Reuse of organic material for biogas production

Project objective, problem to be solved, and main actions

The main objective of the project was to reuse food that inevitably goes to waste, transforming this organic matter into biogas and biofertilizer. The biogas will be used in the school’s stove, the biofertilizer is used in our vegetable garden and part of it is sold in the school community, generating income.

This project started as a continuation of another project: JADes, which works with the issue of food waste at school and aims to reduce this waste. The TESLA science club, seeing these discarded foods, decided to give them a more suitable destination and within the research conducted they found the biodigester and then came the idea of ​​building a homemade biodigester; which in addition to transforming organic matter into a biodigester and biofertilizer was aligned with one of the SDG that is to produce clean and renewable energy.

The project was the idea of ​​the students, who then came to me. The actions were planned based on a survey to choose the best biodigester model to be built. One of the references used was an article by Química Nova na Escola and we still have this prototype to this day. From there, we verified the feasibility of the prototype and we saw later, with the partnership formed with Empresa 2E, that it was not the most viable and then we arrived at the homemade Biodigester that we have today. But for that, we still went through a lot of research related to what kind of materials best fit the proposal and with the lowest possible cost. This is where the financial support offered by the company entered, helping us buy all the material needed to build the two biodigesters that we currently have.

https://www.youtube.com/watch?v=2FWBWkA5uT4

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Deepening into the issue and involvement of the school and local community

This idea arose, primarily to meet the demand of our school, but during development, it was observed that if it were built with easily accessible materials, it could be replicated in other schools and even in students’ homes.

Community participation was direct and constant. We had the support of the entire school; as this project depended on reducing waste since the biodigester holds a maximum of 2 kilos of food daily. We count on the support of the lunch ladies who separated these leftovers to be reused and in return we launched a recipe book for recycling food leftovers and made it available to the entire school community.

We have the support of the company 2E – Eficiência Energética, that donated a Commercial Biodigester and gave us mentorships. Clayss gave us financial support and mentorship for participating in the Solidarity Schools Project in Brazil. We had support from many local traders.

The development of the solution

1st stage: Consists of a theoretical deepening of the main issues to be addressed throughout the project, such as:

• Research on biodigester models;
• Research on stages of anaerobic biodigestion;
• Pollution and diseases transmitted by air pollution;
• Greenhouse effect;
• Inorganic Functions;
• Chemical reactions.
• Gas behavior

The theoretical study can be done in high school books, in specific literary works, or scientific articles available on academic dissemination sites (Scielo, Lilacs, Web of Science, and CAPES Periodicals). The estimated time for this stage is 8 lessons.

2nd stage: Research the best materials to be used in the assembly of a homemade biodigester, considering the practicality and low cost of the materials (giving preference to reusable materials). The estimated time for this stage is 8 lessons.

3rd stage: Assembly of the homemade biodigester, using the chosen materials and seeing the most viable possibilities for building the prototype; always taking care to keep all connections well sealed. The estimated time for this stage is 20 lessons.

4th stage: Assembly of the prototype

5th stage: To prepare the trap we used a 20% calcium hydroxide solution, and the most recent one we used for this system was a wall water filter support. It has the function of capturing the carbonic gasses and hydrogen sulfide produced in biodigestion.

6th stage: With the prototype ready, it’s time for activation – we need anaerobic bacteria – and we find them in cow dung. For this, you have to go to a corral and get this very fresh material. Fill the biodigester with water, add the manure, and then the food scraps. The estimated time for this stage is 6 lessons.

7th stage: The biodigester must be fed daily, and if it has a capacity of 200L, a maximum of 1Kg of food per day is recommended. This stage extends throughout the prototype maintenance period.

8th stage: For monitoring with the Arduino Platform, the following sensors are needed: temperature, methane gas detection, and pH meter.

9th stage: Testing phase using the first prototype, observing what worked, adjusting, and thinking about what to correct for the construction of a second prototype. This stage extends throughout the prototype development period and in parallel with the possible second prototype.

The construction of the prototype

 

We have two biodigesters being tested in our school and when we finish, we want to replicate this model in schools and in the homes of people who are interested in this technology.

Evaluation of the process and the developed solution

In the evaluation process, the following were considered:

• Student attendance, recommending minimum participation in 75% of the total number of meetings;
• Presentation of thematic seminars;
• Preparation of reports and articles;
• Ability to communicate in public;
• Proactivity in solving problems that arise during the educational practice;
• Presentation of work at scientific events, at school, external science fairs, and competitions.

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