The hydrothermal carbonization (HTC) plant as a decentral biorefinery for wet biomass

Abstract

The hydrothermal carbonization (HTC) is a very suitable process to transform wet biomass feedstocks into a peat-like material without drying the biomass input.Therefore, the energetic balance is more favorable than for alternative processes converting biomass as a whole. Further synergies can be achieved when the plant is employed as central hub for a regional biorefinery. Hence, a HTC pilot plant is operated with garden prunings and monitored during two years. It is shown that the elemental composition of HTC carbon is relatively constant. A carbon content of higher than 60%(based on dry, ash-free matter) is achieved. Fixed carbon content and volatile matter show low variation being the volatile content quite high with 61% on average. Dried in a post-process treatment which is less energy-demanding than drying of the raw biomass and pressed into pellets or briquettes the HTC carbon can be used as solid biofuel fulfilling the European standard (EN 14961-6).With a regional thermal valorization of the biofuel the ashes can be returned as phosphorous source to the crop land from which the biomass was harvested. Part of the process water, which involves a high amount of potassium, can be used for crop irrigation. In this way, valuable plant nutrients are recovered for soil remediation.Hence, closing the nutrient cycles a HTC plant can be considered as a sustainable local biorefinery producing a solid biofuel. Thereby, solar energy is exploited which was 2 fixed before by photosynthesis together with the carbon dioxide which is liberated in the combustion of the solid biofuel. Optionally, the process water might serve as an alternative source of energy as it is demonstrated that its carbon content can be exploited for biogas production.3 Graphical Abstract HighlightsThe hydrothermal carbonization process was monitored in a pilot plant over two years HTC carbon fulfills European standard for a type of solid biofuel HTC carbon ashes from garden prunings serve as source for plant nutrients (phosphorous)Potassium levels in the soil can be improved by irrigation with HTC process water Chemical oxygen demand of the process water can be reduced by 95% by biogas production

Sustainable coffee‐based CO2 adsorbents: toward a greener production via hydrothermal carbonization

“…Table reports similar CO 2 uptakes for both experiments (approximately 2.75 wt.%), lower than that for the optimum conditions (2.95 wt.%). Thus, these results confirm the suitability of the temperature range selected on the basis of extensive literature review and point out that the optimum conditions obtained from the analysis by RSM correspond to a global maximum.…”

“…In addition, the high conversion efficiency, elimination of pre‐drying requirement, and relatively low operating temperature make HTC a particularly suitable conversion technique for the production of hydrochar from wet biomass feedstock …”

“…13 In addition, the high conversion efficiency, elimination of pre-drying requirement, and relatively low operating temperature make HTC a particularly suitable conversion technique for the production of hydrochar from wet biomass feedstock. [14][15][16][17] For a given feedstock, the main variables influencing the process, the product distribution, and the properties of the hydrochar produced are temperature, pressure, dwell time, and ratio biomass/water, as well as the eventual addition of chemicals to the reaction media. 18 It has been found that the temperature has the strongest influence on the process [18][19][20][21][22][23] whereas the dwell time has been identified as less important on HTC, especially if long dwell times are used.…”

Hydrothermal Carbonization of Waste Biomass: Process Design, Modeling, Energy Efficiency and Cost Analysis

“…While a substantial amount of lab-scale experimental research on HTC reactions has been published, assessments of potential technical performance of industrial-scale HTC facilities are absent from the scientific literature. Though some pilot-scale HTC plants have been constructed in recent years [14], to date the detailed structure of such plants and their efficiency are still unknown to the vast majority of those involved in the HTC research field. Moreover, only a few authors have analyzed the energy efficiency of HTC plants by means of a modeling approach [15,16].…”

Estudio de los residuos y subproductos agroindustriales de la Región de Murcia: opciones de valorización mediante compostaje y biometanización

“…Numerosos estudios indican que los lodos aerobios pueden ser co-digeridos con otros materiales para realizar una gestión integrada (Righi et al, 2013), mantener estable el sistema e incrementar el potencial de producción de biogás, con las mejoras ambientales y económicas que ello supone. La adición de residuos de alimentos a la digestión de lodos de depuración ha sido ampliamente referenciada en la bibliografía (Mata-Alvarez et al, 2000, 2014la Cour Jansen et al, 2004;Aymerich et al, 2013;Dai et al, 2013;Ros et al, 2013;Fonoll et al, 2015). Con ello, los residuos orgánicos son gestionados de acuerdo a la normativa actual, y el producto final producido denominado digerido o digestato, puede llegar a ser un fertilizante mejorado en términos de su disponibilidad para las plantas (Tafdrup, 1995) y su reología (Pain y Hepherd, 1985).…”