Energy & Fuels 2007, 21, 1183-1187
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Bermudagrass for Biofuels: Effect of Two Genotypes on Pyrolysis Product Yield† A. A. Boateng,*,‡ W. F. Anderson,§ and J. G. Phillips‡ USDA-ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PennsylVania 19038, and USDA-ARS, Coastal Plain Experiment Station, 115 Coastal Way, Tifton, Georgia 31793 ReceiVed September 11, 2006. ReVised Manuscript ReceiVed NoVember 13, 2006
Bermudagrass is a perennial grass used as forage for livestock and harvested as hay on 10-15 million acres in the southern United States. It has potential as an energy crop for the production of biofuels through the lignocellulosic conversion program. Coastal was released in 1943 and was the primary forage genotype until the development of Tifton 85 which has greater yield and quality for ruminants. Pyrolysis of these two genotypes harvested at the same maturity and separated into leaf and stem was carried out to establish their effect on the yield of pyrolysis products. The pyrolysis was carried out in an analytical pyrolysis-gas chromatography system at 500, 700, and 900 °C temperatures. The noncondensable gas yielded, comprising CO, CO2, H2, and low molecular weight hydrocarbons, was estimated between 10 and 12.5 wt %. The char yielded ranged between 5.5 and 16 wt % with remainder, comprising condensable aerosols that constitute bio-oils when condensed, was 73-82 wt % estimated as the difference between the biomass and the produced gas and char. Statistical analysis of variance showed no significant difference between pyrolysis products due to genotype or whether the sample was leaf or stem. However, there was a strong significant effect of pyrolysis temperature on the product yields with the maximum gas yield and minimum char yield occurring at 900 °C. The calorific value of the gas reached 2300-2500 kcal/kg for both genotypes, about 20-25% of the heating value of natural gas. The study helps to ascertain that when harvested at the same maturity, the effect of bermudagrass genotype and plant part on pyrolysis gas and char yields may not be significant during thermochemical conversion. However, the condensable liquids were not analyzed.
1. Introduction Bermudagrass (Cynodon spp.) currently covers over 10 million acres of land in southern United States and is primarily used as a forage for livestock. Some of this pasture is cut for hay. Because of the vast acreage of bermudagrass currently grown in the US, it can be a potential biomass feedstock for biofuel production. The planting of bermudagrass as a forage began after the development and release of the Coastal bermudagrass genotype in 1943. Coastal has been the standard forage bermudagrass against which all cultivars have been measured since 1943. Through the years, other improved forage bermudagrass hybrids have been released. The most recent genotype, Tifton 85, yields 20% higher biomass (Table 1) and has 10% higher digestibility than Coastal. Tifton 85 is currently the bermudagrass of choice for growers who are taking row crops out of production and replacing them with pasture in much of the southern U.S. These two cultivars are very distinct grasses. Coastal is a cross of a local Cynodon dactylon landrace “Tift” and a C. dactylon from South Africa. It has moderately fine stems and leaves. Tifton 85, however, has much coarser stems and leaves. It is a cross of Tifton 68 and a plant introduction from South Africa with fall armyworm resistance. Parent Tifton 68 was developed from † Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. * Corresponding author. Tel.: 215 2336493. Fax: 215 2336559. Email:
[email protected]. ‡ Eastern Regional Research Center. § Coastal Plain Experiment Station.
10.1021/ef0604590
Table 1. Average Forage Yield of Coastal and Tifton 85 Bermudagrass at Griffin, Calhoun, and Tifton, GA, in 2003-2005a kg/ha oven-dry forage varieties
Griffin
Calhoun
Tifton
state-wide avg
Tifton 85 Coastal CVb (%) LSD.05
14606C
19868C
15395C
13015D 7 778
14251D 12 1390
12801D 7 844
16623 13355
a Any two means in the same column with no letter in common are significantly different (p < 0.05) by the Bonferroni least-square difference (LSD) technique. b cvscoefficient of variance.
a cross between two C. nlemfuensis introductions that had the highest digestibility by ruminants among over 400 accessions tested. Thus, Tifton 85 also has very high digestibility. Two potential conversion platforms are currently being considered under the biomass initiative program. The first, known as the sugar platform, is the bioconversion by simultaneous saccharification and fermentation (SSF) of lignocellulosic feedstock. The second is the thermochemical conversion platform for the production of synthesis gas (syngas), pyrolytic oils, and related fuels and chemicals. Sun and Cheng1 carried out enzymatic hydrolysis of acid-pretreated bermudagrass found in the southeastern US for the purpose of bioconversion of the lignocellulosic material into reducing sugars. In their work, cellulases supplemented with β-glucosidase were used as the biocatalysts to obtain about 45% ethanol conversion efficiency. (1) Sun, Y.; Cheng, J. Enzymatic hydrolysis of rye straw and bermudagrass using cellulases supplemented with β-glucosidase. Trans. ASAE 2004, 47 (1), 343-349.
