Electricity generation from Nopal biogas effluent using a surface modified clay cup (cantarito) microbial fuel cell oleh Sathish-Kumar Kamaraj, Alejandro Esqueda Rivera, Selvasankar Murugesan, Jaime García-Mena, Otoniel Maya, Claudio Frausto-Reyes, José Tapia-Ramírez, Hector Silos Espino, Felipe Caballero-Briones