Young people from the city of Penalva, Brazil, noticed that the excess of water hyacinth plants in the region’s lakes made it difficult for fishermen to navigate. On the other hand, they saw that part of the community was using wood stoves, a cheaper alternative to cooking gas, which causes respiratory and environmental problems due to smoke and wood extraction. To solve these local challenges, the group discovered in class how to transform water hyacinth into a more sustainable fuel option. The innovation won second place in Solve for Tomorrow in the country in 2023.
The “Produção de biogás e biofertilizante” (Biogas and Biofertilizer Production, in English) project was developed by five students in their first year of high school (the penultimate year of compulsory schooling), and the biology teacher Geovane Muniz was the mediator. The team is part of the Centro de Ensino Sabino Barros school, located in the Jacaré community, 18 kilometers from the center of Penalva. The city is located on the shores of Cajari lake, in Maranhão, a state in the Brazilian Northeast. Families in the rural area of the municipality live mainly from fishing, vegetable production, and social assistance programs.
The starting point was an elective course called “Innovation and Sustainability: Boosting the Future,” which aims to raise environmental and political awareness and foster the creation of innovative solutions with social impact. During the classes, the team tested mixing crushed water hyacinth with cow dung, chicken feces, and cassava juice. The idea is that fermenting the plant with anaerobic bacteria (which do not need oxygen to grow) would produce methane gas, a biogas that can be used to light kitchen stoves.
The lesson this taught to students is that if you don’t practice, if you don’t make it a routine, you won’t be able to learn. It’s the day-to-day mistakes that will make you get it right, says Muniz.
He emphasizes that the connection between the STEM (Science, Technology, Engineering, and Mathematics) areas was fundamental to progress in the project. “I have always worked with interdisciplinarity. Mathematics contributed a lot to our work, as well as biology itself. Chemistry was the main fuel for this project, not to mention physics and Portuguese. These disciplines supported us, even though they were not exactly STEM methodology at the beginning,” says the educator.
Tests and discoveries
“We developed the prototype, making mistakes and getting things right. Then came the opportunity for mentoring from Solve for Tomorrow and we produced a prototype that is still undergoing improvements so that it can be adapted for the community”, he highlights.
Through practical tests and trial and error in the quantity of materials, the team arrived at a more functional prototype: an alternative, homemade, low-cost, and 100% recycled biodigester. It consists of two 20-liter bottles, hoses, and a conventional gas cylinder valve. All of these materials were easily acquired in the community itself, at almost no cost. If the experiment were to be reproduced, the cost would be approximately 40 reais [around 7 American dollars] for the hoses and valve.
Although it is not yet completely safe for large-scale use, the prototype generates 18 liters of gas for every 20 liters of biomass. “A gas cylinder costs around 120 reais [around 22 American dollars]. This amount is a huge burden for communities that live off social programs and receive less than the minimum wage. So, it would be a huge saving,” he highlights.
The prototype also generated a biofertilizer
The young people discovered that, after the gas is produced, what remains is an organic material called digestate, which can still be reused as fertilizer. The team tested vegetables available in the community itself and obtained satisfactory results. They used coriander in this stage, due to the species’ rapid growth. In 15 days, it was possible to observe greater development of the plants that received the biofertilizer made from water hyacinth, compared to those that did not receive it. “The biofertilizer proved to be rich to be used on vegetables and greens grown by the community’s residents, with low cost and home production. It is an additional benefit for the project’s clientele”, reports the teacher.
Projects that motivate the school and the entire community
Geovane Muniz emphasizes that the Solve for Tomorrow mentoring sessions were also a source of learning for those who teach. “There is a lot of wealth of knowledge in these training sessions. After participating in the program, I felt like I had another graduation because of everything I learned in such a fleeting time. I am grateful for this opportunity that came into our lives,” he emphasized. The example has influenced other educators and students, inside and outside the school walls, and the teacher says he is more motivated after the results of the biogas and biofertilizer project.
For him, the greatest reward is the recognition from the Jacaré community itself. “There was a lot of publicity, a particularly good spread, and even today there is an impact of our group being a finalist. We are growing: the school is gaining notoriety, and the teachers and students are becoming more valued,” he says.
When they returned from the awards ceremony, the team was welcomed with two days of celebration in the community. Now, the new students who arrive at the Centro Profesor Sabino Barros are already expecting to participate in scientific projects. “Those who participated in the project are now seen as outstanding students, even though they are from public schools. We received recognition from the state network and regional awards. The community has seen the school in a different light, and this is a tremendous change,” adds Muniz.
