**2. Energy aspects of biomass utilization**

The intensive production of biomass as raw material for fuel or bioenergy production would lead to fast exhausting of the soil and dramatic increasing the production costs without intensive fertilization. Except nitrogen, all of the nutrients (P, K) and microelements can be recycled by reprocessing the residues of the biomass work up or biomass utilizing energy producing technologies. The nitrogen fertilization, however, always requires fossil energy source, since the base material of the two most typical nitrogen fertilizer (ammonia and urea) is the natural gas. It is one of the main reasons of the opposite statements about energy intake and output balance of the biomass based fuel and energy productions. Otherwise, the conversion of the waste to fertilizers (to supply other elements like P, K, S and microelements) should also be the integrated part of the sustainable and economic biomass production system.

Fig. 1. Waste free biofuel production cycle

stalk can also be used as solid fuel (after drying with the low heating value warm water) in biomass power plants. Generally, the green biomass can be utilized in biogas plant and the dried ones as solid combustion fuel in power plants. The residues of the sugar derivatives producing plants (sugar sorghum, corn, etc.) can supply a biomass power plant with their dried stalk. The complete waste processing in these energy producing units and recirculation of other wastes (potassium sulfate, calcium sulfate or biomass power plant ash) of the integrated system as fertilizers into the agriculture contribute to a sustainable biomass

The intensive production of biomass as raw material for fuel or bioenergy production would lead to fast exhausting of the soil and dramatic increasing the production costs without intensive fertilization. Except nitrogen, all of the nutrients (P, K) and microelements can be recycled by reprocessing the residues of the biomass work up or biomass utilizing energy producing technologies. The nitrogen fertilization, however, always requires fossil energy source, since the base material of the two most typical nitrogen fertilizer (ammonia and urea) is the natural gas. It is one of the main reasons of the opposite statements about energy intake and output balance of the biomass based fuel and energy productions. Otherwise, the conversion of the waste to fertilizers (to supply other elements like P, K, S and microelements) should also be

the integrated part of the sustainable and economic biomass production system.

production and fuel production, as well.

Fig. 1. Waste free biofuel production cycle

**2. Energy aspects of biomass utilization** 

The review of the energy inputs required for the production of the raw materials like corn, switchgrass or sunflower, or the cost of the biofuel production form these agricultural materials (Pimental and Petzek, 2005) unambiguously show, that the climate (crop amount), type of the agricultural plant and the type of the processing technologies basically determines the feasibility of an energy positive biofuel production. The energy saving in the production of the various biofuel components from various sources is compared to the production costs related to petrochemical raw materials (Arlie, 1983) is given in Table 1. Selection of the biomass produced and the fuel type prepared from this biomass requires that environmental, economic and energetic viewpoints (Hill et al., 2006) should also be taken into consideration. The social-economic viewpoints play also key role in this decision. That is obvious, that there is not any type of biomass plant which could completely be turned into biofuel, only integrated systems can solve this problem, when more than one type of biomass plants are in synchronized operation. More than one energy producing system is used to utilize the various type of green biomass, and more than one type of biofuel are produced from the various parts of each type of biomass plants. At the same time the energy producing plants or the waste producing and nutrient reprocessing plant (fertilizer plant) can use the wastes of each technological step as raw material to ensure the recyclability.


Table 1. Energy gain of sugar-based biofuel components (ton of oil equivalent/ton)

Since the energetically favorable components as BuOH, EtOH and acetone can be produced from biomass the use of these in biofuel including biodiesel production seems to be essential and unavoidable step. The EU biofuel standards now declare that rapeseed oil and ethanol as raw materials are permitted and standardized as biofuels within European Community. Due to the limits of the agricultural area and the productivity of rape in this climate and low energy content of ethanol, however, requires changing this statement and the use of other type of biofuels should be also permitted. Thus, in our integrated system we incorporate new type of blend materials, mainly butanol for replacing the ethanol, and new kind of blends are produced from the wastes of biodiesel and biobutanol production as well. In order to increase the amount of biodiesel produced from one unit of vegetable oil, butyl ester production is suggested instead of the methyl esters, and butoxylation or blending with pure butanol are also possible increments in increasing the efficiency of the biofuel production related to one hectare of the agricultural area.

