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Biodiesel production from rice straw and restaurant waste employing black soldier fly assisted by microbes
Energy 47 (2012) 225e229
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Biodiesel production from rice straw and restaurant waste employing black soldier fly assisted by microbes Longyu Zheng a, Yanfei Hou a, Wu Li d, Sen Yang a, Qing Li a, b, c, **, Ziniu Yu a, * a
State Key Laboratory of Agricultural Microbiology, National Engineering Research Centre of Microbial Pesticides, Huazhong Agricultural University, Wuhan, PR China Biomass and Bioenergy Research Center, Huazhong Agricultural University, Wuhan, PR China c College of Science, Huazhong Agricultural University, Wuhan, PR China d College of Engineering and Technology, Huazhong Agricultural University, Wuhan, PR China b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 20 January 2012 Received in revised form 4 August 2012 Accepted 1 September 2012 Available online 1 October 2012
Biodiesel has become attractive as an alternative renewable fuel, but its large-scale production has been restricted because of the high cost of feedstock. Therefore, alternative feedstock is urgently needed to enable biodiesel production from cheap raw materials. Toward this goal, a co-conversion process using BSFL (black soldier fly larvae) and microbes (Rid-X) was established to convert rice straw and RSW (restaurant solid waste) into the larval grease of black soldier fly. In this study, about 43.8 g biodiesel was produced from 2000 BSFL grown on 1000 g mixed feed of rice straw (30%) and RSW (70%) within 10 days. About 65.5% of cellulose, 56.3% of hemicellulose, 8.8% of the lignin, 91.6% of protein and 71.6% of lipid in the feed were digested and utilized for insect biomass accumulation with the aid of Rid-X. The results showed that grease from BSFL fed on rice straw and RSW was suitable for biodiesel and most of the fuel properties were corresponding to the requirements of the standard EN 14214. The new alternative method was introduced to produce biodiesel from lignocellulose abundant materials by insect and microbes, partly bypassing the complex pretreatment of lignocellulose that needed by other biofuel technologies. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Black soldier fly Biodiesel Insect bioenergy Lignocellulose Restaurant waste Rice straw
1. Introduction Despite many benefits, biodiesel is hampered by the production of oilseed plants. Biodiesel is mostly produced from edible oils, such as vegetable oils and animal fats, using conventional technology; using edible oil for biodiesel instead of food is unacceptable [1]. As food is a basic requirement for human, biodiesel feedstock should not affect the food supply [2]. Moreover, the cost of feedstock is a major economic factor in the development of biodiesel [3]. Therefore, alternative feedstock is urgently needed to enable biodiesel production from cheaper and non-food materials. To reduce feedstock cost and relieve food resource contradictions, a lot of research effort has been targeted to find new feedstock, such as microalgae [4], Madhuca indica [5], waste grease [6e8], Jatropha
* Corresponding author. Tel.: þ86 27 87280802; fax: þ86 27 87393882. ** Corresponding author. State Key Laboratory of Agricultural Microbiology, National Engineering Research Centre of Microbial Pesticides, Huazhong Agricultural University, Wuhan 430070, PR China. Tel.: þ86 27 87280802; fax: þ86 27 87393882. E-mail addresses: [email protected] (Q. Li), [email protected] (Z. Yu). 0360-5442/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.energy.2012.09.006
curcas [9] and muskmelon seed oil [10]. But these new methods face many challenges, while most are still at laboratory scale. As is known to all, seeking solutions to energy must not affect the environmental and societal benefits, thus it is important to develop non-food biomass [2]. The alternative feedstock should be technically feasible, economically competitive, environmentally acceptable, and easily available [11]. Recently, microbial lipids have been suggested as the alternative feedstock for biodiesel, but the cost of microbial lipids production is still high [12]. Rice straw is particularly an attractive lignocellulosic material for biofuel production. However, there are several challenges and limitations for its utilization, especially in the process of pretreatment [13]. Pretreatment, usually with acidolysis and enzymolysis, is the essential process to degrade this composite into monosaccharide for subsequent fermentation or other use. Excess acid usage and enzyme requirement lead to less environmental friendly and high cost for biofuel industry from rice straw and other lignocellulosic materials [14]. Fortunately, many insects showed high efficiency to degrade lignocellulosic substrates and use it as their nutrition supply [15]. People began to pay attention to insect, especially the scavengers for understanding of their mechanism of lignocellulose digestion
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and development of enzymes with new or better functions. Hermetia illucens L. (Diptera: Stratiomyidae), which is usually known as black soldier fly, is inclined to live in the outdoors and often associated with livestock, usually around decaying organic wastes such as animal manure or plant material [16]. The complex organic materials were converted into soluble organic molecules, and then incorporated into insect biomass rich in protein and grease. Grease from black soldier fly larvae (BSFL) is a low cost biodiesel feedstock, and the bioconversion of organic wastes into biodiesel has a beneficial effect on the environment [17]. We hypothesized that BSFL also has the potential to degrade rice straw for biodiesel production, partly bypassing the conventional pretreatment for monosaccharide. Restaurant solid waste (RSW) was used in this study for nutrition supplement during conversion. Rid-X, a commercial commodity containing functional microbes and enzymes was selected to further enhance the conversion rate of the substrates. A suitable condition for co-conversion was determined, including ratio of rice straw and RSW and inoculum concentration of microbes. Utilization efficiency of different components in the substrate by co-conversion, such as cellulose, hemicellulose, lignin, protein and lipid were evaluated. Composition and properties of the biodiesel from BSFL and Rid-X co-conversion were also assessed. This technology was established to exploit cheap and lignocellulose abundant materials for bioenergy production by insect and microbes. 2. Materials and methods 2.1. Raw materials BSFL used in this study was from the Huazhong Agricultural University colony. This colony was established in fall 2005 from the eggs of a colony at the Texas Agricultural Experiment Station, Stephenville, TX, which originated from the eggs from a laboratory colony at the Coastal Plain Experiment Station, University of Georgia, Tifton, GA, USA. BSFL were fed for about 6 days with standard colony diet before being used for this study [16]. Rid-X (SKU: 019200803069) was purchased from Reckitt Benckiser Inc. Parsippany, NJ 07054-0224. Restaurant waste is often generated in large quantities in cities. It is a potential hazardous material to environment without proper disposal [17]. Restaurant waste was collected from restaurants in Wuhan city, China, by Hubei Tianji Bioengineer Co. Ltd.; a government authorized biodiesel processing plant located in Huazhong Agricultural University. After removal of the waste grease for biodiesel production by the plant, the restaurant solid waste (RSW) was sampled and used for this study. Rice straw was obtained from the Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan, China. Rice straw was firstly heated at 110e120 C for 10 min to inactivate the enzymes, cut into small pieces, and then ground with a knifemill until the entire sample passes through the 40 mesh screen. 2.2. Co-conversion of rice straw and RSW by BSFL and microbes (Rid-X) RSW and rice straw were mixed at a certain ratio to feed BSFL for insect biomass accumulation; the co-conversion process was shown in Fig. 1. Based on preliminary trials, about 2000 of 6 days old larvae
