Empirical correlations over a diverse range of biomass feedstocks have been developed for prediction of resultant biochar properties using experimental data of more than thirty slow-pyrolysis batch reactions. Biochar was produced under a standard set of conditions; including 550 degrees C higher heating temperature (HHT), 7 degrees C/min heating rate, atmospheric pressure, and 40 min residence time. Analysis of the experimental results complimented with literature data showed that calculating biochar yields based on a conservation of the ash method was a valid approach to estimating solid yields in cases where gravimetry is difficult or inconvenient. Increasing the proportion of feedstock ash is observed to increase the biochar yield semilinearly, with the greatest deviation from this observation in low-ash feedstocks. The developed empirical correlation is provided here. When considering highly diverse feedstocks of varying origins, including extensive literature data, the dominating influence of feedstock ash content on the biochar produced is clearly observed in this work. A second-order polynomial relationship between the starting feedstock ash and final biochar ash content was observed, even when including literature results for biochar obtained under widely varied experimental programs. This result suggests a dependency between the amount of the organic material removed from a feedstock and the amount of feedstock ash initially present. This dependency appears to overshadow expected reliance on the heating rate or HHT (within the range of 1-15 degrees C/min and 450-800 degrees C respectively). Empirical correlations have been developed and verified and will be of use to the ones doing greenhouse gas, mass and energy balances, or business case modeling for slow-pyrolysis processes utilizing a range of feedstocks, particularly in the case of high-ash and waste-derived sources.

The purpose of this study was to evaluate the suitability and optimum rate of addition of Urban Biochar (UB) as an alternative to standard coir peat in plant growing media. UB was prepared through pyrolysis of 2: 1 ratio of biosolids to greenwaste on a dry mass basis. Two incubation experiments are reported both with five different growing media mixtures which were subjected to periodic wetting and drying. Media mixtures consisted of different rates of UB (100%, 60%, 40%, 20%) mixed with composted pine bark on a volume basis and compared to an industry standard media with 0% UB. The physical and chemical properties of the mixtures were compared pre and post incubation. Substituting coir peat with UB increased media pH, C:N mass ratio, nutrient content, air filled porosity and bulk density. Furthermore, addition of UB to media also increased the proportion of particles in the desirable range for growing media (0.25-2 mm). UB amended mixes were found to be most stable in terms of both bulk density and resistance to particle breakdown. Fourier transform infrared spectroscopy analysis suggested that periodic wetting and drying enhanced surface oxidation. We found that UB amended substrates, up to 60% biochar on a volume basis, could deliver similar physical and chemical benefits to those of coir peat based industry standard media. (C) 2015 Elsevier Ltd. All rights reserved.

Biochar produced from mixture of biodegradable urban resources such as biosolids and greenwaste was slowly pyrolysed at 650 degrees C and characterised for its chemical and physical properties. The biochar was then compared to published values for growing media. It was found that this biochar has high surface area, inherent nutrient content, high porosity, high stability, desirable water holding capacity, air filled pore space and bulk density. Comparing the results of characterisation of this biochar with ideal potting substrate showed the highly porous and nutrient rich biochar were desirable however the high salt content was problematic. Fourier transform infrared analysis shows that carboxyl/carbonyl bands were very weak in biochar spectra due to loss of carboxyl groups in the decomposition of carbohydrates in high temperature pyrolysis which also contributed to low cation exchange capacity. The pyrolysis process has multiple advantages such as waste management, energy generation in the form of syngas and long term sequestration of carbon in biochar. (C) 2015 Elsevier B.V. All rights reserved.

This investigation examines different approaches for the GHG flux accounting of activities within a tight boundary of biomass C cycling, with scope limited to exclude all other aspects of the lifecycle. Alternative approaches are examined that a) account for all emissions including biogenic CO2 cycling – the biogenic method; b) account for the quantity of C that is moved to and maintained in the non-atmospheric pool – the stock method; and c) assume that the net balance of C taken up by biomass is neutral over the short-term and hence there is no requirement to include this C in the calculation – the simplified method. This investigation demonstrates the inaccuracies in both emissions forecasting and abatement calculations that result from the use of the simplified method, which is commonly accepted for use. It has been found that the stock method is the most accurate and appropriate approach for use in calculating GHG inventories, however short-comings of this approach emerge when applied to abatement projects, as it does not account for the increase in biogenic CO2 emissions that are generated when non-CO2 GHG emissions in the business-as-usual case are offset. Therefore the biogenic method or a modified version of the stock method should be used to accurately estimate GHG emissions abatement achieved by a project. This investigation uses both the derivation of methodology equations from first principles and worked examples to explore the fundamental differences in the alternative approaches. Examples are developed for three project scenarios including; landfill, combustion and slow-pyrolysis (biochar) of biomass.

We hypothesised that amending an acidic ferralsol with biochar would improve the productivity of a subtropical dairy pasture via reducing soil acidity related constraints and result in improved nitrogen use efficiency. We examined two contrasting biochars with different carbon, nutrient content and acid neutralising values.

