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Anaerobic digestate animal effluent (ADAE) contains high N and P nutrients which need to be treated. In this study, an integrated process was proposed using a microalgae consortium of Chlorella and Scenedesmus. The system was designed for 71 m 3 /d (medium-sized) and 355 m 3 /d (large-sized) animals of ADAE. Process simulation estimated to produce 83-417 kg d -1 of microalgae biomass which can be used as further products. As much as 2 kg of animal feed and 36-180 L/d of bio-oil can be produced during the treatment of 1 m 3 /d of ADAE. The produced biogas can generate 247-1,217 MWh y -1 of electricity. Likewise, the process can reduce greenhouse gas emissions by 2 kg-CO 2 eq kg -1 of hot standard carcass weight (HSCW). This integrated system offers merits in treating ADAE as well as producing chemicals and energy with low environmental burdens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study aims to determine the eco-friendliness of microalgae-based renewable energy production in several scenarios based on life cycle assessment (LCA). The LCA provides critical data for sustainable decision-making and energy requirement analysis, including net energy ratio (NER) and cumulative energy demand (CED). The Centrum voor Milieuwetenschappen Leiden (CML) IA-Baseline was used on environmental impact assessment method by SimaPro v9.3.0.3® software and energy analysis of biofuel production using native polyculture microalgae biomass in municipal wastewater treatment plants (WWTP) Bojongsoang, Bandung, Indonesia. The study was analyzed under three scenarios: (1) the current scenario; (2) the algae scenario without waste heat and carbon dioxide (CO 2 ); and (3) the algae scenario with waste heat and carbon dioxide (CO 2 ). Waste heat and CO 2 were obtained from an industrial zone near the WWTP. The results disclosed that the microalgae scenario with waste heat and CO 2 utilization is the most promising scenario with the lowest environmental impact (- 0.139 kg CO 2 eq/MJ), positive energy balance of 1.23 MJ/m 3 wastewater (NER > 1), and lower CED value across various impact categories. It indicates that utilizing the waste heat and CO 2 has a positive impact on energy efficiency. Based on the environmental impact, NER and CED values, this study suggests that the microalgae scenario with waste heat and CO 2 is more feasible and sustainable to adopt and could be implemented at the Bojongsoang WWTP., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Microalgae have potential as biomass energy sources with higher photosynthetic efficiency compared to terrestrial plants. The use of polyculture systems such as native microalgae communities for microalgae cultivation has several advantages, as well as challenges due to indeterminate species composition and growth rate variation between species. This paper presents an artificial neural network (ANN) model to estimate the growth of polyculture microalgae in a semi-continuous open raceway pond (ORP). The model was comprised of a multilayer backpropagation neural network with eight input parameters, one hidden layer, and one output parameter. The model was developed using datasets collected from the cultivation of polyculture microalgae in Minamisoma City, Fukushima Prefecture, Japan. The input parameters are as follows: initial algal concentration, harvesting period (between two and three days after the growth have begun), hydraulic retention time, addition of sodium acetate, average solar radiation (μmole m−2 s−1), average temperature (oC), pH condition, and nitrate ion ( NO 3 − ) concentration. The output variable is the microalgae concentration observed during the cultivation period. The output is represented using a single neuron. The result of the study showed that the designed three-layer ANN achieved a high prediction accuracy (R2 = 0.93) for all combinations of inputs. Highlights • ANN model was proposed to estimate the growth of polyculture microalgae. • Developed using 553 datasets collected from semi-continuous Open Raceway Pond. • ANN model was able to estimate the growth of polyculture microalgae. • Model achieved R2 more than 0.9 for all input variation. • Key variables to estimate microalgal growth were solar irradiance and temperature. [ABSTRACT FROM AUTHOR]

The environmental load of continuous bioenergy production from palm oil ( Elaeis guineensis ) included with a proposed 10 ha of microalgae production system were assessed to be implemented in Indonesia. Material and energy balances, greenhouse gas (GHG) emission, nutrient requirement and also water scarcity during bioenergy production cycle were evaluated. The integrated system was developed for 60 tons h −1 of fresh fruit bunch (FFB) processing capacity of a conventional mill. Aggregate of energy-profit ratio from the proposed system was 5.20, which indicates a positive balance. The total water footprint for each palm oil and microalgae cultivation was 3.18 and 2.85 m 3  kg −1 of biodiesel production, respectively. Microalgae mix-culture has the potential to treat organic compounds from palm oil mill effluent (POME) and combined with flue gases from biomass and biogas power plant as the alternative nutrient sources contributed to net-reduction of GHG emission for 158.8 tons ha −1 of microalgae culture, annually. The integrated system produced 26,471 tons of biodiesel that included 223 tons from microalgae and contribute to 39.90% of total GHG emission reduction from diesel fuel substitute. Additional co-product of 520.33 tons year −1 of animal feed from defatted biomass also possible to be produced and have potential for environmental benefits. [ABSTRACT FROM AUTHOR]

