**2. The exchange of mass and energy in waste management**

Circulation of matter and energy flow are the two main environmental laws describing the basic rules for the functioning of ecosystems on Earth. Life on our planet is possible, thanks to

**Figure 1.** Value chains in bioeconomy [5]

Thanks to that, "the bio-industry," which is the main component of the EU economy referred to as "bio-economy" ("bioeconomy"), will play an important role in stimulating sustainable growth and increasing Europe's competitiveness by reindustrialization and the revitalization of rural areas, providing tens of thousands of jobs in the field of research, development, and

The Bioeconomy Program for Europe is going to be an evolutionary program. Expected to develop so-called value chains, the implementation of which will ultimately lead to the creation of so-called biorefinery that a comprehensive and zero-waste will be recycled biomass. The most important technological challenges, political and market, therefore will be prior to commercialization of innovative solutions to full scale. These challenges cannot be overcome by an individual company or dispersed industry, so it is necessary to approach the whole

This is important because of the need to reverse the current trend of significant bioeconomic investments in non-European regions, where conditions seem to be more attractive. The longterm research and innovation jointly financed by public and private entities can help solve this problem. This process will be implemented through the creation and implementation of appropriate and developed value chains, which will lead to reducing the risk of investment in

As part of the preparatory work for the start-up of the scope of the European bio-economy, there was a plan developed for Strategic Innovation and Research Agenda (SIRA). This document proposes a coherent set of actions that should be implemented through established

**•** Implementation of projects aimed toward the integration and implementation of technology and scientific results and the introduction of technology on a commercial scale by imple‐

**•** Implementation of development projects aimed at filling the gaps in research and techno‐

As it can be seen from the schematic products, semi-finished and all residues of the process as a result of the implementation of the objectives set in the value chains should be directed to biorefinery systems, in order to complete the transformation into energy carriers and bio‐

Circulation of matter and energy flow are the two main environmental laws describing the basic rules for the functioning of ecosystems on Earth. Life on our planet is possible, thanks to

demonstration projects on the implementation of innovative processes.

production over the next decade [3].

428 Biofuels - Status and Perspective

system of management system biomass [4].

"Biobased Industry Consortium" (BIC), namely:

menting demonstration and flagship projects

**•** Supporting projects taking challenges cross-sectors [5]

Schematically, the areas covered by value chains are shown in Fig.1.

**2. The exchange of mass and energy in waste management**

logical innovation

chemicals for various purposes.

the constant influx of solar energy. This energy flows through the ecosystem and partly returns to space in the form of thermal energy emitted by the Earth. Only a small portion of solar energy is accumulated in living organisms, and they even lose most of it forever. However, despite the exchange of energy, the Earth does not mention the matter with the environment. Earth is thus a closed system. The amount of matter on Earth is constant and circulates in the ecosystem. Under the influence of solar radiation, simple ingredients such as water and carbon dioxide are synthesized biomass, which forms a complex structure such as plants and other biological life forms, which in turn ensure the survival of other more complex forms of biological life and after their death through the action of decomposers and the way the carbon cycle and the nitrogen return to its original state [6].

Behavior of matter and energy is the subject of thermodynamics. The first law of thermody‐ namics states that energy can neither be created nor destroyed. It can only change its form. This means that everything which is delivered for processing must be accumulated in products in the technosphere1 or leave them as waste in solid, liquid, or gas form. In addition, the system cannot get more energy than it was put into the system. Every economic activity of man is connected inextricably with the generation of waste, and it should be noted that all industrial products become waste sooner or later. The increasing amount of waste causes obvious environmental problems [7, 8].

All processes in the environment are irreversible processes, in other words, the real processes. In nature, the reversible processes are unique. This is because the reverse process cannot undergo energy dissipation that occurs in the actual process, even, for example, in effect of friction. Similarly, the industrial installations are open systems that interact with the environ‐ ment together with its products. The energy introduced into the system is transformed from

<sup>1</sup> Sphere of human intervention in nature, spreading in the environment

a less useful form, which is more organized, in a more useful form, which is less organized. This interaction can be described by the change in entropy2 , that is state function, which is postulated by the second law of thermodynamics [9].

Entropy is a measure of the degree of disorder of the system, a measure of the "quality" of the energy stored in the system. One version of the second law of thermodynamics states that "the arrangement is reduced (the degree of disorder increases) in any spontaneous process." Energy and matter cannot be destroyed, but their quality is changed. Together they seek a greater mess, so their entropy increases [6, 10, 11].

According to the second law of thermodynamics for a longer period of time, entropy always increases. Each physical system, which is capable of free energy dissipation, does so in such a way that the entropy increases and the amount of used energy decreases [12, 13].

