Bioenergy Production through Mono and Co-Digestion of Tomato Residues

Patrícia V. Almeida, Rafaela P. Rodrigues, Leonor M. Teixeira, Andreia F. Santos, Rui C. Martins and Margarida J. Quina
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Patrícia V. Almeida: Department of Chemical Engineering, CIEPQPF—Chemical Process Engineering and Forest Products Research Centre, University of Coimbra, Rua Sílvio Lima, Pólo II—Pinhal de Marrocos, 3030-790 Coimbra, Portugal
Rafaela P. Rodrigues: Department of Chemical Engineering, CIEPQPF—Chemical Process Engineering and Forest Products Research Centre, University of Coimbra, Rua Sílvio Lima, Pólo II—Pinhal de Marrocos, 3030-790 Coimbra, Portugal
Leonor M. Teixeira: Department of Chemical Engineering, CIEPQPF—Chemical Process Engineering and Forest Products Research Centre, University of Coimbra, Rua Sílvio Lima, Pólo II—Pinhal de Marrocos, 3030-790 Coimbra, Portugal
Andreia F. Santos: Department of Chemical Engineering, CIEPQPF—Chemical Process Engineering and Forest Products Research Centre, University of Coimbra, Rua Sílvio Lima, Pólo II—Pinhal de Marrocos, 3030-790 Coimbra, Portugal
Rui C. Martins: Department of Chemical Engineering, CIEPQPF—Chemical Process Engineering and Forest Products Research Centre, University of Coimbra, Rua Sílvio Lima, Pólo II—Pinhal de Marrocos, 3030-790 Coimbra, Portugal
Margarida J. Quina: Department of Chemical Engineering, CIEPQPF—Chemical Process Engineering and Forest Products Research Centre, University of Coimbra, Rua Sílvio Lima, Pólo II—Pinhal de Marrocos, 3030-790 Coimbra, Portugal

Energies, 2021, vol. 14, issue 17, 1-16

Abstract: The agro-industry of tomato generates three types of residues: ripe rotten tomato (unfit for consumption) (RT), green (unripe) tomato (GT), and tomato branches including leaves and stems (TB). These materials are commonly wasted or used as feed for livestock. Energy production through anaerobic digestion is an alternative way to manage and simultaneously valorise these materials. Initially, the operating conditions of mono anaerobic digestion were investigated using RT. Thus, a design of experiments based on a two-level fractional factorial design with resolution V was performed to determine the factors that affect biochemical methane potential (BMP). The substrate to inoculum ratio (SIR), total volatile solids concentration (VS t ), working volume (WV), presence of nutrients (Nu), and the pre-incubation of the inoculum (Inc) were investigated. The results showed that SIR is the most important factor. The maximum BMP for RT was 297 NmL CH4 /g VS with SIR = 0.5; tVS = 20 g/L; WV = 20%; no pre-incubation and the presence of nutrients. Using these optimum operating conditions, co-digestion was investigated through a mixture design approach. The substrates RT and GT presented similar BMP values, whereas TB led to a significantly lower BMP. Indeed, when high concentrations of TB were used, a significant decrease in methane production was observed. Nonetheless, the highest BMP was achieved with a mixture of 63% RT + 20% GT + 17% TB, with a production of 324 NmL CH4 /g VS , corresponding to a synergetic co-digestion performance index of about 1.20. In general, although the substrate RT generates the highest BMP, the mixture with GT did not impair the methane yield. Overall, the co-digestion of tomato residues must be conducted with SIR close to 0.5 and the content of tomato branches in the reaction mixture should be kept low (up to 20%).

Keywords: agro-industrial residues; anaerobic digestion; co-digestion; biochemical methane potential; design of experiments (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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