An Integrated Waste-Free Biomass Utilization

System for an Increased Productivity of Biofuel and Bioenergy 205

oil molar ratio with 1 % KOH a catalyst. The reaction is almost completed within 30 min even at room temperature. By using 5 % of butylglycol, the reaction time is 5-10 min. Since the butyl glycol acts also as an alcohol ( not only as an ether), thus not only methyl esters but 2-butoxyethyl esters – R-C(O)-O-C2H4-OC4H9 - are also formed. These esters are formed in an amount of 2-3 %w/w and act as fuel components. In this way, the phase mixing agents built into the ester phase and they contribute to the mass of the biodiesel and do not need to recover it which simplifies the production technology. The catalyst solution prepared from KOH, butylglycol and methanol was used in our plant scale experiment performed in Hungary in 2009, when a continuous trans-esterification process with continuous separator was put into operation. The method could be combined with the ion exchange type removal and recycling of the neutralization agent (KHSO4, chapter 3. 2), because the reaction takes place at room temperature and the amount of soaps formed and appeared in the ester phase was very small. The catalyst distribution between the ester and glycerol phase is around 2:98. The ester phase has been neutralized with KHSO4, when the potassium content is decreased with the continuous operation mode below 50 ppm without any further washing. The further purification steps, washing with water and removing the residual MeOH in vacuum, are the same as in the classical biodiesel technologies, however, the amount of the dissolved MeOH, due to the lack of soaps and residual catalyst is much lower than in the

In order to decrease the length of the tube reactor and the residence time of the mixture in the apparatus, a two-stage trans-esterification seems to be the most reliable, when after decreasing the rate of the reaction, after the first separator a further amount of methanol and catalyst are added, when the reaction rate is suddenly increases: it is attributed to the extra methanol ensuring a large excess for the residual triglyceride, thus the conversion reaches 98 % in 20-30 min reaction time. We have used 50 m3 tanks for the esterification with intensive stirring. Separators for removing the glycerol phase, and the same volume of the separator was used to separate the neutralization agent and the ester phase which was mixed in a tube

In spite of the efforts to produce solid phase non-soluble alkaline catalysts or highly active acidic (super-acidic) catalysts (Di Serio et al, 2008; Leung et al., 2010; Soriano et al., 2009), the homogeneous catalytic (KOH or NaOMe catalyzed) trans-esterification of vegetable oils have been the most commonly used method in the biodiesel industry (Huber et al., 2006). However, soap formation during the alkaline-catalyzed trans-esterification is the most problematic by-reaction. In case of low water and carboxylic acid containing vegetable oils the main source of the soap formation is the hydrolysis of the formed methyl esters during washing, which is a strongly pH dependent process. Thus the neutralization preceding the washing is an essential step to minimize the saponification by-reactions. The amount and type of the formed soap is strongly affected by the separation characteristics of the glycerol and the ester phase. The acid treatment is generally needed to start or quicken the phase separation process producing aqueous glycerol solution. It is well known that the distribution of the catalyst between the glycerol and the methyl ester phase is strongly depends on the temperature, type of the catalyst, excess of methanol and the composition of the two separated phases [Chiu et al., 2005; Di Felice et al., 2008; Zhou and Boocock, 2006). Table 2 shows the distribution of 1 % KOH and 0.5 % of H2SO4 distribution at different temperatures depending on the amount of methanol at biodiesel : glycerol molar ratio of 1:3.

usual technologies. The flow-sheet of the technology is shown in Fig 2.

after exit of the first separator and before entering into the second one.

**3.2 Removal of the residual catalyst from the biodiesel (decontamination)** 