Rice straw and SRW
Table 1 Relative contents of the main components in the rice straw. Component
Soluble sugar
Starch
Hemicellulose
Cellulose
Lignin
Ash
(wt.%)
11.5
0.5
27.3
32.6
18.4
14.2
(about 3 mg/larva) were inoculated into 1000 g mixture of RSW and rice straw. All the experiments were carried out in a greenhouse at 27 C with 70% air moisture. Conversion was terminated when prepupae accounted for about half of the larvae. The larvae were separated from the residue, water washed, and inactivated at 110 C for 10 min and dried at 50 C until constant weight was gained. After being ground with micro-mill larval biomass was stored at 4 C until grease extraction could be performed. To evaluate the effect of the mixing ratio of rice straw and RSW on the yield of insect biomass and larval grease yield, which is closely related to the final biodiesel yield, the organic mixture of RSW and rice straw was made at the following ratio: A) 100% rice straw (control), B) 20% RSW, C) 40% RSW, D) 60% RSW, E) 80% RSW and F) 100% RSW. There are great deal of lignocellulose, proteins and fats in the complex of RSW and rice straw. It is necessary to add microbial treatment (Rid-X) to increase the efficiency of conversion. Rid-X was inoculated at a series of dosage, from 0.05% to 0.5% (w/w), into the mixture of RSW and rice straw to determine its effect on BSFL biomass production and larval grease output. The next, uniform design was applied to obtain a suitable coconversion condition, including the mixing ratio of rice straw and RSW, and inoculum concentration of Rid-X. Table U5 (53) was used based on the results obtained from the trials mentioned above. 2.3. Crude grease extraction by Soxhlet extractor To determine the larval grease content in each sample, the extraction of grease was accomplished by a previously reported method with some modification [16]. A classical Soxhlet system with cellulose extraction cartridges was employed. Instead of refluxing extraction for 16 h, petroleum ether (200 ml) extraction was conducted twice for 8 h in Soxhlet extractor. Crude grease was obtained by combining the leaching liquor and evaporating petroleum ether with a rotary evaporator, and then the crude grease was calculated by weight. 2.4. Production of biodiesel The extracted grease contained various kinds of impurities. Therefore, it was necessary to be purified by adding 0.5% H2SO4. A two-step method: acid-catalyzed esterification of free fatty acids (to decrease the acidity of the crude grease), and alkaline-catalyzed transesterification was chosen for biodiesel production [16]. 2.5. Analysis Acid value of grease and biodiesel was determined by standard titrimetry methods (ASTMD 664-07), while kinematic viscosity and cloud point were determined by ASTM D-445 and ASTM D-2500 respectively. The compositions of biodiesel were analyzed by
Co-conversion by BSFL and Rid-X
Larval Grease
Fig. 1. Co-conversion process of rice straw and RSW by BSFL and Rid-X.
Biodiesel
L. Zheng et al. / Energy 47 (2012) 225e229 Table 2 Relative contents of the main components in the restaurant solid waste (RSW). Component
Water
Protein
Cellulose
Grease
Starch
Impurities
(wt.%)
81.2
4.2
1.6
3.4
3.8
0.2
GC/MS. Hemicellulose, cellulose and Klason lignin were determined as previously reported [18]. Hexoses in the solution were measured by the anthrone/H2SO4 method; pentoses were determined by the orcinol/HCL method. Hemicellulose was determined as the sum of pentoses, whereas cellulose as the sum of hexoses. Automatic Kjeldahl apparatus method (Kjeltec 8400) was used for determination of protein content. All experiments were carried out in triplicates.
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feed because of lack of nutrition (data not shown). Insect biomass yield and the grease content reduced to 96.9 g and 32.0% when 100% of RSW was used. RSW was considered to be a better diet for BSFL than other type of organic waste, such as animal manure, grease content in the insect biomass can reach 39.2% when BSFL were fed with RSW [17]. The reason why the larval grease content in this study was lower than previous reported may be due to the higher larval inoculum amount which was designed for better degradation of lignocellulosic components in rice straw. To obtain maximum biomass and grease yield, one can see from Fig. 2A, the optimal mixing ratio of RSW and rice straw should be around 8:2. Hence, this maxing ratio was further used to evaluate the effect of Rid-X on the conversion rate and grease yield. 3.3. Effect of the amount of Rid-X on the BSFL grease yield
3. Results and discussion 3.1. Raw material properties The relative content of the main components of rice straw were determined before being used for the study and showed in Table 1. Restaurant waste includes uneaten food and food preparation leftovers from residences, commercial establishments such as restaurants, institutional sources like school cafeterias, and industrial sources like factory lunchrooms. As shown in Table 2, the RSW used in this study included water (81.2%), starch (3.8%), cellulose (1.6%), protein (4.2%), grease (3.4%) and impurities (0.2%). 3.2. Effect of different ratio of RSW and rice straw on the BSFL grease yield RSW is rich in grease and protein, but poor in lignocellulose (Table 2); while rice straw is lignocellulose-rich, but poor in grease and protein (Table 1). Nutrition balance of feed for BSFL was therefore tested by mixing RSW and rice straw together in different ratio. The organic materials in RSW and rice straw were converted into soluble organic molecules such as sugar, amino acids, and fatty acids firstly, and incorporated into the biomass of BSFL. Larval grease was extracted and weighed to evaluate the effect of different ratio. When RSW ratio increased from 20% to 80%, insect biomass and grease relative content increased from 62.5 g to 98.7 g (dry matter, DM), and 28.7% to 33.7%, respectively. Accordingly, as shown in Fig. 2A, the larval grease yield increased from 17.9 g to 33.3 g. The larvae were unable to grow when rice straw was used as the sole
Rid-X contains millions of natural active bacteria that facilitate in breaking down the solid organic wastes, and the active ingredients are cellulase, lipase, protease and amylase. For better utilization of organic matter in rice straw and RSW, microbial agents were added to improve the conversion efficiency, especially the degradation of cellulose and hemicellulose in the rice straw. Different concentration of Rid-X was added to mixture of RSW (80%) and rice straw (20%) for co-conversion. The results (Fig. 2B) indicated that when the amount of Rid-X was added from 0.05% to 0.4% (w/w) into the substrate, the insect biomass and larval grease yield increased correspondingly, showing a positive relationship between Rid-X dosage and grease accumulation. With the assistance of microbes and its associated enzymatic degradation, more nutritive from the substrate became available for the development of BSFL. Some microbes may also aid in the digestion of food. This phenomenon has also been confirmed in the previous studies [19]. Although more data is needed, shorter production cycle may be expected by this co-conversion technology. However, when inoculum dosage was higher than 0.4%, the larval grease yield increased only slightly. It is indicated that the optimal dosage of Rid-X for the co-conversion should be about 0.4%. Therefore, mixing ratio (8:2) and 0.4% of Rid-X addition was used as a reference for the further optimization by uniform design. 3.4. Optimization of conversion parameters The uniform design table U5 (53) was selected to study the appropriate conditions for co-conversion to maximize the yield of
B
A
45
Grease yield (g)
Grease yield (g)
40 30 20 10
40 35 30 25
0
20
2:8
4:6
6:4
8:2
10:0
Ratio of RSW and rice straw (w/w)
0
0.1 0.2 0.3 0.4 0.5 0.6 Inoculum amount of Rid-X (%,w/w)
Fig. 2. Single-factor effect of feed maxing ratio and inoculum amount of microbes on BSFL grease yield. (A) Effect of ratio of RSW and rice straw on BSFL grease yield. (B) Effect of inoculum amount of Rid-X on BSFL grease yield.
