key for ii mid exam of self study course Green Engineering - GEC LIBRARY


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2. Energy conservation in industrial ecology:
                         Energy conservation in industrial ecology is to be studied carefully for many reasons.  At present, use of fossil fuels is more to generate the power, which is being used for the purpose of transforming materials of various kinds into their new forms suitable for use i.e., products.  But fossil fuels are fixed in quantity.  Hence fast depletion of these reserves leads to deprivation of energy resources to future generations.  Energy residues in the form of heat and exhaust gases are emitted by industrial organisms into surroundings causing global warming and pollution of air.  Hence energy analysis is the urgent need to reduce the impact on environment and to achieve the sustainability for energy.It encompasses products as well as manufacturing facilities.
                        In the case of products, that use energy during their service lifetimes – engines, computers, buildings and so on, there is a particular premium on designs that minimize energy consumption.
                        It is usually the case that the initial extraction of resources is quite energy intensive because of the separation and purification involved.  Wherever possible, use of recycled material is desirable from both a material and energy perspective.
                        Energy conservation can be accomplished by undertaking energy audit at each stage of material extraction, processing and manufacturing.
                        Assessment of product life cycle is another mode of calculating the energy use and resultant emissions at each stage.  For example material substitution can be thought of as one of the alternate solutions for energy conservation.  For example substitution of magnesium or aluminium parts such as body, doors, hoods, wheels, wheel hubs sheet frames, for steel parts in a mid size automobile.  It not only saves the energy during manufacture but also during use.  Because vehicle become lighter which leads to fuel efficiency.
                        For lighting purpose only LED bulbs may be used.  Even renewable energy sources like solar energy is a viable solution in the longrun.  Strict discipline and judicious use of appliances naturally leads to energy conservation.
3. Water Conservation in Sustainability Engineering:
                        Many actions of industry involve use of water, water budgets and responses to what the budgets reveal are inherently part of industrial ecology.  Water intensity differs greatly with industrial sector and with life stage.  In principle a life-cycle water analysis for any commercial substance or product of choice must be conducted to quantity the use of water at each substance or product life stage and resulting environmental impacts.  Some industries which use highest rates of water are petroleum and coal processing, primary metals, chemicals and paper.
§  Promote designs that minimize water consumption during product use.
§  Water needed for extraction of material is more for recycling the material.  Hence use of recycling materials is desirable from both material and water perspective.
§  To improve the air quality and to reduce the use of fossil fuels electric vehicles are coming on to the roads.  But water needed for electric vehicles are more compared to vehicles using gasoline.
§  Water must be carefully recycled and can be used for different purposes.  For example It can be used once for high – purity manufacturing, a second time for toilets and a third time (after some filtration) for irrigation of the property.
§  Re-use of components automatically prevents usage of water.
4.  Definition of a model and the need of a model in industrial ecology:
                         A model is a simplified representation of a real life system or a real operation or a real process, in which only the basic aspects of the system are considered.  The model puts the uncertainties or complexities of the problem into a logical frame work, which is amenable to comprehensive analysis.
                        Industrial ecology is the study of material and energy flows through industrial systems.  It seeks to quantity the material flows and industrial processes that make modern society function.  Industrial ecologists are often concerned with the impacts that industrial activities have on the environment, with use of the planet’s supply of natural resources, and with problems of waste disposal.
                        The intellectual construct that attempts to describe those interrelationships is termed as ‘Model’
                        Varieties of models can be used to study industrial ecology.
                        At the most basic level is conceptual model.  It only describes structural aspects of the system.  Such a model represents the components of the system of interest and the potential for interaction among the components.
                        Next level of modeling is mathematical modeling.  If the objective of study is to understand the structure of the system and its operation, then there arises a need to estimate the magnitude of the interactions among the system components.  In these circumstances a mathematical model must be used.  In the present context ‘Multidisciplinary industrial ecology models’ which comprise technological and human components’ come under this category.
The ultimate in industrial ecology models is the incorporation of technological human and environmental components and their interactions and interrelationships in some detail.  These  are known as comprehensive industrial ecology models
Building a particular type of model depends on the objective of study.  Once the objective of study is determined, next step is to decide what type of information is required to complete the study.  Next step is to decide the extent of information and the source of information.  As an example the questions (objectives) are presented to understand the necessity of a particular type of model.
                I.            What fraction of lead in discarded computers in country A was recycled in year 2000?
             II.            What are the environmental impacts of human use of lead in country A in 2000?
          III.            How do human choices produce the environmental impacts of lead in country A in 2000?
To address each of the above questions the magnitude of the data and their sources differ and there arises a need to use a particular type of model.

Note to students

    The answers provided must be taken as guidance only. They are advised to go through the text book and are encouraged to discuss among themselves regarding a topic. 

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