Fermentation Wastewater Research Articles

Study and valorisation of wastewaters generated in the production of bacterial nanocellulose.

Two culture media were tested for the production of bacterial nanocellulose (BNC) under static culture fermentation, one containing molasses (Mol-HS), the other molasses and corn steep liquor (Mol-CSL), as a source of carbon and nitrogen, respectively. These are low-cost nutrients widely available, which provide very good BNC productivities. However, the use of these substrates generates wastewaters with high organic loads. Anaerobic digestion is one of the most promising treatments for industrial wastewaters with high organic loads since, beyond removal of the organic matter, it generates energy, in form of biogas. The wastewaters from BNC fermentation were thus evaluated for their biochemical methane potential through anaerobic digestion. For this, two wastewaters streams were collected: (i) the culture medium obtained after fermentation (WaF) and (ii) the WaF combined with BNC washing wastewaters (WaW). These two effluents-WaF and WaW-were characterized regarding their chemical oxygen demand, total nitrogen, total and volatile solids, to assess their suitability for anaerobic digestion. The biochemical methane potential of WaF and WaW from Mol-CSL wastewaters was (387 ± 14 L kg-1 VS) and (354 ± 4 L kg-1 VS), corresponding to a methanization percentage of (86.9 ± 3.1) % and (79.5 ± 0.9) %, respectively. After treatment, the chemical oxygen demand of WaF and WaW was reduced by (89.2 ± 0.4) and (88.7 ± 1.5), respectively. An exploratory test using an Upflow Anaerobic Sludge Blanket reactor for WaW treatment was also performed. The reactor was operated with aorganic loading rate of [(6.5 ± 0.1) g L-1d-1] and hydraulic retention time of 3.33 days, allowing a chemical oxygen demand removal of 58% of WaW. Results here obtained demonstrate, for the first time, the high potential of AD for the valorisation of the BNC fermentation wastewaters.

Biochar prepared from maize straw and molasses fermentation wastewater: application for soil improvement.

A novel method was applied to improve biochar properties and its soil application by introducing molasses fermentation wastewater into a maize straw pyrolysis process. In this study, maize straw biochar (MSB) was prepared from maize straw mixed with different amounts (1, 2 and 3 mL g−1 straw, v/w) of molasses fermentation wastewater which contained high organics and nitrogen contents. Characterization results indicated that the yield, carbon content, N/C, and cation exchange capacity (CEC) of MSB increased gradually with the increasing dosage of fermentation wastewater. In addition, the prepared MSB was added into sandy soil with four mixing proportions (1%, 3%, 5% and 10%, w/w) to investigate its effects on plant growth, soil properties and soil catalase activity (CAT) by pot experiments. The results indicated that MSB amendments increased soil pH, soil total organic carbon (TOC) and nutrients contents (TN, TP). It was suggested that 5% biochar proportion in soil derived from maize straw with 2 mL g−1 fermentation wastewater addition was more suitable for ryegrass growth, soil fertility and CAT activity improvement. This study provides a promising way to realize the resource utilization of fermentation wastewater and agricultural wastes at the same time.

Utilization of marigold (Tagetes erecta) flower fermentation wastewater as a fertilizer and its effect on microbial community structure in maize rhizosphere and non-rhizosphere soil

Marigold (Tagetes erecta L.) flowers can be used to produce lutein, but the production process generates fermentation wastewater, which is rich in lactic acid. Currently, most fermentation wastewater treatment methods are relatively expensive and time-consuming. To develop a practical marigold flower fermentation wastewater treatment method, in this study, we treated the fermentation wastewater with calcium oxide to prepare a neutralization solution, which was then used to irrigate maize that in turn exhibited a significant increase in growth. Then, we investigated soil pH, conductivity and enzyme activity, as well as microbial community and diversity of the maize rhizosphere and non-rhizosphere soil. Compared with the control group, the neutralization solution had no significant effect on soil pH and four kinds of enzyme (soil urease, catalase, sucrase and acid phosphatase) activity, but the electrical conductivity of the treatment group increased by 24.3%. The 16s rDNA and ITS rDNA sequencing results showed that the neutralization solution treatment influenced the diversity and abundance of bacteria and fungi in the non-rhizosphere samples, as well as the number of bacterial species in rhizosphere soil. The effect of neutralization solution treatment on bacteria was greater than that on fungi. Proteobacteria and Ascomycota were the predominant bacterial and fungal phyla in maize rhizosphere soil. The relative abundance of Paenibacillus, Bacillus and Penicillium genera significantly increased in non-rhizosphere soils. We hereby present a potential method for treating marigold flower fermentation wastewater for fertilizer utilization and show that the neutralization solution promotes maize growth and influences the soil microbial structure.