This article not subject to U.S. Copyright. Published 2007 by the American Chemical Society Published on Web 12/29/2006
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In a related work,2 the authors found that about 50-66% of the xylan in the biomass was hydrolyzed into monomeric xylose and about 27-33% of glucan from bermudagrass could be converted into glucose. In a recent work by the USDA-ARS at Tifton, GA, on enzyme pretreatment of grass lignocelluloses,3 bermudagrass of the Tifton 85 genotype was shown to produce 12% more ethanol than Coastal when evaluated under similar low stringency acid hydrolysis pretreatments and subsequent fermentation of released sugars by SSF. While there has been work going on in the bioconversion of bermudagrass to ethanol, similar information on the thermochemical conversion of bermudagrass is lacking in the open literature. However, thermochemical conversion processes such as pyrolysis and gasification are economically viable methods of converting lignocellulosic plant materials to useful energy or energy carriers. The syngas produced can, in turn, be converted to fuel alcohols via the Fischer-Tropsch process.4 It has also been demonstrated that5 synthesis gas derived from the gasification of switchgrass and bermudagrass can be converted to fuel ethanol by fermentation using strains isolated from an agricultural lagoon. In both cases, the quality and composition of the syngas is important to the downstream conversion process. This study is performed to evaluate the thermochemical conversion potential of Coastal and Tifton 85 bermudagrass by quantifying the products of their pyrolysis. 2. Experimental Details The bermudagrass samples used in the pyrolysis study were of the Coastal and Tifton 85 genotypes harvested at 12 weeks old from replicate samples in areas of large breeder plots at Tifton, GA. The fields were maintained without irrigation and with 22.7 kg/ha of nitrogen in March 2004. Fields were cut and hay cleared on August 9, 2004. A 1-m2 area of regrowth at three locations in the field was harvested by hand with scissors on November 1, 2004 (Table 1). Tifton 85 and Coastal grasses were 62 and 52 cm tall, respectively. The leaves of both Coastal and Tifton 85 were handseparated from the stems. The leaf and stem materials were weighed wet and oven dried at 50 °C, and dry weights were taken. The percentages of leaf were 52.4% for Coastal and 58.6% for Tifton 85 on a total dry matter basis. For the purpose of the pyrolysis work, the biomass samples were ground with a Wiley mill through a 1-mm screen prior to analysis. Material was compared to determine differences in percent dry matter, leaf/stem ratios, and digestibility (Table 2). The percentage of lignin (2.8-3.2%) between the two genotypes was very similar as measured through acid detergent lignin procedures. Proximate and ultimate analysis of the leaf portion of the plant is shown in Table 3. A CDS Analytical (Oxford, PA) Pyroprobe was used for the pyrolysis. It consisted of a 1-cm quartz tube heated by a platinum filament of 2-3 mm in diameter, which is capable of maintaining up to a 1200-°C temperature at a nominal heating rate of 20 °C/ ms. Pulverized samples were sifted, and particle sizes with 90% passing a 500-µm screen were used for the pyrolysis experiments. The average weight charged into the pyrolyzer (PY) was about 1 (2) Sun, Y.; Cheng, J. Dilute acid pretreatment of rye straw and bermudagrass for ethanol production. Bioresour. Technol. 2005, 96, 343349. (3) Anderson, W. F.; Paterson, J.; Akin, D. E.; Morrison, W. H., III. Enzyme pretreatment of grass lignocellulose for potential high-value coproducts and an improved fermentable substrate. Appl. Biochem. Biotechnol. 2005, 121, 303-310. (4) Boateng, A. A.; Hicks, K. B.; Vogel, K. P. Pyrolysis of Switchgrass (Panicum Virgatum) Harvested at Several Stages of Maturity. J. Anal. Appl. Pyrolysis 2006, 75, 55-64. (5) Ahmed, A.; Lewis, R. S.; Cateni, B. G.; Bellmer, D. D.; Huhnke, R. L.; Tanner, R. S. Fermentation of synthesis gas to fuel ethanol. Oral presentation, School of Chemical Engineering, Oklahama State University, Oklahoma, June 2002.
