Lesson Plan
Title – Don’t let it go waste!Description –Students design a prototype of a power generating system that uses wet waste to produce electricity.
Target Grade- 8, 9
Subject- Environmental Science, Biology, Physics
Goals –
- To demonstrate that heat energy is released during decomposition of organic wastes.
- To introduce students to the concept of engineering design
Prerequisites –(knowledge about)
- Definition of Energy and different forms of energy
- Law of conversion of Energy
- Assembling electrical circuits
Instructional Objective(s)
At the end of the lesson, students should be able to:
- Demonstrate that energy changes its form (Heat to electrical in this case)
- Apply the concept of transformation of energy
- Design a generator
- Analyse, evaluate and modify the kitchen waste based power generator
Material Needed
For each student:
- KWL Chart
- Engineering design process workbook
For each group:
- Printout of the support material document
- Wet garbage
- Resources mentioned in the support material document
For the entire class:
Access to Internet to explore the topic and to view the links provided at the end of this lesson plan
Instructional Resources
Introduction -
Engineering Designing
Introduction
I)Biodegradable Wastes
Biodegradable wasteincludes anyorganic matterinwastewhich can be broken down into carbon dioxide, water, methane or simple organic molecules by micro-organisms and other living things usingcomposting,aerobic digestion,anaerobic digestionor similar processes. In waste management, it also includes some inorganic materials which can be decomposed by bacteria. Such materials includegypsumand its products such asplasterboardand other simple organicsulfateswhich can be decomposed to yieldhydrogen sulfidein anaerobic land-fill conditions.[1][2]
In domestic waste collection, the scope of biodegradable waste may be narrowed to include only those degradable wastes capable of being handled in the local waste handling facilities.
Biodegradable waste can be commonly found inmunicipal solid waste(sometimes called biodegradable municipal waste, or BMW) asgreen waste,food waste,paperwaste, andbiodegradable plastics. Otherbiodegradablewastes includehuman waste,manure,sewage,sewage sludgeandslaughterhouse waste.Biodegradable waste can be used for composting or a resource for heat, electricity and fuel by means ofincinerationoranaerobic digestion.
II) Decomposition
The process of decomposition — the breakdown of raw organic materials to a finished compost — is a gradual complex process, one in which both chemical and biological processes must occur in order for organic matter to change into compost.
The decomposition (stabilization) of organic matter by biological action has been taking place in nature since life first appeared on our planet. In recent times, man has attempted to control and directly utilize the process for sanitary recycling and reclamation of organic waste material. Such organic materials as vegetable matter, animal manure and other organic refuse can be converted from otherwise wasted materials to a more stable form for use as a soil amendment by this process. This process is called “composting” and the final product of composting is called “compost”. Generally speaking there are two processes that yield compost:
- ANAEROBIC(without oxygen) decomposition.
- AEROBIC(with oxygen) decomposition and stabilization.
Anaerobic Decomposition (Fermentation)
Anaerobic decomposition takes place in nature, as in the decomposition of the organic muds at the bottom of marshes and in buried organic materials to which oxygen does not have access. Intensive reduction of organic matter by putrefaction is usually accompanied by disagreeable odors of hydrogen sulfide and reduced organic compounds which contain sulfur, such as mercaptans (any sulfur-containing organic compound).
Putrefactive breakdown of organic material takes place anaerobically. Organic compounds break down by the action of living organisms that do not require air in the normal sense. These organisms use nitrogen, phosphorus, and other nutrients to live and to develop cell protoplasm, but they reduce the organic nitrogen to organic acids and ammonia. The carbon from the organic compounds which is not utilized in the cell protein is liberated mainly in the reduced form of methane (CH4). A small portion of carbon may be respired as carbon dioxide (C02).
Since anaerobic destruction of organic matter is a reduction process, the final product, humus, is subject to some aerobic oxidation when put on the soil, that is, it may appear to decompose further after being exposed to air. This oxidation is minor, takes place rapidly, and is of no consequence in the utilization of the material on the soil. In other words, much less heat is generated in anaerobic decomposition than in aerobic decomposition.
The lack of heat generated in the anaerobic destruction of organic matter is a definite disadvantage if contaminated materials areused for composting. High temperatures are needed for the destruction of pathogens and parasites. In anaerobic decomposition the pathogenic organisms do eventually disappear in the organic mass, as a result of the unfavorable environment and biological antagonisms. The disappearance is slow, and the material must be held for periods of six months to a year to ensure relatively complete destruction of pathogens, such as the eggs of Ascaris, nematodes which are among the most resistant of the fecal-borne disease parasites in wastes. Therefore, make compost this year and use it next year.However, organic material can be decomposed anaerobically to produce compost. For instance, a heavy plastic bag can be used to decompose grass clippings or other high nitrogen materials, shredded leaves, kitchen trimmings, a small amount of stable manure or other compostable materials. However, as anaerobic compost can have a strong odor (and may need to be aired prior to using), it is not usually the first choice for home owners.
