O Brasil é um dos maiores produtores mundiais de suco de laranja, da mesma forma que a produção é elevada, a geração de resíduos também é significativa. Sabe-se que estes resíduos, os quais incluem sementes, cascas e restos de polpa são ricos em nutrientes que poderiam ser utilizados como substrato por micro-organismos, seja para o crescimento ou para a obtenção de subprodutos. Esporos de Bacillus atrophaeus ATCC 9372 são utilizados como indicadores biológicos, IBs, em processos térmicos por formarem esporos termorresistentes. O objetivo deste trabalho foi avaliar o uso de resíduos do processamento de suco de laranja como um meio de cultura alternativo para obtenção de esporos de B. atrophaeus, para serem aplicados em processos industriais. Ao bagaço de laranja (de 1,0 g a 20,0 g), obtido por processamento em centrífuga de frutas, foram adicionados 100 mL de água, e incubados a 150 rpm / 37 ºC por até 6 dias. Evidenciada a viabilidade de crescimento celular (µmáx = 0,0238 h-1 e Px = 0,0787 g/L.h, para 5,0 g de bagaço) procedeu-se ao estudo de planejamento experimental fatorial 22 em formato estrela com 6 pontos centrais, considerando a concentração de bagaço e o volume de meio. Foram determinados os valores de pH, de biomassa, de esporos viáveis e a resistência térmica dos mesmos a 102 ºC. Observou-se que houve aumento nos valores de pH após o cultivo e que as maiores concentrações de esporos foram de 1,73 x 109 esporos /mL e 5,75 x 109 esporos /mL após 3 e 6 dias de cultivo e os tempos de redução decimal determinados variaram de D102C = 0,92 min a D102C = 2,71 min e de D102C = 1,34 min a D102C = 3,98 min após 3 e 6 dias de cultivo, respectivamente. Com base no planejamento proposto e a análise de regressão, o desenvolvimento de esporos em bagaço segue a relação: Esporos = {-1,15 + 0,0303* [bagaço (g)] - 0,00611* [volume (mL)] + 0,611* [tempo (dias)]}, p=0,000, R2 =0,452, sendo o tempo (p=0,000) o fator de maior influência na formação de esporos. Os meios preparados com bagaço de laranja apresentaram-se viáveis para a produção de esporos de B. atrophaeus termorresistentes, produto de interesse farmacêutico e industrial, agregando valor ao resíduo que seria descartado. / Brazil is one of the world´s largest producers of oranges juice, in the same way that the production is high the amount of generated waste is also significant. It is well known that these residues, which include seeds, peel and pulp, are rich in nutrients that could be used as substrate by microorganisms whether for growth or for obtaining by-products. Bacillus atrophaeus ATCC 9372 spores are used as biological indicators, BIs, in thermal processes due to their ability to form heat-resistant spores. This study aimed to evaluate the use of orange juice processing waste as an alternative culture media to obtain B. atrophaeus spores, to be applied in industrial processes. To orange\'s bagasse (from 1.0 g to 20.0 g), obtained by processing in a fruit\'s centrifuge, 100 mL of water was added, and sterilized at 121 ºC. An aliquot of 0.1g/L of Bacillus atrophaeus spores was inoculated to bagasses\'s media and incubated at 150 rpm / 37 ºC up to 6 days. As cells (µmáx = 0.0238 h-1 and Px = 0.0787 g/L.h, for 5.0 g of bagasse) were obtained, a factorial experimental design 22, with star-shaped model and 6 central points, was performed considering the bagasse concentration and the media volume used. Values of pH, biomass, viable spores and their thermal resistance at 102 ºC were determined. It was observed that pH increased after cultivation and major values of spore concentration achieved were 1.73 x 109 spores /mL and 5.75 x 109 spores /mL after 3 and 6 days, respectively. Decimal reduction times determined ranged from D102C = 0.92 min to D102C = 2.71 min and from D102C = 1.34 min to D102C = 3.98 min after 3 and 6 days of incubation, correspondingly. The regression analysis showed that the development of spores in bagasse can be defined by the equation: Spores = , p=0.000, R2 =0.452 and time has a positive influence in the spore formation. Results demonstrated media prepared with oranges\' bagasse were capable to grow and to develop B. atrophaeus heat-resistant spores, being an alternative to add value to a waste that would be discarded, generating a product of great importance in the pharmaceutical field.

