Ligno-cellulose

Fig. 5.2 The main crop-to-energy chains. BtL Biomass-to-Liquid, GtL Gas-to-Liquid, ETBE Ethyl tert-butyl ether, MTBE Methyl tert-butyl ether, MeOH Methanol, DME Dimethyl ether. Pyrolysis oil, HTU-Diesel (Hydro Thermal Upgrading), ethanol and hydrogen from ligno-cellulosic species are not considered here because of their minor practical relevance in the near future...

Another option to extend the ligno-cellulosic feedstock base is the development of BTL through biomass gasification and subsequent Fischer-Tropsch synthesis. Although BTL is fully compatible with diesel fuel, ligno-cellulosic BTL has not yet been commercialised. 

Several different plant layouts for ligno-cellulosic biomass conversion to ethanol are known using enzymatic hydrolysis ... 

Also, a Spanish company (Abengoa Bioenergy) has developed a process for the conversion of ligno-cellulosic biomass to ethanol based on SSF. A demonstration plant on the basis of wheat and barley straw has been operating in Salamanca since 2006, with an annual production capacity of five million litres of ethanol (Abengoa, 2006). 

The compactness and complexity of (ligno)cellulose makes it much more difficult to attack by enzymes with respect to starch. Therefore, the cost of bioethanol production is higher [23], To be cost competitive with grain-derived ethanol, the enzymes used for biomass hydrolysis must become more efficient and far less expensive. In addition, the presence of non-glucose sugars in the feedstock complicates the fermentation process, because conversion of pentose sugars into ethanol is less efficient than conversion of the hexose sugars. 

The passage from the lst-generation of biofuels, which use agricultural products, to 2 nd-generation biofuels that use all the structural components of plants and trees, e.g., able to process (ligno)cellulose, requires the following developments ... 

As discussed in previous sections, sugars, starch and (ligno)cellulose can be converted into ethanol by fermentation, the latter via preliminary chemical and physical pretreatment followed by enzymatic breakdown of the biopolymers. Pure ethanol can be added to gasoline or diesel. However, this requires an energy-intensive distillation step. This and the energy used in fertilizers, transportation... 

The most promising second-generation biofuel technology - ligno-cellulosic processing - is already well advanced. In Europe, for example, three pilot plants have been established, in Sweden, Spain and Denmark. Other technologies to convert biomass into liquid biofuels (BtL) include Fischer-Tropsch biodiesel and bio-DME (dimethyl ether). Demonstration plants are in operation in Germany and Sweden. 

Fig. 3 Schematic flowsheet of ligno-cellulose transformations in a biorefinery.

New catalytic approaches for the pretreatment and hydrolysis of (ligno)cellulose biomass to fermentable sugars... 

Mansour, O.Y., Nagaty, A. and Beshay, A-F. (1982). Grafting of some vinyl monomers onto ligno-cellulose and cellulose in the presence of lignin. In Graft Polymerisation of Lignocellulosic Fibers, Hon, D.N.S. (Ed.). ACS Symposium, 187, pp. 253-268. 

Peill, P.L.D. (1946). Permanent bleaching of ligno-cellulosic materials. Aafure, 158, 554. 

Figure 10.11 Example of a biorefinery. A ligno-cellulosic biorefinery.

Ethanol production from ligno-cellulosic biomass... 

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