Lignocellulosic biorefinery

Type of raw materials used whole crop biorefineries (W CBRs), oleochemical biorefineries, lignocellulosic feedstock biorefineries, green biorefineries, and marine biorefineries. 

This chapter surveys different process options to convert terpenes, plant oils, carbohydrates and lignocellulosic materials into valuable chemicals and polymers. Three different strategies of conversion processes integrated in a biorefinery scheme are proposed from biomass to bioproducts via degraded molecules , from platform molecules to bioproducts , and from biomass to bioproducts via new synthesis routes . Selected examples representative of the three options are given. Attention is focused on conversions based on one-pot reactions involving one or several catalytic steps that could be used to replace conventional synthetic routes developed for hydrocarbons. 

The expansion of the market, however, will depend considerably on the possibility of an efficient use of other biomass sources, particularly lignocellulosic-based materials, fast growing dedicated crops, and waste resources. Effective integration of bioethanol production into biorefineries will also be a key aspect in decreasing the price by a better use of all the components of biomass. 

Biogas can be produced from dedicated crops (eg., corn without kernels), lignocellulosics wastes of biorefineries, as well as from plant and animal wastes... 

Figure 1.5 Simplified schematic diagram of a lignocellulosic feedstock biorefinery...

In reality, while the sole products of existing pulp and paper manufacturing facilities today are pulp and paper (phase I biorefinery), these facilities are geared to collect and process substantial amounts of lignocellulosic biomass. They thus provide an ideal foundation to develop advanced lignocellulose feedstock biorefineries. Additional processes could be built around pulp mills, either as an extension or as an across-the-fence -type company (Agenda 2020). 

The first step will be to separate the seed from the straw (collection will obviously occur simultaneously, to minimise energy use and labour cost). The seeds may then be processed to produce starch and a wide variety of products, including ethanol and bioplastics (e.g. polylactic acid). The straw can be processed to products via various conversion processes, as described above for a lignocellulosic feedstock biorefinery. 

Thorsell, S., F.M. Epplin, R.L. Huhnke and C.M. Taliaferro, Economics of a Coordinated Biorefinery Feedstock Harvest System lignocellulosic Biomass Harvest Cost, Biomass and Bioenergy, 27, 327-337 (2004). 

Carbohydrates would be the predominant raw materials for future biorefineries. The major polysaccharides found in nature are cellulose, hemicellulose and starch (see Chapter 1). These molecules would be mainly utilised after they are broken down to their respective monomers via enzymatic hydrolysis, thermochemical degradation or a combination of these two. Cellulose and hemicellulose, together with lignin, constitute the main structural components of biomass. Starch is the major constituent of cereal crops. This section would focus on the potential utilisation of carbohydrates and lignocellulosic biomass for chemical production. 

Conversion efficiency and robust fermentation of mixed-sugar lignocellulose-derived hydrolysates are critical for producing ethanol at low cost to realize a commercially viable biorefinery. Biomass sugars are typically released by thermochemical pretreatment followed by enzymatic hydrolysis of chopped or milled biomass. The pretreated soluble fraction of biomass is called the hydrolysate and the hydrolysate containing the insoluble... 

One can envisage the future production of liquid fuels and commodity chemicals in a biorefinery Biomass is first subjected to extraction to remove waxes and essential oils. Various options are possible for conversion of the remaining biofeedstock, which consists primarily of lignocellulose. It can be converted to synthesis gas (CO + H2) by gasification, for example, and subsequently to methanol. Alternatively, it can be subjected to hydrothermal upgrading (HTU), affording liquid biofuels from which known transport fuels and bulk chemicals can be produced. An appealing option is bioconversion to ethanol by fermentation. The ethanol can be used directly as a liquid fuel and/or converted to ethylene as a base chemical. Such a hiorefinery is depicted in Fig. 8.1. 

Kamm B, Kamm M, Schmidt M, Hirth T, Schulze M (2006) Lignocellulose-based chemical products and product family trees. In Kamm B, Gruber PR, Kamm M (eds) Biorefineries industrial processes and products. Wiley-VCH, Weinheim... 

S. cerevisiae and other yeasts are valuable platform hosts for biorefinery apph-cations where sugar, starch, or lignocellulose are converted to biofuels or value-added chemicals [15]. Beside bioethanol, biologically produced hpids represent... 

Tolan, J.S. (2005) logon s demonstration process for producing ethanol from lignocellulosic biomass, in Biorefineries-Industrial Processes and Products (eds B. Kamm, P. Gruber, and M. Kamm), Wiley-VCH Verlag GmbH, Weinheim, pp. 193-207. 

As discussed in detail in Chapter 1 [1], the chemical-catalytic approach to biomass valorization is poised to come to the fore of biorefinery operations due to its advantages over microbial and thermochemical processing of lignocellulosic feedstocks. Below, we consider three mainstream platform chemicals, collectively referred to as furanics, that are derived from the acid-catalyzed dehydration of carbohydrates. The first, 5-(hydroxymethyl)furfural, or HMF 1, is an icon of the biorefinery movement. With derivatives that branch out over multiple product manifolds, HMF is a recognized commercial opportunity for whoever can manage to produce it economically, and approaches towards the realization of this aim will be discussed. 

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