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In this study calculation over material and energy balances for bio-refinery product upgrading using membrane filtration (MF, UF, and RO), distillation, and ion-exchanger has been performed. Tests have been made with UF filtration in a pilot plant, separation tests made at lab with ion-exchanger and simulation using ASPEN plus simulator for distillation. Rough economic analysis has been made for the different solutions/techniques.

This study evaluates alternative fertilizers, including sewage sludge products (sludge, biochar, reject water) and 8 urine, for basil cultivation in controlled environment agriculture (CEA). Alongside traditional growth and elemental analysis, handheld near-infrared (NIR) spectroscopy combined with Aquaphotomics approach was used to non-invasively monitor used irrigation solutions as well as plant leaves. The research aims to establish links between specific Water Absorbance Spectral Patterns (WASPs) and nutrient availability, treatment type, and plant physiological status, assessing the potential of Aquaphotomics as a real-time monitoring tool for utilizing diverse circular nutrient sources in agriculture. 

This article summarizes and performs a systematic analysis using experimental results from recent research on ammonium recovery from aqueous sources using biochar. Numerous studies have focused on using different materials to produce biochar adsorbents, and many have attempted to draw conclusions about the physical or chemical characteristics that dominate the adsorption to infer the mechanism. However, to date, there has not been statistical analysis performed on a large set of adsorption data and physical/chemical characteristics of chars to be able to draw conclusions about ammonium adsorption mechanisms. From this analysis, it was found that consistency in experimental methods and characteristic measurement reporting is lacking, and therefore it is difficult to perform metadata analysis and draw conclusions about ammonium adsorption on biochar. Among the important factors influencing ammonia recovery proposed in literature, the meta-analysis only strongly supports the effect of BET surface area and NH4+ concentration, with weaker support for the importance of cation exchange capacity and pyrolysis temperature. This suggests that standard procedures for biochar production, experiments and analysis of physical and chemical characteristics are needed to usefully compare results across different studies. Examples of the present difficulty in identifying trends across studies are shown by comparing clusters in the data identified by the analysis. The ability to make such comparisons would provide clearer direction in how best to further improve the adsorption capacity of biochars.

Nitrogen recovery from wastewater treatment for fertilizers is a research topic that exists at the intersection of multiple topics important to the future of sustainable society. First, nitrogen recovery from wastewater implies a departure from the current methods of nitrogen mitigation, which involve nitrogen removal by conversion of various aqueous species to inert nitrogen gas. Secondly, by recovering nitrogen from wastewater specifically, there is the opportunity to begin a circular economy where value added products can be obtained from material that has historically been seen as a “waste”. Current wastewater treatment involves nitrogen removal through the biological transformation of aqueous nitrogen species to inert nitrogen gas. This process is energy intensive and risks the production of air pollutants such as N2O as intermediates in the biological transformation. If this nitrogen can be captured in a form that can be reused, a valuable product can be achieved with the potential reduction of both the energy required at the wastewater treatment plant as well as the carbon footprint. Finally, by recovering nitrogen in a form that can be used in agriculture as a fertilizer, additional environmental benefits can be realized by reducing reliance on Haber-Bosch based ammonia production, which is also energy intensive and contributes harmful emissions to the atmosphere.

The work described in the following licentiate aims to consider the current status of nitrogen recovery from wastewater for fertilizers as a research topic. Literature was analytically examined to compare different techniques in terms of energy requirements, cost for fertilizer production, market for final fertilizer product, and technological readiness. The most interesting findings from this review were that there seems to be a disconnect between the fertilizer product produced by nitrogen recovery techniques and the market, which will become a challenge if these techniques are implemented at a large scale. The attitude of the farmers with regards to fertilizers from waste was overall positive, with their concerns mainly focused on the performance ability and cost of the product. Additionally, many techniques such as microbial fuel cells and microbial electrolysis cells have been unable to move past the laboratory phase despite being researched for many years. This indicates there are cost and technological barriers that are preventing the further scale up and implementation of these techniques. Energy and cost analyses will be crucial to motivate investment into these processes, and these are missing for many of the techniques found around this topic.

