Production of Biofuel from Waste Paper - Literature review Example

Production of Biofuel from Waste Paper Production of Biofuel from Waste Paper Past, present and future methods of producing biofuel from waste paper One of the most promising substitutes to the use of conventional petroleum-based fuels is the production of biofuel from renewable resources like plant biomass (Guerfali, Saidi, Gargouri, Belghith, 2014). Biofuels such as ethanol can be produced from a wide range of lignocellulosic biomass like weeds, forestry and agricultural residues, waste paper, herbaceous and woody energy crops, and a significant proportion of municipal solid waste among other types of wastes (Agrimi, Pisano & Palmieri, 2012; Sarin, 2012; Wyman, 1996). Different of types of waste papers (for instance office papers, newspapers, cardboards and magazine papers) with a carbohydrate content in the range of 50 to 73 percent (weight per weight oven dry weight) have a significant potential as raw materials for the production of ethanol (Wang, Templer, Murphy, 2012). Given that paper is one of the types of wastes that are produced in large quantities across the world (Brummer, Skryja, Jurena, Hlavacek & Stehlik, 2014), recycling waste paper to produce biofuel is without doubt a good practice. As argued by Guerfali et al. (2014), “waste paper is particularly attractive as feedstock for bioethanol production because it is readily available” (p. 2). Over the years, many methods have been suggested and used in hydrolyzing waste cellulose in order to have it used as a source of alcohol (Kamakura & Kaetsu, 1982). Past studies dating as far back as 1982 and even recent studies document how radiation has been used in the degradation of cellulosic matter such as waste paper, chaff, rice straw and saw dust (Kamakura & Kaetsu, 1982; Saini, Aggarwal, Sharma & Yadav, 2015). The use of radiation has been widely employed because it was found that it is difficult to hydrolyze cellulosic materials enzymatically or using acid hydrolysis given that cellulose has high molecular weight and is not soluble in water (Kamakura & Kaetsu, 1982). Therefore, radiation has been applied in the pretreatment of cellulosic materials to make them more susceptible to hydrolysis by use of enzymes (Kamakura & Kaetsu, 1982). A study that was conducted by Kamakura and Kaetsu (1982) showed that after irradiating waste papers by more than 107 rads of gamma rays, the degree of polymerization of the paper decreased significantly. As a result of the reduced level of polymerization of waste paper, the paper’s water-soluble content as well as reducing sugar yield increased abruptly for irradiation doses exceeding 107 rad. What this means is that upon irradiating waste paper, compounds with low molecular weight contained in the paper – such as oligosaccharides that are able to dissolve in water – are produced. The production of biofuel from waste paper is an evolving phenomenon, and today, many methods are being tried to convert waste paper into usable fuels. Radiation treatment, enzymatic hydrolysis and acid hydrolysis are some of the processes that are used to break down waste paper into a form that can be used to produce biofuels such as ethanol (Guerfali et al., 2014; Saini et al. 2015). Irradiation is primarily used as a pretreatment method. During the biomass irradiation process, biomass such as waste paper is subjected to high energy radiations like microwaves, ultrasonic waves, electron beams and gamma rays. The efficiency of treatment is dependent on a wide array of factors, which include the period of exposure, the frequency of radiations, the composition of the biomass that is being used, and the nature of radiations by the mediums between the biomass and radiations. The radiations, which have high energy levels, increase the size of the biomass’s specific surface area, reduce the degree of polymerization as well as crystallinity of cellulose, and party hydrolyze the lignin and hemicellulose components of the biomass such as waste paper (Saini et al. 2015). Enzymatic hydrolysis of waste paper involves the use of enzymes such as cellulases (Walpot, 1986). The process involves the cleavage of internal glycosidic bonds in the cellulose through the action of endo-β-(1, 4)-glucanase, which is followed by the combined action of endo-glucanases and exo-glucanases. The final hydrolysis of oligosaccharides is catalyzed by β-(1, 4) glucosidase. The progressive interaction between the exo-glucanase and endo-glucanase has been established by use of electron microscopy (Brummer et al., 2014). Enzymatic hydrolysis, also referred to as paper saccharification, has been shown to yield glucose from waste paper in the range of 56 percent for cardboard and 59 percent for sludge at a solids loading of six percent (w/w) in a process known as simultaneous saccharification and fermentation (SSF) (Wang et al., 2012). Enzymatic hydrolysis can also be carried out as separate hydrolysis and fermentation (SHF), where fermentation and saccharification are done separately (Wang et al., 2012). This method (SHF) is associated with the advantages of permitting both enzymes and microorganisms to function at their optimum temperature levels. In addition, in case of an accidental failure of fermentation or hydrolysis, the problem would not affect the other phases of the entire process (Wang et al., 2012). In the future, biofuel will become an important source of energy as levels of petroleum based fuels continue declining. Also, bio-fuels from waste biomass such as paper will be crucial because of the aspects of conserving the environment and the less pollution that is associated with biofuels compared with other fuels such as fossil fuels. New methods of breaking down cellulose, such as semi simultaneous saccharification and fermentation (SSSF), have already been tried and successfully produced ethanol from waste paper (International Service for the Acquisition of Agri-Biotech Applications (ISAAA), 2013). Such an achievement will provide a foundation for research into more innovative methods that can be used to convert waste paper into high concentrations of biofuels like ethanol. There are also different irradiation technologies that can be used at various stages in the process of converting waste paper into biofuel, in combination with saccharification and fermentation. These include the use of microwaves, sonication, electron beam, and gamma irradiation. There are also new methods of pretreatment of waste paper that are being researched, such as the use of liquid hot water, which is advantageous because it does not require additional chemicals (Franceschin, Favaron & Bertucco, 2010). Various methods of processing waste paper into biofuel 1. Irradiation pretreatment Various types of irradiation can be used. Irradiation is used to treat cellulose materials because as it was noted above, it is difficult to hydrolyze cellulosic materials by relying solely on enzymes since cellulose has high molecular weight and most of its components are not water soluble (Kamakura & Kaetsu, 1982; Saini et al., 2015). Therefore, the use of high radiations serves to increase the biomass’s specific surface area, reduce the biomass’s degree of polymerization and crystallinity, and help in hydrolyzing the lignin and hemicellulosic components (Saini et al., 2015). In general, pretreatment of cellulosic biomass helps ensure that the crystalline structure and the lignin seal of the waste material are destroyed prior to hydrolysis of the material (Franceschin et al., 2010). Radiation using gamma rays involves the use of very high energy radiations that comprise photons with a high level of energy. Gamma rays have deep penetration power and are produced by the disintegration of atomic nuclei as they return to a low energy state from a high energy state. When used together with enzymatic and acid hydrolysis, gamma radiation has been shown to enhance the yield of sugars and other soluble cellulosic components (Saini et al., 2015). Sonication (use of sound waves), use of microwaves and use of electron beams work in much the same way as the use of gamma rays, save for the fact that different kinds of high energy particles are used to bombard and destroy the crystalline structure and the lignin components of waste paper (Saini et al., 2015). Overall, the feature of irradiation can be used either directly or indirectly in all steps of producing biofuel from waste paper, i.e. pretreatment, saccharification, and fermentation (Saini et al., 2015). 2. Hydrolysis/ Saccharification Hydrolysis/saccharification and fermentation processes are closely related. Hydrolysis is a process that involves the digestion of cellulose by aid of acids or enzymes known as cellulases (Guerfali et al., 2014; Singh & Trivedi, 2014). Cellulases are largely derived from various microorganisms, one example of them being Trichoderma reesei, a filamentous fungus (Guerfali et al., 2014). Cellulases are capable of hydrolyzing or breaking down cellulose. Cellulases are produced by organisms like Trichoderma reesei among others only in the presence of cellobiose, cellulose, sophorose, lactose and other glucans that contain β-(1, 4) glucosidic linkages (Brummer et al., 2014; Guerfali et al., 2014). In the absence of dissolved nutrients, microorganisms such as Trichoderma reesei are able to gradually synthesize enzymes that remove insoluble substrate from biomass such as waste paper (Brummer et al., 2014). 