Potential Cost Effective Feedstocks for the Production of Carbon Nanomaterials at Larger Scales and Scope of Further Research

Sharma DK

Published on: 2023-12-26


Newer and interesting applications of carbon nanomaterial’s (CNMs) is pushing their demand in the market. The need for developing CNMs having good quality at industrial scales is increasing. There is also a need of using cost competitive raw materials for their manufacture in industries. Presently the production of CNMs using low cost feedstock’s such as coal, lignin, biomass, waste plastics, organic wastes etc. has been reviewed the use of CO2 and biogas for the production of CNMs has been discussed. Dry reforming of CH4 can yield H2 as well as CNMs, however, some suitable catalysts may have to be designed with the establishment of favorable reaction conditions. Gasification of coal and biomass can also be practiced to produce H2 and CNTs. Further research work is required in the area of process engineering to develop scaled up processes for the production of CNMs of good quality in larger yields by using the environmentally and economically sustainable processes.


Microplastics Nanofibers Lignocellulosic Nanoparticles


Carbon nanomaterials (CNMs) have shown great potential in enhancing the efficiency of solar cells, storage batteries, supercapacitors, fuel cells etc... The CNMs can also be used to produce nanocomposites with enhanced material and heat strength, conductivity, biomedical etc. applications [1, 2]. These also have excellent potential in enhancing the properties in material, biomedical and pharmaceutical areas [3]. CNM market in the world is around $ 4 billion and this is expected to grow almost 10 times during the next 10 years. Therefore there would be a need to not only produce these at larger scales but there is also a need to reduce the cost of their production to make their use sustainable. There would also be a need for using cheaper raw materials for the production of good quality carbon nanotubes (CNTs), graphene, fullerenes, carbon nanoparticles, quantum dots etc.

Traditionally aromatic hydrocarbons, alkenes. Alkanes, organic acids etc. have been used to produce CNMs. However, efforts have been made to use other raw materials with an aim to reduce the cost of raw material and improve the yield and quality of the CNMs. Presently the research work on the use of inexpensive raw materials for the production of CNMs has been reviewed.

Production of CNMs Using Coal

Since coal is polyaromatic polymer therefore this can be depolymerised thermally for degrading the aromatics down to form CNMs [4, 5]. Have reported on the production of carbon nanotubes (CNTs), graphene, and carbon nanoparticles etc. by using cheaper feedstocks such as bituminous coal, lignite, super clean coals, chemically leached coals, waste plastics (bakellite) etc. By using arc-discharge method. No catalyst was used in this process. The CNTs and graphene produced were characterized and used for the production of polystyrene nanocomposites [6]. In fact in order to prevent the interference by inorganic mineral matter of coal, the coal was demineralised through the organo-refining to produce super clean having less than 1-2 % ash [7]. Production of carbon nanoparticles was also observed. The use of super clean avoids the contaminations due to inorganic mineral matter and obviates the need of cleaning the CNMs produced. In fact organo-refining can remove almost 95-99 % mineral matter [8] and inorgano- chemical leaching [9] can remove almost 80 % mineral matter from coal. The use of the demineralised coal obtained after inorgano-chemical leaching was also made. The use of super clean coal was found to be a better choice [10] have described the production of single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) and graphene from Indian bituminous coals using an arc-discharge technique by using Fe and Ni-Y catalysts. The SWCNTs, MWCNTs and graphene produced were characterized and these authors have attempted to describe the mechanism of the formation of nanomaterials from coals. The use of cleaner coals obtained through organo-refining and inorgano- chemical leaching techniques would not only remove the mineral matter from coals but this would also disrupt and disintegrate the coal favourably for the graphitisation and production of CNMs [4, 5]. This would also save on the cost involved in purifying the CNMs produced. Moreover these chemical refining pre-treatments beneficially disrupt and disintegrate the coal structure for thermal depolymerization based degradation to generate CNMs through arc discharge method. The reaction conditions may be optimised to improve and control the quality and quantity of CNMs produced. Process intensification and reaction engineering work in this area may be extended [11]. Have reviewed the research work on the production of different types of CNMs from the various types of cheaper coals such as lignite, bituminous coal and anthracite. Aromaticity of anthracites is more whereas lignite and brown coals have lower aromaticity. Obviously anthracites would be better choice as the raw materials, however bituminous coals are more reactive chemically and would be thus more thermolabile to generate reactive free radicals.

