Abstract
Technologists are facing increasing demands to achieve ecologically sustainable industrial practices. Currently the concrete industry is a significant contributor to greenhouse gas emissions. On the other hand, the scaling up of cellulosic ethanol technology has not been a very easy task. In this context, the integration of “greener” concrete with cellulosic ethanol technology may open up promising possibilities. The solid byproducts from cellulosic ethanol production process have been demonstrated to increase the strength of concrete structures when used as a partial cement replacement. Such a delicate integration can also lead to reduction in both carbon footprint and product cost. The possible commercialization of the integrated technologies would provide win-win benefits for both industries.
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Use of Byproduct from Cellulosic Ethanol Production as an Additive for Concrete: A Possible Win-win Strategy?
Xiangwei Hao,a Chenghao Liu,c Huazhen Cao,d Yuhua Liu,e Haiyan Peng,a,* and Jing Shen b
Technologists are facing increasing demands to achieve ecologically sustainable industrial practices. Currently the concrete industry is a significant contributor to greenhouse gas emissions. On the other hand, the scaling up of cellulosic ethanol technology has not been a very easy task. In this context, the integration of “greener” concrete with cellulosic ethanol technology may open up promising possibilities. The solid byproducts from cellulosic ethanol production process have been demonstrated to increase the strength of concrete structures when used as a partial cement replacement. Such a delicate integration can also lead to reduction in both carbon footprint and product cost. The possible commercialization of the integrated technologies would provide win-win benefits for both industries.
Keywords: Concrete; Cement; Cellulosic ethanol; Byproduct; Sustainability
Contact information: a: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China; b: Key Laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040, China; c: Rizhao Polytechnic, Rizhao 276826, China; d: Asia Symbol (Shandong) Paper Co., Ltd, Rizhao 276826, China; e: Weifang University of Science and Technology, Shouguang 262700, China; *Corresponding author: phy_77@126.com (Haiyan Peng)
Concrete and the Greenhouse Gas Emission
Concrete is a frequently used construction material in the building industry and can be found everywhere in the world. It is used globally to build roads, buildings, bridges, runways, and sidewalks (Sullivan 2009; Rubenstein 2012). The development of civilization has been highly dependent upon the use of concrete.
Essentially, concrete is made from three major components: cement, water, and aggregate (Kansas State University 2013). Cement and water combine to form cement paste for use as the binder for the aggregate. The terms “concrete” and “cement” may be used interchangeably (Houghton Mifflin Company 2005), but it would be better and more reasonable to understand these terms separately.
The greenhouse impact associated with concrete production is very significant (Amato 2013). In this regard, cement is the predominate contributor. Despite the fact that making concrete is less energy-intensive than making steel or other building materials, concrete production can account for between 3 to 8 percent of global carbon dioxide emissions (Rubenstein 2012; Kansas State University 2013). Note that carbon dioxide is the primary greenhouse gas released as a result of human activities. The carbon dioxide emission from concrete production can be derived from the calcination process that releases carbon dioxide. Carbon dioxide also is released due to the energy input to the production processes and for transportation of materials (Rubenstein 2012). As a construction material, concrete is not likely to be truly sustainable, but it is possible to reduce its impact on the environment using various technologies (Leung 2009).
Cellulosic Ethanol and the Possibilities Associated with the Use of Its Byproduct in Concrete
The replacement of fossil-derived nonrenewable fuels with biofuels is essential to a sustainable future. As a combustible liquid suitable for use as a transportation fuel, a versatile solvent, and a chemical raw material, ethanol can be produced from inedible lignocellulosic feedstocks including wood chips, forest wastes, agricultural crop residues, industrial wastes, and energy crops (Wang et al. 2011). While first-generation bioethanol is derived from sugar or starch produced by food crops (e.g., wheat, corn, sugar beet, sugar cane), cellulosic ethanol may be considered as second-generation bioethanol. The feedstocks for cellulosic ethanol production are more abundant and generally considered to be more sustainable (EBTP 2015). A process for the production of cellulosic ethanol is illustrated in Fig. 1. It is noted that although hemicellulosic components of lignocellulosic feedstocks may also be utilized to produce ethanol, the process still is named “cellulosic ethanol”.
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Fig. 1. Schematic of an example of cellulosic ethanol production process
(Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science)
Currently, there are some commercial-scale plants around the globe for production of cellulosic ethanol. It may be predicted that ongoing efforts to commercialize this clean energy would lead the world to a more independent energy future (Christian 2015). However, partly due to the complex and not-easily-accessible structure of lignocellulosic feedstocks, scaling up the cellulosic ethanol technology has proven difficult and costly (Fitzpatrick 2015). Overcoming the barriers to cellulosic ethanol may involve a combination of different strategies (Fig. 2). In this sense, making better use of the waste streams for the production of value-added products can facilitate the survival and sustainable growth of the cellulosic ethanol biorefinery industry. On the other hand, the government policies and economic factors would play a significant role.