Biotechnological approach to generate green biohydrogen through the utilization of succinate-rich fermentation wastewater

Photofermentation seems to be an attractive mode of generating biohydrogen from fermentation effluent. Use of succinate fermentation effluent, however, has not been reported. Rhodobacter sphaeroides KKU-PS1 and Rhodopseudomonas palustris were acclimatised in succinate. It was determined that the KKU-PS1 was superior with respect to hydrogen productivity and was selected for further experiments. Photofermentation in succinate by the KKU-PS1 validated, generating 1217 mL H2/L of cumulative hydrogen at a maximum rate of 6.7 mL H2/L/h. Photofermentation from each single carbon sources that are components of effluent was performed and it was determined that acetate and succinate promoted the fastest growth of KKU-PS1 and hydrogen evolution, respectively. Photofermentation by the strain using mixed substrates mimicking diluted bio-succinate effluent produced yielded 1005 mL H2/L cumulative hydrogen at a maximum rate of 4.1 mL H2/L/h. The study highlighted potential of utilizing bio-succinate fermentation effluent for biohydrogen production, with further optimization required.

Volatile fatty acid production from semi-synthetic milk processing wastewater under alkali pH: The pearls and pitfalls of microbial culture.

Volatile fatty acids (VFA) are one of the most promising sustainable and environmentally friendly bioproduct owing to their wide usage area and high market demand. For this reason, in this study, the evaluation of VFA production from pure and mixed bacterial cultures was aimed. Three different mixed cultures with C. aceticum, C. butyricum and P. acidipropionici as pure cultures were used for inoculation of milk processing wastewater fermentation under pH 10 for 15days. The mixed culture fermentation had the highest VFA production efficiency whereas the highest amount of acetic, butyric and propionic acid productions were obtained by C. aceticum, C. butyricum and P. acidipropionici, respectively. Also, the mixed cultures demonstrated faster pH regulation and acclimation than the pure cultures tested. Therefore, development of synthetic cultures may offer a useful approach to produce VFA mixtures with one-dominant acid type and with high production efficiency.

Nanoscale phase transition seeds-assisted low temperature preparation of α-Al2O3 ultrafiltration membrane

Abstract α-Al2O3 nanoparticles with a particle size of ~10 nm were synthesized from aluminum alkoxide precursor chelated by oxalic acid at 500 °C and added to boehmite sol as phase transition seeds (PTS) in low temperature preparation of α-Al2O3 ultrafiltration (UF) membrane. With the PTS doping of 2.5 wt%, a single phase α-Al2O3 membrane with small pore size of 7.2 nm was prepared at 950 °C. After long-term static and dynamic corrosion tests, the as-prepared α-Al2O3 UF membrane was found to no significant degradation in performance, displaying a stable MWCO and water permeability of 15 kDa and 85 L/(m2 h bar) respectively. In the decolorization of vinegar fermentation wastewater, the COD removal was 63% whereas the color removal could reach 98%. Furthermore, the contaminated membrane could be reused many times after cleaning, confirming the excellent durability and practicality of α-Al2O3 UF membrane in wastewater treatment.

Exploitation of Algal-Bacterial Consortia in Combined Biohydrogen Generation and Wastewater Treatment

Microalgae cultivation in municipal, industrial and agricultural wastewater is an emerging, highly effective approach for resource recovery and concomitant bioenergy generation. Wastewater effluents represent ideal sources of nutrients for eukaryotic green algal species. However, the performance of photosynthetic green algae is strongly dependent on the associated bacterial partners present in the effluents. Our combined wastewater treatment and biohydrogen evolution approach applied green microalgae-based photoheterotrophic degradation using dark fermentation wastewater effluent as substrate. The results showed that condition-dependent mutualistic relationships between the microbial and Chlorella algae populations had direct impact on the biodegradation efficiency and also on algal biohydrogen production. Metagenome analysis of the novel hybrid biodegradation system together with total nitrogen and phosphorous analytics provided important clues for the primary importance of the green algae partner in nitrogen and phosphorous removal. Bacterial bin genome data also indicated algal growth promotion by bacterial partners. With further development and optimization this new approach can lead to a highly efficient simultaneous organic waste mitigation and renewable energy production technology.

