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Artigo Técnico

Artigos Técnicos | Artigo | 23.06.2022




NEGATIVE CARBON-DIOXIDE EMISSIONS FROM EUCALYPTUS PULP MILL INCLUDING BIOSLUDGE HTC TREATMENT


O PAPEL vol. 83, N.o 6, pp. 83 - 89 - JUNE 2022

Authors: Clara Mendoza-Martinez1,2, Katja Kuparinen2 , Mateus Martins1 , Marcelo Cardoso1 , Esa Vakkilainen2 , Jussi Saari2 1 Federal University of Minas Gerais. Belo Horizonte - MG, Brazil. 2 Lappeenranta University of Technology - LUT Energy, Lappeenranta, Finland 

ABSTRACT Kraft pulp mills produce CO2 for the most part in combustion processes. The recovery boiler, the biomass boiler, and the lime kiln are the largest sources of CO2. As these CO2 emissions originate almost entirely from burning biomass (bioenergy), the pulp mill can be considered already nearly carbon neutral as long as the wood feedstock is obtained from sustainable sources. By applying to this bioenergy use carbon capture and storage (BECCS) or use (BECCU) to permanently remove some of the carbon from circulation, pulp mills can, therefore, provide some of the negative emissions needed for climate-change mitigation. An alternative way of creating negative emissions in a pulp mill is converting process residues that are currently disposed of by landfilling or incineration into material that can serve as a stable permanent carbon storage; ideally the residues could also be converted into additional products resulting in additional revenue for the plant. In BECCS technology, the CO2 is captured, transported, and permanently stored in an appropriate geological formation, resulting in negative net carbon dioxide emissions. In BECCU, the captured biogenic CO2 can be used as a raw material for bioproducts. Potential processes for CO2 utilization in pulp mills include tall oil manufacturing, lignin extraction, and production of precipitated calcium carbonate (PCC), depending on mill specificities and local conditions. CO2 can be captured from a stream of flue gases by absorption in an aqueous solvent. Chemical absorption by alkanolamines (amine scrubbing) appears to offer an attractive alternative for CO2 separation from combustion flue gases at pulp mills. In addition to BECCS/BECCU technologies, carbon can also be permanently removed from circulation by applying conversion technologies other than combustion on some of the biomass streams containing carbon. In the case of lignin extraction, by removing lignin from the black liquor before combustion in the recovery boiler, some of the CO2 emissions can also be avoided altogether. Hydrothermal carbonization of the biosludge generated during primary (chemical) and secondary (biological) wastewater treatment processes is another possibility of removing carbon in a pulp mill. The hydrochar produced is an inert substance and resistant to biological degradation. It has potential use, for example, as adsorbents for environmental applications. When mixed in soil, it can improve its carbon organic matter, reduce N2O emissions, as well as form a permanent carbon storage. In this paper the potential of the above-mentioned technologies – post-combustion amine scrubbing for BECCU, and hydrothermal carbonization of biosludge – are evaluated. Keywords: Bioenergy with carbon capture and storage BECCS; Bioenergy with carbon capture and utilization BECCU; Kraft pulp mill; Climate change mitigation; Negative CO2; Hydrothermal carbonization