**3. Sustainability in the course of processing waste**

Sustainable development requires an assessment of the extent to which natural resources are in sufficient quantity and availability, to meet those needs while reducing the amount of waste (both process and also final, generated during the processing and usage of these resources).

The degree of loading of the Earth, which is the environmental capacity of the Earth, is the limited size and is determined by three interrelated factors: the size of the human population, the activity of each human being, and the impact on the environment, which is a result of this activity. The relationship of these factors and their influence on the degree of loading of the Earth is defined by the formula (1)

$$\text{ELL} = \left[ \text{HI}\_1 \cdot \text{A}\_1 \cdot \left( \pm \text{E}\_1 \right) \right] + \left[ \text{HI}\_2 \cdot \text{A}\_2 \cdot \left( \pm \text{E}\_2 \right) \right] + \left[ \text{HI}\_3 \cdot \text{A}\_3 \cdot \left( \pm \text{E}\_3 \right) \right] + \dots + \left[ \text{HI}\_{\mathcal{T}\text{mld}} \cdot \text{A}\_{\mathcal{T}\text{mld}} \cdot \left( \pm \text{E}\_{\mathcal{T}\text{mld}} \right) \right] \tag{1}$$

where:

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

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

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

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

measure of the quality of various forms of energy [16, 17].

in the calculation of the external losses [18, 19].

on them through the process [20].

432 Biofuels - Status and Perspective

**EL** – **l**oading **l**evel of the Earth


At the present time, there is a continuous and exponential growth of the human population on Earth observed and thus human activity aimed at creating wealth – as a result, omnipresent consumerism is growing globally. In results, there is greater impact on the environment through the use of its resources. To lower the burden on the environment, the value of human activity and the impact of each of the human individual through this activity should be reduced. Human activity cannot be reduced, but this type of activity can be develop on the way of environmental education. In the same way, you can indirectly seek to reduce the environmental impact and the burden of every human activity [25, 26, 27].

There are two ways to reduce the environmental load. The first of these is to limit the use of resources, which is called dematerialization, which is gradually reducing usage of resources in technological processes. The next step should be the determined counteraction character of the life of a consumer society in developing countries and developed countries. Another way to limit the use of natural resources, including energy ones, is to replace the current raw materials for other unknown resources, by-products, or wastes from other processes, which is called transmaterialization [7, 28].

Both of the abovementioned proceedings road are independent, but only their parallel application can provide the most tangible effect of actions to reduce the impact of human activities, including industrial environment. The Earth and its biosphere are thermodynamic systems exchanging with the environment energy only. The components of the biosphere subsystems, however, are open systems, exchanging with their environment both energy and matter. One of the subsystems, so-called man-made technosystem, collects raw materials from the environment and excretes waste. Systematic expansion of the technosystem and its impact not only contributes to an imbalance in the biosphere but also causes a real threat to its future existence [29, 30].

In the context of this situation arises question about the possibility of avoiding further destruction of the biosphere. Following Johansson, there are two possibilities for remedying this problem.

The first one is the complete separation of the technosystem of the biosphere, creating a closed technosystem. This method would involve major technological challenges for the modification of existing technologies for closing circuits of waste, which will entail a significant increase in energy consumption. Note also that technosystem separated from the biosphere would have to thus eliminate human intervention [7].

The second method proposed by Johansson is the adaptation of the technosystem to the environment in such a way that its action plays the strategy and action, which uses nature. In this solution, however, certainly limitation of many existing technological capabilities would occur, including reduction in the size and density of the local industrial activities, which, at this stage of the development of civilization, have already been exceeded in many cases. Implementation of this strategy would involve fundamental reorganization of the existing technological structure which would entail the search for new technological solutions [7].

Due to the fundamental problem of modern society as of a linear flow of matter from its source as raw materials to the waste stage and the accumulation of products of human activity in this form in order to maintain good environmental status as long as possible, our society must in its actions be inspired by nature, reducing the negative environmental impact to a minimum. A society that wishes to survive must maintain the activity causing disorder within order, possible to achieve by the energy captured from the sun. In addition, waste (degraded material with a high degree of disorder, which comes from industries and households) should be converted back to natural resources [31].

From above it follows that the least favorable from the energy point of view is depositing waste in landfills, where primary energy accumulated in the waste is dissipated during their long storage, without its prior use. In this case, the relatively long time of the energy dissipation is ensured, but the benefit of the use of this energy and hence saving in the use of primary energy is equal to zero. Burning of waste in incinerators is a better solution for the landfill, because it allows you to recover some of the energy from waste, and this energy can be used in other processes. However, the processing of the same material by pyrolysis and gasification is even more preferred environmentally and economically in view of the minimization of oxides and heavy metal migration into the exhaust gases, as well as because of the higher efficiency of cogeneration systems. In addition, in these processes is formed synthesis gas or, in the pyrolysis process, post-pyrolysis oil, which both can be repeatedly used for the production of energy in various forms, including the ability to convert it to transport fuel. Hence, the more energy is consumed for the processing of raw materials, the more waste is created, because of the identity of mass and energy. In nature, there is a balance between the processes of formation of ordered matter, as of organic compounds in living organisms and the production of waste. Nature produces no waste and does not deplete resources, because in nature, nothing is really a waste – something that for one organism means waste is feed for another. In other words, everything is used in the life cycle [8, 32].