Carbon based nanomaterials such as SWCNTs, MWCNTs, graphene etc. have attracted the attention due to their superior and excellent and exceptional physical, chemical, thermal, biological and mechanical properties in advancing the scope of future applications [1, 2]. There is a great demand for the production of these nanomaterials through environment – friendly and cost effective techniques. Precursors used for the growth and production of these nanomaterials play a crucial role in the success of the emerging technologies [12] Have also reviewed the research work on the production of CNTs from coals and suggested that the use of the arc - discharge and plasma jet technique results in the production of good quality CNTs however this process cannot be used at larger scales. Therefore, further research work would be required on the development of chemical vapour deposition (CVD) or ultra-flash cracking technique for the generation of CNTs from coals and coal based materials [13]. Reported the production of CNTs from coal through pyrolysis. They used pyrolysis gases by employing CVD technique. These authors used mainly methane and CO gases to produce the CNTs from coal pyrolysis at an optimum temperature between 400-500oC. These authors have also suggested a kinetics model for the production of CNTs through pyrolysis reactions [14]. Have recently reported the production of carbon nanodots and graphene from the coal by using laser blasting technique. These quantum dots may be used for biomedical applications involving optic imaging [15]. Have reviewed the research work on the production of nil dimensional quantum dot CNMs from coal. The use of coal tar, coke breeze, pitches etc. can also be made [16]. Have reported the synthesis of MWCNTs having high aspect ratio in good yield through catalytic pyrolysis of coal tar pitch. Cobalt was used as a catalyst.

Coal may be gasified and the syn gas generated may be used for generating CNMs. The dry reforming of CH4 generates MWCNTs where CO2 is used for reforming [17]. The nickel on alumina was used as a catalyst at temperatures above 500 O C to generate CNMs.

Gasification of coal [6] can generate syn gas and the CO generated in the syn gas may be converted to CNMs through catalytic conversion in high temperature and high pressure reactors. Syngas can also be subjected to the shift reaction to generate CO2 and H2. The details of the process have been discussed later in the text.

Even the CO2 - gasification of coal can generate CO and both CO and CO2 may be utilized to generate CNMs as discussed later in the text. Thus, coal may be utilized for the production of CNMs through conversion routes of carbonization, liquefaction and gasification also.

Production of CNMs by using biomass – A Regenerable Source

Lignocellulosic biomass contains mainly cellulose, hemicellulose, lignin and extractives containing flavonoids, terpenes etc. Plenty of biomass is available as agroresidues, forest residues, grasses, fruit and vegetable wastes. Several techniques of biomass conversion are known [18]. Even aquatic biomass including sea weeds, macroalgae and microalgae are available for exploitation as carbon sources [19, 20] have reported the synthesis of CNTs and carbon nanofibers from wood sawdust by using a tubular reactor. The formation of CNMs proceeded through graphitization stages. The production of nanomaterials in a tubular reactor seems to be an environmental friendly way this process also involves deoxygenation and dehydrogenation reactions besides carbonization and free radical reactions. Therefore, production of hydrogen and the other gases was also observed [21]. Have used rice husk powder in the presence of catalyst ferrocene to produce CNTs. The microwave oven was used to generate plasma conditions [22] have reported the production of CNTs and activated carbon from Miscanthus giganteous a lignocellulosic biomass (a grass) having high growth rate and this is a potential candidate for biofuel production in biorefineries. The silicates were removed through two stage activation using phosphoric acid followed by alkali treatment. The activated carbonaceous biomass having larger surface area and porosity was mixed with a nitrogenous materials and used for the production of CNTs by using iron precursor at higher pyrolytic temperatures.

The use of algal biomass has also been extended for the production of CNMs [23]. Have used microalgal biomass for the production of CNMs through microwave treatments [24]. Produced the CNMs using algal biochar using microwave technique. In fact ultra-flash cracking techniques may also be used to convert microalgae, macroalgae or other aquatic biomass to CNMs and further research in this direction may be extended and algae seem to be a good raw material for the production of CNMs.

