**5. Other aspects of the integrated biomass utilization system**

It is an obvious question that which bioalcohol should be used for the replacement of methanol in biodiesel production, or it is worth to change the ethanol blends of fuels to butanol which has much better fuel properties and energy content than the ethanol.

Comparison of technical and economical assessment for corn and switch grass fermented by yeast into ethanol and C. acetobutylicum into butanol showed (Pfromm et al., 2010) that biobutanol production is not competitive with ethanol production. As an example, the carbon balances for corn are illustrated in Fig. 3. However, involving new technologies, new raw materials (e.g. sugar sorghum) and the extractive fermentation processes combined with immobilized cell techniques, and decrease the production cost by means of the new separation technologies, the butanol becomes competitive as blending or reactive component in biofuel production.

An Integrated Waste-Free Biomass Utilization

microorganisms,



content of the mash can be avoided The main problems are;

system to produce ABE solvents has been developed.

Fig. 4. Flow-sheet of continuous butanol fermentation with outer extraction

Heptanal, which has distribution coefficient for butanol of KB=11.3 has been selected for the new technique. The toxicity of the heptanal is avoided via a by-pass extraction and a post-extractive purification for removal of traces of extractant from the ferment liquor before recycling it to the fermentation. The flow-sheet of particular method can be seen in Fig. 4. The technology using immobilized bacteria and heptanal as solvent is under development now. After starting the fermentation and before reaching the toxic level of butanol, a part of the ferment liquor is pumped out into a counter-current extractor filled with heptanal. The extraction is a continuous process. It means that the raffinate phase is

System for an Increased Productivity of Biofuel and Bioenergy 217

By using immobilized microorganism and in situ extraction the continuous production of butanol and ABE solvents can be performed easily, especially, if the integrated biomass utilization system ensures the sugar solution from sorghum processing. Thus, a large amount of ballast materials from corn or starch hydrolysis which increase the dry material

1. that the solvents which have high selectivity to the ABE solvents are very toxic to the

2. the best distribution coefficients for butanol found among the non-toxic solvents is only 3.5 (oleyl alcohol). In order to apply the high distribution coefficient of a toxic solvent associated with the requirements of the continuous production of butanol, a special




Fig. 3. Comparison of the carbon balances in the fermentation of corn into ethanol (yeast) and ABE (bacteria)

#### **5.1 New trends in biobutanol technology**

The industrial production of biobutanol has roughly a 100 years history, here only some new trends are reviewed in order to indicate the new perspectives of the biobutanol technology. The so called ABE fermentation produces acetone, butanol and ethanol in a ratio of about 2:1:7 or 3:1:6 depending on the bacteria and the fermentation conditions. A small amount of acetic acid and butyric acid are also formed. The starting materials are C5 and C6 sugars, e.g. starch or cellulose hydrolizates, and there are some bacteria strain as well which can utilize cellulose directly. The main problem of the biotechnological butanol production is the toxicity of the solvents formed (mainly the butanol) towards the microorganism (Costa, 1981). The most intensively studied area of the developments is the genetic engineering to produce butanol tolerant bacterium strains or produce less sensitive genetically modified yeast and saving the microorganism from the toxic effects, e.g. by immobilization and capsulation of the bacteria (Park et al., 1989), or by the removal of the accumulated solvents before reaching the toxicity level (Papadopoulos and Linke, 2009; Schmidt et al., 1988;). Combination of the methods provides a good chance to start a continuous ABE fermentation (Hartmeier et al., 1991, Ishii et al., 1985, Kótai and Balogh, 2011). Since the energy demand of the butanol recovery from the dilute solution is one of the main cost factor extraction with a suitable solvent or adsorption on a cheap heterogeneous carrier can be candidates for the development of energy efficient butanol production. Due to the low adsorption capacity of known adsorbents like activated carbon, or the affinity of solid sorbents towards water allowed only utilization at low level. The extraction seemed to be more effective, but the solvents have to meet serious requirements like:


Fig. 3. Comparison of the carbon balances in the fermentation of corn into ethanol (yeast)