This study investigates the potential of microalgae oil production as an alternative renewable energy source, in a pilot project located at Minamisoma City in the Fukushima Prefecture of Japan. The algal communities used in this research were the locally mixed species, which were mainly composed of Desmodesmus collected from the Minamisoma pilot project. The microalgae oil-production processes in Minamisoma consisted of three stages: cultivation, dewatering, and extraction. The estimated theoretical input-energy requirement for extracting oil was 137.25 MJ to process 50 m3 of microalgae, which was divided into cultivation 15.40 MJ, centrifuge 13.39 MJ, drum filter 14.17 MJ, and hydrothermal liquefaction (HTL) 94.29 MJ. The energy profit ratio (EPR) was 1.41. The total energy requirement was highest in the HTL process (68%) followed by cultivation (11%) and the drum filter (10%). The EPR value increased along with the yield in the cultivation process. Using HTL, the microalgae biomass could be converted to bio-crude oil to increase the oil yield in the extraction process. Therefore, in the long run, the HTL process could help lower production costs, due to the lack of chemical additions, for extracting oil in the downstream estimation of the energy requirements for microalgae oil production. [ABSTRACT FROM AUTHOR]

A comparative evaluation of economic efficiency was performed for native polyculture microalgae oil production in an oxidation ditch (OD) process wastewater treatment plant (WWTP). A cost function was developed for the process. The operational cost per 1 m3 of wastewater (w.w.) was 1.34 $/m3-w.w. in the existing scenario, 1.29 $/m3-w.w. in algal scenario A (no cost for CO2 and waste heat) and 1.36 $/m3-w.w. in algal scenario B (no cost for CO2). The conditions were set as follows: hydraulic retention time (HRT): 4 days, microalgal productivity: 0.148 g/L and daily treatment volume: 81.6 m3-w.w./d. The cost differences were related to the increase in polymer flocculants for algae separation (+0.23 $/m3-w.w), carbon credits from CO2 absorption (−0.01 $/m3-w.w), the sales of biocrude (−0.04 $/m3-w.w) and sludge disposal (−0.18 $/m3-w.w). Hence, the introduction of the algae scenario was the same cost-effective as the existing scenario. Microalgae oil production in an OD process WWTP can serve as a new energy system and reduce the environmental load in a society with a declining population. [ABSTRACT FROM AUTHOR]

A comparative evaluation of energy requirement and CO2 emission was performed for native polyculture microalgae oil production in a wastewater treatment plant (WWTP). The wastewater provided nutrients for algae growth. Datasets of microalgae oil production and their details were collected from the Minamisoma pilot plant. Environmental impact estimation from direct energy and material balance was analyzed using SimaPro® v8.0.4. in two scenarios: existing and algal scenarios. In the existing scenario, CO2 emission sources were from wastewater treatment, sludge treatment, and import of crude oil. In the algal scenario, CO2 emission with microalgae production was considered using wastewater treatment, CO2 absorption from growing algae, and hydrothermal liquefaction (HTL) for extraction, along with the exclusion of exhausted CO2 emission for growing algae and use of discharged heat for HTL. In these two scenarios, 1 m3 of wastewater was treated, and 2.17 MJ higher heating value (HHV) output was obtained. Consequently, 2.76 kg-CO2 eq/m3-wastewater in the existing scenario and 1.59 kg-CO2 eq/m3-wastewater in the algal scenario were calculated. In the HTL process, 21.5 MJ/m3-wastewater of the discharged heat energy was required in the algal scenario. Hence, the efficiency of the biocrude production system will surpass those of the WWTP and imported crude oil. [ABSTRACT FROM AUTHOR]

This article presents an engineering study of an integrated system to produce bio-oil from microalgae biomass. The analysis is based on a pilot plant located at Minami-soma Fukushima, Japan, which further simulates 1 ha based-cultivation. Municipal wastewater and flue gases were utilized as nutrient sources for the microalgae culture of the proposed design. A flow sheet diagram of the integrated plant was synthesized by process engineering software to allow simulation of a continuous system. The design and sizing of the process equipment were performed to obtain a realistic estimation of possible production cost. The results demonstrated that nutrient savings was achieved by wastewater and CO2 utilization to the polyculture of native microalgae. Process simulation gave an estimated CO2 sequestration of 82.77 to 140.58 tons ha−1year−1 with 63 to 107 tons ha−1year−1 of potential biomass production. The integrated process significantly improved the energy balance and economics of biofuel production and also the wastewater treatment plant (WWTP). The economic analysis confirmed that higher biomass production and technology improvement were required to achieve operational feasibility and profitability of the current microalgae-based bio-oil production. [ABSTRACT FROM AUTHOR]