3. Saccharification and fermentation Ethanol conversion usually entails saccharification, or the breakdown of carbohydrates into simple sugars (ISAAA, 2013). Saccharification and fermentation processes can be carried out simultaneously as simultaneous saccharification and fermentation (SSF) or separately as separate hydrolysis and fermentation (SHF) (Wang et al., 2012). When working on waste paper to produce biofuels such as bioethanol, it is important to note that both SSF and SHF can be applied, but there are some points that must be taken into consideration. Notably, the optimum temperature for the growth of yeast and functioning of hydrolytic enzymes vary, which implies that the conditions for SSF cannot be optimal for both yeast and enzymes and might cause lower efficiency as well as lower yield (Guerfali et al., 2014). On the other hand, SHF has been proven to be a better approach of obtaining higher efficiency in ethanol production because of the separation of saccharification and fermentation processes (Guerfali et al., 2014; Wang et al., 2012). One of the latest methods used in saccharification and fermentation is the use of a process known as semi simultaneous saccharification and fermentation (SSSF). In a news release of 2013, ISAAA noted that researchers from the Institute of Food Research (IFR) of the UK had successfully used SSSF to “produce a high concentration of ethanol from waste paper for the first time” (ISAAA, 2013). The success of the strategy was based on the fact that the researchers used a specialized bioreactor that was capable of mixing and digesting raw materials fed in batches into the ethanol production system. It also involved early addition of enzymes followed by addition of the waste paper substrate in batches, resulting in a yield of ethanol of concentration up to 11.6 percent, which matched the levels of ethanol produced from first generation feedstock such as corn, wheat and sugarcane (ISAAA, 2013). References Agrimi, G., Pisano, I., & Palmieri, L. (2012). Process development and metabolic engineering for bioethanol production from lignocellulosic biomass. In M. Aresta, A. Dibenedetto & F. Dumeignil (Eds), Biorefinery: From biomass to chemicals and fuels (207-230). Berlin/Boston: Walter de Gruyter GmbH & Co. KG. Brummer, V., Skryja, P., Jurena, T., Hlavacek, V., & Stehlik, P. (2014). Suitable technological conditions for enzymatic hydrolysis of waste paper by Novozymes® Enzymes NS50013 and NS50010. Applied Biochemistry and Biotechnology. New York: Springer. DOI 10.1007/s12010-014-1119-4. Franceschin, G., Favaron, C., & Bertucco, A. (2010). Waste paper as carbohydrate source for biofuel production: An experimental investigation. Retrieved from http://www.aidic.it/ibic2010/webpapers/40Franceschin.pdf Guerfali, M., Saidi, A., Gargouri, A., & Belghith, H. (2014). Enhanced enzymatic hydrolysis of waste paper for ethanol production using separate saccharification and fermentation. Applied Biochemistry and Biotechnology. New York: Springer. DOI 10.1007/s12010-014-1243-1. International Service for the Acquisition of Agri-Biotech Applications (ISAAA). (2013). Researchers turn waste paper to biofuel. Retrieved from http://www.isaaa.org/kc/cropbiotechupdate/article/default.asp?ID=11322 Kamakura, M., & Kaetsu, I. (1982). Radiation degradation and the subsequent enzymatic hydrolysis of waste papers. Biotechnology and Bioengineering, XXIV, 991-997. Saini, A., Aggarwal, N. K., Sharma, A., & Yadav, A. (2015). Prospects for irradiation in cellulosic ethanol production. Biotechnology Research International Review Article. Sarin, A. (2012). Biodiesel: Production and properties. Cambridge, UK: The Royal Society of Chemistry. Singh, D. P., & Trivedi, R. K. (2014). Biofuel from wastes an economic and environmentally feasible resource. Energy Procedia, 54, 634–641. Walpot, J. I. (1986). Enzymatic hydrolysis of waste paper. Conservation & Recycling, 9(1), 127 -136. Wang, L., Templer, R., & Murphy, R. J. (2012). High-solids loading enzymatic hydrolysis of waste papers for biofuel production. Applied Energy, 99, 23–31. Wyman, C.E. (ed) (1996). Handbook on bioethanol: Production and utilization. Washington, DC: Taylor & Francis. Read More