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The management and disposal of wastewater treatment sludge can be a costly and resource-intensive process. To provide a cost-effective and sustainable alternative, Sludge Treatment Wetlands (STW) have emerged as a viable solution for enhancing sludge quality through dewatering and biodegradation. In this study, the effectiveness of a full-scale STW for stabilizing and dewatering digested microalgal biomass from a domestic and agricultural wastewater treatment system was evaluated. The properties of the treated digestate in the STW were assessed after 35 weeks of operation and a resting period of 4 weeks. The dry matter content was found to be 12.8%, and the average macronutrient content was K: 3.8 mg/g DW, P: 4.9 mg/g DW, and Ca: 95 mg/g DW. The highest contents of micronutrients were for Fe: 7.8 mg/g DW and Mg: 7.6 mg/g DW, while heavy metals and pathogen contents were below the EC limits for sewage sludge reuse in agriculture. The STW was found to be a cost-effective and environmentally friendly option for treating mixed wastewater-based sludge for land application. The STW outperformed reference systems using centrifuge dewatering techniques, particularly in terms of eutrophication potential and acidification potential. However, the STW’s economic performance was slightly worse than that of the dewatering system in terms of unit production cost. This study is the first in the literature to investigate the use of STW for treating digested microalgae and its possible reuse in arable land, suggesting that STW infrastructures have great potential for the development of sustainable and eco-friendly sludge treatment technologies

High Rate Algae Ponds (HRAPs) are a promising technology for the treatment of municipal wastewater in locations with sufficient space and solar radiation. Algae-based processes do not require aeration, and thus have the potential to be less energy-intensive than activated sludge processes. We used a combination of LCA and LCCA analysis to evaluate the sustainability of HRAP systems, using data from the construction and operation of two demonstration-scale systems in Almería and Cádiz, Spain. As a reference for comparison, we used data from an activated sludge-based Sequencing Batch Reactor (SBR) treatment system in operation in Leppersdorf, Germany, which has comparable removal rates for a similar inflow. We focused solely on the actual wastewater treatment aspect of these technologies, excluding sludge treatment from this analysis. Based on our analysis, the current HRAP technology is more energy-efficient than activated sludge-based SBRs and requires only 22% of its electricity consumption. In addition, HRAP is more advantageous both economically (0.18 €/m3 versus 0.26 €/m3) and environmentally, with both lower global warming and eutrophication potentials (146.27 vs. 458.27 × 10−3 kg CO2 equiv./m3; 126.14 vs. 158.01 × 10−6 kg PO4 equiv./m3). However, the Net Environmental Benefit of SBR was slightly more favorable than of HRAP because of the higher removal rate for nutrients of SBR., Accepted Author Manuscript, Environmental Technology and Design, BT/Environmental Biotechnology

The bio-based production of aromatics is experiencing a renaissance with systems and synthetic biology approaches promising to deliver bio-catalysts that will reach yields, rates, and titers comparable to already existing bulk bio-processes for the production of amino acids for instance. However, aromatic building blocks derived from petrochemical routes have a huge economic advantage, they are cheap, and very cheap in fact. In this article, we are trying to shed light on an important aspect of biocatalyst development that is frequently overlooked when working on strain development: economic and environmental impact of the production process. We estimate the production cost and environmental impact of a microbial fermentation process depending on culture pH, carbon source and process scale. As a model molecule we use para-hydroxybenzoic acid (pHBA), but the results are readily transferrable to other shikimate derived aromatics with similar carbon yields and production rates.

A large-scale biogas upgrading plant using the CarboTech® technology with a treatment capacity of 1333 Nm3 biogas per hour was analyzed. Our scope of evaluation encompasses all technology steps that are necessary for upgrading biogas, i.e., both pretreatment and biogas upgrade. A cradle-to-gate life-cycle and life-cycle cost assessment (LCA and LCCA) methodology was used with the functional unit (FU) of 1 Nm3 of biogas upgraded in order to ease comparison with other biogas upgrading technologies. The calculation was made using the GaBi8 LCA software and databases of GaBi Professional, Construction materials, Food&Feed, and the ecoinvent3. We applied the CML characterization model with all its mid-point indicators. The mid-point indicators of the CML characterization model were aggregated after normalization by the CML2001 - Jan.2016 normalization factors. The normalized environmental impact was 541.74·10−15/Nm3 raw biogas. The highest environmental impacts were the marine aquatic ecotoxicity potential (15.705 kg dichlorobenzene-equiv./Nm3 raw biogas), the abiotic depletion potential (1.037 MJ/Nm3 raw biogas), and global warming potential (0.113 kg CO2-equiv./Nm3 raw biogas). The unit production cost of the PSA technology was 0.05-0.063 €/Nm3 raw biogas. The most considerable source of expenses was the operational cost from which 77% was spent on electricity. The initial investment, personal costs, and the reinvestment amounted to only 34% of the total costs for the whole life cycle. Strategies to lower the environmental burden of the PSA technology are to use green electricity and to optimize the size of the plant in order to reduce unnecessary material flows of building material and their indirect energy use. This can also lower investment expenditures while automatization and remote control may spare personnel costs.

Sustainability assessment using a life‐cycle approach is indispensable to contemporary bioprocess development. This assessment is particularly important for early‐stage bioprocess development. As early‐stage investigations of bioprocesses involve the evaluation of their ecological and socioeconomic effects, they can be adjusted more effectively and improved towards sustainability, thereby reducing environmental risk and production costs. Early‐stage sustainability assessment is an important precautionary practice and, despite limited data, a unique opportunity to determine the primary impacts of bioprocess development. To this end, a simple and robust method was applied based on the standardized life‐cycle sustainability assessment methodology and commercially available datasets. In our study, we elaborated on the yeast‐based citric acid production process with Yarrowia lipolytica assessing 11 different substrates in different process modes. The focus of our analysis comprised both cultivation and down‐stream processing. According to our results, the repeated batch raw glycerol based bioprocess alternative showed the best environmental performance. The second‐ and third‐best options were also glycerol‐based. The least sustainable processes were those using molasses, chemically produced ethanol, and soy bean oil. The aggregated results of environmental, economic, and social impacts display waste frying oil as the best‐ranked alternative. The bioprocess with sunflower oil in the batch mode ranked second. The least favorable alternatives were the chemically produced ethanol‐, soy oil‐, refined glycerol‐, and molasses‐based citric acid production processes. The scenario analysis demonstrated that the environmental impact of nutrients and wastewater treatment is negligible, but energy demand of cultivation and down‐stream processing dominated the production process. However, without energy demand the omission of neutralizers almost halves the total impact, and neglecting