrophobic, carbonrich, stable, high nutrient featured HTC biochar with a substantial surface area.14−16 Subcritical water, the temperature between 180 and 280 °C, has maximum ionic product, which means water behaves as a catalyst during HTC.17 Hydrolysis is the first step of the HTC, where extractive compound, hemicellulose, and cellulose are degraded into monomers, aldehydes, and intermediates primarily depending on HTC temperature.18 Reactive intermediate species promote other chemical reactions such as decarboxylation, dehydration, aromatization, and condensation−polymerization in the presence of subcritical water. As a result of these reactions, many intermediates (re)-polymerize into solids and thus enhance the solid−solid reaction.18 Recent studies mentioned that HTC is a promising technology for converting biomass into lignite-type coal,13,19 into a soil amendment,20 into a sorbent,21 into nanostructure carbon material,22 into a carbon catalyst,23 or into carbon material for increasing fuel cell efficiency.24 The focus of this work was to demonstrate the potential of producing a valuable, hydrophobic, energy-dense solid hydrochar from CEGB and RERB through hydrothermal carbonization. HTC was applied to both CEGB and RERB along with their unextracted feedstocks. The solid product was evaluated to determine its energy content as well as the fate of ash constituents and compared with unextracted ones. Pelletization was evaluated for the raw feedstocks and corresponding hydrochars for further energy densification. In addition, the aqueous products of HTC treatment were evaluated through multiple laboratory analyses to identify high-value chemicals and chemical changes during HTC.
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EXPERIMENTAL SECTION
Materials. Grindelia was harvested from the test field at the Agriculture Station of the University of Nevada, Reno in 2014, when the B
DOI: 10.1021/acssuschemeng.5b01176 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
Research Article
ACS Sustainable Chemistry & Engineering Table 1. Mass Balance of HTC of Grindelia, Rabbitbrush, CEGB, and RERB input feedstock grindelia
CEGB
rabbitbrush
RERB
output
HTC temperature (°C)
biomass
water
hydrochar
liquid
nonvolatile residue
gas (estimate)
200 230 260 200 230 260 200 230 260 200 230 260
1 1 1 1 1 1 1 1 1 1 1 1
5.70 ± 0.50 5.46 ± 0.06 5.50 ± 0.05 5.50 ± 0.03 5.56 ± 0.06 5.49 ± 0.02 5.04 ± 0.03 5.06 ± 0.07 5.11 ± 0.08 5.00 ± 0.01 5.05 ± 0.06 5.05 ± 0.04
0.59 ± 0.04 0.57 ± 0.01 0.50 ± 0.01 0.6 ± 0.02 0.51 ± 0.06 0.44 ± 0.02 0.79 ± 0.05 0.70 ± 0.01 0.62 ± 0.09 0.69 ± 0.01 0.62 ± 0.01 0.57 ± 0.02
5.66 ± 0.48 4.78 ± 0.56 5.33 ± 0.09 5.40 ± 0.05 5.56 ± 0.07 5.36 ± 0.18 4.67 ± 0.10 4.41 ± 0.50 5.17 ± 0.07 4.75 ± 0.20 4.71 ± 0.15 4.83 ± 0.15
0.25 ± 0.03 0.18 ± 0.03 0.19 ± 0.01 0.26 ± 0.02 0.19 ± 0.02 0.25 ± 0.31 0.20 ± 0.03 0.11 ± 0.01 0.10 ± 0.02 0.21 ± 0.03 0.13 ± 0.00 0.13 ± 0.00
0.20 ± 0.06 0.39 ± 0.14 0.49 ± 0.12 0.25 ± 0.04 0.31 ± 0.01 0.45 ± 0.17 0.23 ± 0.03 0.37 ± 0.08 0.39 ± 0.08 0.35 ± 0.22 0.58 ± 0.21 0.53 ± 0.15