Synthesis of Activated Carbon from Citric Acid Residue by Phosphoric Acid Activation for the Removal of Chemical Oxygen Demand from Sugar-Containing Wastewater

Over 2 million tons of citric acid residue (CAR) are generated from citric acid production in China each year. Thus, it is of great significance to find a suitable method for recycling the waste products of citric acid fermentation. Herein, activated carbon (AC) samples were prepared from CAR with phosphoric acid activation. Effects of impregnation ratio, activation time, and activation temperature on pore structure and surface functional group formation were evaluated. AC prepared by 1.5 h of pyrolysis in nitrogen at 550°C from CAR and phosphoric acid at an impregnation ratio of 2.0 (CAR-AC-2.0) had the largest specific surface area (786 m2/g) and total pore volume (0.71 mL/g). The surface morphologies and chemical properties of AC samples were characterized by scanning electron microscopy, thermogravimetric analysis, elemental analysis, and Fourier transform infrared spectroscopy (FTIR), and their adsorption capacities for methylene blue (MB) and iodine were tested. There were rare functional groups on the surfaces of CAR-AC-2.0, and the adsorption amounts of CAR-AC-2.0 for iodine and MB reached up to 729 and 121 mg/g, respectively. CAR-AC-2.0 was an ideal adsorbent for removing organic matters from solutions and wastewater. Adsorption efficiency of CAR-AC-2.0 for chemical oxygen demand (COD) from sugar-containing wastewater was 291.6 mg/g, and the removal efficiency was 80.9% when the dosage was 15 g/L. This study provided a new strategy for removing COD from fermentation wastewater with high efficiency and low cost.

Power generation and microbial community analysis in microbial fuel cells: A promising system to treat organic acid fermentation wastewater

To explore a sustainable and efficient treatment approach for organic acid fermentation wastewater, two microbial fuel cells (MFCs) systems inoculated with wastewater or domesticated microbial community were constructed in this study. Compared with the MFC inoculated with domesticated microbial community, the MFC inoculated with wastewater not only showed higher power density (543.75 mW m−2) and coulomb efficiency (22.10%), but also exhibited higher removal rates of chemical oxygen demand (75.59%), total nitrogen (76.15%), and ammonia nitrogen (83.23%), meeting the demand of wastewater discharge standard of China. Sequencing analysis revealed that the MFC inoculated with wastewater were richer in microbial community, and some bacteria such as Saprospiraceae and Caldilineaceae were beneficial for its good performance. In contrast, the microbial community of the MFC inoculated with domesticated microbial community was relatively simple. These results indicated that MFCs may be a sustainable method for organic acid fermentation wastewater treatment without any preprocessing.

Encapsulation of polyphenols from fermented wastewater of Miang processing by freeze drying using a maltodextrin/gum Arabic mixture as coating material

Freeze drying using a maltodextrin/gum Arabic mixture (50 : 50%w/w) as coating material could be used to encapsulate phenolic compounds of wastewater from Miang (fermented tea leaf) production. The effect of concentrated fermented Miang water: coating material ratios of 10:1, 30:1, and 50:1 on the encapsulation efficiency was investigated. The result revealed that as the weight ratio of concentrated fermented Miang water to maltodextrin/gum Arabic mixture increased, the encapsulation efficiency decreased while the antioxidant capacity of Miang powder increased due to a higher phenolic concentration in the encapsulation process. The weight ratio of concentrated fermented Miang water to maltodextrin/gum Arabic mixture of 10 : 1 was the suitable ratio to encapsulate phenolic compounds with the efficiency as high as 99.40%. The IC50 values of DPPH and ABTS assays for the obtained Miang powder were 24.19 and 332.75 µg/ml, respectively. Additionally, the Miang powder contained gallocatechin, epigallocatechin, catechin, epicatechin, gallocatechin gallate, gallic acid, and caffeine. Practical applications Fermented Miang water (fermented tea leaf; Camellia sinensis var. assamica) as wastewater from Miang production is an attractive source of natural bioactive compounds, particularly phenolic compounds with antioxidant activity. These phenolic compounds were efficiently encapsulated by freeze drying using a maltodextrin/gum Arabic mixture as coating material. The phenolic compounds identified in Miang powder were gallocatechin, epigallocatechin, catechin, epicatechin, gallocatechin gallate, gallic acid, and caffeine. Therefore, the fermented Miang water that is thrown away and not used for other processes could be produced as Miang powder that is applied as an alternative source of natural antioxidants for food supplements, pharmaceuticals, cosmetics and other health products.