To contribute to this field, experimental work was also included to assess the potential for ammonium adsorption from concentrated wastewater for fertilizer production. The experimental work focused on the utilization of the solid product of pyrolysis of sewage sludge (biochar) for adsorption and explored the potential enhancement of the char with various chemical treatments. The char with the best ammonium adsorption performance was found to be using a treatment of HNO3 followed by and NaOH, with an adsorption capacity of 4 mg NH4/g biochar. This char was compared with commercially activated carbon and clinoptilolite for full scale applications. It was found that even with this increased adsorption capacity, the use of chemically enhanced sewage sludge biochar for full scale applications is not realistic. The amount of raw material required for the complete recovery of ammonium from reject water at the municipal wastewater treatment plants exceeds the total amount of sewage sludge generated. Therefore it is recommended that the goal of incorporating sewage sludge biochar with wastewater treatment is to produce a solid fertilizer product loaded with ammonium (which would provide ammonium-N and phosphorus for plant growth, as well as carbon and other minerals for soil amendment) rather than having the goal be complete ammonium recovery from the wastewater stream.

NH4-N-loaded biochars are suitable candidates for soil amendment and fertilization. Sewage sludge-based biochar and biochar from the invasive species black wattle were used as sorbents for the adsorption of ammonia from a concentrated solution to mimic the wastewater treatment plant reject water stream. To increase ammonium recovery efficiency, two post-pyrolysis activation techniques were compared: steam activation and hydrogen peroxide treatment. It was found that the success of the treatment options was material dependent; therefore, post-pyrolysis treatments will require optimization for different applications based on feedstock. A simplified version of an adsorption process simulated in Aspen Tech predicts that NH4-N may be recovered at an energy cost lower than that of the Haber-Bosch process for black wattle biochar yields of below 19.5%. The biooil and syngas produced during pyrolysis can be used to lessen the energy requirements of the process, so that the solid portion may be utilized as an adsorbent and soil fertilizer. The energy-based sustainability of this technology warrants a more in-depth investigation for evaluation of the techno-economic feasibility for this class of loaded sorbents, and whether this method of nitrogen capture from wastewater is a suitable replacement of the costly Haber-Bosch process.

NH4-N-loaded steam-activated biochar (BC) is found to be a suitable candidate for soil amendment and fertilization. Compared with four other char-based sorbents, H2O-activated BC adsorbed the highest amount of NH4-N (1440 mgNH4 −N. kg−1BC ) sourced from a high nitrogen wastewater sample, and showed a limited desorption of 19.6 % under acidic conditions. In comparison, neat BC and activated carbon (AC) achieved lower adsorption capabilities, with theoretical maxima of −1 1028 mgNH4 −N. kgBC and 733 mgNH4 −N. kg−1AC, respectively. While neat AC obtained a lower desorption of 19.5 %, neat BC showed similar desorption capabilities to that of the H2 O-activated BC. Oxidative treatment using 10 % H2 O2 reduced adsorption for BC (520 mgNH4 −N. kg−1BC ) and AC (545 mgNH4 −N. kg−1AC ) and increased desorption to 47.9 % and 41.9 %, respectively. From these results, H2O-activated biochar clearly is the most suitable for soil amendment that is resistant to leaching, is environmentally-friendly, and is an energy-efficient nitrogen adjunct. A simplified version of an adsorption process simulated in AspenTech predicts that NH4-N may be recovered at an energy cost lower than that of the Haber-Bosch process for AC yields of below 19.5 %. A more in-depth investigation still needs to be completed to evaluate the techno-economic feasibility for this class of loaded sorbents, and whether this means of nitrogen capture from wastewater is a suitable replacement of the costly Haber Bosch process.

This paper is built on a study performed to investigate the possibilities to take care of fiber sludge from a former pulp mill in the city Tampere, Finland. A pilot plant biorefinery process has been developed by Finnoflag and tested during 2018-2019 for the conversion of the cellulosic material into useful chemical products by the help of a microbial process. The results from this are used as input to a study on downstream processing performed through lab and pilot plant tests of different technologies, as well as system simulations. An economic analysis is also performed with respect to installation costs for the different alternatives of downstream processing – ion exchange, distillation and membrane filtration. It was found that all three processes would successfully concentrate the main product (lactic acid), however distillation would likely be energy intensive, and ion-exchange costly for materials. Therefore, the recommendation from this study is to focus on reverse osmosis after ultrafiltration, with the addition of evaporation if necessary. Besides the resulting chemicals fraction the biorefinery produced hydrogen, and the residues could be converted effectively into methane. These gases provided energy for the industrial unit and could be converted into energy, too. On the other hand, the feasible production of the chemicals gave an economic justification for the energy producing units.