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L. Zheng et al. / Energy 47 (2012) 225e229
Table 3 Uniform design of Rid-X dosage and mixing ratio of RSW and Rice straw using table U5 (53). Experiment no.
Ratio of RSW and rice straw
Rid-X (w/w)
Insect biomass (g, DM)
1 2 3 4 5
4:6 5:5 6:4 7:3 8:2
0.3% 0.40% 0.25% 0.35% 0.45%
86.2 91.8 106.4 122.8 115.5
Grease content (%) 1.2 2.1 2.4 1.2 0.2
35.7 37.8 36.7 39.6 37.2
1.4 1.5 1.8 1.7 1.3
Grease yield (g) 30.7 34.7 39.1 48.6 42.9
0.7 1.2 1.5 0.9 0.7
insect larval grease. The two factors (ratio of RSW and rice straw, the amount of Rid-X) were optimized at 5 levels. As shown in Table 3, when 0.35% of Rid-X was inoculated in to the mixed medium of RSW and rice straw (7:3), the insect biomass, larval grease yield of BSFL reached the highest. From visual analysis, an operating condition was determined as 7:3 of RSW and rice straw and 0.35% of microbes (w/w) and selected for further evaluation. 3.5. Compositional changes of RSW and rice straw after coconversion Selected components of the original mixed medium (RSW:Rice straw, 7:3) and the digested residual after 10 days co-conversion were analyzed for comparison and to determine the conversion rate of the components. One can see from Fig. 3 that in the absence of Rid-X, about 27.9% of cellulose and 32.6% of hemicellulose were degraded by BSFL. This result is in accord with the previous report that larvae can digest the lignocellulosic components in dairy manure [16]. Conversion rate of cellulose and hemicellulose was significantly enhanced when 0.35% of Rid-X was introduced to the conversion system. With the aid of cellulase and fermentation of microbes, about 65.5% of cellulose and 56.3% of hemicellulose could be digested into sugar when the two agents worked together as shown in Fig. 3. The sugar was then absorbed by BSFL for development. However, BSFL can hardly use the lignin component in the feed (0.8%). Rid-X showed a feeblish ability for lignin degradation because about 8.8% of the lignin was reduced when Rid-X was added. BSFL could digest about 74.4% of protein in the mixed feed, and more protein (91.6%) was utilized when BSFL and Rid-X function together. Lipid conversion showed no significant difference in
Table 4 Selected characteristics of BSFL grease fed on RSW and rice straw in comparison with rapeseed oil and waste cooking oil. Properties
BSFL grease
Rapeseed oil [20]
Waste cooking oil [22]
Acid value (mg KOH/g) Iodine value (gI/100 g) (m/m) Saponification value (mg KOH/g) Cloud point ( C) Peroxide value (meq/kg)
8.2 89 157
1.14 115.5 188.6 [21]
e 108.4 183.4
6.8 0.18
3.9 0.75
e 16.4
the presence and absence of Rid-X. More nutrients in RSW and rice straw were utilized and incorporated into BSFL biomass with the aid of Rid-X, resulting in promoted biomass and grease yield. Grease was extracted from BSFL and further processed for biodiesel. 3.6. Biodiesel production from BSFL grease After 10 days co-conversion with the aid of Rid-X (0.35%, w/w), about 43.8 g biodiesel was produced by a two-step method from 2000 BSFL grown on 1000 g mixed feed of rice straw (30%) and RSW (70%). The properties of BSFL grease were described in Table 4, the results showed great similarities to the previous reports [16,17]. It is indicated that BSFL grease held a quite stable property in different feeding conditions. This larval grease is suitable to serve as the feedstock of biodiesel when compared with rapeseed oil. Furthermore, the properties of this BSFL grease based biodiesel further demonstrated that BSFL grease is suitable for biodiesel production. The compositions of FAME (fatty acid methyl ester) in BSFL biodiesel were presented in Table 5. With a little change in the relative content, FAME compositions of BSFL biodiesel from this study were very close to the fatty acids profile of BSFL fed on other type of waste [17]. In the meantime, the properties of BSFL biodiesel were comparable to rapeseed biodiesel, and most of the factors were in reasonable agreement with the specifications of standard EN 14214 as shown in Table 6. It is further demonstrated that BSFL grease could be a viable biodiesel feedstock and this insect based biodiesel could be a promising substitute of conventional diesel fuel. The major challenge of biofuel production from lignocellulose is the pretreatment [26]. BSFL provided a potential feedstock for biodiesel to bypass this complex pretreatment. With the aid of RidX, BSFL possesses a good ability to manage organic waste and
Table 5 Fatty acid compositions of BSFL grease-based biodiesel fed on RSW and rice straw, rapeseed oil-based biodiesel and waste cooking oil-based biodiesel. Fatty acids
Fig. 3. Degradation rate of selected components in the mixed medium of RSW (70%) and rice straw (30%) after conversion by BSFL with or without Rid-X (0.35%).
Saturated fatty acid Capric acid (10:0) Lauric acid (12:0) Myristic acid (14:0) Palmitic acid (16:0) Stearic acid (18:0) Unsaturated fatty acid Palmitoleic acid (16:1) Oleic acid (18:1) Linoleic acid (18:2) Linolenic acid (18:3) Odd carbochain fatty acid Pentadecanoic acid (15:0) Heptadecanoic acid (17:0) Nonadecanoic acid (19:0)
BSFL biodiesel
Rapeseed biodiesel [23]
Waste cooking oil biodiesel [24]
3.8 27.8 8.1 14.2 7.6
e e e 3.49 0.85
e e 0.11 8.22 2.10
4.5 22.5 1.8 2.1
e 64.40 22.30 8.23
5.18 59.7 19.31 6.82
1.5 0.8 1.7
e e e
e e e
L. Zheng et al. / Energy 47 (2012) 225e229 Table 6 Properties of BSFL grease-based biodiesel fed on rice straw and RSW, rapeseed oilbased biodiesel, waste cooking oil-based biodiesel and in comparison with standards of EN 14214. Properties
EN 14214
BSFL biodiesel
Rapeseed biodiesel [25]
Waste cooking oil biodiesel [8]
Ester content (%) Density (Kg/m3) Viscosity at 40 C (mm2/s) Water content (mg/Kg) Flash point (closed cup) ( C) Cetane number Acid number (mg KOH/g) Cloud Point ( C) Methanol or Ethanol (m/m) Distillation
96.5 min. 860e900 3.5e5.0
96.6 895 5.96
e 911 4.40
e 877 5.23
500 max.