Boateng et al. Table 2. Percent Leaf, Percent Dry Matter (DM), and in vitro Dry Matter Digestibility (IVDMD) of Leaf and Stem for 12 Week Old Bermudagrass Harvested on November 1, 2004, at Tifton, GAd genotype
plant part
% leaf
% DM
IVDMD
Coastal Coastal Tifton 85 Tifton 85
Leaf Stem Leaf Stem
52.4a
61.0a 50.9b 52.2b 38.5c
35.5b 34.8b 47.8a 48.5a
58.6a
d Any two means in the same column with no letter in common are significantly different (p < 0.05) by the Bonferroni least significant difference (LSD) technique.
Table 3. Proximate and Ultimate Analyses of Bermudagrass Samples Used in the Pyrolysis Experimenta Coastal leaf moisture ash VM fixed C (by difference)
3.8 3.52 77.83 14.86
Ultimate Analysis (wt % DB) H 6.12 C 46.80 N 0.91 S 0.25 Cl 0.12 ash 3.65 O (by difference) 41.66 heating value (MJ/kg) DB 18.67
Tifton 85 leaf 5.56 4.63 74.72 15.09 6.08 45.97 0.93 0.26 0.22 4.90 41.64 18.192
a Reported values are averages of duplicates with (0.5% standard error. dbsdry basis. vmsvolatile matter.
mg (0.96-1.12) and occupied about 1-1.5 mm in height in the quartz tube holder over packed quartz wool. Helium, the carrier gas for the GC, was also used to purge air in the sample prior to pyrolysis and the pyrolysis gas yield to the GC. Although the nominal heating rate is about 20 °C ms-1, the sample heating rate can be much lower and typically estimated at 300 °C s-1.6 The experimental sample preparation procedure is reported in ref 4 and is consistent with others reported in the literature.6 Using samples weighing less than 2 mg did not significantly change the gas yield.6 The pyrolyzer was interfaced to a gas chromatograph (SRI, CA). With the pyroprobe/gas chromatograph (PY-GC) system, a variety of compounds formed during flash pyrolysis could be characterized. Pyrolysis noncondensable gas products were separated using a Shincarbon ST 80/100, 2 m × 2.0 mm packed column (Restek, Bellefonte, PA). The GC was programmed to maintain 45 °C for 3 min after injection, followed by a 10 °C/min ramp to 250 °C, and then held at 250 °C for 10 min for a total time of 34.4 min. Hydrogen was detected using the TCD SRI Instruments Wheatstone bridge with four filaments. The yields of the major noncondensable gas products from primary and secondary pyrolysis reactions were quantified by calibration with a standard gas mixture consisting of CO, CO2, CH4, C2H4, C2H6, C3H8, and C4H10 in helium (custommixed by Scott Specialty Gases, Plumsteadville, PA). Gas yields were quantified based on a linear relationship between the mass and area counts of the programs. The coefficient of determination, R2, for the linear fits ranged between 70% (CO) and 97% (CH4). Char yield was determined gravimetrically. All other gases, including the condensable gases such as reaction water and pyrolytic oil vapors, plus the noncondensable gases that were not calibrated, were considered as “tar.” These included hydrocarbon gases greater than C4H10. The condensable gas yield was calculated as the difference between the biomass pyrolyzed and the sum of the measured gases and the residual char. Three samples of Coastal stem and leaf and three sets of Tifton 85 stem and leaf were pyrolyzed at a set of pyrolysis temperatures (500, 700, and 900 °C) for 20 s of retention time. At this time, there was no change, and therefore, the devolatilization reaction (6) Caballero, J. A.; Font, R.; Marcilla, A.; Garcia, A. N. J. Anal. Appl. Pyrolysis 1993, 27, 221-244.