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The higher heating values (HHV) for the untreated biomass and the biochar products were measured in a Parr 1241 adiabatic oxygen bomb calorimeter (Moline, IL) fitted with continuous temperature recording. Around 0.5 g of dried sample was pelletized prior to calorimetry. In this study, HHV values are reported on a dry, ash free basis (daf). Solid samples were analyzed with PerkinElmer TGA-7 thermogravimetric analyzer (Waltham, MA) to determine the volatile matter and fixed carbon content in dry hydrochars. Thermogravimetric analysis was carried out under inert atmosphere using nitrogen flow at a constant rate of 40 mL min−1 to prevent oxidation of samples. Samples were first heated from room temperature to 105 °C at the rate of 10 °C min−1, held 105 °C for 10 min as isothermal step, then increased to 800 °C at the rate of 50 °C min−1 and held for 10 min. Mass evolved at 105 °C is said to be moisture. Mass evolved at temperatures between 105 and 800 °C is considered as volatiles. Mass remaining at the end is fixed carbon and ash. Final content was subtracted by ash (determined separately) to calculate fixed carbon. Pelletization of CEGB and RERB Hydrochars. A bench-top single press pelletizer SPEX 3000 pellet press (Metuchen, NJ) was used for pelletization of hydrochars. The HTC biochar was first exposed to ambient conditions for 3 weeks prior to pelletization to stabilize the moisture content. Approximately 1 g of the pretreated biomass was placed manually into a 13 mm diameter die. A 500 W band heater was used to heat the sample with a controller maintaining the temperature of the sample at about 140 °C. A compressive force of 15 ton was applied. After a holding time of 1 min, the pressure was released gradually by 1 min, and the heater was turned off simultaneously. The pellet was removed from the die and left undisturbed for 2−5 min. It was then stored at room temperature before further analysis. The L:D (length to diameter) ratio of the pellets ranged from 0.6 to 0.75 in this study. Mass and energy densities of the pellets were measured by pellet dimension, weight, and HHV. Characterization of HTC Process Liquid. Qualitative GC/MS analysis was performed for the identification of unknown components in the aqueous phase. The silylation derivitization of the polar components was performed in order to perform qualitative GC/MS analysis and identification of unknown components in the aqueous phase. For a silylation derivatization, 125 μL of liquid was lyophilized overnight in deactivated 1.5 mL vials. To the dried solids was added 100 μL of acetonitrile, and the solution was mixed to allow the solids to dissolve. Then 50 μL of pyridine and 100 μL of BSFTA with TMCS (99:1) were added. The capped vials were placed in a water bath maintained at 65 °C for 2 h to allow complete silylation. After silylation, the samples were cooled, and a 100 μL mixture was taken to be diluted with 1.4 mL of dichloromethane. The sample were injected in an Agilent 6890 series GC/MS instrument equipped with an Agilent DB5-MS column (30 m × 0.25 mm ID, 0.25 μm film thickness) and Agilent 5973 mass selective detector. The column temperature was maintained at 80 °C for 2 min and then ramped at 10 °C/min to 260 °C and held at 260 °C for 2 min.