300
300
e
120 min.
123
e
157
51 min. <0.5
55 0.6
45 1.14
48 0.21
e 0.2%
4.2 0.3%
3.9 e
1 e
e
91% at 360 C
91% at 352 C
e
lignocellulosic materials for biodiesel production. The cellulose, hemicellulose, grease and protein in RSW and rice straw were degraded into soluble organic molecules with a relatively high conversion efficiency, such as sugar, amino acids, and fatty acids, and then these soluble organic molecules were further converted into the BSFL grease. The grease provided a renewable and noncontroversial source for biodiesel. Compared with the traditional biodiesel plant, BSFL biodiesel appears to be an attractive energy resource due to its renewability, sustainable supplement, favorable environmental properties and significant economic potential. Additionally, BSFL has high reproductive capacity and short lifecycle, while plant has a long lifecycle and needs a plenty of land. It can be believed that insect bioenergy will bring new force to the Waste-to-energy technology. 4. Conclusions A co-conversion strategy was established, providing a practical and promising method for converting rice straw and RSW into biodiesel. Biodiesel was produced from wastes by insect and microbes, and sustainable solutions for wastes are on the horizon to find an alternative to traditional biodiesel. When 0.35% of Rid-X was added in the 1000 g mixed feed (RSW:Rice straw, 7:3), 122.8 g of insect biomass was obtained and BSFL grease content reaches 39.6%, yielding 43.8 g biodiesel from 2000 larvae. These results are important in selecting an appropriate feedstock for biodiesel. From comprehensive analysis of society, economy and environment, it can be concluded that BSFL with the assist of microbes have the potential to recycle lignocellulose abundant materials into biodiesel, and reduce environmental pollution of the wastes. Acknowledgments This research was supported by the Fundamental Research Funds for the Central Universities (No. 2011JC016) and National
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Natural Science Foundation of China (4004-114014). Special thanks to Dr. Jeffery K. Tomberlin, Texas A&M University, for his generous gift of the black soldier fly colony. References [1] Marina OSD, Adriano VE, Silvia AN, Rubens MF, Carlos EVR, Maria RWM. Production of bioethanol and other bio-based materials from sugarcane bagasse: integration to conventional bioethanol production process. Chem Eng Res Des 2009;87:1206e16. [2] David T, Robert S, Jonathan AF, Jason H, Eric L, Lee L, et al. Beneficial biofuelsthe food, energy, and environment trilemma. Science 2009;17(325):270e1. [3] Fatih MD, Mustafa B, Havva B. Biowastes-to-biofuels. Energ Convers Manage 2011;52(4):1815e28. [4] Huang G, Chen F, Wei D, Zhang X, Chen G. Biodiesel production by microalgal biotechnology. Appl Energ 2010;87(1):38e46. [5] Ghadge SV, Raheman H. Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids. Biomass Bioenerg 2005;28:601e5. [6] Mustafa C. The potential of restaurant waste lipids as biodiesel feedstock. Bioresour Technol 2007;98(1):183e90. [7] Gui MM, Lee KT, Bhatia S. Feasibility of edible oil vs. non-edible oil vs. waste edible oil as biodiesel feedstock. Energy 2008;33:1646e53. [8] Kumaran P, Mazlini N, Hussein I, Nazrain M, Khairul M. Technical feasibility studies for Langkawi WCO (waste cooking oil) derived-biodiesel. Energy 2011; 36:1386e93. [9] Lu H, Liu Y, Zhou H, Yang Y, Chen M, Liang B. Production of biodiesel from Jatropha curcas L. oil. Comput Chem Eng 2009;33:1091e6. [10] Rashid U, Rehman HA, Hussain I, Ibrahim M, Haider MS. Muskmelon (Cucumis melo) seed oil: a potential non-food oil source for biodiesel production. Energy 2011;36:5632e9. [11] Lang X, Dalai AK, Bakhshi NN. Preparation and characterization of bio-diesels from various bio-oils. Bioresour Technol 2001;80(1):53e62. [12] Hu C, Wu S, Wang Q, Jin G, Shen H, Zhao Z. Simultaneous utilization of glucose and xylose for lipid production by Trichosporon cutaneum. Biotechnol Biofuels 2011;4(25):1e8. [13] Parameswaran B, Raveendran S, Reeta RS, Surender V, Lalitha D, Satya N, et al. Bioethanol production from rice straw: an overview. Bioresour Technol 2010; 101(13):4767e74. [14] Parveen K, Diane MB, Michael JD, Pieter S. Methods for pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production. Ind Eng Chem Res 2009;48(8):3713e29. [15] Jonathan D, Willis CO, Jurat-Fuentes Juan L. Methods for discovery and characterization of cellulolytic enzymes from insects. Insect Sci 2010;17(3): 184e98. [16] Li Q, Zheng L, Qiu N, Cai H, Tomberlin JK, Yu Z. Bioconversion of dairy manure by black soldier fly (Diptera: Stratiomyidae) for biodiesel and sugar production. Waste Manage 2011;31:1316e20. [17] Zheng L, Li Q, Zhang J, Yu Z. Double the biodiesel yield: rearing black soldier fly larvae, Hermetia illucens, on solid residual fraction of restaurant waste after grease extraction for biodiesel production. Renew Energ 2011;41:75e9. [18] Theander O, Westerlund EA. Studies of dietary fiber, 3. Improved procedures for analysis of dietary fiber. J Agri Food Chem 1986;34(2):330e6. [19] Yu G, Cheng P, Chen Y, Li Y, Yang Z, Chen Y, et al. Inoculating poultry manure with companion bacteria influences growth and development of black soldier fly (diptera: Stratiomyidae) larvae. Environ Entomol 2011;40:30e5. [20] Rakesh S, Meeta S, Arif A. Terminalia belerica Roxb. seed oil: a potential biodiesel resource. Bioresour Technol 2010;101(4):1380e4. [21] Bandonien D, Pukalskas A, Venskutonis PR, Gruzdien D. Preliminary screening of antioxidant activity of some plant extracts in rapeseed oil. Food Res Int 2000;33(9):785e91. [22] Bautista LF, Vicente G, Rosalıa R, Pacheco M. Optimisation of FAME production from waste cooking oil for biodiesel use. Biomass Bioenerg 2009;33: 862e72. [23] Canakci M, Sanli H. Biodiesel production from various feedstock and their effects on the fuel properties. J Ind Microbiol Biot 2008;35(4):431e41. [24] Arjun B, Chhetri K, Watts C, Islam RM. Waste cooking oil as an alternate feedstock for biodiesel production. Energies 2008;1:3e18. [25] Gerhard K. Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Technol 2005;86:1059e70. [26] Seungdo K, Bruce ED. Life cycle assessment of various cropping systems utilized for producing biofuels: bioethanol and biodiesel. Biomass Bioenerg 2005;29:426e39.