The first law of thermodynamics is a universal law of nature, from which there are no exceptions. The second law of thermodynamics is based on the concept of probability, due to the fact that it is possible when the entropy decreases. There are unlikely but possible situa‐ tions. The second law of thermodynamics indicates the most likely direction of the incident and does not exclude the other less probable incidents.

Fossil natural resources used by man naturally are ordered matter of a certain structure. The products of human consumption are waste, in which the degree of order of matter is much lower, despite the fact that the elements present in the waste as well as natural resources are the same.

Entropy changes can occur either within the system or may be discharged to the environment. Export of entropy outside of the system is caused precisely by the fact that the processes are irreversible that causes irreversible increase in entropy which is the reduction in the degree of ordering. Reduction of changes in the form of entropy, for example, in the course of the technological process reduces the energy expenditure in obtaining the same effect as a final product, resulting in minimizing the losses in the process and consequently a reduction in the degree of impact on the environment. This can be done, e.g., on the way to limit the number of unit processes in technology, keeping in mind that the total entropy of unit processes will always be higher than the sum process entropy [6, 11].

The concept of entropy resulting in the way of irreversible processes occurring in the natural environment is due to spontaneity of overlapping of these processes. Spontaneous processes are irreversible processes, extending with a predetermined rate in such direction to achieve a state of balance. So it is not possible to restore the state before the occurrence of irreversible process while maintaining all the parameters of both the system and the environment. For example, if the process is reversed and the parameters of the system will return to the initial values, the environment will not return to the previous state because of the entropy emission into the environment as a result of reactions in the system.

Analysis of processes for entropic changes enables optimization of technological processes used in the industry, as well as optimizing the use of raw materials and energy in order to

<sup>2</sup> A measure of the degree of order – the higher entropy of the system, the lower the degree of order.

obtain specific products. The essence of these considerations is the production of entropy, which determines the degree of energy loss in the process, and so is the energy efficiency of the process. As it was mentioned earlier reduction of entropy production as a result of optimization technology, the substrates used and the energy introduced into the process reduce their impact on the environment. This is possible through the pursuit of the process to reversible process conditions and thus to obtain the equilibrium parameters. However, the pursuit causes inconveniences in the form of diminution of other important parameters of installation, such as enlargement of device size, which in many cases leads to the elimination of some of this type of technologies.

a less useful form, which is more organized, in a more useful form, which is less organized.

Entropy is a measure of the degree of disorder of the system, a measure of the "quality" of the energy stored in the system. One version of the second law of thermodynamics states that "the arrangement is reduced (the degree of disorder increases) in any spontaneous process." Energy and matter cannot be destroyed, but their quality is changed. Together they seek a greater

According to the second law of thermodynamics for a longer period of time, entropy always increases. Each physical system, which is capable of free energy dissipation, does so in such a

The first law of thermodynamics is a universal law of nature, from which there are no exceptions. The second law of thermodynamics is based on the concept of probability, due to the fact that it is possible when the entropy decreases. There are unlikely but possible situa‐ tions. The second law of thermodynamics indicates the most likely direction of the incident

Fossil natural resources used by man naturally are ordered matter of a certain structure. The products of human consumption are waste, in which the degree of order of matter is much lower, despite the fact that the elements present in the waste as well as natural resources are

Entropy changes can occur either within the system or may be discharged to the environment. Export of entropy outside of the system is caused precisely by the fact that the processes are irreversible that causes irreversible increase in entropy which is the reduction in the degree of ordering. Reduction of changes in the form of entropy, for example, in the course of the technological process reduces the energy expenditure in obtaining the same effect as a final product, resulting in minimizing the losses in the process and consequently a reduction in the degree of impact on the environment. This can be done, e.g., on the way to limit the number of unit processes in technology, keeping in mind that the total entropy of unit processes will

The concept of entropy resulting in the way of irreversible processes occurring in the natural environment is due to spontaneity of overlapping of these processes. Spontaneous processes are irreversible processes, extending with a predetermined rate in such direction to achieve a state of balance. So it is not possible to restore the state before the occurrence of irreversible process while maintaining all the parameters of both the system and the environment. For example, if the process is reversed and the parameters of the system will return to the initial values, the environment will not return to the previous state because of the entropy emission

Analysis of processes for entropic changes enables optimization of technological processes used in the industry, as well as optimizing the use of raw materials and energy in order to

2 A measure of the degree of order – the higher entropy of the system, the lower the degree of order.

way that the entropy increases and the amount of used energy decreases [12, 13].

