Bioelectricity from mining waste

Bioelectricity by CCMs using mining tailings with a microalgae biocathode and removing heavy metals at the anode by microbial biotransformation.

Artisanal mining in Ecuador is an activity on which close to 100,000 people directly depend. Artisanal mining extraction processes use chemical products, which has caused contamination by heavy metals such as Hg, Pb, As, Mg, Zn and Cd in rivers, soils or effluents and these exceed the maximum permissible limit and the little knowledge of people has caused serious environmental problems in these mining areas. Poor waste management and little knowledge of how to take advantage of the large amounts of wastewater and sludge generated within this industry has also had a negative impact within these places.

One of the most conflictive artisanal mining areas in Ecuador is located in the province of Morona Santiago in the Nambija sector; In the 1980s, the Nambija sector attracted more than 20,000 people, who, due to the need for economic income, became artisanal miners, which gave rise to a disorderly settlement in precarious and insecure living conditions, added to anti-technical exploitation. where between 40 and 60% of the gold was not recovered.

The excessive use of fossil fuels and the increase in energy demand have led to the search for sustainable energy sources. There is a huge need for efficient transformation, distribution and use of energy. Fossil fuels are not being formed at a significant rate and are finite

Sustainable energy supply is essential in all economies for lighting, heating, communication, technology, industrial equipment, transportation, etc. Energy purchases represent 5 to 10% of GNP in developed economies. In developing countries, imports of fossil fuels such as coal, oil and gas cost more than half the value of total exports. These economies are unsustainable.

Current energy production generates CO2 emissions, the most abundant greenhouse gas responsible for global warming, as well as polluting gases such as Sulfur Oxides and Nitrogen Oxides.

The objective of the research was to generate bioelectricity through microbial fuel cells using wastewater and mine tailings from gold mining with Micractinium inermum as a biocatalyst in the cathodic chamber, and to evaluate the removal of heavy metals such as mercury, lead, copper in the anodic chamber. . For which the microalga Micractinium inermum extracted from the Rodeococha Lagoon of the Llanganates National Park, a native microalga and easy to use by people, was isolated. The experiment was carried out in four single-chamber microbial fuel cells (SMFC) where CM1, CM2, CM3 had Micractinium inermum as biocatalyst and CM4 without biocatalyst each with 150 ml of wastewater and 150 g of mine tailings. Cellophane paper was used as a proton exchange membrane (due to its low cost) which separates the anaerobic part from the aerobic part by 1 cm, for the anode and cathode electrodes carbon fiber was used and they were subjected to treatments to eliminate impurities and favor the formation of the biofilm. Voltage was recorded on an NI 6212 DAQ over a 21-day period. The results show that the CCM with Micractinium inermum microalgae are successful in the generation of bioelectricity compared to the control cell, having a higher voltage production by 31.6% and 21.35%. Through physicochemical analysis, a removal of heavy metals was determined, during the first phase the CCM1 had a greater removal of 92% in Mercury and 95% in Copper; and the CCM4 94% in Lead. In the second phase, CCM4 had a removal of 97%, 95.3% and 95% for Mercury, Copper and Lead, respectively, due to the biotransformation of autochthonous microorganisms from the Nambija area.

It can be concluded that the cathodes assisted by Micractinium inermum show greater stability and voltage generation in the CCM and that using autochthonous microorganisms from the area are useful in the removal of contaminants.

Artisanal and illegal mining in Ecuador has generated multiple impacts on the environment, the lack of regulation has caused the use of harmful chemicals such as cyanide, mercury and other toxins that have caused the contamination of rivers and soil, which are the resources used by the indigenous communities of the surrounding areas, causing damage to crops, animals and residents. During the last years, the presence of alterations of the nervous system has been determined, the same ones that are generated by the continuous exposure of neurotoxic contaminants. This solution will help decontaminate contaminated water and soil.

