The extent of softening during biomass pyrolysis is of high importance for fundamentals and reactors design but was not yet quantified in situ. We provide the first in situ rheology and 1H NMR analysis during the pyrolysis of biomass (Miscanthus), microgranular cellulose, ethanol organosolv lignin, and xylan. In situ rheology reveals the viscoelastic behavior of the materials. The softening, resolidification (char formation), swelling, and shrinking behaviors are quantified during pyrolysis in real-time. These phenomena are discussed. The 1H NMR analysis gives the mobility of protons developed during pyrolysis. A viscous and mobile material is formed during cellulose and xylan pyrolysis, even at a slow heating rate (5 K min–1), by products at liquid phase under reaction temperatures. For lignin, a soft material and mobility are first formed by glass transition phase, then overlapped with covalent bond scission, leading to a completely mobile material. The comparison between 1H NMR and rheology results shows that mobile liquid-like products are trapped inside elastic solid-like cavities. Strong interactions between polymers in the native biomass network are evidenced. Cellulose tends to impose its visco-elastic behaviors to the polymers network during biomass pyrolysis. Rheological signatures are also of practical interest to design feeders and reactors for polymers biosourcing, biomass gasification, or combustion.

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This study investigates the effect of water pressure on hydrocarbon generation and maturation of coals. Using a 25 ml Hastalloy pressure vessel, two high-volatile coals (Longannet, UK 0.75% Ro, and perhydrous Svalbard (Spitsbergen), Norway 0.68% Ro) were pyrolysed under non-hydrous, hydrous at 175 bar pressure, and high water pressure hydrous (500 bar and 900 bar) conditions at 350 °C for 24 h. The bitumen yield obtained during pyrolysis, together with the Rock-Eval S2, hydrogen index (HI) and vitrinite reflectance (VR) results from the pyrolysed coal residues indicated that water under relatively low pressure (175 bar) hydrous conditions promoted hydrocarbon generation and coal maturation in relation to non-hydrous conditions, consistent with previous work. However, under high water pressure (500 and 900 bar) conditions, a combination of the hydrocarbon gas (C1-C4) and bitumen yields, RockEval S2, HI, VR and solid state 13C NMR results demonstrated that the changes in reaction pathways occurring with increasing pressure resulted in both hydrocarbon generation and maturation being retarded. The observed effect of pressure implies that for Type III source rocks, hydrocarbon generation will be retarded in high pressure geological basins, with gas yields being proportionally reduced more than bitumen yields. Source rock maturation (or coalification) is also retarded, with the decreases in vitrinite reflectance and carbon aromaticity being relatively small but significant in terms of explaining retardation in geological basins.

Abstract. Decomposition of plant litter is a key control over carbon (C) storage in the soil. The biochemistry of the litter being produced, the environment in which the decomposition is taking place, and the community composition and metabolism of the decomposer organisms exert a combined influence over decomposition rates. As deciduous shrubs and trees are expanding into tundra ecosystems as a result of regional climate warming, this change in vegetation represents a change in litter input to tundra soils and a change in the environment in which litter decomposes. To test the importance of litter biochemistry and environment in determining litter mass loss, we reciprocally transplanted litter between heath (Empetrum nigrum), shrub (Betula nana), and forest (Betula pubescens) at a sub-Arctic treeline in Sweden. As expansion of shrubs and trees promotes deeper snow, we also used a snow fence experiment in a tundra heath environment to understand the importance of snow depth, relative to other factors, in the decomposition of litter. Our results show that B. pubescens and B. nana leaf litter decomposed at faster rates than E. nigrum litter across all environments, while all litter species decomposed at faster rates in the forest and shrub environments than in the tundra heath. The effect of increased snow on decomposition was minimal, leading us to conclude that microbial activity over summer in the productive forest and shrub vegetation is driving increased mass loss compared to the heath. Using B. pubescens and E. nigrum litter, we demonstrate that degradation of carbohydrate-C is a significant driver of mass loss in the forest. This pathway was less prominent in the heath, which is consistent with observations that tundra soils typically have high concentrations of "labile" C. This experiment suggests that further expansion of shrubs and trees may stimulate the loss of undecomposed carbohydrate C in the tundra.

The thermochemical conversion of lignocellulosic biomass feedstocks offers an important potential route for the production of biofuels and value-added green chemicals. Pyrolysis is the first phenomenon involved in all biomass thermochemical processes and it controls to a major extent the product composition. The composition of pyrolysis products can be affected markedly by the extent of softening that occurs. In spite of extensive work on biomass pyrolysis, the development of fluidity during the pyrolysis of biomass has not been quantified. This paper provides the first experimental investigation of proton mobility during biomass pyrolysis by in situ (1)H NMR spectroscopy. The origin of mobility is discussed for cellulose, lignin and xylan. The effect of minerals on cellulose mobility is also investigated. Interactions between polymers in the native biomass network are revealed by in situ (1)H NMR analysis.