Co-culture of Bacillus coagulans and Candida utilis efficiently treats Lactobacillus fermentation wastewater

Co-culture of Bacillus coagulans and Candida utilis was firstly investigated in the efficient treatment of Lactobacillus fermentation wastewater (LFW) containing total organic carbon (TOC) of 22.0 g/L and total nitrogen (TN) of 2.4 g/L. The utilization of lactic acid by C. utilis was responsible for the relief of feedback inhibition to promote the growth of B. coagulans. The removal ratio of TOC by B. coagulans and C. utilis was only 9.1% and 22.7%, respectively, which was improved to 49.0% by co-culture. The removal ratio of TN by B. coagulans and C. utilis was merely 6.3% and 12.5%, respectively, which was also promoted to 44.6% by co-culture. Both the high growth of B. coagulans and the efficient removal of TOC and TN from LFW was achieved with the co-culture, which is not previously reported and very important in the production of probiotics with the resource utilization of LFW.

Reduction of Wastewater Discharge toward Second-Generation Acetone–Butanol–Ethanol Production: Broth Recycling by the Fermentation–Pervaporation Hybrid Process

To reduce the butanol fermentation wastewater (BFW) discharge and to address the difficulties in BFW treatment, a novel fermentation–pervaporation hybrid process was performed. After each batch of acetone–butanol–ethanol (ABE) fermentation, ABE in the fermentation broth was ex situ separated by pervaporation. The retentate was used as the buffer and the solution for the following batches of enzymatic hydrolysis and fermentation, respectively. Results showed that there were little negative influences of the phenols and acid inhibitors on the fermentation performances using the recycled BFW. Benefits from the process for BFW discharge reduction were obvious. After 4 cycles of BFW, ∼86% of the BFW was saved. Over 94% of ABE with concentrations of 42.5–50.2 g/L was recovered by pervaporation. Therefore, the novel process can effectively eliminate the disadvantage of large BFW discharge in the ABE fermentation processes.

Recovery and conversion of acetic acid from a phosphonium phosphinate ionic liquid to enable valorization of fermented wastewater

A method was developed to recover and convert a carboxylic acid from a phosphonium phosphinate ionic liquid.

Volatile fatty acids impacting phototrophic growth kinetics of purple bacteria: Paving the way for protein production on fermented wastewater

Nutrient losses in our food chain severely surpass our planetary boundaries. Resource recovery can contribute to mitigation, for instance through converting wastewater resources to microbial protein for animal feed. Wastewater typically holds a complex mixture of organics, posing a challenge to selectively produce heterotrophic biomass. Ensuring the product's quality could be achieved by anaerobic generation of volatile fatty acids (VFAs) followed by photoheterotrophic production of purple non-sulfur bacteria (PNSB) with infrared light. This study aimed to determine the most suitable PNSB culture for VFA conversion and map the effect of acetate, propionate, butyrate and a VFA mixture on growth and biomass yield. Six cultures were screened in batch: (i) Rhodopseudomonas palustris, (ii) Rhodobacter sphaeroides, (iii) Rhodospirillum rubrum, (iv) a 3-species synthetic community (i+ii+iii), (v) a community enriched on VFA holding Rb. capsulatus, and (vi) Rb. capsulatus (isolate ‘v’). The VFA mixture elevated growth rates with a factor 1.3–2.5 compared to individual VFA. Rb. capsulatus showed the highest growth rates: 1.8–2.2 d−1 (enriched) and 2.3–3.8 d−1 (isolated). In a photobioreactor (PBR) inoculated with the Rb. capsulatus enrichment, decreasing sludge retention time (SRT) yielded lower biomass concentrations, yet increased productivities, reaching 1.7 g dry weight (DW) L−1 d−1, the highest phototrophic rate reported thus far, and a growth rate of up to 5 d−1. PNSB represented 26–57% of the community and the diversity index was low (3–7), with a dominance of Rhodopseudomonas at long SRT and Rhodobacter at short SRT. The biomass yield for all cultures, in batch and reactor cultivation, approached 1 g CODBiomass g−1 CODRemoved. An economic estimation for a two-stage approach on brewery wastewater (load 2427 kg COD d−1) showed that 0.5 d SRT allowed for the lowest production cost (€ 10 kg−1 DW; equal shares for capex and opex). The findings strengthen the potential for a novel two-stage approach for resource recovery from industrial wastewater, enabling high-rate PNSB production.