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Biodiesel production from rice straw and restaurant waste employing black soldier fly assisted by microbes Longyu Zheng a, Yanfei Hou a, Wu Li d, Sen Yang a, Qing Li a, b, c, **, Ziniu Yu a, * a
State Key Laboratory of Agricultural Microbiology, National Engineering Research Centre of Microbial Pesticides, Huazhong Agricultural University, Wuhan, PR China Biomass and Bioenergy Research Center, Huazhong Agricultural University, Wuhan, PR China c College of Science, Huazhong Agricultural University, Wuhan, PR China d College of Engineering and Technology, Huazhong Agricultural University, Wuhan, PR China b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 20 January 2012 Received in revised form 4 August 2012 Accepted 1 September 2012 Available online 1 October 2012
Biodiesel has become attractive as an alternative renewable fuel, but its large-scale production has been restricted because of the high cost of feedstock. Therefore, alternative feedstock is urgently needed to enable biodiesel production from cheap raw materials. Toward this goal, a co-conversion process using BSFL (black soldier fly larvae) and microbes (Rid-X) was established to convert rice straw and RSW (restaurant solid waste) into the larval grease of black soldier fly. In this study, about 43.8 g biodiesel was produced from 2000 BSFL grown on 1000 g mixed feed of rice straw (30%) and RSW (70%) within 10 days. About 65.5% of cellulose, 56.3% of hemicellulose, 8.8% of the lignin, 91.6% of protein and 71.6% of lipid in the feed were digested and utilized for insect biomass accumulation with the aid of Rid-X. The results showed that grease from BSFL fed on rice straw and RSW was suitable for biodiesel and most of the fuel properties were corresponding to the requirements of the standard EN 14214. The new alternative method was introduced to produce biodiesel from lignocellulose abundant materials by insect and microbes, partly bypassing the complex pretreatment of lignocellulose that needed by other biofuel technologies. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Black soldier fly Biodiesel Insect bioenergy Lignocellulose Restaurant waste Rice straw
1. Introduction Despite many benefits, biodiesel is hampered by the production of oilseed plants. Biodiesel is mostly produced from edible oils, such as vegetable oils and animal fats, using conventional technology; using edible oil for biodiesel instead of food is unacceptable [1]. As food is a basic requirement for human, biodiesel feedstock should not affect the food supply [2]. Moreover, the cost of feedstock is a major economic factor in the development of biodiesel [3]. Therefore, alternative feedstock is urgently needed to enable biodiesel production from cheaper and non-food materials. To reduce feedstock cost and relieve food resource contradictions, a lot of research effort has been targeted to find new feedstock, such as microalgae [4], Madhuca indica [5], waste grease [6e8], Jatropha
* Corresponding author. Tel.: þ86 27 87280802; fax: þ86 27 87393882. ** Corresponding author. State Key Laboratory of Agricultural Microbiology, National Engineering Research Centre of Microbial Pesticides, Huazhong Agricultural University, Wuhan 430070, PR China. Tel.: þ86 27 87280802; fax: þ86 27 87393882. E-mail addresses: [email protected] (Q. Li), [email protected] (Z. Yu). 0360-5442/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.energy.2012.09.006
curcas [9] and muskmelon seed oil [10]. But these new methods face many challenges, while most are still at laboratory scale. As is known to all, seeking solutions to energy must not affect the environmental and societal benefits, thus it is important to develop non-food biomass [2]. The alternative feedstock should be technically feasible, economically competitive, environmentally acceptable, and easily available [11]. Recently, microbial lipids have been suggested as the alternative feedstock for biodiesel, but the cost of microbial lipids production is still high [12]. Rice straw is particularly an attractive lignocellulosic material for biofuel production. However, there are several challenges and limitations for its utilization, especially in the process of pretreatment [13]. Pretreatment, usually with acidolysis and enzymolysis, is the essential process to degrade this composite into monosaccharide for subsequent fermentation or other use. Excess acid usage and enzyme requirement lead to less environmental friendly and high cost for biofuel industry from rice straw and other lignocellulosic materials [14]. Fortunately, many insects showed high efficiency to degrade lignocellulosic substrates and use it as their nutrition supply [15]. People began to pay attention to insect, especially the scavengers for understanding of their mechanism of lignocellulose digestion
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and development of enzymes with new or better functions. Hermetia illucens L. (Diptera: Stratiomyidae), which is usually known as black soldier fly, is inclined to live in the outdoors and often associated with livestock, usually around decaying organic wastes such as animal manure or plant material [16]. The complex organic materials were converted into soluble organic molecules, and then incorporated into insect biomass rich in protein and grease. Grease from black soldier fly larvae (BSFL) is a low cost biodiesel feedstock, and the bioconversion of organic wastes into biodiesel has a beneficial effect on the environment [17]. We hypothesized that BSFL also has the potential to degrade rice straw for biodiesel production, partly bypassing the conventional pretreatment for monosaccharide. Restaurant solid waste (RSW) was used in this study for nutrition supplement during conversion. Rid-X, a commercial commodity containing functional microbes and enzymes was selected to further enhance the conversion rate of the substrates. A suitable condition for co-conversion was determined, including ratio of rice straw and RSW and inoculum concentration of microbes. Utilization efficiency of different components in the substrate by co-conversion, such as cellulose, hemicellulose, lignin, protein and lipid were evaluated. Composition and properties of the biodiesel from BSFL and Rid-X co-conversion were also assessed. This technology was established to exploit cheap and lignocellulose abundant materials for bioenergy production by insect and microbes. 2. Materials and methods 2.1. Raw materials BSFL used in this study was from the Huazhong Agricultural University colony. This colony was established in fall 2005 from the eggs of a colony at the Texas Agricultural Experiment Station, Stephenville, TX, which originated from the eggs from a laboratory colony at the Coastal Plain Experiment Station, University of Georgia, Tifton, GA, USA. BSFL were fed for about 6 days with standard colony diet before being used for this study [16]. Rid-X (SKU: 019200803069) was purchased from Reckitt Benckiser Inc. Parsippany, NJ 07054-0224. Restaurant waste is often generated in large quantities in cities. It is a potential hazardous material to environment without proper disposal [17]. Restaurant waste was collected from restaurants in Wuhan city, China, by Hubei Tianji Bioengineer Co. Ltd.; a government authorized biodiesel processing plant located in Huazhong Agricultural University. After removal of the waste grease for biodiesel production by the plant, the restaurant solid waste (RSW) was sampled and used for this study. Rice straw was obtained from the Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan, China. Rice straw was firstly heated at 110e120 C for 10 min to inactivate the enzymes, cut into small pieces, and then ground with a knifemill until the entire sample passes through the 40 mesh screen. 2.2. Co-conversion of rice straw and RSW by BSFL and microbes (Rid-X) RSW and rice straw were mixed at a certain ratio to feed BSFL for insect biomass accumulation; the co-conversion process was shown in Fig. 1. Based on preliminary trials, about 2000 of 6 days old larvae