Production of CNMs Using Lignin

Lignin in the lignocellulosic biomass is the aromatic component and this is a suitable raw material for the generation of CNMs and extensive research in this area has also been reported as this could be a regenerable source of CNMs. Lignin is available as a waste in the form of black liquor from the paper and pulp industries. Lignin can also be obtained as byproduct from the production of bioethanol from lignocellulosic biomass wastes through acidic or enzymatic hydrolysis [25, 26, and 18]. Research in the area of conversion of lignin to CNMs has been extended by several researchers. Lignin is a polyaromatic material and its polymeric structure becomes lose and labile after delignification processes, when this is separated from other components of lignocellulosic biomass. Exhaustive thermal degradation of lignin releases several aromatic moieties which undergo a chain of reactions in the free radical states [27] have used Kraft lignin employing iron powders as catalyst at 1000 °C to produce graphene. The graphene thus produced were characterized and these workers also produced CNTs from the Kraft lignin [28]. Have suggested the use of lignin available from paper and pulp industries, bioethanol manufacture and from the animal manure [29] have reviewed the research work on the use of lignin for the production of CNMs by thermochemical conversion processes [30] have reported the production of graphene sheets and CNTs from the Kraft lignin by using an iron catalyst at almost one third the ratio of lignin at 1000 o C in a tubular reactor for more than1.5 h. The prolonged reaction for more than 1h and 45 mins respectively produced CNTs. The graphene sheets and CNTs produced were characterized [31]. Reported on the synthesis of CNTs from Kraft lignin by cracking at temperatures above 1900 O C [32] have described the production of lignin based carbon nanomaterial’s, which can be used for the several biomedical applications. These can also be used in the preparation of nanocomposites and in drug delivery and gene delivery vehicles [33] have reported that the utilization of lignin is important for the success of biorefineries .Bio-CNMs from lignin seem to be value added products having several potential uses. Several techniques can be used for the recovery of lignin from waste biomass through several delignification techniques such as steam explosion, aqueous alkali treatment or milling etc [34].

Have reported that there is possibility of production of CNMs such as graphene having a wide range of potentially great applications in different areas. Use of CVD and pyrolysis techniques seems to be promising. Thus lignin seems to be a better suitable low cost raw material than biomass for the production of CNMs. Here delignification and acidic hydrolytic treatments [25, 26, and 18] also appear to be a suitable pretreatment for making lignin more thermally reactive for degradations and rearrangement to nanosized particles.

Production of CNMs Using Vegetable Oils and Waste Cooking Oils

Plenty of seed/vegetable oils are available which include edible as well as nonedible seed oils. These contain basically the lipids i.e., fatty glycerides. These can also undergo drastic thermal degradation to yield CNMs. The use of seed oils such as Jatropha oil, Pongamia oil, Palm oil or the waste cooking oil (from domestic and hotel sources) may be made for the production of CNTs. graphene, carbon nanoparticles etc. The use of Pongamia oil resulted in the formation of MWCNTs using CVD technique by employing ferrocene as the catalyst [35]. The CNTs and graphene obtained by using Pongamia oil were characterised and were found to be of good quality. The CNTs produced from the Pongamia oil were used for the synthesis of polystyrene based nanocomposites which showed enhancement of mechanical, thermal and electrical conductivity, EMI shielding etc. properties [35, 36] have reviewed the research work on the production of CNMs from the vegetable oils such as palm oil. The use of CVD, thermal cracking and microwave reactors has been made for the production of CNMs by the several workers in the past by using toluene and other conventional raw materials [37].

Have synthesized the CNTs using waste cooking oil by using MgO/Mo/Co catalyst and characterized these. These displayed good results in the wastewater treatment for the removal of contaminants. These studies showed a good potential for use of vegetable oils and waste cooking oil as a feedstock for the production of CNMs through CVD and ultra-thermal or flash pyrolysis routes [38].

Further studies in this direction by following 2 stage techniques i.e., by using cracked oil products in the solar heated high temperature reactors may be extended.