Aerobic Decomposition
When organic materials decompose in the presence of oxygen, the process is called “aerobic.” The aerobic process is most common in nature. For example, it takes place on ground surfaces such as the forest floor, where droppings from trees and animals are converted into a relatively stable humus. There is no accompanying bad smell when there is adequate oxygen present.
In aerobic decomposition, living organisms, which use oxygen, feed upon the organic matter. They use the nitrogen, phosphorus, some of the carbon, and other required nutrients. Much of the carbon serves as a source of energy for the organisms and is burned up and respired as carbon dioxide (C02). Since carbon serves both as a source of energy and as an element in the cell protoplasm, much more carbon than nitrogen is needed. During composting a great deal of energy is released in the form of heat in the oxidation of the carbon to C02. For example, if a gram-molecule of glucose is dissimilated under aerobic conditions, 484 to 674 kilogram calories (kcal) of heat may be released. If the organic material is in a pile or is otherwise arranged to provide some insulation, the temperature of the material during decomposition will rise to over 170°F. If the temperature exceeds 162°F to 172°F, however, the bacterial activity is decreased and stabilization is slowed down.
Aerobic oxidation of organic matter produces no objectionable odor. If odors are noticeable, either the process is not entirely aerobic or there are some special conditions or materials present which are creating an odor. Aerobic decomposition or composting can be accomplished in pits, bins, stacks, or piles, if adequate oxygen is provided. Turning the material at intervals or other techniques for adding oxygen is useful in maintaining aerobic conditions.
Compost piles under aerobic conditions attain a temperature of 140°F to 160°F in one to five days depending upon the material and the condition of the composting operation. This temperature can also be maintained for several days before further aeration. The heat necessary to produce and maintain this temperature must come from aerobic decomposition which requires oxygen. After a period of time, the material will become anaerobic unless it is aerated.
III) Power Generation
Electricity generationis the process of generatingelectric powerfrom sources ofprimary energy. Forelectric utilities, it is the first process in the delivery of electricity to consumers. The other processes astransmission,distribution,energy storageand recovery usingpumped-storagemethods are normally carried out by theelectric power industry. Electricity is most often generated at apower stationbyelectromechanicalgenerators, primarily driven byheat enginesfuelled bycombustionornuclear fissionbut also by other means such as thekinetic energyof flowing water and wind. Other energy sources include solarphotovoltaicsandgeothermal power.
Part – 1 –
Start the class with asking questions like:
- What is waste?
- What are biodegradable and non-biodegradable wastes?
- What are the different kinds of wastes that are generated at a typical home?
- What are the constituents of biodegradable wastes?
- How are biodegradable wastes disposed off at your home?
- What are the different ways biodegradable wastes can be put to use?
Inform the students about the design based project: To design a system of producing electricity using the biodegradable wastes generated at home.
Part – 2 -
Divide the students into groups of four each.
Hand-over the KWL chart to all the students and ask them to fill-in the K and W part of the chart.
Discuss the resources with them as mentioned in the support document.
Leave them to discuss the design and planning within their groups.
Motivate them to explore and take ideas from the links suggested at the end of this lesson.
Part – 3 -
Assess students’ plans and designs for the power generation set-ups. Offer suggestions where required.
Extensions
Students can be asked to design a similar system for the community they’re part of or for their school.
Assessment and Rubrics
Pre activity – Discussion questions
- What is waste?
- What are biodegradable and non-biodegradable wastes?
- What are the different kinds of wastes that are generated at a typical home?
- What are the constituents of biodegradable wastes?
- How are biodegradable wastes disposed off at your home?
- What are the different ways biodegradable wastes can be put to use?
Activity Embedded –
Evaluation of students’ plans and designs for the power generation set-ups.
Post activity –
Assessment Rubrics:
Criteria / Excellent / Good / Average
Design and Employability / The design of the power generating system is easy to assemble and uses easily available resources / The design of the power generating system is slightly difficult to assemble and uses resources that are slightly difficult to procure / The design of the power generating system is difficult to assemble and uses resources that are slightly difficult to procure
Output / The output of the system is such that 2-3 small appliances can be made to run using it / The output of the system is such that 1-2 small appliances can be made to run using it / The output of the system is such that anyone small appliance can be made to run using it
Environmental effectiveness / The system (digester) effectively contributes to waste management as it uses all biodegradable waste generated over a week / The system (digester) contributes to waste management as it uses most of the biodegradable waste generated over a week / The system (digester) hardly contributes to waste management as it uses only some of the biodegradable waste generated over a week
Team dynamics / All team members contributed equally to the design and execution of the project / Only two team members contributed to the design and execution of the project / Only one team member contributed to the design and execution of the project
Credits and Reference:
Prof. Suvarna Ranpise
Prof. Dr. Seema Damle
Modern College of Education, Pune, India.