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Table 4. Analysis of Variance Showing the Effect of Variety, Type, and Temperature on Noncondensable Gas (NCG) Yield in weight percentageg obj
variety
type
temp
CO2
CO
CH4
C2H6
C3H8
H2
NCG
HC
char
CG
1 2 3 4 5 6 7 8 9 10 11 12
Coastal Coastal Coastal Coastal Coastal Coastal Tifton 85 Tifton 85 Tifton 85 Tifton 85 Tifton 85 Tifton 85 std error
L L L S S S L L L S S S
500 700 900 500 700 900 500 700 900 500 700 900
7.44A 8.03A 8.17A 8.43A 7.69A 8.29A 8.65A 7.11A 10.67A 8.11A 8.03A 9.92A 0.889
2.22A 1.53A 1.07A 1.86A 1.03A 1.38A 1.61A 1.29A 1.51A 1.87A 1.34A 1.46A 0.315
0.16D 0.77ABCD 1.22ABC 0.15D 0.72BCD 1.32AB 0.45D 0.60CD 1.34AB 0.17D 0.56D 1.36A 0.115
0.07E 0.32AB 0.35AB 0.06E 0.25BC 0.38A 0.07E 0.27BC 0.39A 0.10DE 0.20CD 0.34AB 0.021
0.04F 0.15CD 0.23A 0.02F 0.11DE 0.21ABC 0.03F 0.12DE 0.22AB 0.02F 0.08EF 0.17BCD 0.011
0.0002B 0.002B 0.017A 0.0003B 0.0021B 0.019A 0.0003B 0.0019B 0.021A 0.0004B 0.002B 0.026A 0.003
9.93AB 10.82AB 11.07AB 10.52AB 9.80AB 11.60AB 10.81AB 9.39B 14.15A 10.27AB 10.20AB 13.27AB 0.837
0.27D 1.25AB 1.80A 0.24D 1.07B 1.90A 0.55BCD 0.99BC 1.95A 0.29CD 0.84BCD 1.87A 0.132
19.32A 10.06ABC 7.47BC 15.46AB 12.60ABC 4.18C 14.63AB 8.05BC 4.00C 16.55AB 8.17BC 6.51BC 1.876
70.76C 79.12ABC 81.46ABC 74.02ABC 77.60ABC 84.22A 74.55ABC 82.55AB 81.85AB 73.17BC 81.63AB 80.21ABC 1.97
g Any two means in the same column with no letter in common are significantly different (p < 0.05) by the Bonferroni least significant difference (LSD) technique. The letters A-F refer to the highest estimates to the least.
Figure 1. Distribution of product yields for bermudagrass pyrolysis.
was complete. There were three field samples each for Coastal stem, Coastal leaf, Tifton 85 stem, and Tifton 85 leaf. Pyrolysis for each of the three field samples was carried out at the three temperatures specified in triplicate. The average of the three field samples are reported for the pyrolysis temperature.
3. Results and Discussion Digestibility of the samples as measured by in vitro dry matter digestibility (IVDMD) was 35% and 48% for Coastal and Tifton 85, respectively (Table 2). These results are approximately 15% lower in absolute terms than what would be expected for these cultivars when harvested at the 4-6-week intervals as normally practiced. For example, leaf digestibilities of these genotypes were higher when harvested at 4 weeks (Coastal ) 49%, Tifton 85 ) 62%) from previous cuttings in August 2004). There was no significant difference in digestibility between the leaf and stem within cultivars (Table 2). The pyrolysis product distributions for all 12 field averages are presented in Figure 1. These comprise the noncondensable gas (NCG), 10-12.5 wt %; char, 5.5-16.5 wt %; and the condensable gas (CG), 71-83 wt % estimated by difference. Differences in the yields of char and the gas components including CO, CO2, H2, and low molecular weight hydrocarbons were compared by genotype, plant part (leaf or stem), and pyrolysis temperature using statistical analysis of variance (ANOVA). The 12 different combinations in the statistical analysis performed composed of genotype (Coastal and Tifton 85), plant part (leaf and stem), and temperature (500, 700, and 900 °C) with each data point representing an average of three samples. The results of the factorial design are discussed as follows: 3.1. Noncondensable Gas Yield. Yields of individual noncondensable gases, i.e., CO, CO2, H2, CH4, C2H6, and C3H8, and the total quantity (NCG) were subjected to analysis of variance. Also tested statistically were the combinations of (CO + H2) and (CO2 + H2). The former is the sum of the major
components of synthesis gas from air gasification, and its evolution path is important to gas quality required for FischerTropsch liquids production. The latter is important because it is the product of the water gas shift reaction, a reversible reaction between water and CO in gas-phase steam reforming of pyrolysis gas. Hence, the extent of the forward reaction to yield hydrogen will be dependent on the initial pyrolysis yield of the combined gas. Table 4 summarizes the PY-GC quantitative data of the noncondensable gas and its components. These are averages of three field replicates. Of the NCGs, CO2 was the most intense derivative. The CO2 yield was not significant (p < 0.05) regardless of cultivar variety, leaf and stem, or temperature effects. Surprisingly, similar results were found for CO. CH4 yield was temperature dependent (p < 0.001) but was not significantly different with respect to genotype or whether it was leaf or stem. Similar results were found for C2H6 and H2. Propane yield, however, was significantly different with respect to temperature and type, i.e., leaf and stem (p < 0.001). Like the other hydrocarbons, it was not