Each year, around 44 billion cigarettes are sold in France, which makes it one of the world’s largest tobacco consumers. In addition to the harmful effects on smokers’ health, cigarettes are also highly harmful to the environment. Indeed, more than 30 billion cigarettes are thrown on the ground each year in France and 4 300 billion in the world, producing a very polluting waste: the cigarette butt. As cigarettes are comprising more than 4 000 harmful substances, the resulting cigarette butts contain just as many. In addition to that, the cigarette butt and more particularly the filter, is made of a plastic material, the cellulose acetate. This plastic slows down the natural degradation of this waste, which can take from 10 to 15 years. Thus, all these substances are found for several years in our soils, groundwater and oceans, creating a major environmental issue.
In this context, the aim of our project is to valorize the filter of cigarette butts by degrading it with bacteria in order to produce electricity.
The power generation system is based on the functioning of a Microbial Fuel Cell (MFC). Indeed, a MFC or microbial battery, is a method that allows to generate an electric current from microorganisms (e.g. bacteria). By degrading nutrients during their growth, bacteria produce electrons that are then transported to an anode in order to generate electrical current, which can then either be used or recovered.
Cigarette butts are made of cellulose acetate, which are carbohydrates that can serve as substrate for bacteria. To do this, the cigarette butts will first be crushed in order to separate the cellulose acetate fibres from each other.
These fibers will then be degraded by the Escherichia Coli bacteria via different enzymes in order to produce 2 carbohydrates: Glucose and acetate.
E. coli would metabolize the 2 carbohydrates to produce lactate. Lactate would then be excreted by the bacteria and Shewanella oneidensis, an electrogenic bacteria strain, could metabolize it and produce electrons which would then be transmitted to the MFC electrode
In other terms, the Shewanella bacteria has the ability to give their final electrons to a solid conductor and thus to produce electricity.
The final objective of our project is to collect the electricity produced and to store it in a battery or accumulator in order to obtain an interesting yield