RESULTS AND DISCUSSION Mass Balance of HTC of Grindelia, Rabbitbrush, CEGB, and RERB. Mass balances of HTC of grindelia, rabbitbrush, and their bagasse are performed according to a previous study.27 Table 1 shows input and output streams in the experimental batch HTC process. All the streams in the Table 1 are normalized to 1 g of raw dry feedstock. The input stream includes raw dry feedstock and water. According to the separation procedure (described in the Experimental Section), the output is divided into four streams: solid hydrochar, nonvolatile residues, liquid, and gases. Hydrochar is that left after drying the filter cake, and nonvolatile residue is that which remains after drying the filtrate, assumed to contain primarily sugars. The mass loss during drying both is the liquid product. According to conservation of mass, the sum of these four products should equal the sum of water and biomass input. In this study, the quantity of gas is determined by balance and not measured directly. From Table 1, it can be found that HTC temperature significantly affects solid hydrochar yield, and decreases with the increase of HTC temperature for all the feedstocks. However, the amount differs for each feedstock. Around 50% of grindelia and 56% of CEGB solid mass were removed during HTC at 260 °C, whereas 38% and 47% of rabbitbrush and RERB were removed for the same HTC condition. At lower HTC temperature (e.g., 200 °C), grindelia and CEGB show lower mass yields than rabbitbrush and RERB. Solid mass yields, especially at lower HTC temperatures, may indicate the possible difference in fiber content among the feedstocks. To extract biocrude from grindelia, whole plant was harvested and treated. Meanwhile, only woody stems were collected and processed for rubber production from rabbitbrush. Thus, the mass yields of HTC for grindelia and CEGB follow similar behaviors as the grassy biomass, whereas rabbitbrush and RERB follow woody biomass behaviors.15,27,29−31 During HTC, lignocellulosic feedstocks hydrolyze into various volatile products, which then removed from solid structure as liquid or gas.18 As a result, a significant mass decrease can be observed. Higher HTC temperature facilitates the hydrolysis as well as further degradation of hydrolysis products, thus the solid mass loss increases with HTC temperature.18 Comparing HTC of bagasse with corresponding whole biomass, bagasse produces less hydrochar at any HTC condition than whole biomass. The reason for the discrepancy can be evaluated from the fiber and FTIR analyses, which will be explained in the later sections. For both grindelia and rabbitbrush and their corresponding bagasse, nonvolatile residues (NVR) contents are the highest for C
DOI: 10.1021/acssuschemeng.5b01176 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
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ACS Sustainable Chemistry & Engineering
Figure 1. IR spectra of (a) grindelia hydrochars, (b) CEGB hydrochars, (c) rabbitbrush hydrochars, and (d) RERB hydrochars. Note: for each figure, top-to-bottom: raw, HTC-200-x, HTC-230-x, and HTC-260-x IR spectra.
HTC 200 °C, consistent with HTC of other lignocellulosic biomass.9.19 In fact, about ∼25% NVR was found for both the grindelia and CEGB, and ∼20% for rabbitbrush and RERB. NVR was decreased for 230 °C for all the feedstocks, but slightly increased at HTC-260. Grindelia and CEGB produce more NVR than rabbitbrush and RERB in any HTC condition. NVR contents of rabbitbrush and RERB are similar to the NVR of HTC woods according to earlier publications.32,33 Production of gas increases with HTC temperature for all feedstocks. In fact, it doubled for HTC-230-grindelia than HTC-200-grindelia and produced even more for HTC-260-grindelia. In the case of CEGB, the gas content increases; however, not as much as raw grindelia. The quantity of liquid products is very similar to the added water to the reactor for grindelia and CEGB but slightly different for rabbitbrush and RERB. There are two main significant