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