Rice straw and SRW
Table 1 Relative contents of the main components in the rice straw. Component
Soluble sugar
Starch
Hemicellulose
Cellulose
Lignin
Ash
(wt.%)
11.5
0.5
27.3
32.6
18.4
14.2
(about 3 mg/larva) were inoculated into 1000 g mixture of RSW and rice straw. All the experiments were carried out in a greenhouse at 27 C with 70% air moisture. Conversion was terminated when prepupae accounted for about half of the larvae. The larvae were separated from the residue, water washed, and inactivated at 110 C for 10 min and dried at 50 C until constant weight was gained. After being ground with micro-mill larval biomass was stored at 4 C until grease extraction could be performed. To evaluate the effect of the mixing ratio of rice straw and RSW on the yield of insect biomass and larval grease yield, which is closely related to the final biodiesel yield, the organic mixture of RSW and rice straw was made at the following ratio: A) 100% rice straw (control), B) 20% RSW, C) 40% RSW, D) 60% RSW, E) 80% RSW and F) 100% RSW. There are great deal of lignocellulose, proteins and fats in the complex of RSW and rice straw. It is necessary to add microbial treatment (Rid-X) to increase the efficiency of conversion. Rid-X was inoculated at a series of dosage, from 0.05% to 0.5% (w/w), into the mixture of RSW and rice straw to determine its effect on BSFL biomass production and larval grease output. The next, uniform design was applied to obtain a suitable coconversion condition, including the mixing ratio of rice straw and RSW, and inoculum concentration of Rid-X. Table U5 (53) was used based on the results obtained from the trials mentioned above. 2.3. Crude grease extraction by Soxhlet extractor To determine the larval grease content in each sample, the extraction of grease was accomplished by a previously reported method with some modification [16]. A classical Soxhlet system with cellulose extraction cartridges was employed. Instead of refluxing extraction for 16 h, petroleum ether (200 ml) extraction was conducted twice for 8 h in Soxhlet extractor. Crude grease was obtained by combining the leaching liquor and evaporating petroleum ether with a rotary evaporator, and then the crude grease was calculated by weight. 2.4. Production of biodiesel The extracted grease contained various kinds of impurities. Therefore, it was necessary to be purified by adding 0.5% H2SO4. A two-step method: acid-catalyzed esterification of free fatty acids (to decrease the acidity of the crude grease), and alkaline-catalyzed transesterification was chosen for biodiesel production [16]. 2.5. Analysis Acid value of grease and biodiesel was determined by standard titrimetry methods (ASTMD 664-07), while kinematic viscosity and cloud point were determined by ASTM D-445 and ASTM D-2500 respectively. The compositions of biodiesel were analyzed by
Co-conversion by BSFL and Rid-X
Larval Grease
Fig. 1. Co-conversion process of rice straw and RSW by BSFL and Rid-X.
Biodiesel
L. Zheng et al. / Energy 47 (2012) 225e229 Table 2 Relative contents of the main components in the restaurant solid waste (RSW). Component
Water
Protein
Cellulose
Grease
Starch
Impurities
(wt.%)
81.2
4.2
1.6
3.4
3.8
0.2
GC/MS. Hemicellulose, cellulose and Klason lignin were determined as previously reported [18]. Hexoses in the solution were measured by the anthrone/H2SO4 method; pentoses were determined by the orcinol/HCL method. Hemicellulose was determined as the sum of pentoses, whereas cellulose as the sum of hexoses. Automatic Kjeldahl apparatus method (Kjeltec 8400) was used for determination of protein content. All experiments were carried out in triplicates.
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feed because of lack of nutrition (data not shown). Insect biomass yield and the grease content reduced to 96.9 g and 32.0% when 100% of RSW was used. RSW was considered to be a better diet for BSFL than other type of organic waste, such as animal manure, grease content in the insect biomass can reach 39.2% when BSFL were fed with RSW [17]. The reason why the larval grease content in this study was lower than previous reported may be due to the higher larval inoculum amount which was designed for better degradation of lignocellulosic components in rice straw. To obtain maximum biomass and grease yield, one can see from Fig. 2A, the optimal mixing ratio of RSW and rice straw should be around 8:2. Hence, this maxing ratio was further used to evaluate the effect of Rid-X on the conversion rate and grease yield. 3.3. Effect of the amount of Rid-X on the BSFL grease yield
3. Results and discussion 3.1. Raw material properties The relative content of the main components of rice straw were determined before being used for the study and showed in Table 1. Restaurant waste includes uneaten food and food preparation leftovers from residences, commercial establishments such as restaurants, institutional sources like school cafeterias, and industrial sources like factory lunchrooms. As shown in Table 2, the RSW used in this study included water (81.2%), starch (3.8%), cellulose (1.6%), protein (4.2%), grease (3.4%) and impurities (0.2%). 3.2. Effect of different ratio of RSW and rice straw on the BSFL grease yield RSW is rich in grease and protein, but poor in lignocellulose (Table 2); while rice straw is lignocellulose-rich, but poor in grease and protein (Table 1). Nutrition balance of feed for BSFL was therefore tested by mixing RSW and rice straw together in different ratio. The organic materials in RSW and rice straw were converted into soluble organic molecules such as sugar, amino acids, and fatty acids firstly, and incorporated into the biomass of BSFL. Larval grease was extracted and weighed to evaluate the effect of different ratio. When RSW ratio increased from 20% to 80%, insect biomass and grease relative content increased from 62.5 g to 98.7 g (dry matter, DM), and 28.7% to 33.7%, respectively. Accordingly, as shown in Fig. 2A, the larval grease yield increased from 17.9 g to 33.3 g. The larvae were unable to grow when rice straw was used as the sole
Rid-X contains millions of natural active bacteria that facilitate in breaking down the solid organic wastes, and the active ingredients are cellulase, lipase, protease and amylase. For better utilization of organic matter in rice straw and RSW, microbial agents were added to improve the conversion efficiency, especially the degradation of cellulose and hemicellulose in the rice straw. Different concentration of Rid-X was added to mixture of RSW (80%) and rice straw (20%) for co-conversion. The results (Fig. 2B) indicated that when the amount of Rid-X was added from 0.05% to 0.4% (w/w) into the substrate, the insect biomass and larval grease yield increased correspondingly, showing a positive relationship between Rid-X dosage and grease accumulation. With the assistance of microbes and its associated enzymatic degradation, more nutritive from the substrate became available for the development of BSFL. Some microbes may also aid in the digestion of food. This phenomenon has also been confirmed in the previous studies [19]. Although more data is needed, shorter production cycle may be expected by this co-conversion technology. However, when inoculum dosage was higher than 0.4%, the larval grease yield increased only slightly. It is indicated that the optimal dosage of Rid-X for the co-conversion should be about 0.4%. Therefore, mixing ratio (8:2) and 0.4% of Rid-X addition was used as a reference for the further optimization by uniform design. 3.4. Optimization of conversion parameters The uniform design table U5 (53) was selected to study the appropriate conditions for co-conversion to maximize the yield of
B
A
45
Grease yield (g)
Grease yield (g)
40 30 20 10
40 35 30 25
0
20
2:8
4:6
6:4
8:2
10:0
Ratio of RSW and rice straw (w/w)
0
0.1 0.2 0.3 0.4 0.5 0.6 Inoculum amount of Rid-X (%,w/w)
Fig. 2. Single-factor effect of feed maxing ratio and inoculum amount of microbes on BSFL grease yield. (A) Effect of ratio of RSW and rice straw on BSFL grease yield. (B) Effect of inoculum amount of Rid-X on BSFL grease yield.