The industrial production of biobutanol has roughly a 100 years history, here only some new trends are reviewed in order to indicate the new perspectives of the biobutanol technology. The so called ABE fermentation produces acetone, butanol and ethanol in a ratio of about 2:1:7 or 3:1:6 depending on the bacteria and the fermentation conditions. A small amount of acetic acid and butyric acid are also formed. The starting materials are C5 and C6 sugars, e.g. starch or cellulose hydrolizates, and there are some bacteria strain as well which can utilize cellulose directly. The main problem of the biotechnological butanol production is the toxicity of the solvents formed (mainly the butanol) towards the microorganism (Costa, 1981). The most intensively studied area of the developments is the genetic engineering to produce butanol tolerant bacterium strains or produce less sensitive genetically modified yeast and saving the microorganism from the toxic effects, e.g. by immobilization and capsulation of the bacteria (Park et al., 1989), or by the removal of the accumulated solvents before reaching the toxicity level (Papadopoulos and Linke, 2009; Schmidt et al., 1988;). Combination of the methods provides a good chance to start a continuous ABE fermentation (Hartmeier et al., 1991, Ishii et al., 1985, Kótai and Balogh, 2011). Since the energy demand of the butanol recovery from the dilute solution is one of the main cost factor extraction with a suitable solvent or adsorption on a cheap heterogeneous carrier can be candidates for the development of energy efficient butanol production. Due to the low adsorption capacity of known adsorbents like activated carbon, or the affinity of solid sorbents towards water allowed only utilization at low level. The extraction seemed to

be more effective, but the solvents have to meet serious requirements like:

and ABE (bacteria)

**5.1 New trends in biobutanol technology** 


By using immobilized microorganism and in situ extraction the continuous production of butanol and ABE solvents can be performed easily, especially, if the integrated biomass utilization system ensures the sugar solution from sorghum processing. Thus, a large amount of ballast materials from corn or starch hydrolysis which increase the dry material content of the mash can be avoided The main problems are;


Fig. 4. Flow-sheet of continuous butanol fermentation with outer extraction

Heptanal, which has distribution coefficient for butanol of KB=11.3 has been selected for the new technique. The toxicity of the heptanal is avoided via a by-pass extraction and a post-extractive purification for removal of traces of extractant from the ferment liquor before recycling it to the fermentation. The flow-sheet of particular method can be seen in Fig. 4. The technology using immobilized bacteria and heptanal as solvent is under development now. After starting the fermentation and before reaching the toxic level of butanol, a part of the ferment liquor is pumped out into a counter-current extractor filled with heptanal. The extraction is a continuous process. It means that the raffinate phase is

An Integrated Waste-Free Biomass Utilization

System for an Increased Productivity of Biofuel and Bioenergy 219

force, the ABE solvents is produced continuously at the A side (including the extraction step) and the extracted solvents are continuously removed at the B side of the wall, e.g. vacuum distillation, sorption by solid solvents as sulfonated styrene-divinyl-benzene copolymers (Kótai and Balogh, 2011), or with other methods. Due to their higher affinity towards water than the ABE solvents these copolymers ca not remove the AB solvents from the water directly. The Varion KSM sulfonated styrene-divinylbenzene copolymer can

**Solvent Amount, g/100g Solvent Amount, g/100g**  Water 87 acetone 40 MeOH 75 heptanal 35 EtOH 73 Oleyl alcohol 35 BuOH 63 Hexane 30 Table 8. The adsorbed amount of solvents by solid sorbent based on sulfonated polymer

By using waste ion-exchangers, metal-containing activated carbons or metal-free carbons were prepared by leaching of metals from these metal-containing carbons [Kótai and Angyal, 2011], which are candidates as selective spherical sorbents with low hydrodynamic resistance for removing residual extractants and absorb the contaminants occurring in small amount in the ferment liquor. The Fe-containing sorbent are magnetic and could be separated very easily (without filtering) with an electromagnet (Kótai and Angyal, 2011). Elastic waste tires were also sulfonated for the preparation of sulfonated organic polymers

The supplement of the continuous reactor with sugar solution from the sorghum processing results a much cleaner technology than the process using the corn mash containing a lot of solid ballast material. Additional advantage of the method is the small volume of the B extract, because the small volume of invaluable solvents (water) needs small volume and investment of the distillation unit. A rough comparison of the energy and material balance shows, that selecting the appropriate bacteria and conditions, it is possible to reach the almost maximal theoretical utilization of glucose (0.37 g butanol/g glucose), so the amount of waste water and

Combination of these techniques with new developments in membrane technologies, mainly with selective membrane separation and pervaporation (Liu et al., 2005;

Combustion of biomass to produce energy (heat or electricity) always leaves back ash in various amount and composition depending on the biomass used as raw materials in the furnaces. This ash highly alkaline due to its potassium carbonate content (pH >10). Therefore it cannot be used directly as a fertilizer; only very small amount can be applied even for acidic soils. Since the ash contains all microelements and non-volatile elements in the amount absorbed and used by the plants harvested from the given area, their amount and ratio is optimal for the plant. Its insoluble content (e.g. phosphates) can be converted via digestion to utilizable material. In addition, it can be also supplemented with nitrogen fertilizers or other additives. In this way the processed ash becomes a useful material called

the energy to produce a unit of butanol in principle can be decreased to 25-50 %.