significantly different with respect to genotype. The total noncondensable gas yield was temperature dependent (p < 0.05). The combined effect of genotype and temperature was slightly significantly different (p < 0.06). Because the yields of CO, CO2, and H2 were only significantly different with temperature, their combinations, i.e., (CO + H2) and CO2 + H2), were not significantly different with respect to genotype or plant part except for the effect of temperature. Similar results were found for the combined hydrocarbons. The temperature effects on the noncondensable gas yield and associated components are presented in Figures 2 and 3. There was a strong temperature effect on the yields of all the hydrocarbons and H2 with the yields increasing rapidly to, at times, 2-fold between 500 and 700 °C and about the same amount from a 700 to 900 °C pyrolysis temperature. For all genotypes and plant parts (leaf or stem), there were negligible amounts of H2 produced at 500 °C. However, between 700 and 900 °C, H2 yield increased by an order of magnitude; nonetheless, the values were still very low compared with the rest of the gases. Although CO2 yield was affected by pyrolysis temperature, the effect was marginal. Similar temperature trends were observed for CO. For the pyrolysis of other perennial grasses, e.g., switchgrass, reed canarygrass, and eastern gamagrass in a PY-GC/MS, CO was observed to increase with temperature.4,7 The combined effect of pyrolysis temperature (7) Boateng, A. A.; Jung, H. G.; Adler, P. R. Pyrolysis of energy crops including alfalfa stems, reed canarygrass, and eastern gamagrass. Fuel 2006, 85 (17-18), 2450-2457.
1186 Energy & Fuels, Vol. 21, No. 2, 2007
Figure 2. Effect of temperature on CO, CO2, and CH4 yields for the cultivars tested.
Boateng et al.
small, and hence, the total NCG yield was statistically about the same between 500 and 900 °C. 3.2. Residual Char and Condensable Gas (CG) Yield. The char remaining after pyrolysis is usually a strong function of temperature because of the continuation of char pyrolysis after initial rapid volatile evolution. This is indeed the case for the bermudagrass varieties studied (Figure 4). For both genotypes and parts (leaf or stem), char yield decreased with temperature resulting in an estimated average of 16.5 wt % remaining at 500 °C pyrolysis to about 5.5 wt % remaining at 900 °C for all samples. This result is consistent with other warm-seasoned grasses (e.g., switchgrass and eastern gamagrass) as well as coolseasoned grass (e.g., reed canarygrass).4,7 As Table 4 indicates, the effect of genotype and plant part (leaf or stem) on char remaining after pyrolysis for the bermudagrass samples tested was not significantly different at p < 0.05 by the Bonferroni least-squares difference (LSD) technique. It is worth mentioning that all the bermudagrass samples tested were harvested at the same maturity level. It was indicated that for these samples the lignin content was about the same. TGA investigation of biomass pyrolysis based on the three major components (i.e., cellulose, hemicellulose, and lignin)8 found that lignin produced the highest char remaining after pyrolysis. Hence, the result presented herein might imply that the char yield is a function of the lignin content and not a function of genotype or plant part. Yields of condensable gas (CG), which are the aerosols in the pyrolysis gas comprising organic acids, aldehydes and hydroxyaldehydes, ketones, anhydrous sugars, and lignin aromatic units, that would form pyrolytic oils (bio-oils) when condensed, were estimated as the difference between the biomass sample and the sum of the NCG and the char. There was no significant difference between the CG yields for bermudagrass variety and type except for temperature. The yield at 500 °C was significantly different from that at both 700 and 900 °C, but the yields at 700 and 900 °C were not. It has been established that bio-oil yields are maximized at around 500 °C,9 but this was not the case as the higher temperature pyrolysis yielded relatively more condensable gas (Figure 4). Although there were no significant differences in the total CG, there could be an effect on the composition of the condensable gas which was not quantified. Galletti et al.10 found the composition of pyrolysis liquids from maize hybrids to be significantly different and attributed the difference to proportions of cell-wall lignin and polysaccharides. 3.3. Cold Gas Efficiency. The energy content of the pyrolysis gas produced from bermudagrass was evaluated using the theoretical heat of combustion of the individual gas components, HHVgi as
HHVg )
∑([HHV]gi × {%wtgi/%wtNCG})
(1)
Figure 5 shows that this could be as much as 2300 kcal/kg of gas produced at 900 °C, about 20-25% of the heating value of pipeline natural gas.
