(635f) Comparison of the Biochemical and Thermochemical Ways for Use of Lignin

Lignocellulosic biomass (LB) is nowadays an important raw material due to its cellulose, hemicellulose and lignin content. These materials can be used to obtain high value-added products. The annual production of these materials is of approximately 200 million tonnes. The main lignin producer is the paper industry. For 2010 this industry produced 50 millions of tonnes of lignin represented as black liquor that is obtained in pulping paper. Only the 5% was used to produce adhesives, dispersants, surfactants, antioxidants and rubbers, while the remaining 95% was used to produce energy in cogeneration systems. Lignin is an organic polymer which alike the cellulose has an important production in the vegetable world. Some high value-added compounds that can be derived from lignin correspond to the binders and cosmetic, among others. These compounds have important uses in the cosmetic, pharmaceutical and chemical industries. Lignin is commonly used to produce bioenergy in cogeneration system. However, lignin heat capacity is lower than the conventional fuels.

Some applications of lignin combine the use of different technologies that involve some degree of maturity such as thermochemical and biochemical processes. Thermochemical technologies have been developed over the year to convert biomass into other more valuable forms of energy [1]. The thermochemical techniques such as pyrolysis, solvolysis, liquefaction and gasification are the most interesting concepts investigated, focussing on the depolymerization of naturally occurring biopolymers such as lignin [1]. Biomass such as energy crops, agricultural residues, and woody materials have been widely used as feedstocks for gasification and pyrolysis [2]. These technologies have been applied not only because of its flexibility and acceptance of a wide range of feedstocks but also because of producing a wide range of products with high efficiencies [3]. On the other hand, the biochemical technologies having lignin holds great potential as a renewable source of fuels and aromatic chemicals. However, lignin valorization technologies are substantially less developed than those for the polysaccharides (C6-C5). Difficulties in catalytic processing, high affinity for the formation of a more condensed structure when thermochemically processed, poor selectivity and ease of use as a solid fuel are the major barriers towards the development of a lignin-based biorefining technologies. However the massive amounts of lignin available in the pulp mills (paper industry) and in future biorefineries establishment of lignin conversion processes will open routes for the production of platforms products such as aromatics, phenol derivates, biopolymers and low carbon biofuels that can be able to improve the economic viability and reduce environmental impacts produced in a biorefinery [4].

The zoca coffee was selected as raw material for the development of the biochemical route. The raw material was characterized based on International Methods according to NREL (National Renewable Energy Laboratory, Golden, CO, USA) and was obtained extractive content (10-20 %p/p), holocellulose content (40-50 %p/p and 16-20 %p/p for cellulose and hemicellulose respectively) and lignin content (20-30 %p/p). In the same way, the acid pretreatment has been experimentally assessed as well as the ethanol production from the resulting sugar-rich (C6-C5) liquor using Zymomonas mobilis ZM4 (pZB5) where yields higher than 60% of ethanol have been obtained. Residual lignin from the ethanol process was used to obtain three different products: phenolic acids (ferulic and p-coumaric acids), activated carbon and aromatics BTX. On the other hand, for the thermochemical way gasification was performed to obtain electric energy in a gasifier “GEK Gasifier (10 KW/h) Power Pallet”. This equipment allows producing 10 kW / h per kg of fed raw material, also gas produced was analyzed (CO, H2, CO2) by means of an analyzer (GASBOARD-3100P, Portable syngas infrared analyzer). All the experimental stages have been developed in the Biotechnological and Agroindustrial laboratory of Universidad Nacional de Colombia Sede Manizales.

Finally this work presents an economic and environmental assessment for two scenarios. In the first scenario bioenergy production through gasification was evaluated. The second scenario consists on the integrated production of bioethanol, aromatic chemicals, phenolic acids and activated carbon. Both scenarios were evaluated in order to determine the most promising scenario using the commercial package Aspen Economic Analyzer. On the other hand, eight environmental categories were evaluated using the waste reduction algorithm developed by the Environmental Protection Agency (EPA). As a result, the scenario 2 is the most attractive alternative since the lignin is currently burned without taking advantages of its potential.

References

[1]      H. Roy, P. P. Kundu, and S. Kumar, “Thermochemical comparison of lignin separated by electrolysis and acid precipitation from soda black liquor of agricultural residues,” Thermochim. Acta, vol. 502, no. 1–2, pp. 85–89, 2010.

[2]      B. Holmelid, M. Kleinert, and T. Barth, “Reactivity and reaction pathways in thermochemical treatment of selected lignin-like model compounds under hydrogen rich conditions,” J. Anal. Appl. Pyrolysis, vol. 98, pp. 37–44, 2012.

[3]      V. Pasangulapati, K. D. Ramachandriya, A. Kumar, M. R. Wilkins, C. L. Jones, and R. L. Huhnke, “Effects of cellulose , hemicellulose and lignin on thermochemical conversion characteristics of the selected biomass,” Bioresour. Technol., vol. 114, pp. 663–669, 2012.

[4]      P. Azadi, O. R. Inderwildi, R. Farnood, and D. a. King, “Liquid fuels, hydrogen and chemicals from lignin: A critical review,” Renew. Sustain. Energy Rev., vol. 21, pp. 506–523, May 2013.