eChapter Name: Pre-Treatment of Lignocellulosic Wastes for Biofuel Production
9789372196429
eBook Name: BIOFUELS PRODUCTION USING SUSTAINABLE BIOPROCESSING TECHNOLOGIES
1. Introduction
The growing demand for fossil fuels around the world and their extensive use, which degrades the environment, have been serious issues. More precisely, it is predicted that global energy consumption will rise by 49% between 2007 and 2035 due to social pressure, population growth, and economic expansion (Cheah et al., 2016; Prasad et al., 2016). In order to replace fossil fuels, alternative energy resources must be developed, according to energy security and environmental sustainability. The most promising bio-fuel among the alternatives to gasoline is bio-ethanol, which can be used as the only fuel in compatible automobile engines or blended with gasoline up to 30% without requiring engine changes (Safarian and Unnthorsson, 2018). Bio-ethanol has a higher-octane number, which enables engines to run at high compression ratios, and a high oxygen content, which improves combustion efficiency (Branco et al., 2019). Grain, sugar beets, corn, and sugarcane could all be used to make bio-ethanol. Together, Brazil and the United States account for over 90% of the world’s bio-ethanol production, with 59% and 27% coming from each country, respectively (Branco et al., 2019).The Policy Energy Act and Energy Independence and Security Act, which aim to consume 136 billion gallons of bio-ethanol by 2022, are the main drivers of the USA’s remarkably high production rate (Menon and Rao, 2012; Tran et al., 2019). Unfortunately, the world’s food security is now in jeopardy due to the manufacture of bio-ethanol from the aforementioned edible energy crops. For the synthesis of bio-ethanol, lignocellulosic biomass-such as agricultural residues, forest woody residues, micro-algae, and even municipal solid waste is consequently a more advantageous source. Cellulose, hemicellulose, and lignin make up the lignocellulosic complex structure. While hemicellulose is in charge of binding and 88 | Biofuels Production Using Sustainable Bioprocessing Technologies lignin guarantees the toughness of the entire stricture, cellulose, a polymer made of glucose, gives plants structural support (Kumar et al., 2016; Prasad et al., 2016). According to Tran et al. (2019), pre-treatment is a crucial step in order to: (i) increase the amorphous area to facilitate hydrolysis; (ii) improve the porosity of the porous matrix to facilitate enzymatic and chemical hydrolysis; and (iii) separate cellulose from lignin and hemicellulose. The majority of the most successful pre-treatment techniques now in use are physio-chemical and chemical techniques, which also produce harmful compounds such furfural (Liyamen and Ricke, 2012). Other techniques are also used, each with advantages and disadvantages. For example, biological pre-treatment is environmentally benign but does not generate large amounts of material. Compared to the thermochemical approach, the biochemical conversion process performed better and was more ecologically friendly (Mu et al., 2010; Liyamen and Ricke, 2012; Kumar et al., 2019). It should be mentioned that the pre-treatment cost should also include the expense of detoxifying harmful inhibitors, which are created as a result of the pre-treatment technique (Liyamen and Ricke, 2012). All things considered, a successful pre-treatment ought to be both financially and environmentally responsible. It’s also critical to make sure that other advantageous aspect like maximum energy savings, waste and wastewater recycling, material recovery, and the use of a biorefinery method are taken into account throughout the lignocellulosic bioethanol production process (Kumar et al., 2019). Figure 1. Overview of how ILs typically pre-treat lignocellulosic biomass for the manufacture of biofuel (cheah et al., 2020).
