No abstract

There is an increasing realisation that biomass and organic wastes are valuable feedstocks for second generation biorefining processes that give rise to platform chemicals to substitute for dwindling petrochemical resources, and for pyrolysis processes that produce syngas, bio-oil, and biochar from biomass, organic wastes, and the biorefining residuals of the future. The experimental work described has focused on physical properties and compositions of biochars produced from miscanthus (Miscanthus x giganteus), willow (Salix spp) and pine (Pinus sylvestris) at 500°C and at 400, 500, and 600°C in the case of the miscanthus. Although the morphologies of the cell structures were maintained in the pyrolysis, the surface area of the miscanthus biochar was greatly increased by heating at 600°C for 60 min. Nuclear magnetic resonance spectra showed the disappearance of evidence for the carbohydrate and lignin plant components as the pyrolysis temperature was raised, and the compositions of miscanthus biochars after heating for 10 and for 60 min at 600°C were very similar and composed of fused aromatic structures and with no traces of the aliphatic components in the starting materials. In greenhouse and growth chamber experiments the growth of maize (Zea mays L) seedlings was found to be inhibited by soil amendments with biochar from miscanthus formed at 400°C for 10 min, but stimulated by miscanthus char formed at 600°C for 60 min. In the course of discussion the relevance of the results obtained is related to the roles that soil amendments with biochar can have on soil fertility, carbon sequestration, on the emissions of greenhouse gases from soil, on fertilizer requirements, and on waste management. It is clear that biochar soil amendments can have definite agronomic and environmental benefits, but it will be essential to have clear guidelines for biochar production from various feedstocks and under varying pyrolysis parameters. It will be equally important to have a classification system for biochars that clearly indicate the product compositions that will meet acceptable standards. A case can be made for sets of standard biochars from different substrates that meet the required criteria.

A catalyst reactor coupled with analytical pyrolysis gas chromatography/mass spectroscopy (Py-GC/MS) was used to carry out online analysis of the product vapors from the fast pyrolysis of Miscanthus x giganteus, Scots pine, and mahogany. Pyrolysis was carried out in both an inert atmosphere of He gas and in a highly reducing atmosphere of H 2 . Significant changes in the vapor compositions were achieved with the use of H 2 as the carrier gas. The most notable of these were the increases in the hydrocarbon compositions. The roles of ZSM-5, Ni/ZSM-5, MCM-41, and of Ni/MCM-41 catalysts on the compositions of the pyrolysis vapors were investigated. Lower amounts of the higher molecular weight phenolic compounds and larger amounts of the lighter phenols were observed in the presence of Ni supported on ZSM-5 and MCM-41. This effect was more evident for the 10% than for the 2.5% Ni loadings. Overall, the results both from the use of H 2 as the carrier gas and from all the catalysts demonstrates significant improvements in the composition of the vapors. However, this resulted in the lowering of the quantities of condensable products.

No abstract

Plants rely on microorganisms to mobilize organically and inorganically bound sulfur (S) and phosphorus (P) in which the plant can then readily utilize. The aim of this study was to investigate the role of S- and P-mobilizing bacteria in plant growth promotion in biochar-amended soil, which has been rarely investigated so far. Pot experiments of Lolium perenne were established on S and P limited soil with 1% or 2% biochar (Miscanthus × giganteus) or without biochar (control) for a period of 126 days. Both biochar amendments resulted in significant plant growth promotion. Rhizobacteria capable of growing with (1) S from aromatic sulfonates, (2) P from phosphate esters, (3) P from phosphonates, and (4) P from tri-calcium phosphates as sole source of S or P, respectively, were significantly more abundant in the biochar treatments. 16S rRNA gene-based rhizobacteria community analysis revealed a significant biochar treatment effect. Abundance of nematodes feeding on bacteria was also significantly increased in the biochar treatments. Diversity analysis of rhizospheric asfA and phnJ genes revealed broad sequence diversities in bacterial sulfonate and phosphonate-mineralizing capabilities. These findings suggest that biochar amendment enhances microbially mediated nutrient mobilization of S and P resulting in improved plant growth.