Recent advances in hydrothermal carbonisation:from tailored carbon materials and biochemicals to applications and bioenergy

Introduced in the literature in 1913 by Bergius, who at the time was studying biomass coalification, hydrothermal carbonisation, as many other technologies based on renewables, was forgotten during the "industrial revolution". It was rediscovered back in 2005, on the one hand, to follow the trend set by Bergius of biomass to coal conversion for decentralised energy generation, and on the other hand as a novel green method to prepare advanced carbon materials and chemicals from biomass in water, at mild temperature, for energy storage and conversion and environmental protection. In this review, we will present an overview on the latest trends in hydrothermal carbonisation including biomass to bioenergy conversion, upgrading of hydrothermal carbons to fuels over heterogeneous catalysts, advanced carbon materials and their applications in batteries, electrocatalysis and heterogeneous catalysis and finally an analysis of the chemicals in the liquid phase as well as a new family of fluorescent nanomaterials formed at the interface between the liquid and solid phases, known as hydrothermal carbon nanodots

Hydrothermal carbonisation and its role in catalysis

This chapter provides an overview of the most recent advances in the mechanistic study of hydrothermal carbonisation (HTC) and the strategies to improve the conversion by using carbon-based catalysts. HTC, although not a recent discovery, has lately been receiving increasingly attention by both academic and industrial sectors due to the possibility to exploit this process to perform a simple, green and inexpensive conversion of bio-derived waste material into valuable chemicals and advanced materials and, as such, this chapter will also look into the use of hydrochars formed in HTC and their application in catalysis, more specifically heterogeneous catalysis with a mention on electrocatalysis. The versatility and tuneability of these solids give rise to the great range of applicability in different fields. A detailed overview of the HTC process is presented and the main uses of hydrochars in catalysis is then shown, highlighting their use as solid acid catalysts, as pristine solid catalysts, as sacrificial agents in synthesis, since their removal through combustion is easy, and the niche application of these solids in electrocatalysis for future research perspective.DOI till boken 10.5281/zenodo.3233733Green Carbo

Activated Carbon from Palm Date Seeds for CO2 Capture

The process of carbon dioxide capture and storage is seen as a critical strategy to mitigate the so-called greenhouse effect and the planetary climate changes associated with it. In this study, we investigated the CO2 adsorption capacity of various microporous carbon materials originating from palm date seeds (PDS) using green chemistry synthesis. The PDS was used as a precursor for the hydrochar and activated carbon (AC). Typically, by using the hydrothermal carbonization (HTC) process, we obtained a powder that was then subjected to an activation step using KOH, H3PO4 or CO2, thereby producing the activated HTC-PDS samples. Beyond their morphological and textural characteristics, we investigated the chemical composition and lattice ordering. Most PDS-derived powders have a high surface area (>1000 m2 g−1) and large micropore volume (>0.5 cm3 g−1). However, the defining characteristic for the maximal CO2 uptake (5.44 mmol g−1, by one of the alkaline activated samples) was the lattice restructuring that occurred. This work highlights the need to conduct structural and elemental analysis of carbon powders used as gas adsorbents and activated with chemicals that can produce graphite intercalation compounds

Effects of microplastics on microbial community dynamics in sediments from the Volturno River ecosystem, Italy

In this study, the sources, abundance, and ecological implications of microplastic (MP) pollution in Volturno, one of the main rivers in southern Italy, were explored by investigating the MP concentration levels in sediments collected along the watercourse. The samples were sieved through 5- and 2-mm sieves and treated with selective organic solvents. The polymer classes polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), nylon 6 (PA6), and nylon 6,6 (PA66) were quantified using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and high-performance liquid chromatography (HPLC). Furthermore, a 16S rRNA metagenomic analysis was performed using next-generation sequencing in Ion TorrentTM to explore the bacterial taxonomy and ecological dynamics of sediment samples. The MPs were detected in all samples collected from the study area. PP and PET were the most abundant and frequently detected polymer types in the analysed samples. The total MP concentration ranged from 1.05 to 14.55 ppm (parts per million), identifying two distinct data populations: high- and low-MP-contaminated sediments. According to the Polymer Hazard Index (PHI), MP pollution was categorised as hazard levels III and IV (corresponding to the danger category). Metagenomic data revealed that the presence of MPs significantly affected the abundance of bacterial taxa; Flavobacteraceae and Nocardiaceae, which are known to degrade polymeric substances, were present in high-MP-contaminated sediments. This study provides new insights into the ecological relevance of MP pollution and suggests that microorganisms may serve as biomarkers of MP pollution

Microplastic pollution affect sediment microbial communities structure: evidences from Volturno River (Southern Italy)

For the first time, we explored sources, abundance, and ecological implications of microplastics (MPs) pollution in the one of the main river of Southern Italy (Volturno) by investigating MPs concentration levels of sediments collected along the watercourse. Samples were analysed by the Polymer Identification and Specific Analysis (PISA) protocol to quantify the total mass of individual polymer types: after sieving at <2 mm the sediments were sequentially extracted with selective organic solvents and the polymer classes polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polycarbonates (PC), Nylon 6 (PA6) and Nylon 6,6 (PA66) were quantified by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and HPLC. This method enables an accurate and specific quantification of micron and submicron scale polymers. Furthermore, in the light of current evaluations about the impact produced by anthropogenic activities in natural habitats through the study of their microbial diversity, we investigated the 16S metagenomics of Volturno river using next generation sequencing in Ion TorrentTM, to explore bacterial taxonomy and ecological dynamics of sediment samples. We detected MPs in all samples taken from the study area. Total MPs concentration ranged from 1.05 to 14.55 ppm and identify two distinct data population: high-MPs contaminated and low-MPs contaminated sediments. Overall PP and PET were the dominant polymer types. According to the Polymer Hazard Index (PHI), the risk of MPs pollution of the analysed sediments was categorized as Hazard level III/IV (corresponding to Danger category). Metagenomic data revealed that the presence of MPs significantly affects bacterial taxa abundance, evidencing Flavobacteraceae and Nocardiaceae, known to degrade polymeric substances in high-MPs contaminated sediments. This study provide new insights of ecological relevance related to MPs pollution and suggests priorities for the management of one of the main Southern Italy’s river. In addition, the study advise that monitoring programs of river ecosystems should address also bacterial communities