The physical properties of biochars contribute to their function as a tool for environmental management. Their physical characteristics can be both directly and indirectly related to the way in which they affect soil systems. Soils each have their own distinct physical properties depending upon the nature of mineral and organic matter, their relative amounts and the way in which minerals and organic matter are associated (Brady and Weil, 2008). When biochar is present in the soil mixture, its contribution to the physical nature of the system may be significant, influencing depth, texture, structure, porosity and consistency through changing the bulk surface area, pore-size distribution, particle-size distribution, density and packing. Biochar’s effect on soil physical properties may then have a direct impact upon plant growth because the penetration depth and availability of air and water within the root zone is determined largely by the physical make-up of soil horizons.The pres-ence of biochar will, by affecting these physical characteristics, directly affect the soil’s response to water, its aggregation, workability during soil preparation, swellingshrinking dynamics and permeability, as well as its capacity to retain cations and its response to ambient temperature changes. In addition, indirectly, many chemical and biological aspects of soil fertility can be inferred from physical properties, such as the physical presentation of sites for chemical reactions and the provision of protective habitats for soil microbes (Brady and Weil, 2008).

Biochar has the potential to make a major contribution to the mitigation of climate change, and enhancement of plant production. However, in order for biochar to fulfill this promise, the industry and regulating bodies must take steps to manage potential environmental threats and address negative perceptions. The potential threats to the sustainability of biochar systems, at each stage of the biochar life cycle, were reviewed. We propose that a sustainability framework for biochar could be adapted from existing frameworks developed for bioenergy. Sustainable land use policies, combined with effective regulation of biochar production facilities and incentives for efficient utilization of energy, and improved knowledge of biochar impacts on ecosystem health and productivity could provide a strong framework for the development of a robust sustainable biochar industry. Sustainability certification could be introduced to provide confidence to consumers that sustainable practices have been employed along the production chain, particularly where biochar is traded internationally.

The sugarcane industry in many parts of the world produces food and energy (stationary and fuel). The industry is well positioned to offer greenhouse gas abatement and climate change mitigation. The thermal conversion, via a slow pyrolysis process, of cane residues such as green harvest trash and bagasse can produce thermal or electrical energy as well as biochar. Studies have shown that a commercial slow pyrolysis unit could generate over 1 MWhr of electricity from every two tonnes of trash (dry basis), with a biochar recover of between 31.3–33.6 %. Due to its highly stable nature, biochar has recently been suggested as a sequestration pathway to remove CO2 from the atmosphere. One tonne of bagasse derived biochar would sequester in the order of 2.3 tonnes of CO2 equivalents. In addition to C sequestration, biochar has other significant benefits (when used as a soil amendment) such as offering improved soil quality, higher CEC and nutrient availability, and improved soil physical characteristics. This work demonstrates that biochar application can reduce emissions of greenhouse gases from cane soils, such as nitrous oxide. Biochars derived from cane trash and bagasse were applied in incubation studies to soils from the Burdekin region in Australia. We found declines in emissions of the greenhouse gas nitrous oxide (N2O), from urea-fertilised soil when bagasse biochar was applied at a rate of 10 t/ha. The agronomic performance of biochar is being assessed in a 15 plot trial conducted on a sugar cane property in the Tweed Valley, NSW. Biochars (from non-sugarcane sources) were tested using relevant controls. Each plot consists of 3 rows of cane and was 30 m in length to enable commercial-scale harvesting. Although no significant effects in yield have been recorded this trial is expected to continue for several more seasons allowing additional data on yield effects to be evaluated. Our work has demonstrated that implementing slow pyrolysis and biochar utilisation in the sugarcane industry has potential to provide (1) renewable energy (2) income from waste (3) climate mitigation through stabilisation of carbon and (4) climate mitigation through reduced emission of N2O from soil. Further research is required to demonstrate agronomic benefits of sugarcane biochars and to develop an understanding of how they may address soil constraints in these systems.

Soils developed on the sites of Australian Aboriginal oven mounds along the Murray River in SE Australia, classified as Cumulic Anthtoposols under the Australian Soil Classification, are shown to have traits similar to the Terra Preta de Indio of the Amazon basin. Seven such sites were characterised and compared with adjacent soils. The Cumulic Anthroposols contained significantly (p < 0.05) more soil carbon (C), compared to adjacent non-Anthroposols. Solid-state C-13 NMR spectroscopy showed that the C in the Cumulic Anthroposols was predominantly aromatic, especially at depth, confirming the presence of charcoal. Radiocarbon analysis carried out on charcoal collected from two of these sites showed that it was deposited 650 +/- 30 years BP at one site and 1609 +/- 34 years BP at the other site, demonstrating its recalcitrance in soil. The charcoal originated from plant material, as shown by SEM, and had high levels of Ca agglomeration on its surfaces. The Cumulic Anthroposols were shown to have altered nutrient status, with total N, P, K and Ca being significantly greater than in the adjacent soils throughout the profile. This was also reflected in the higher mean CEC of 31.2 cmol (+) kg(-1) and higher pH by 1.3 units, compared to the adjacent soils. Based on the similarity of these Cumulic Anthroposols with the Terra Preta de Indio of the Amazon, we suggest that these Cumulic Anthroposols can be classified as Terra Preta Australis. The existence of these soils demonstrates that Australian soils, in temperate climates, are capable of storing C in much higher quantities than has been previously recognised, and that this capability is founded on the unique stability and properties of charred organic matter. Furthermore, the addition of charcoal appears to have improved the physical and chemical properties of these soils. Together, this provides important support for the concept of.;oil amendment with "biochar", the charred residue produced by pyrolysis of biomass, as a means for sequestering C and enhancing agricultural productivity. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

