Life‐cycle assessment of the production of cationized tannins from Norway spruce bark as flocculants in wastewater treatment

Abstract

It will be necessary to make efficient use of our resources if our society is to be converted into a bio-based economy. Every year large side streams of bark are produced in sawmills and pulp mills. In addition to utilizing the bark for heat and electricity production, as happens today, high-value chemical components could be extracted prior to energy conversion. These components include tannins. Cationized tannins have already been indicated as promising renewable flocculants in wastewater treatment. However, today's industrial production of tannins uses species from subtropical or temperate climates, and there has so far been little attention to the use of tannins from Norway spruce (Picea abies), an important species in forestry in the subarctic climate. The present life-cycle assessment (LCA) was undertaken to understand the environmental performance of the production of cationized tannins from the bark of Norway spruce and how the environmental impact is distributed along the production system. This work was connected to the Interreg Botnia-Atlantica TanWat research project, which studies the production and use of cationized tannins from Norway spruce for wastewater treatment at a pilot scale. The present LCA shows that the main environmental impact stems from the reagents used in the cationization step. The purification step could also be a significant issue depending on the possibility of reusing the eluent (ethanol) and the lifetime of the resin. The importance of running the processes with as concentrated streams as possible to minimize the need of process water and energy was also confirmed

Life Cycle Assessment of a Vegetable Tannin-Based Agent Production for Waters Treatment

“…Therefore, seeking a broader and more generic analysis, it was decided to use the amount of 1 kg of each of the evaluated products as a functional unit, understanding, however, the need to include this discussion in view of the conclusions obtained. The same approach was performed by Carlqvist et al [10] who argue that this FU could facilitate the future use of their LCA and comparison with other agents. Note: * Removal of total suspended solids.…”

“…The method used was ReCiPe 2016 Midpoint (H) with the following environmental categories: fine particulate matter formation; fossil resource scarcity; freshwater ecotoxicity; freshwater eutrophication; global warming; human carcinogenic toxicity; human non-carcinogenic toxicity; land use; marine ecotoxicity; marine eutrophication; mineral resource scarcity; ozone formation, human health ozone formation, terrestrial ecosystems; stratospheric ozone depletion; terrestrial acidification; terrestrial ecotoxicity; and water consumption. The use of this impact assessment methodology is due to their use in previous works that performed an LCA of tannin-based materials [10,14,15].…”

“…In complement to that, there is a scarcity of studies that use life cycle assessment to evaluate the impact of TBAs production. One can cite the study by Carlqvist et al [10], whose objective was to assess the environmental effects of the production of grafted tannin-based agents. However, no data from the manufacturing process already implemented on an industrial scale were used.…”

Moringa oleifera Lam. as a Bioflocculant for Harvesting Microalgae Grown on Agricultural Wastewaters for Feed Production

“…This study showed that a simple mill grinding was effective in upscaling the production of the used seed powder and that different granulometries did not impact the harvesting efficiency, resulting in a low-energy and zero-chemical process for the production of the flocculant. The production of tannin-based flocculants, identified by Yang et al as the most promising of the ones tested in their study, includes several process steps, including the use of a chemical modification with significant environmental impact [53].…”

Optimising and scaling up hot water extraction of tannins from Norway spruce and Scots pine bark

“…The extraction temperature and chemical additions all have an effect on tannin yield, which can vary considerably even within one tree species (Bianchi et al, 2016). The concentration and purification steps for producing tannins from spruce bark can have a large environmental footprint (Carlqvist et al, 2020;Ding et al, 2017) and thus, processes need to be chosen carefully depending on applications and end-use.…”