Production of CNMs Using Waste Plastics

Plenty of plastics are available as nonbiodegradable wastes which is posing a very serious environmental degradation problem including that of microplastics. Research work has been reported on the utilization of waste plastics for the production of CNMs [5] used the waste plastics such as bakelite for the production of CNTs through Arc- discharge method without using any catalyst. The use of bakelite char for the production of CNM was found to have good potential [39] have reported the production of graphene from plastic wastes by using a two-step process of pyrolysis at 400 o C, followed by further pyrolysis at 750 o C [40] have also reviewed the processes of production of CNTs and graphene from plastic wastes through pyrolysis techniques. Pyrolysis is a technique that involves depolymerization through thermal cracking and then rearrangement reactions involving fusion and condensation reactions. Primary reactions would lead to the production of liquid and gaseous products mainly [41]. However, several secondary and tertiary reactions lead to the formation of solid char products through ring fusion and ring condensation reactions. Pyrolysis under extensive thermal conditions i.e., thermally induced reactive cracking would produce carbon nanostructures such as CNTs, graphene, fullerene, nanoparticles etc. Several free radicals are formed which react under higher thermal regimes to yield different nano-moieties leading to the formation of CNMs. Complex reactions involved in upstream and downstream processes should be studied to understand and manipulate the different complex molecular and particle dynamics involved. The transition metals are used as catalysts and promoters. The processes are controlled by temperature, catalyst, and the kind of cursory materials generated. Understanding these processes would pave the ways for opening the newer possibilities of production of CNMs commercially through sustainable and economic techniques [42].

Have reviewed the research work on the production of CNTs from plastic wastes. Several fixed or fluidized bed reactors under ambient or high pressure conditions had been used for the cat-cracking of plastics down to the nano - sizes... There are large number of different plastics having varying polymeric structures and thus different plastic types had been used with varying results. There is a need to establish the process conditions for each polymer type and characterize the CNMs produced under different conditions. The depolymerization and molecular dynamics of catalytic cracking reactions should be studied. Lot of work on process engineering also remains to be done in this area.

Production of CNMs Using Organic Wastes

Reported the use of low cost feedstocks for the production of CNMs [43]. These authors have suggested more than 20-25 organic wastes which have the potential of being exploited for the production of CNMs. These raw materials are available as waste or as low cost materials which may be utilized in industries. For the production of CNMs and carbon nanoconposites at larger scales at lower processing costs by industries. Thus, further research may be extended in this direction [34] have reported the production of graphene from food, insects and organic wastes. In fact, the organic carbon waste undergoes thermal degradations and thermal transformation of dehydrogenation, fusion, condensation and other carbon – carbon interactive reactions under higher temperature conditions to give graphene [44]. Have also reviewed the use of different organic wastes such as agroresidues, food waste, industrial wastes such as spent battery wastes, polythene etc [22] also reviewed the use of different industrial wastes such as plastic and electronic waste, used papers, lignocellulosics plant or tree waste, solid fuels, animal or bug waste etc. in the production of graphene. Graphene were generated by either growing from smaller size to bigger or conversely from bigger size to smaller i.e.nano sizes. Physical or chemical exfoliation or drastic thermal degradation can be used. Each technique has its own merits and demerits.

Several workers are making efforts to develop newer techniques to produce high quality graphene at larger scales at lower costs by using ecofriendly techniques by using low cost raw materials. Several patents were reviewed earlier (Mass production of high quality graphene: An analysis of worldwide patents - Nano werk,), [44] have reported on the recycling of inexpensive carbon wastes to produce graphene and CNTs.

The use of organic gases and solid carbonaceous materials has been made for the production of carbon nanomaterials as reported by [20]. These authors have used low cost or rather disposable materials such as waste or used food stuffs such as biscuits, hay, insect parts and dung to grow graphene directly on copper foil at its reverse side near 1000 0 C under H2/inert gas atmosphere. The solid matter formed after the treatment consisting of graphene was easily recovered from the copper foil. The graphene generated were analyzed and were found to be of good quality. However, a care would be required in the choice of suitable organic waste considering the costs involved in purification and in improving the quality of CNMs thus produced.

