Plant biorefineries

The Whole-Plant Biorefinery Concept—From Plants to Industrial Products... 

THE WHOLE-PLANT BIOREFINERY CONCEPT—FROM PLANTS TO INDUSTRIAL PRODUCTS... 

To compete with the traditional fossil-based refineries, biorefineries have to exploit optimally raw materials firom plants and create multiple value chains. Therefore, the concept of a whole-plant biorefinery appears as a more convenient model. Despite the diversity of oil crops, such as soy, rapeseed, sunflower, and palm, the whole-plant biorefinery concept can be applied similarly to all of them. Differences can emerge due to the nature of the plant and the way to recover its seeds containing the vegetable oil. Palm trees, for instance, remain in the soil, and their fruits are harvested, where plants such as rapeseed or sunflower are cut every year. In both cases, the first step of the biorefinery process is to separate the oil-rich seeds firom the lignocellulosic fraction of the plant. 

Figure 5.4 depicts the general map of the biorefinery of an oil crop such as rapeseed. The whole-plant biorefinery can be divided into three different stages agricultural productions, the biorefinery itself, and the main industrial markets of the produas obtained fi m the biorefinery. 

A whole plant biorefinery appears as a preferable concept, especially if the transformation units are located close to the crop production sites. Thus, the location of a biorefinery plant can be dictated by the nature of the oleaginous crop, and therefore, the place where its production, linked to the climate, is performed. Depending on the scale of production, the size of the biorefinery will be adapted. If possible the close-by proximity of bioproducts users will be ideal, but if it is not the case, it will be preferable to build a new biorefinery in an industrially rich area where heat integration can be performed. Moreover, this location will also be rich in transportation facilities. To be efficient, the territorial biorefinery should be adapted to multiple feedstocks and multiple bioproduct production in order to comply with crop management techniques. By opposition, another type of biorefinery, focused on transportation hubs such as the Port of Rotterdam or the Port of Ghent, is based on the same model as petrol. The type of biomass is often limited to a few crops and so is the number of large scale bioproducts. In this case, the long distance travels of the feedstocks can appear detrimental in their sustainability evaluation. 

We showed that oleaginous crops are particularly efficient to produce a large variety of oils and numerous by-products that can be valorized into multiple commodity chemicals. By applying the concept of the whole-plant biorefinery, triglycerides, fatty acids, glycerol, and lignoceUulose are converted into chemicals that can find applications in several markets. 

Figure 1.12 Afuture biorefinery model based on a biochemical production plant.

The Department of Energy (DOE) is helping six firms build cellulosic biorefineries with grants totaling about 385 million. When fully operational, the six plants will produce more than 130 million gallons of cellulosic ethanol a year. DOE is also investing 375 million into three new Bioenergy Research Centers to speed up the development of cellulosic ethanol and other biofuels. 

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. 

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

Valorization, retreatment or disposal of co-products and wastes from biorefinery by catalytic treatments. This includes the utilization of plant and biomass fractions that are residual after the production of, for example, bioethanol and from other production chains (e.g., production of methane). 

The alternative pathway is the biochemical route. It processes starches/sugars into ethanol, a standard technology with installations world-wide, but in a biorefinery the start is the whole-plant material or biomass residues containing hemicel-lulose, which is broken into sugars that then can be fermented to ethanol and/or other alcohols such as butanol. As mentioned before, there is the need to develop novel and/or improved biocatalysts for alternative organic fuels, such as biobutanol, by fermentation processes. 

The valorization of by-products in biomass conversion is a key factor for introducing a biomass based energy and chemistry. There is the need to develop new (catalytic) solutions for the utilization of plant and biomass fractions that are residual after the production of bioethanol and other biofuels or production chains. Valorization, retreatment or disposal of co-products and wastes from a biorefinery is also an important consideration in the overall bioreftnery system, because, for example, the production of waste water will be much larger than in oil-based refineries. A typical oil-based refinery treats about 25 000 t d-1 and produces about 15 000 t d 1 of waste water. The relative amount of waste water may increase by a factor 10 or more, depending on the type of feed and production, in a biorefinery. Evidently, new solutions are needed, including improved catalytic methods to eliminate some of the toxic chemicals present in the waste water (e.g., phenols). 

Biorefineries New catalytic pretreatment of plant materials Valorization, pretreatment or disposal of co-products and wastes from biorefinery by catalytic treatments New and/or improved catalytic processes for chemicals production through the integration of the biorefinery concept and products into the existing chemical production chain New advanced catalytic solutions to reduce waste emissions (solid, air and, especially, water) New catalysts to selectively de-oxygenate products from biomass transformation Catalysts to selectively convert chemicals in complex multicomponent feedstocks New biomimetic catalysts able to operate under mild conditions Small catalytic pyrolysis process to produce stabilized oil for further processing in larger plants... 

Many improvements are still needed to make really effective use of renewable raw materials in biorefineries. Full utilization of the plants is needed instead of the current under utilization, as well as the development of processes to add value to all fractions of the plant and to valorize the by-products of other industrial... 

Biorefineries convert the plant fibre into cellulose ethanol, electricity and CO2... 

Biorefinery A refinery that produces fuels from biomass. These fuels may include bioethanol (produced from com or other plant matter) or biodiesel (produced from plant or animal matter). 

Thus, the 20t incentive made up for the difference between small and large biorefineries. The result was that rather than one or two 100 million gal/yr plants, by 2002 Minnesota was home to 15 ethanol plants, the average capacity of which was 15 million gal/yr. The scale of the plants also encouraged farmer ownership. In 2002,12 of the 15 plants were owned by more than 9000 grain farmers. These plants provided almost 10% of the transportation fuel sold in the state. 

A still lower-cost route to PHAs is genetic modification of plants to directly produce the final polymer. Monsanto (and others) pursued this approach and is currently being cofunded by the US Department of Energy (DOE) in a collaborative research project led by Metabolix. Switchgrass will be modified to produce PHAs, which can then be extracted from the plant material and processed to obtain a consistent composition and the desired material properties. The plant material remaining after PHA extraction can be used to produce fuels, power, or other products, creating the opportunity for a "plants as factories" biorefinery. Applications for polymers with properties similar to those of PHAs consume on the order of 13.6 million metric t annually, and it is possible that in the future PHAs will figure prominently in the plastics market. 

Currently, most biorefineries are based mainly on a single product line with potentially one or two byproducts. Thus, an ethanol plant produces ethanol from corn starch, with distiller s grain as a byproduct. Greater product flexibility and, consequently, greater opportunities for profitability would derive from a plant producing a variety of alcohols, especially higher alcohols whose market prices range from 0.77 to 1.87/kg. 

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