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Table 3 Uniform design of Rid-X dosage and mixing ratio of RSW and Rice straw using table U5 (53). Experiment no.
Ratio of RSW and rice straw
Rid-X (w/w)
Insect biomass (g, DM)
1 2 3 4 5
4:6 5:5 6:4 7:3 8:2
0.3% 0.40% 0.25% 0.35% 0.45%
86.2 91.8 106.4 122.8 115.5
Grease content (%) 1.2 2.1 2.4 1.2 0.2
35.7 37.8 36.7 39.6 37.2
1.4 1.5 1.8 1.7 1.3
Grease yield (g) 30.7 34.7 39.1 48.6 42.9
0.7 1.2 1.5 0.9 0.7
insect larval grease. The two factors (ratio of RSW and rice straw, the amount of Rid-X) were optimized at 5 levels. As shown in Table 3, when 0.35% of Rid-X was inoculated in to the mixed medium of RSW and rice straw (7:3), the insect biomass, larval grease yield of BSFL reached the highest. From visual analysis, an operating condition was determined as 7:3 of RSW and rice straw and 0.35% of microbes (w/w) and selected for further evaluation. 3.5. Compositional changes of RSW and rice straw after coconversion Selected components of the original mixed medium (RSW:Rice straw, 7:3) and the digested residual after 10 days co-conversion were analyzed for comparison and to determine the conversion rate of the components. One can see from Fig. 3 that in the absence of Rid-X, about 27.9% of cellulose and 32.6% of hemicellulose were degraded by BSFL. This result is in accord with the previous report that larvae can digest the lignocellulosic components in dairy manure [16]. Conversion rate of cellulose and hemicellulose was significantly enhanced when 0.35% of Rid-X was introduced to the conversion system. With the aid of cellulase and fermentation of microbes, about 65.5% of cellulose and 56.3% of hemicellulose could be digested into sugar when the two agents worked together as shown in Fig. 3. The sugar was then absorbed by BSFL for development. However, BSFL can hardly use the lignin component in the feed (0.8%). Rid-X showed a feeblish ability for lignin degradation because about 8.8% of the lignin was reduced when Rid-X was added. BSFL could digest about 74.4% of protein in the mixed feed, and more protein (91.6%) was utilized when BSFL and Rid-X function together. Lipid conversion showed no significant difference in
Table 4 Selected characteristics of BSFL grease fed on RSW and rice straw in comparison with rapeseed oil and waste cooking oil. Properties
BSFL grease
Rapeseed oil [20]
Waste cooking oil [22]
Acid value (mg KOH/g) Iodine value (gI/100 g) (m/m) Saponification value (mg KOH/g) Cloud point ( C) Peroxide value (meq/kg)
8.2 89 157
1.14 115.5 188.6 [21]
e 108.4 183.4
6.8 0.18
3.9 0.75
e 16.4
the presence and absence of Rid-X. More nutrients in RSW and rice straw were utilized and incorporated into BSFL biomass with the aid of Rid-X, resulting in promoted biomass and grease yield. Grease was extracted from BSFL and further processed for biodiesel. 3.6. Biodiesel production from BSFL grease After 10 days co-conversion with the aid of Rid-X (0.35%, w/w), about 43.8 g biodiesel was produced by a two-step method from 2000 BSFL grown on 1000 g mixed feed of rice straw (30%) and RSW (70%). The properties of BSFL grease were described in Table 4, the results showed great similarities to the previous reports [16,17]. It is indicated that BSFL grease held a quite stable property in different feeding conditions. This larval grease is suitable to serve as the feedstock of biodiesel when compared with rapeseed oil. Furthermore, the properties of this BSFL grease based biodiesel further demonstrated that BSFL grease is suitable for biodiesel production. The compositions of FAME (fatty acid methyl ester) in BSFL biodiesel were presented in Table 5. With a little change in the relative content, FAME compositions of BSFL biodiesel from this study were very close to the fatty acids profile of BSFL fed on other type of waste [17]. In the meantime, the properties of BSFL biodiesel were comparable to rapeseed biodiesel, and most of the factors were in reasonable agreement with the specifications of standard EN 14214 as shown in Table 6. It is further demonstrated that BSFL grease could be a viable biodiesel feedstock and this insect based biodiesel could be a promising substitute of conventional diesel fuel. The major challenge of biofuel production from lignocellulose is the pretreatment [26]. BSFL provided a potential feedstock for biodiesel to bypass this complex pretreatment. With the aid of RidX, BSFL possesses a good ability to manage organic waste and
Table 5 Fatty acid compositions of BSFL grease-based biodiesel fed on RSW and rice straw, rapeseed oil-based biodiesel and waste cooking oil-based biodiesel. Fatty acids
Fig. 3. Degradation rate of selected components in the mixed medium of RSW (70%) and rice straw (30%) after conversion by BSFL with or without Rid-X (0.35%).
Saturated fatty acid Capric acid (10:0) Lauric acid (12:0) Myristic acid (14:0) Palmitic acid (16:0) Stearic acid (18:0) Unsaturated fatty acid Palmitoleic acid (16:1) Oleic acid (18:1) Linoleic acid (18:2) Linolenic acid (18:3) Odd carbochain fatty acid Pentadecanoic acid (15:0) Heptadecanoic acid (17:0) Nonadecanoic acid (19:0)
BSFL biodiesel
Rapeseed biodiesel [23]
Waste cooking oil biodiesel [24]
3.8 27.8 8.1 14.2 7.6
e e e 3.49 0.85
e e 0.11 8.22 2.10
4.5 22.5 1.8 2.1
e 64.40 22.30 8.23
5.18 59.7 19.31 6.82
1.5 0.8 1.7
e e e
e e e
L. Zheng et al. / Energy 47 (2012) 225e229 Table 6 Properties of BSFL grease-based biodiesel fed on rice straw and RSW, rapeseed oilbased biodiesel, waste cooking oil-based biodiesel and in comparison with standards of EN 14214. Properties
EN 14214
BSFL biodiesel
Rapeseed biodiesel [25]
Waste cooking oil biodiesel [8]
Ester content (%) Density (Kg/m3) Viscosity at 40 C (mm2/s) Water content (mg/Kg) Flash point (closed cup) ( C) Cetane number Acid number (mg KOH/g) Cloud Point ( C) Methanol or Ethanol (m/m) Distillation
96.5 min. 860e900 3.5e5.0
96.6 895 5.96
e 911 4.40
e 877 5.23
500 max.