reactions associated with water, namely, hydrolysis and dehydration, which occur during HTC. One of them requires water (hydrolysis) and other releases (dehydration) water. In the case of a hydrolysis dominant reaction, an overall decrease of water can be observed. However, a similar liquid output for grindelia and CEGB indicates somewhat similar domination of hydrolysis and dehydration. Meanwhile, a decrease of output liquid was observed for rabbitbrush and RERB, except for HTC260-rabbitbrush. The dominance of hydrolysis over dehydration may be the reason for the net consumption of liquid. It was reported earlier that overall water is consumed for loblolly pine when treated at 200 °C, whereas water is produced at 260 °C and is neutral at 230 °C.18 Rabbitbrush behaves somewhat similar to
the HTC pine; however, RERB seems to consume more liquid than rabbitbrush. Solvents usage during the rubber extraction might affect the structure of rabbitbrush; as a result, more hydrolysis than dehydration occurs in RERB. FTIR and van-Soest Fiber Analysis of Hydrochars. To understand the chemical changes in hydrochar during HTC for various feedstocks, ATR-FTIR and van-Soest fiber analysis were performed for all hydrochar samples along with raw feedstocks. FTIR spectra can be found in Figure 1, and the fiber analysis results are shown in Figure 2. IR spectra of raw grindelia and raw rabbitbrush are very similar to raw CEGB and RERB, respectively. Crude and rubber extraction from grindelia and rabbitbrush have negligible effect on bagasse according to IR spectra. The only visible difference is in the band 850 and 1750 cm−1, corresponding to the aliphatic CH and ketone (CO), respectively, are either disappeared or weaker with crude extraction from grindelia. Meanwhile, RERB shows a few differences at wavenumbers 1240, 1500, and 1650 cm−1, corresponding to alcohol CO, lignin OCH3, and alkenes CC, respectively, which are either stronger or appeared after rubber extraction. Fiber analysis is also in agreement with FTIR spectra, where fiber content of CEGB and RERB are very similar to grindelia and rabbitbrush. Comparing fiber contents of raw biomass, less extractives, more cellulose and more lignin were observed for rabbitbrush than grindelia. Moreover, fiber compositions (hemicellulose, cellulose, lignin, and ash) of raw rabbitbrush are similar to woody biomass,34 whereas grindelia has fiber compositions similar to grassy biomass.29 The findings of fiber analysis support the mass balance results. D
DOI: 10.1021/acssuschemeng.5b01176 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
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ACS Sustainable Chemistry & Engineering
Figure 2. Fiber analysis of hydrochars produced from (a) grindelia and CEGB, and (b) rabbitbrush and RERB.
Table 2. HTC Process Liquid pH and Elemental Analysis, Proximate Analysis, And Energy Content of Grindelia, Rabbitbrush, And Corresponding Hydrochars elemental analysis
grindelia
CEGB
rabbitbrush
RERB
proximate analysis
energy content
condition
pH
C (%)
N (%)
H (%)
O (%)
S (%)
volatile carbon (%)
fixed carbon (%)
ash (%)
HHV (daf MJ kg−1)
raw 200 230 260 raw 200 230 260 raw 200 230 260 raw 200 230 260
N/A 5.1 ± 0.0 4.1 ± 0.1 3.9 ± 0.1 N/A 5.1 ± 0.1 4.4 ± 0.1 4.0 ± 0.1 N/A 3.8 ± 0.0 3.6 ± 0.1 3.3 ± 0.0 N/A 3.9 ± 0.0 3.5 ± 0.0 3.3 ± 0.0
45.2 ± 0.2 52.3 ± 1.8 54.0 ± 0.4 60.6 ± 0.4 45.6 ± 0.5 52.4 ± 0.8 55.4 ± 0.4 60.6 ± 1.5 48.2 ± 0.4 52.6 ± 0.8 57.0 ± 1.5 61.4 ± 1.1 48.3 ± 0.0 50.9 ± 0.2 57.1 ± 1.6 59.7 ± 1.1
1.9 ± 0.0 1.7 ± 0.1 1.6 ± 0.0 1.8 ± 0.1 1.9 ± 0.1 2.0 ± 0.0 1.8 ± 0.0 2.2 ± 0.0 0.44 ± 0.1 0.50 ± 0.0 0.60 ± 0.0 0.60 ± 0.0 0.60 ± 0.1 0.60 ± 0.1 0.80 ± 0.1 0.80 ± 0.0
5.7 ± 0.1 6.1 ± 0.1 6.1 ± 0.1 5.7 ± 0.0 5.3 ± 0.1 6.1 ± 0.2 6.2 ± 0.0 5.7 ± 0.1 6.5 ± 0.3 6.7 ± 0.4 7.4 ± 0.5 6.7 ± 0.4 6.6 ± 0.1 7.0 ± 0.7 6.9 ± 0.3 6.6 ± 0.4
39.3 ± 0.7 35.6 ± 0.5 33.0 ± 1.7 28.3 ± 0.4 37.8 ± 0.2 31.0 ± 0.7 30.5 ± 0.8 23.4 ± 0.6 39.7 ± 4.0 40.4 ± 1.3 28.8 ± 3.3 30.5 ± 2.2 41.6 ± 0.7 38.1 ± 2.6 33.2 ± 1.9 34.0 ± 1.7