Impact of operational conditions on development of the hydrogen-producing microbial consortium in an AnSBBR from cassava wastewater rich in lactic acid

Biohydrogen production from cassava starch wastewater was evaluated in anaerobic sequencing batch biofilm reactor (AnSBBR) using different inoculum (mixed cultures from naturally fermented wastewater and anaerobic sludge thermally treated) and feeding strategies (batch and fed-batch). The highest hydrogen productivity (2.4 LH2 L−1 d−1) and yield (11.7 molH2 kg−1Carbohydrates) were verified in low and intermediate organic load rates (12 and 14 g L−1 d−1) and longer cycle time (4 h), respectively. The productivity was favored by fed-batch strategy, and yield by batch. The hydrogen production was verified in both inoculum sources. However, in the assays inoculated from naturally fermented wastewater, with higher organic load rate (18 g L−1 d−1) and intermediate cycle time (3 h) no hydrogen was observed, regardless the feeding strategy, indicating that the inhibitory effects of the indigenous microorganisms present in cassava starch wastewater were more expressive in these conditions. The operational conditions applied to hydrogen production in AnSBBR from cassava starch wastewater may influence the microflora development in the reactor. In this study three possible scenarios were verified: hydrogen-producing bacteria (HPB) growth; hydrogen-producing bacteria inhibition or coexistence between ones and lactic acid bacteria (LAB), which are autochthones of this wastewater.

Effect of humic acid on photofermentative hydrogen production of volatile fatty acids derived from wastewater fermentation

Abstract Humic acid (HA) containing in the inoculated waste activated sludge (WAS) would be released into the fermentation liquid during dark fermentative hydrogen production. Nevertheless, the influence of HA on the photofermentative hydrogen production from volatile fatty acids (VFAs) left in the dark fermentation liquid by photosynthetic bacteria (PSB) had not been investigated. This study measured the effects of sludge humic acid (SHA) and AQS (anthraquinone-2-sulfonic acid, model humic acid) on the photofermentative hydrogen production from VFAs. Results showed that the photofermentative hydrogen production was reduced by 12.0% and 35.4% in synthetic wastewater with 100 mg/L of the added SHA or AQS, respectively. Mechanistic studies showed that high concentrations of SHA and AQS inhibited the activity of nitrogenase and development of PSB biomass, as well as damaging the cell membranes and causing significant death of PSB, leading ultimately to a significant decrease of photofermentative hydrogen production. Moreover, fluorescence spectra showed that SHA had a small molecular weight and a low degree of humification compared to that of AQS, which caused more negatively influence of AQS on photo hydrogen generation from VFAs. Finally, the feasibility of removing SHA from anaerobic dark fermentation liquid of wastewater to improve photofermentative hydrogen production was testified.

Development of a method for the valorization of fermentation wastewater and algal-residue extract in docosahexaenoic acid production by Schizochytrium sp.

Fermentation wastewater (FW) and algal residue are major by-products of docosahexaenoic acid (DHA) fermentations utilizing Schizochytrium sp. In order to reduce production costs and environmental pollution, we explored the application of FW and algal-residue extract (AE) for DHA production. Components analysis showed that FW and AE contained some mineral elements and protein residues, respectively. When they were used for DHA fermentation, results showed that 20% replacement of fresh water by FW and 80% replacement of yeast extract nitrogen by AE reached DHA content of 22.23 g/L and 27.10 g/L, respectively. Furthermore, a novel medium that utilizes a mixture of FW and AE was applied for DHA fermentation, whereby the final DHA yield reached 28.45 g/L, 24.56% higher than conventional medium. The strategy of valorizing fermentation waste provides a new method for reducing the costs and reducing environmental pollution of microbial fermentations.