Biochar technology has been proposed as a geoengineering solution that has potential to actively reduce the atmospheric concentrations of greenhouse gases and enhance the sustainability of agriculture. The magnitude of the technologies' net benefit must be considered in relation to the associated risks. Hazards posed by biochar technology need to be managed to a level that the resulting risks are deemed acceptable by society; identification of hazards is an essential first step. Effectively implemented risk management and sustainability guidelines, driven by informed policy directives, will result in biochar technology being an important tool for environmental and atmospheric greenhouse gas management.

Biochar technologies have the potential to significantly contribute to climate change mitigation and enhance global food security. Biochar application may improve the physical, chemical and biological properties of soils, reduce fertiliser requirements and stimulate plant growth, though the results vary between biochars, soil types and plant species. The effectiveness of biochar for the improvement of soil properties is influenced by the biomass feedstock and the pyrolysis conditions. Climate change mitigation impacts arise largely from the stabilisation of soil organic matter, the reduction in fertiliser requirements and gaseous emissions in soils, and the production of renewable energy which can displace fossil fuel consumption. However, mechanisms for the observed agronomic and environmental benefits from biochar application are not well understood. Furthermore, to achieve its projected billion-tonne scale (on annual basis) avoided emissions potential, highly efficient and clean processing technologies, using sustainably supplied biomass, need to be implemented globally.

The effect of a low mineral ash biochar on biomass production and nitrogen (N) uptake into plants was tested with wheat and radish in a Yellow Earth used for commercial vegetable production. The biochar had an acid neutralising capacity <0.5% CaCO3, a total C content of 75%, and a molar H/C ratio of 0.45, indicating stability due to its aromaticity. A pot trial was established under climate-controlled conditions. Five rates of N fertiliser (0, 17, 44, 88, 177 kg N/ha) were applied as urea in combination with 5 biochar rates (0, 1.1, 2.2, 4.4, 11% w/w). Analysis of biomass production revealed a significant biochar × N fertiliser interaction. In particular, increasing biochar concentrations improved biomass production in both crop species at lower N application rates. The highest biochar application rate resulted in significantly greater accumulation of NO3 –-N in the soil and lower NH4 +-N averaged across the 5 N application rates. The biochar also decreased available P, and significantly increased microbial activity measured using the fluorescein diacetate method. Increasing N fertiliser application resulted in greater accumulation of NO3 –-N with no changes to NH4 +-N averaged across the 5 biochar application rates. Nitrogen fertiliser application did not influence microbial activity or biomass C. The trial suggests that in some cropping systems, biochar application will enable reduced N fertiliser input while maintaining productivity.

We examined the retention ability of a New Zealand dairy farm soil amended with 3 types of biochar produced from a variety of feedstocks for a steroid hormone (oestradiol, E2) and its primary transformation product (estrone, E1). Biochars produced from corn cob (CC), pine sawdust (PSD) and green waste (GW) were characterised by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and solid-state 13C nuclear magnetic resonance spectroscopy. Batch sorption studies were performed on soil amended with each biochar (0.5% and 1% by weight) using a complex solvent extraction scheme, and isotherms were fitted to the Freundlich model. All isotherms were highly non-linear, with N values in the range 0.46–0.83 (E2) and 0.66–0.88 (E1) in soil amended with different percentages of biochars. Overall, addition of all 3 biochars was found to increase the soil sorption affinity for the hormones, with E2 sorption being the highest in the soil amended with 1% PSD biochar. There was no marked difference in hormone sorption ability in the other 2 treatments (soil treated with 1% CC biochar and 1% GW biochar). Overall, the effective distribution coefficient (Kdeff) values for E2 at the lowest equilibrium concentration (Cw 0.5 mg/L) ranged from 35 to 311 L/kg in soil amended with the 3 types of biochar. Addition of 0.5% of PSD biochar resulted in ~560% increase in the Kdeff value for E2, while at 1% addition of PSD biochar, uptake of E2 was nearly 1400% higher than the control. For E1, the percentage increase in Kdeff was comparatively smaller than E2; however, it still ranged from 40 to 280%, and 60 to >320% at addition of 0.5% and 1% PSD biochar, respectively, compared with the control soil. Highest treatment temperature and associated greater surface area, low ash content, higher carbon content, and the abundance of polar functional groups (e.g. –OH, C=O) may explain why the soil amended with PSD biochar exhibited high sorptive capacity for the hormones.