Combination of anaerobic digestion and sludge biochar for bioenergy conversion: Estimation and evaluation of energy production, CO2 emission, and cost analysis

Matheus Antônio da Silva; Bruna Sampaio de Mello; Brenda Clara Gomes Rodrigues; Clovis Augusto Ribeiro; Ieda Aparecida Pastre Fertonani; Arnaldo Sarti

doi:10.1016/j.jenvman.2024.123974

Combination of anaerobic digestion and sludge biochar for bioenergy conversion: Estimation and evaluation of energy production, CO₂ emission, and cost analysis

J Environ Manage. 2025 Jan 7:374:123974. doi: 10.1016/j.jenvman.2024.123974. Online ahead of print.

Authors

Matheus Antônio da Silva¹, Bruna Sampaio de Mello², Brenda Clara Gomes Rodrigues², Clovis Augusto Ribeiro¹, Ieda Aparecida Pastre Fertonani³, Arnaldo Sarti⁴

Affiliations

¹ São Paulo State University (UNESP), Institute of Chemistry, Campus Araraquara, Department of Analytical Chemistry, Physical Chemistry and Inorganic Chemistry, Brazil.
² Bioenergy Research Institute - IPBEN, UNESP, Institute of Chemistry, Araraquara, SP, Brazil; São Paulo State University (UNESP), Institute of Chemistry, Campus Araraquara, Department of Engineering, Physics and Mathematics, Rua Prof. Francisco Degni, 55, 14800-900, Araraquara, SP, Brazil.
³ São Paulo State University (UNESP), Institute of Bioscience, Linguistics and Exact Sciences, Campus Araraquara, Department of Chemistry and Environmental Science, Rua Cristovão Colombo, 2265, 15054-000, Rio Preto, SP, Brazil.
⁴ Bioenergy Research Institute - IPBEN, UNESP, Institute of Chemistry, Araraquara, SP, Brazil; São Paulo State University (UNESP), Institute of Chemistry, Campus Araraquara, Department of Engineering, Physics and Mathematics, Rua Prof. Francisco Degni, 55, 14800-900, Araraquara, SP, Brazil. Electronic address: arnaldo.sarti@unesp.br.

PMID: 39778348
DOI: 10.1016/j.jenvman.2024.123974

Abstract

Waste-to-energy technologies involve the conversion of several wastes to useful energy forms like biogas and biochar, which include biological and thermochemical processes, as well as the combination of both systems. Assessing the economic and environmental impacts is an important step to integrate sustainability and economic viability at anaerobic digestion systems and its waste management. Energy production, CO₂ emissions, cost analysis, and an overall process evaluation were conducted, relying on findings from both laboratory and pilot-scale experiments. The digestate generated during anaerobic digestion proved to be an effective approach for mitigating some CO₂ emissions while managing sludge waste within the anaerobic digestion and CHP system. Incorporating biochar production and application in soil into the process led to a 3.5 % reduction in CO₂ emissions, which contributed to a more sustainable form of energy production while offering the potential for the generation of carbon credits through a carbon-negative process. The employment of digestate biochar for energy production seems a feasible way to reduce the amount of residue to final disposal in landfill with a minimal reduction of profit per GWh and a slight increase in the CO₂ emissions by 2.7 %.

Keywords: Biodigester; Methane; Slow pyrolysis; Soybean molasses; Torrefaction.