300
300
e
120 min.
123
e
157
51 min. <0.5
55 0.6
45 1.14
48 0.21
e 0.2%
4.2 0.3%
3.9 e
1 e
e
91% at 360 C
91% at 352 C
e
lignocellulosic materials for biodiesel production. The cellulose, hemicellulose, grease and protein in RSW and rice straw were degraded into soluble organic molecules with a relatively high conversion efficiency, such as sugar, amino acids, and fatty acids, and then these soluble organic molecules were further converted into the BSFL grease. The grease provided a renewable and noncontroversial source for biodiesel. Compared with the traditional biodiesel plant, BSFL biodiesel appears to be an attractive energy resource due to its renewability, sustainable supplement, favorable environmental properties and significant economic potential. Additionally, BSFL has high reproductive capacity and short lifecycle, while plant has a long lifecycle and needs a plenty of land. It can be believed that insect bioenergy will bring new force to the Waste-to-energy technology. 4. Conclusions A co-conversion strategy was established, providing a practical and promising method for converting rice straw and RSW into biodiesel. Biodiesel was produced from wastes by insect and microbes, and sustainable solutions for wastes are on the horizon to find an alternative to traditional biodiesel. When 0.35% of Rid-X was added in the 1000 g mixed feed (RSW:Rice straw, 7:3), 122.8 g of insect biomass was obtained and BSFL grease content reaches 39.6%, yielding 43.8 g biodiesel from 2000 larvae. These results are important in selecting an appropriate feedstock for biodiesel. From comprehensive analysis of society, economy and environment, it can be concluded that BSFL with the assist of microbes have the potential to recycle lignocellulose abundant materials into biodiesel, and reduce environmental pollution of the wastes. Acknowledgments This research was supported by the Fundamental Research Funds for the Central Universities (No. 2011JC016) and National
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Natural Science Foundation of China (4004-114014). Special thanks to Dr. Jeffery K. Tomberlin, Texas A&M University, for his generous gift of the black soldier fly colony. References [1] Marina OSD, Adriano VE, Silvia AN, Rubens MF, Carlos EVR, Maria RWM. Production of bioethanol and other bio-based materials from sugarcane bagasse: integration to conventional bioethanol production process. Chem Eng Res Des 2009;87:1206e16. [2] David T, Robert S, Jonathan AF, Jason H, Eric L, Lee L, et al. Beneficial biofuelsthe food, energy, and environment trilemma. Science 2009;17(325):270e1. [3] Fatih MD, Mustafa B, Havva B. Biowastes-to-biofuels. Energ Convers Manage 2011;52(4):1815e28. [4] Huang G, Chen F, Wei D, Zhang X, Chen G. Biodiesel production by microalgal biotechnology. Appl Energ 2010;87(1):38e46. [5] Ghadge SV, Raheman H. Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids. Biomass Bioenerg 2005;28:601e5. [6] Mustafa C. The potential of restaurant waste lipids as biodiesel feedstock. Bioresour Technol 2007;98(1):183e90. [7] Gui MM, Lee KT, Bhatia S. Feasibility of edible oil vs. non-edible oil vs. waste edible oil as biodiesel feedstock. Energy 2008;33:1646e53. [8] Kumaran P, Mazlini N, Hussein I, Nazrain M, Khairul M. Technical feasibility studies for Langkawi WCO (waste cooking oil) derived-biodiesel. Energy 2011; 36:1386e93. [9] Lu H, Liu Y, Zhou H, Yang Y, Chen M, Liang B. Production of biodiesel from Jatropha curcas L. oil. Comput Chem Eng 2009;33:1091e6. [10] Rashid U, Rehman HA, Hussain I, Ibrahim M, Haider MS. Muskmelon (Cucumis melo) seed oil: a potential non-food oil source for biodiesel production. Energy 2011;36:5632e9. [11] Lang X, Dalai AK, Bakhshi NN. Preparation and characterization of bio-diesels from various bio-oils. Bioresour Technol 2001;80(1):53e62. [12] Hu C, Wu S, Wang Q, Jin G, Shen H, Zhao Z. Simultaneous utilization of glucose and xylose for lipid production by Trichosporon cutaneum. Biotechnol Biofuels 2011;4(25):1e8. [13] Parameswaran B, Raveendran S, Reeta RS, Surender V, Lalitha D, Satya N, et al. Bioethanol production from rice straw: an overview. Bioresour Technol 2010; 101(13):4767e74. [14] Parveen K, Diane MB, Michael JD, Pieter S. Methods for pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production. Ind Eng Chem Res 2009;48(8):3713e29. [15] Jonathan D, Willis CO, Jurat-Fuentes Juan L. Methods for discovery and characterization of cellulolytic enzymes from insects. Insect Sci 2010;17(3): 184e98. [16] Li Q, Zheng L, Qiu N, Cai H, Tomberlin JK, Yu Z. Bioconversion of dairy manure by black soldier fly (Diptera: Stratiomyidae) for biodiesel and sugar production. Waste Manage 2011;31:1316e20. [17] Zheng L, Li Q, Zhang J, Yu Z. Double the biodiesel yield: rearing black soldier fly larvae, Hermetia illucens, on solid residual fraction of restaurant waste after grease extraction for biodiesel production. Renew Energ 2011;41:75e9. [18] Theander O, Westerlund EA. Studies of dietary fiber, 3. Improved procedures for analysis of dietary fiber. J Agri Food Chem 1986;34(2):330e6. [19] Yu G, Cheng P, Chen Y, Li Y, Yang Z, Chen Y, et al. Inoculating poultry manure with companion bacteria influences growth and development of black soldier fly (diptera: Stratiomyidae) larvae. Environ Entomol 2011;40:30e5. [20] Rakesh S, Meeta S, Arif A. Terminalia belerica Roxb. seed oil: a potential biodiesel resource. Bioresour Technol 2010;101(4):1380e4. [21] Bandonien D, Pukalskas A, Venskutonis PR, Gruzdien D. Preliminary screening of antioxidant activity of some plant extracts in rapeseed oil. Food Res Int 2000;33(9):785e91. [22] Bautista LF, Vicente G, Rosalıa R, Pacheco M. Optimisation of FAME production from waste cooking oil for biodiesel use. Biomass Bioenerg 2009;33: 862e72. [23] Canakci M, Sanli H. Biodiesel production from various feedstock and their effects on the fuel properties. J Ind Microbiol Biot 2008;35(4):431e41. [24] Arjun B, Chhetri K, Watts C, Islam RM. Waste cooking oil as an alternate feedstock for biodiesel production. Energies 2008;1:3e18. [25] Gerhard K. Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Technol 2005;86:1059e70. [26] Seungdo K, Bruce ED. Life cycle assessment of various cropping systems utilized for producing biofuels: bioethanol and biodiesel. Biomass Bioenerg 2005;29:426e39.