Page 312 - Biofuels for a More Sustainable Future

278 Biofuels for a More Sustainable Future

biodiesel from oil crops, fat, waste oil, algae, and cyanobacteria, where
fatty acids and triglycerides are chemically converted to fatty acid alkyl
esters used as biodiesel (Fjerbaek et al., 2009; Ma and Hanna, 1999). With
catalysts (e.g., acids, alkali, enzymes), reactions happen in the temperature
of 35–90°C(Fjerbaek et al., 2009). For this conversion pathway, prepro-
cessing sites are needed in BSC design. For example, oil crop feedstocks
(e.g., soybean and canola) in grain form need to be preprocessed to extract
the vegetable oil in crushers or extractors (Lea ˜oetal.,2011). Preprocessing
may not be needed for algae as oil is exacted from algae in an extraction
chamber with chloroform methanol before transesterification (L€uet al.,
2011). Alternatively, direct transesterification can be used for either
dry or wet algae with catalysts and solvent (e.g., chloroform, hexane,
petroleum ether, methanol, H 2 SO 4 )( Johnson and Wen, 2009). With
technology options for algae, optimizing the technology variables and
considering the uncertainties existing in production stages are crucial
(Wang et al., 2015).
Mechanical processes are typically processes without changing the state
or components of materials. A common type of mechanical process is pel-
letization (Cherubini, 2010). Although pellet can be burned for energy, pel-
lets were not considered as final products in most of previous studies for BSC
design. Fig. 10.1 shows common biomass feedstock type, conversion tech-
nology, and end product categories in the BSC.

Biomass feedstocks Biofuel production technology Biofuels
Oil crops Transesterification Biodiesel

Algae
cyanobacteria Hydroprocessing
Pyrolysis- Hydrocarbons
hydrogenation /bio-oil
Fischer-Tropsch

Lignocellulosic Gasification Synthetic gas

Sugar and starch Fermentation Ethanol/butanol
Wet biomass Anaerobic digestion Biogas
Fig. 10.1 Categories of main process technologies and biofuel types (Yue et al., 2014;
Sharma et al., 2013).