Production of CNMs Using CO2, CO, CH4 and Biogas

Two potential feedstocks for the production of CNMs are CO2 and CH4. Plenty of CO2 gas is available from the flue gases by burning the fossil fuels such as coal, lignite, oil and natural gas. This is a greenhouse gas responsible for the climate change. Utilization of this gas commercially would help in mitigating the greenhouse effect [1, 2]. Have used this gas for the production of graphene by using burning Mg ribbon on the dry ice i.e., solid CO2. These authors have even used the promoters such as Ni and Zn for enhancing the yield and quality of graphene from the CO2. The graphene obtained was characterized and these were found to be of good quality. The graphene thus obtained were used in the synthesis of polystyrene and polycarbonate based nanocomposites which showed enhanced electrical conductivity, EMI shielding, mechanical and thermal properties [35, 45] reported the production of CNMs from CO2 at temperatures above 600 O C. The use of Mg and ferrocene was made as catalysts. The process of [35] appears to be simpler to generate graphene which may be converted to other CNMs.

The quality of the nanomaterials thus produced may be studied and improved if required. Presently, author has also suggested the use of some more raw materials which may be exploited as cost effective feedstocks for the production of CNMs in industries after their careful studies in the laboratory [46].

Developed the process of production of CNTs by using sodium salts such as NaCl. These workers were able to generate CNTs from CO2 through CVD technique by using sodium chloride as a catalyst at around 390 O C. Na could be easily removed through annealing later on. The authors have suggested that this is a simpler and cost effective process of generating CNTs from CO2 and other hydrocarbon gases [47]. Have reported the production of CNMs and H2 from the biogas by using biochar produced from the cracking of solid waste generated from the wastewater treatment. Thermolysis at 900 o C resulted in more than 70 % conversion to CNMs and H2.

Dry reforming of CH4 involves the reaction between methane and CO2 in the presence of different bi-metallic or trimetallic catalysts and this leads to the generation of syn gas. However, it has been observed that this reaction can also lead to the production of CNMs by the suitable choice of catalyst and reaction conditions. This way the CO2 and CH4 can be converted into CNM and H2. There seems to be a good scope of further research in these areas [48].

Have reported the production of CNMs along with syn gas from biogas through dry reforming at 600-700 O C employing alumina based nickel catalyst under ambient pressure conditions. Thus, H2, syngas and CNMs can be produced through reforming reactions. Further research work on dry reforming and tri-reforming of methane and biogas may be done to study the production of good quality of CNMs in good yields along with H2. This would also take care of the greenhouse effect by reducing the CO2 and CH4 contents through their effective and sustainable utilization [49]. Reviewed the production of CNMs from CO2 and coal fly ash. These authors have reported the use of CVD, thermal reactors and electrolytic techniques. The quality and type of CNTs varied with the employment of different process conditions such as pressure, temperature, electrolytic transformation etc As noted by [1, 35] earlier there appears to be a great scope of production of CNMs by using a free of cost material such as CO2 by using simpler technique of burning Mg in presence of other promoters as discussed before [50]. Reported the production of CNM from CO2 through electrolysis using steel and nickel electrodes. Electricity may be generated using renewable sources [51].

Have reported the production of CNMs from the CO by using iron catalyst using iron carbonyl in the reactor. The decomposition of carbon monoxide to SWCNTs and carbon dioxide takes place under high pressure and elevated temperature conditions. [51] Has reviewed the research work on this process. The process can be scaled up and thus this may be used for the production of CNTs at larger scales.

Author feels that production of good quality CNMs such as graphene on a larger scales at lower costs is challenging affair and further research in this area may be extended by using CO2.

Low Cost Techniques for Producing CNMs

It is also important to develop low cost sustainable techniques for the production of CNMs in not only good yield but also having good quality and purity and of course stability. Several authors have attempted to develop simpler and cheaper techniques for this purpose [52].