Thongsukmak & Sirkar), can provide a feasible butanol production technology.

absorb the following amount of solvents (Kótai and Balogh, 2011)

to absorb butanol from organic media (Kótai and Balogh, 2011).

**5.2 Recycling of ash from biomass power plants** 

contacted with another non-toxic solvent and/or a sorbent which removes the toxic solvent from the raffinate before recycling it into the fermentation. It should be noted here, that in case of heptanal the distribution of the ABE solvents can be considered to be advantageous.


Table 7. Distribution coefficients of ABE solvents

The boiling point of heptanal is higher than the ABE solvents, thus the evaporation of the heptanal is avoided and does not require energy, By using a special fermentor - extractor system (Fig. 5) the extract phase containing the ABE solvents are contacted with another heptanal phase having a smaller volume (1/10-1/5) than the volume of the primary extract. The contact takes place through a special porous wall based on a pumicite - cement composite (Kótai and Balogh, 2011; Kótai et al., 2011.).

Fig. 5. Fermentor with composite wall

The porous material absorbs the solvents as a sponge, and it acts as a liquid transmitting media. There is no physical mixing only the diffusion controls the distribution of the solvents at the two sides of the wall. In order to keep the concentration difference as driving

contacted with another non-toxic solvent and/or a sorbent which removes the toxic solvent from the raffinate before recycling it into the fermentation. It should be noted here, that in case of heptanal the distribution of the ABE solvents can be considered to be

> **Solvent Heptanal Oleyl alcohol**  Acetone 1.65 0.40 Ethanol 1.01 0.10 Butanol 11.13 3.75

The boiling point of heptanal is higher than the ABE solvents, thus the evaporation of the heptanal is avoided and does not require energy, By using a special fermentor - extractor system (Fig. 5) the extract phase containing the ABE solvents are contacted with another heptanal phase having a smaller volume (1/10-1/5) than the volume of the primary extract. The contact takes place through a special porous wall based on a pumicite - cement

The porous material absorbs the solvents as a sponge, and it acts as a liquid transmitting media. There is no physical mixing only the diffusion controls the distribution of the solvents at the two sides of the wall. In order to keep the concentration difference as driving

advantageous.

Table 7. Distribution coefficients of ABE solvents

composite (Kótai and Balogh, 2011; Kótai et al., 2011.).

Fig. 5. Fermentor with composite wall

force, the ABE solvents is produced continuously at the A side (including the extraction step) and the extracted solvents are continuously removed at the B side of the wall, e.g. vacuum distillation, sorption by solid solvents as sulfonated styrene-divinyl-benzene copolymers (Kótai and Balogh, 2011), or with other methods. Due to their higher affinity towards water than the ABE solvents these copolymers ca not remove the AB solvents from the water directly. The Varion KSM sulfonated styrene-divinylbenzene copolymer can absorb the following amount of solvents (Kótai and Balogh, 2011)


Table 8. The adsorbed amount of solvents by solid sorbent based on sulfonated polymer

By using waste ion-exchangers, metal-containing activated carbons or metal-free carbons were prepared by leaching of metals from these metal-containing carbons [Kótai and Angyal, 2011], which are candidates as selective spherical sorbents with low hydrodynamic resistance for removing residual extractants and absorb the contaminants occurring in small amount in the ferment liquor. The Fe-containing sorbent are magnetic and could be separated very easily (without filtering) with an electromagnet (Kótai and Angyal, 2011). Elastic waste tires were also sulfonated for the preparation of sulfonated organic polymers to absorb butanol from organic media (Kótai and Balogh, 2011).

The supplement of the continuous reactor with sugar solution from the sorghum processing results a much cleaner technology than the process using the corn mash containing a lot of solid ballast material. Additional advantage of the method is the small volume of the B extract, because the small volume of invaluable solvents (water) needs small volume and investment of the distillation unit. A rough comparison of the energy and material balance shows, that selecting the appropriate bacteria and conditions, it is possible to reach the almost maximal theoretical utilization of glucose (0.37 g butanol/g glucose), so the amount of waste water and the energy to produce a unit of butanol in principle can be decreased to 25-50 %.

Combination of these techniques with new developments in membrane technologies, mainly with selective membrane separation and pervaporation (Liu et al., 2005; Thongsukmak & Sirkar), can provide a feasible butanol production technology.