Figure 3. Effect of temperature on C2H6, C3H8, and H2 yields for the cultivars tested.
on the total noncondensable gas yield for both Coastal and Tifton 85 genotypes regardless of leaf or stem was not dramatic. While there were increases in the hydrocarbon fraction of the total gas as the pyrolysis temperature increased, this fraction was
(8) Yang, H.; Yan, R.; Chen, H.; Zheng, C.; Lee, D. H.; Liang, D. T. In-depth investigation of biomass pyrolysis based on three major components: Hemicellulose, cellulose, and lignin. Energy Fuels 2006, 20, 388393. (9) Oasmaa, A.; Leppamaki, E.; Koponen, P.; Lavander, J.; Tapola, E. Physical characterization of biomass-based pyrolysis liquids; VTT Report 306, VTT: Finland, 1997. (10) Galleti, G. C., Reeves, J. B., III; Bocchini, P.; Muscarella, C. I. Compositional differentiation of maize hybrid stovers using analytical pyrolysis and high-performance liquid chromatography. J. Agric. Food Chem. 1997, 45, 1715-1719.
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Figure 4. Effect of temperature on NCG, char, and CG yields for the cultivars tested for Coastal leaf (CL), Coastal stem (CS), Tifton 85 leaf (TL), and Tifton 85 stem (TS). The coefficient of determination, R2, values for the linear plots were 0.90, 0.35, 0.47, and 0.73, respectively.
Figure 6. Effect of temperature on cold gas efficiency for the cultivars tested.
Figure 5. NCG calorific value.
To compare the heating value of the gas with the parent biomass, we define quality as the ratio of the gas heating value to that of the parent biomass as,7
ηg )
HHVg [GCV]b
× 100%
(2)
where [HHV]g (kcal/kg) is the heat of combustion of the product gas component, %wt is the weight percent of the component gas in the produced gas, and [GCV]b is the biomass gross calorific value determined experimentally. The GCV of the biomass shown in Table 3 was determined for leaves only. The value was adjusted for stems by 5% increase. The most efficient noncondensable gas production was at 900 °C (Figure 6). At this peak temperature, the HHV was independent of plant part, reaching a mean of about 2200 kcal/kg for Tifton 85 and 2500 kcal/kg for Coastal, but these are not statistically different. For each genotype, the cold gas efficiency was about the same regardless of whether the sample was leaf or stem, reaching a mean value of about 47% of the parent Tifton 85 and 53% for Coastal biomass. However, the noncondensable gas produced at this temperature was small and did not exceed 14% of the biomass precursor.
4. Conclusions Two potential conversion platforms are currently under consideration for lignocellulosic biomass conversion, i.e., simultaneous saccharification and fermentation (SSF) of lignocellulosic feedstock (the sugar platform) and the thermochemical conversion platform for the production of synthesis gas (syngas), pyrolytic oils, and related fuels and chemicals. Plant genotype, part, and maturity are some of the factors that contribute to biofuel yield. Bermudagrass is considered a potential feedstock for biofuel production. This study investigated the effect of two major genotypes, Coastal and Tifton 85, and plant part, leaf or stem, on pyrolysis products. No significant effect of these characteristics on yields was found although others have reported Tifton 85 to yield 12% more ethanol than Coastal with SSF. Rather, there was significant a effect of temperature on yields. It can be concluded that pyrolysis yield is not affected by the variety of the bermudagrass or the plant part thereof. The heating values of the produced gas from both genotypes and plant parts were also about the same within the statistical margin of error at the temperatures studied. Acknowledgment. The authors wish to thank Richard Cook for technical support. EF0604590