One of the most sustainable pathways of sewage sludge treatment in recent years has been thermal conversion. The benefits of thermal treatment of sewage sludge are the recovery of energy or valuable chemical products, the destruction of harmful organic compounds, the separation of heavy metals from the P-rich coarse ash fraction, and the decreased and sanitized ash volume. The ashes created by these thermal conversion processes of sewage sludge are often rich in P that is mostly present in minerals with low plant-availability such as apatite. Due to the enrichment of P in the created ashes, a variety of post-processing steps have been developed to recover P from sewage sludge ashes. One proven way for the sus-tainable recovery of P from such ashes is thermal post-processing with alkaline salts, e.g., Na2SO4 or K2CO3, which was able to transform less plant-available phosphates in the sewage sludge into more plant-available alkali-bearing phos-phates. Based on these results, one could facilitate creating these phosphates with enhanced plant-availability by providing the chemical potential to form them already during the thermal conversion process of sewage sludge.   This thesis aims to increase the current knowledge about the ash transformation processes of P and to suggest suitable process parameters for the alteration of the phosphate speciation in sewage sludge ashes by co-conversion with alkaline-rich agricultural residues. More specifically, the possibility of incorporating K derived from agricultural residues in phosphate structures derived from sewage sludge was evaluated with respect to the influence of the process temperature, the conver-sion atmosphere, and the fuel mixture. The studied parameters were chosen to generate knowledge relevant for fluidized bed gasification processes, with a spe-cial focus on dual fluidized bed (DFB) gasification systems. The applicability of feldspar bed materials in fluidized bed gasification systems was investigated to enable the substitution of the commonly used olivine, which often contains heavy metals (potentially contaminating recovered ashes), and quartz, which is very reactive towards fuel-derived K and potentially leads to bed material fragmentation and bed agglomeration (Paper I & II). Subsequently, the thermodynamic potential for the alteration of the P-species in sewage sludge ash during co-combustion and co-gasification processes with agricultural residues was investigated (Paper III). Thereafter, an experimental evaluation of the ash transformation chemistry in thermal conversion processes of sewage sludge with different types of alkali-rich agricultural residues in temperatures relevant for flu-idized bed technology was conducted (Paper IV & V). The methodology employed was chosen with respect to the state of technology of the specific investigated process. Paper I & II applied SEM, EDS, XRD, and thermodynamic equilibrium modeling for bed material samples derived from an industrial indirect gasifier. Paper III applied thermodynamic equilibrium calcula-tions to theoretically evaluate ash compositions resulting from co-conversion of sewage sludge and agricultural residues. Paper IV & V employed SEM, EDS, ICP-AES/MS, XRD, and thermochemical modeling on ash samples derived from single pellet lab-scale experiments. The results obtained by analysis of bed material from indirect wood gasification showed the difference in interaction mechanism for K-feldspar and Na-feldspar, most notably the enhanced disintegration of Na-feldspar by K originating from the fuel (Paper I & II). Thermodynamic models employed for fuel mixtures of sewage sludge and agricultural residues showed the thermodynamic preference for the formation of the desired alkali-bearing phosphates (Paper III). Experi-ments conducted with these fuel mixtures (Paper IV & V) supported the theo-retical findings, and the influence of temperature and process conditions could be obtained. However, practical investigations also showed that attainment of the desired ash composition is subject to significant restrictions. Derived from the elaborated results and discussions, it was possible to assess the critical process and fuel parameters for the development of up-scaled gasification processes focusing on the conversion of sewage sludge with the aim of creating improved phosphate formation in the ash. The selection of a suitable bed material in fluidized bed conversion and the transformation mechanisms defining the ash chemistry were found to be of vital importance for future applications. The pur-suit of the predefined aims in reference to P-recovery from sewage sludge has led to a multitude of suggestions for suitable process parameters that must be ad-dressed in future bench- and pilot-scale experimental runs.