Reviewed the work on the production of CNMs at the industrial processing levels. Continuous CVD technique using catalyst may be employed in industries [53]. Have developed a process for the large scale production of graphene from the biomass and other solid organic carbon sources. These authors have described their techniques as involving particle cracking and bridging i.e., a two-step process. There is formation of graphene enclosed structure of solid CNMs in the first stage of catalytic thermolysis. In the second stage these cracked molecular shells open up and these cracked graphene shells get self-bonded or fused to form high quality multi-layered graphene structures. The pyrolytic charring of lignocellulosic biomass is an essential initial step here where cellulose, hemicellulose and mostly lignin are cracked through free radical chain reactions. The improvements of aspect ratios of MWCNTs can lead to an increase in their mechanical strengths [54]. Have developed a cost effective technique of production of CNMs by using electric arc welding under ambient pressure. No metal catalyst was used which spares the need of purification. No pressure was used and this also avoids cleaning and this appears to be a simpler technique. Different plastic wastes such as LDPE, HDPE, polypropylene, polyethylene terephthalate have been used. Various reactors i.e., high pressure thermal reactors, quartz tube reactor, muffle furnace, fluidized bed reactors have been used. Different catalysts have been used to produce MWCNTs from plastic wastes. There appears to be further scope to extend work in this direction. Use of different conditions, catalysts, promoters, reactor type and the quality of plastic wastes may be studied. The yield and quality of CNTs produced may be improved [40]. Have reviewed the synthesis of CNMs such as CNTs, carbon fibers and graphene from organic wastes using pyrolysis techniques.

Simpler flash heating crackers may be used as reactors including fluidized bed crackers. There is a need of carrying out process intensification studies and the scaled up reactors may be designed based on reaction engineering studies.

Use of solar energy for heating the crackers may be made. Alternately the electricity generated by solar or wind energy may be used [24].

Current Research Work on the Production of CNMs from Low Cost Feedstock’s

Have reviewed the research work on the green technology of production of CNMs from renewable feedstocks such as lignocellulosic wastes i.e., agroresidues using microwave ovens. Rapid heating in microwave ovens afford the rapid production of graphene, CNTs and other CNMs. Thermal cracking reactions are accelerated and promoted avoiding mostly the use of solvents and catalysts. However, there are issues in the scale up of such processes though this seems to be an environment friendly approach involving cheaper and regenerable feedstocks [55].

Have reported the cracking- carbonization process i.e., flash cracking for converting waste plastics into CNMs such as graphene which may be converted to CNTs. The process is simpler and avoids the use of solvents and electric flashing, laser blasting method and CVD. Technique. Several drastic degradation and recombination reactions take place under high temperature conditions, it is important to understand their mechanism for the effective control and standardizing the conditions for producing good quality CNMs in high yields at larger industrial scale operations [56]. Have used ultrasound and spinning techniques to separate the CNMs through gel permeation separation methods [57]. Have emphasized the importance of research on developing sustainable processes for the conversion of biomass into CNMs. Good quality CNMs have great potential applications in the energy, pollution abatement and medicinal and battery areas.

There is a need to develop and establish environmentally sound, cost effective, sustainable and scalable processes for the larger scale production of CNMs [58]. Have also emphasised on the utilization of waste biomass for the generation of CNMs through environmentally benign technologies. In fact there is a need to moderate the severe thermal - intensive conditions in the process engineering work by using suitable cheaper catalysts and promoters.

Future Scope of Research

There is a need of producing right quality of CNMs in good yields at larger scales where reproducibility of results and the stability of CNMs may not be an issue. The process should be economically sustainable and environmentally sound. The CNMs can replace the costly metals in the strength and conductivity. Thus, this may save on the cost involved in the energy and other severe metallurgical operations in industries. This would also lead to the reduction of environmental pollution loads. In fact nanocomposites based on CNMs have shown great promise in electrical and mechanical properties such as EMI shielding [59]. The application of CNMs in biomedicine and biomedical engineering fields is also being further discovered with great promise in future. The quality of CNMs can be improved through control of conditions and by derivatization, modification and purification techniques [60] have reviewed research work in this area.

Use of biomass wastes, especially lignin, latex, resins or other biomass based materials (petrocrops) [26, 61] would afford the cleaner manufacture of these materials. In fact the scope and potential of utilization of CNMs is expanding and this is posing a pressure to develop scaled up convenient and economically sustainable processes for their manufacture.