This solution proposes to help decontaminate wastewater from gold mining and achieve the generation of bioelectricity, because these isolated areas of the Ecuadorian Amazon do not have access to electricity, which is one of the resources that promotes progress. of his people. The main beneficiaries of this project would be the inhabitants of the Yutzupino community in the province of Napo and the inhabitants of Nambija in southern Ecuador.

My team is the GRUPO DE ENERGÍAS ALTERNATIVAS Y AMBIENTE (GEEA-ESPOCH) we are a research group led by university professors and researchers. I am currently working as a researcher of alternative energies, and facing the environmental and social problems generated in our country by gold mining at all its scales, especially in illegal and artisanal mining due to the contamination of rivers and soils due to the generation of metals. heavy and toxic substances that emerge the quality of life of the ecosystems. I am an Environmental Engineer by profession, I am 23 years old and I was born in Ecuador, my main skills are the study of Microbiology and bioremediation, for which the solutions I propose are focused on the use of microorganisms thanks to their biotransformation capabilities. My study partner Sandra Daniela Lara Avalos is an electronics and computer engineer, she has extensive knowledge in renewable technologies, especially solar panels, she has been of great help in this project thanks to the implementation of various designs of bio-cells or microbial fuel cells. for obtaining bioelectricity, with which we have obtained good results and we hope to generate bioelectricity and remedy on a large scale.

In our investigation we have gone to the areas most affected by contamination from gold mining such as Nambija, Camilo Ponce Enríquez and Yutzupino. In which we have collected water and soil samples that have subsequently been analyzed in the laboratories of our ESPOCH university. In which we have found that the levels of heavy metals Hg, Cu and Pb exceed the maximum permissible limits by the WHO and the current Ecuadorian environmental regulations. Causing damage to the health of residents and companies, mining concessions are sued for contamination. We are currently working with ASONAMBILE, an association of artisanal miners who exploit around 60.5 hectares and dump their waste into the Nambija River, contaminating it, for which we have socialized the effects of contaminating water resources and how to install a prototype on a scale The largest of the Microbial Fuel Cells will have the benefit of providing electricity to your community and remediating the waste generated in the exploitation of gold.

Our solution is innovative because Microbial Fuel Cells are not used to generate bioelectricity and remove contaminants such as heavy metals from mining extraction, for which it is necessary to apply microorganisms for this process that are autochthonous and can degrade contaminants. We plan to apply ourselves to artisanal mining associations as a solution to the pollution they produce.

Our objectives for this year is to implement in the mining industries and associations for which we need a budget. It must be taken into account that when implementing a pilot scale there would be an increase in the cell volume, the membrane area and the distance between electrodes as there is a proportional relationship with the voltage generation. The mining company discharges its wastewater after the extraction process to a discharge point near a stream, so the proposal would be to implement storage tanks for this wastewater and implement several CCMs within this tank on a pilot scale that can supply for the flow of residual water generated by the mining process.

It should be noted that in order to implement the pilot scale described above, studies of the flow of residual water generated per day should be carried out so that real data can be obtained and the dimensions of the storage tanks can be carried out and, later, the necessary measurements of the CCM for each tank and thus be able to have a better result and bioremediate the residual water generated in mining.

The unit of analysis in the present investigation are Microbial Fuel Cells, which are made up of an anode (biofilm of microorganisms from mine tailings), a cathode (biofilm of Pleurococcus sp), a proton exchange membrane (cellophane paper), substrate (wastewater from gold mining), it is studied under certain optimal conditions to examine the behavior of each of the CCMs with respect to each configuration and substrate administered, with the purpose that each one generates a representative voltage.

Our solution intends to meet the needs of 200 partners of the ASONAMBILES mining concession in Nambija in southern Ecuador, who have been exploiting this area since the 1980s, causing great damage to the environment.

The main barriers we encounter is the implementation of this prototype due to its construction, it is necessary to have bioelectricity studies on a larger scale, to socialize the use of microorganisms and in the financial part, to build our prototype, more money is needed.

As a research group we are working with mining associations such as ASONAMBILE and the indigenous peoples affected by mining.