, that is state function, which is

This interaction can be described by the change in entropy2

postulated by the second law of thermodynamics [9].

and does not exclude the other less probable incidents.

always be higher than the sum process entropy [6, 11].

into the environment as a result of reactions in the system.

mess, so their entropy increases [6, 10, 11].

430 Biofuels - Status and Perspective

the same.

Therefore, the goal of reducing the impact on the environment should be carried out differ‐ ently. It should be noted that the export of entropy, that is, the energy lost from the process, is carried out through the emission of unused waste heat and/or through the generation of waste. Also, the products of the process, after the step of its use, become waste. Various types of systems comprising external and internal recycles of a flow of mass and energy in the form of heat may be constructed to limit the production of all the waste from the process. This type of system, congruent with the concept of biorefinery, is shown in Fig. 2.

**Figure 2.** Scheme of biorefinery system containing recycles of mass and/or energy flow [14]

The stream of biomass (matter) and stream of energy flow into the biorefinery system, which are used and processed in the way of biorefinery processes, which results in obtaining useful products and intermediates, which at this stage are treated as process waste. However, by the internal recycle, these intermediates are used as starting materials in subsequent biorefinery processes. The same happens to the energy that is inserted into the process and allows the incident and which may also be the product of the appropriate process. Generally, part of the energy emitted in the form of heat is waste from the process, which with properly optimized technology can be used as the feed energy flow to a subsequent process. From the example of this biorefinery system of the second row can be seen clearly that by optimizing the use of reactants and waste streams in the process, it is possible to reduce the formation of entropy, which prevents the loss of energy by providing greater energy efficiency of the system [15].

It should be noted that the internal and external recycle systems can be used not only at the level of the process but also at the level of the whole plant, as well as at the level of product user or user of energy produced and on the level of region and state. The effect of this will be reduction of the entropy of the system, reducing the consumption of energy and matter, increasing the efficiency of the process, and finally reducing the impact on the environment.

In the analysis of the energy efficiency of processes, of very help is the function of exergy. The precursors of exergy analysis were G. Gouy and A. Stodola, who formulated the law defining the loss of ability to perform work resulting from a thermodynamic irreversibility. According to the definition of the concept proposed by L. Reikerta, "exergy represents the minimum amount of work to be done, to produce from the commonly occurring components of the surrounding nature a desired substance with the required parameters, using the surrounding nature as a heat source, which is worthless in terms of thermodynamic," which in simple can be captured in the words, "exergy is the maximum capacity of the substance, which is an energy carrier, for the work in relation to the environment." Most simply speaking, the exergy is a measure of the quality of various forms of energy [16, 17].

Determination of loss of exergy is the main task of the exergy analysis, because each exergy loss causes a reduction of useful effects of the process or increases the consumption of fuels for its occurrence. Exergy losses can be divided into internal and external. Internal losses are caused by the irreversible processes extending inside the system (control cover of process). External losses result from the discharge of waste products with positive exergy into the environment, and the loss should preferably be expressed directly using the exergy of waste products. Calculation result of internal losses does not depend on the reference level adopted in the calculation of the external losses [18, 19].

However, any loss of exergy should have economic justification. Admission to the loss of exergy is necessary in order to reduce capital expenditures. For example, the flow of heat without loss of exergy would require an infinitely large surface of heat flow. So exergy analysis indicates on the possibilities of improving the thermal process. According to Jan Szargut, this analysis does not decide on the advisability of the improvements, which should be controlled by means of economic analysis. We cannot agree with this statement, because not only economic considerations will determine the attractiveness of technological solutions but also reduction of energy consumption and increase of the energy efficiency of the process will provide a means to achieving the goal of protecting the environment by reducing the impact on them through the process [20].

Analysis of entropy based on the calculation of exergy process allows for optimization of the manufacturing process and proper assessment of its impact on the environment, taking into account all the components and stages of the production process, starting from the raw material constituting substrates in the process and ending on the disposal of waste from the process and waste resulting from the use and consumption of the final product [21, 22, 23].

Therefore, the comparison of the possible use of exergy or entropy emissions in different technological processes allows the systematization and classification of the different technol‐ ogies in this field. This capability is particularly important in the case of methods of processing and disposal of waste. Among others, the studies showed that the most favorable thermal process in the waste utilization is pyrolysis. This process is ahead of the processes of gasifica‐ tion and combustion for energy. Also, in waste management, this classification is important. Waste actually represents the energy that is correlated with the value of primary energy resources, from which the product was formed and then the waste was produced. Using this energy should be the most efficient and should last as long as possible, and hence, its dissipa‐ tion should take place as long as possible at the time. This is possible only through the repeated use of the energy contained in the products, intermediate products and wastes [24].