The process engineering of the production of CNMs at smaller scales is well known, however there is a need to develop the scaled up processes which are sustainable. There is a need to clearly understand the high temperature chemistry i.e., molecular dynamics especially the down degradation from macro to micro and then to nano - sizes. Reaction engineering involving process intensification, reaction kinetics and mechanisms of thermal chemistry at different temperatures involving different molecular structures may be studied. Mechanisms of dynamics of degradation and molecular rearrangement for recombination through free radical reactions may have to be understood for scale up operations. The role of different catalysts and promoters may have to be clearly understood and established. Derivatization of CNMs also modifies and enhances their effect multifold and research in this also warranted especially in biomedicine applications.

With the detailed understanding of process mechanisms involving thermodynamics and reaction kinetics, the processes may be directed and controlled to produce the CNMs of desired structure and quality. The severity and cost of production of CNMs may be thus reduced.

The use of biomass and biomass derived products i.e. lignin or even coal and petroleum derived products may afford the production of hydrogen and other smart materials as byproducts. The use of latex and resin bearing plants may be made for biomass conversion to CNMs [18]. The use of algal biomass may be extended for the generation of CNMs.

The terpene or hydrocarbon bearing laticiferous and resinous plant biomass [26, 61] agro and forest residues, grasses, coal and petroleum derived low value products, waste plastics, vacuum residues, seed oils, dungs, plant extracts, biogas, CO2 etc. may be utilized as the low cost raw materials for CNMs.

Some research work on the reactive co-cracking of biomass with other wastes in presence of different catalysts and promoters has been reported [43] and the thermal conditions in these processes may be extended to severe cracking stages which may be under fluidized bed conditions and the generation of CNMs may be studied.

Research work on the reactive co-cracking of different plastics, biomass, vacuum residue, coal, vegetable oils etc. may also be extended. Production of cracked products under the severe cracking conditions which may also be under fluidized bed conditions may be studied [62, 41, and 63]. Extending the cracking reactions further may lead to the the generation of CNMs. Even some of the medicinal and petrocrop plants after the recovery of medicines may be subjected to flash cracking to produce CNMs and other valuable products [64, 65].Thus, integrated processes may be developed and designed to make the processes of CNM production economically and environmentally sustainable.

Author feels that coal, biomass and CO2 may afford the production of CNMs at larger scales. The CO2– gasification of coal [66] can generate syn gas. The CO produced may be used to produce H2 and CO2 through shift reaction. The CO2 can be utilized to produce CNMs. In fact the integrated gasification combined cycle power generation process can be used for producing power, H2 and CNMs from coals. Even the process of CO2 - gasification of biomass [67] can be employed to generate CNMs, H2 and power through processes described before.


There is a good scope of using coals for the production of CNMs, the coals may be cleaned through organo-refining technique to produce almost zero ash coal. Reaction conditions may have to be modified to improve the yield and quality of CNMs which may include the use of suitable catalysts.

Use of lignin also seems to be interesting as these have lesser complex structure in comparison to coal and these are more reactive and can be easily depolymerized and thermally downgraded for reconstruction of nanomaterials. The use of biomass and waste plastics may also be made as low cost feedstocks, however, further research in this area would also be required.

Some research work on the reactive catalytic co-cracking of different waste materials has been carried out earlier and with further extension and control of severity of thermal degradation conditions the studies on the production of good quality CNMs in higher yield may be possible. Dry reforming of methane or biogas may lead to the production of CNMs and hydrogen and further research in this area may also be extended with the use of some more effective catalysts. This process can also be easily scaled up in future. There are several organic wastes which may be used to produce CNMs economically, however further research may be required to produce CNMs of good quality in larger yield. Ultimately the use of CO2 may be made for the production of CNMs and several routes are available for that.

Even the coal and biomass can be gasified to generate syn gas which may produce CO2 and H2. The use of CO2 may be made for the production of CNMs. This process can also be easily scaled up. Thus, there are several options for using cheaper raw materials for the production of CNMs and further research may lead to the establishment of certain economically sustainable processes for the production of CNMs of good quality at the industrial scales. Novel derivatization of CNMs through inexpensive chemicals holds further promise of improving the properties of CNMs produced.


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