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Biochars are increasingly used to improve the productivity of agricultural soils as well as for long-term carbon sequestration (Petersen et al., 2023). The wastes from biomass are used to manufacture biochar as a clean and sustainable environmental solution. The pyrolysis of biomass generates biofuel, which can be utilized for generating energy and solid biochar. However, there lacks an understanding about the structural stability of the biochars generated through various pyrolytic processes. The objective of the study is to understand the molecular structural remnants of the biochar from different biomasses and assess the long-term stability of the macromolecule. For this, various agricultural biomass, food wastes and urban sludge are pyrolysed at temperatures ranging from 450-900°C and converted into biochars, which are further analyzed with a pyrolysis-gas chromatography-mass spectrometry. The biochars were flash pyrolysed at 700°C (0.2 min) and the pyrolysis products were studied by GC-MS. The GC temperature was initially set at 50°C, and then ramped up to 300°C at a rate of 10°C/min. The results show that the pyrolysates from the studied biochars produced at lower temperatures (400-500°C) contain larger, 3-4 ring aromatic compounds (PAH) as well as their methylated compounds. Aliphatic compounds are entirely missing. Pyrolysates from the lower pyrolysis temperatures are susceptible to produce secondary compounds, leading to formation of alkylated aromatic compounds. The degree of methylation and aromaticity of biochars produced from different biomass is likely to be function of the ratio of labile:refractory carbon of the feedstock as well as the maximum temperature of pyro lysis at which biochars have been produced. Therefore, biochars produced at low temperatures having large macromolecular size and linked via methyl chains are susceptible to break off at the methylated bonds and further susceptible to microbial and thermal degradation. With the increasing biochar production temperatures, the degree of methylation decreases along with more condensation of the macromolecule. Therefore, the pyrolysates show no methyl bonds and only scarce amount of single or two ring aromatic compounds. Biochars having such condensed macromolecular structure can be utilized as longterm carbon sequestration. [ABSTRACT FROM AUTHOR]

The mudstones of the Upper Eocene - Middle Miocene Lark Formation in the Danish North Sea have not been the subject of a detailed organic petrographic and geochemical investigation despite its importance for paleoclimate studies and as a regional seal for potential CO2 storage sites. This study investigates the characteristics and quantity of organic matter in 391 samples of cuttings obtained from 7 wells from the Danish North Sea. The Hawk pyrolysis was conducted on all cuttings samples while reflected light and fluorescence microscopy was conducted on 38 pellets for determining the reflectance of primary huminite (HRo), the volume percentage of huminite and inertinite (H+I, vol.%) and the intensity ratio of red to green light of alginite (R/G quotient). The results show that the organic matter in the Lark Formation is generally immature (Tmax < 430°C, HRo mean value = 0.3%, R/G mean value = 0.51) and mainly consists of Type III kerogen which is dominated by huminite macerals, with the total organic carbon (TOC) content ranging from 0.33 wt.% to 7.34 wt.% (mean value = 2.54 wt.%). In a north distal site, we observed a long-term decrease in hydrogen index (HI) caused by the increase in TOC outpaced S2 during Oligocene to Early Miocene. In the south distal sites in the Danish Central Graben, we noticed the increase in HI resulted from the jump in TOC and S2 during Early Miocene to Middle Miocene. The increase in TOC was proved to be the result of the increased influx of terrestrial organic matter as we established the positive correlation (R²>0.95) between the volume percentage of total organic carbon (TOC, vol.%) and that of huminite and inertinite (H+I, vol.%). This increased influx proved further being the result of changes in organic matter supply from N to NE and then ENE direction during the Cenozoic Basin Evolution in the Danish North Sea. [ABSTRACT FROM AUTHOR]