Paper Technology International 2024 - Journal - Page 55
PAPERTECHNOLOGYINTERNATIONAL
Deinking sludge is often
incinerated to generate electricity used
at the plant. Also, by incinerating waste,
paper producers reduce the waste
volume making it more suitable for
land昀椀lling. Land昀椀ll sites can be owned
and operated by the industry itself or can
be independently maintained, requiring
payment from the mills. Nevertheless,
land昀椀lling is not recommended, and
stricter rules are being implemented
since land昀椀lling causes environmental
problems related to leaching and
greenhouse gas production (US
Environmental Protection Agency
Resource Conservation and Recovery
Figure 2: Mineral life cycle. a) Mineral quarry; b) Omya plant; c) Paper industry; d)
Act;
European Union Waste Framework
Printing house/converter; e) Supermarket and f) Municipal recycling.
Directive; People’s Republic of China
law on the prevention and control of environmental pollution by
As a mineral supplier, Omya is especially interested in the
solid wastes). Therefore, sustainable practices must be developed
mineral content present in the different waste streams. Waste
focusing on waste valorization by using it as raw material for distinct
quantities, respective estimated mineral percentages and main
applications.
mineral sources can be found in Table 1. The recycling of white
昀椀bers (tissue and paper) generates the largest volumes of byOver the years, Omya has spent a lot of effort in assessing
products, followed by kraft pulping. According to these numbers, a
technologies for an effective recovery of minerals from deinking
very large percentage of minerals is discarded in the different waste
sludges. Omya is currently proposing the utilization of 昀氀y ash
streams. Omya has a long history in mineral recycling, partnering
originating from deinking sludge incineration to be used as a pH
with various start-ups and academic partners, and working on
control agent in the papermaking process. Due to its high alkalinity,
different technologies to valorize different waste streams. However,
昀氀y ash can be used to replace commonly used alkali sources such
mineral recycling is not straightforward. There is a direct correlation
as caustic soda. Controlling the pH during the paper making process
between the quality requirements and the cost of the product.
is essential for process ef昀椀ciency and productivity. Furthermore, due
Therefore, when looking into mineral recycling approaches, the right to the high content of calcium oxide (CaO), these 昀氀y ashes have
balance between mineral availability, cost of the recycling process
important antimicrobial properties. This is of particular importance
and 昀椀nal application must be considered. Furthermore, every
for the production of recycled containerboard, where old corrugated
approach has to be tailored to the speci昀椀c conditions at the mills,
container (OCC) is used as raw material. OCC is a dirty raw
including waste type, amount, and the quality and variation in waste
material, aligned with long residence times in storage towers and
composition.
process conditions (temperature, pH and starch availability) create
the perfect environment for uncontrolled microbial proliferation.
From Table 1, it can be observed that the waste stream
containing the highest amount of minerals is deinking sludge.
By giving a second life to the usually land昀椀lled 昀氀y ashes,
In paper recycling, ink and 昀椀llers are removed by deinking the
Omya is contributing to mineral recycling and taking important steps
recycled paper, generating a waste stream of deinking paper
in the implementation of a sustainable circular economy model in the
sludge. Deinking sludge consists of printing inks (black and colored
pulp and paper industry. Nonetheless, this development will imply
pigments), 昀椀llers and coating pigments, 昀椀bers, 昀椀ber 昀椀nes and
new challenges including the establishment of new business models
adhesive components. More than 55% of the solids removed by
and value chains. Ultimately, waste recycling and conversion into
昀氀otation deinking are inorganic compounds. They are primarily 昀椀llers value-added products will reduce production costs, expand current
and coating pigments such as clay and calcium carbonate. The
product portfolios and boost market opportunities.
concentrations of heavy metals in deinking sludge are generally low
and, overall, they contain fewer contaminants than, for example,
sludges of municipal wastewater treatment.
Table 1: Waste in the pulp and
paper industry. Adapted from
Bajpai, P.; “Management of pulp
and paper mill waste”, 2015 and
Schuivens, J.; “Mineral recovery
from deinking sludges”, 2020.
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