Polysulfone/nanocomposites mixed matrix ultrafiltration membrane for the recovery of Maillard reaction products

Maillard reaction products like melanoidins present in industrial fermentation wastewaters are complex compounds with various functional properties. In this work, novel ultrafiltration (UF) mixed matrix membrane (MMM) composed of polysulfone (PSF) and nanocomposites was prepared through a phase inversion process for the recovery of melanoidins. Nanocomposites were prepared with acid functionalized multiwalled carbon nanotubes (MWCNTs) as the reinforcing filler for chitosan-thermoplastic starch blend. Higher nanocomposites content in the PSF matrix reduced the membrane permeability and melanoidins retention indicating tighter membrane with surface defects. The membrane surface defects could be sealed with dilute polyvinyl alcohol (PVA) solution. The best performing membrane (1% nanocomposites in 18% PSF membrane sealed with 0.25% PVA coating) resulted in uniform melanoidins retention of 98% and permeability of 3.6 L/m2 h bar over a period of 8h. This demonstrates a low fouling PSF membrane for high melanoidins recovery.

Enhancing fermentation wastewater treatment by co-culture of microalgae with volatile fatty acid- and alcohol-degrading bacteria

Co-culture of microalgae and bacteria is a promising method for wastewater treatment. The suitable selection of the bacteria in co-cultures with microalgae is critical for wastewater treatment. Three bacteria, Exiguobacterium aurantiacum, Stenotrophomonas acidaminiphila, and Chryseobacterium scophthalmus, were the dominant bacterial species in fermentation wastewater treated by microalgae and activated sludge. Pure cultures and co-cultures of microalgae (Chlorella sorokiniana L3) and these bacteria were evaluated for the treatment of fermentation wastewater, which contains high concentrations of acetate acid, butyric acid, ethanol and butanol. The performance of the co-cultures was better than that of pure cultures of microalgae or bacteria for the removal of four organic compounds, and the removal efficiency of volatile fatty acids and alcohols in the best co-culture case was increased by 22.70% compared to that of pure cultures. Butanol and butyric acid were much more difficult for microalgae and bacteria to remove than were acetic acid and ethanol. The co-cultures of Chlorella sorokiniana L3 with Stenotrophomonas acidaminiphila or Chryseobacterium scophthalmus had the highest removal efficiencies for the four organic compounds in all treatments. The co-cultures of Chlorella sorokiniana L3 with Exiguobacterium aurantiacum, Stenotrophomonas acidaminiphila or Chryseobacterium scophthalmus promoted not only chlorophyll a + b production but also biomass accumulation of Chlorella sorokiniana L3 during the 3 days of cultivation compared with those in pure cultures. More than 77.8% of NH4+-N, 45.6% of total PO43−-P and 63.7% of COD (chemical oxygen demand) were removed in all co-cultures. These three bacteria are potential candidates for wastewater treatment through co-culture with microalgae.

Production of bacterial cellulose using polysaccharide fermentation wastewater as inexpensive nutrient sources

ABSTRACTBacterial cellulose (BC) is a nanostructured material mainly produced by Gluconacetobacter. The excellent physicochemical and mechanical properties of BC have made it become regarded as a kind of highly functional biopolymer in the application fields of bio-medicine, cosmetics and food industry. Using low-cost carbon sources as raw materials could make BC production more cost-effective. In this study, the pullulan fermentation wastewater with high chemical oxygen demand (COD) value of 39040 mg/L was used as substrate for BC production. After 10 days of fermentation, a BC yield of 1.177 g/L in wastewater was obtained, lower than that (1.757 g/L) produced in Hestrin-Schramm (HS) media. During the fermentation process, 59.49% of monosaccharide coupling with 18.9% of COD in wastewater decreased. There were no differences in the functional groups and crystal patterns of the BC samples produced in wastewater and HS medium. However, more pores and loose three-dimensional networks were observed in the microstructure of BC samples produced in wastewater, resulting in lower crystallinity (56.23%) and Young's modulus (3984.29 MPa) compared to that obtained from HS media. It indicated the nutrients composition of fermentation wastewater showed obvious effects on BC microstructure and mechanical properties. Our work demonstrated the possibility of using polysaccharide fermentation wastewater as inexpensive carbon source for BC production. Further study should be done in the improvements of the physical and chemical properties of BC sheets.