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Item Designing Technosols to reduce salinity and water stress of crops growing under arid conditions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy of Applied Science in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2021) Kong, ChaoSalt- and plant-water stress are widely considered to be major abiotic stresses threatening crop production in dry areas. Innovative methods to alleviate salt and plant-water stress that are both practical and economically efficient are in great demand. While the most common reclamation strategy for salt-affected soils is to flush the salts out of the root zone with low salinity/sodicity water, this is challenged by the fact that water is commonly scarce in areas affected by salt stress. The use of specific soil amendments or a combination of them in such areas may well solve some of these problems. Biochar has, in fact, been shown that, in some instances, it is able to effectively reduce salt stress to plants. Other porous materials, such as pumice, have not yet been considered although pumice has been reported to contribute to water retention under arid conditions. Further potential amendments include organic residues, as they can produce beneficial impacts on plant growth by improving soil functions. To date, however, limited research has attempted to unravel (and compare) the effects of either pumice and/or biochar in alleviating salt and plant-water stress. There is also scant information on (i) how to minimise the impact of biochar on the salinity of soils in dry regions; (ii) the underlying mechanisms explaining how the use of either pumice or biochar amendments can decrease soil salinity under arid conditions; and (iii) whether individual or combined additions of either pumice and/or an organic amendment, algae, to a sandy soil alleviates salt and water-stress on plant growth. Therefore, my objective in this study is to investigate whether these amendments can be used in the formulation of Technosols specifically designed to reduce salinity and water-stress of crops growing under arid environments. A quantitative review of the literature was carried out to evaluate what type of biochar and under what conditions its use is suitable in dryland soils. For this, a meta-analysis of 40 studies published between 2013 and 2020 using pairwise comparisons was carried out to evaluate the short-term effect of biochar on the salinity using electrical conductivity (EC) as the proxy for soils under dry environments (Mediterranean, arid, semi-arid climates, or under simulated dry and saline conditions). The results indicated that in terms of the risk of biochar increasing soil salinity, (i) biochars made from high-ash material should not be applied to soils in dry regions; and (ii) the addition of biochars made from relatively low-ash ligneous material at application rates ≤ 20 t ha-1 is suitable as an amendment to soils under dry environments. The use of a leaching fraction is recommended. Water-borne salt transport in soils under arid conditions is strongly related to the influence of amendments on the soil’s mobile-immobile water fractions. For this, the influence of the porosity and pore-size distribution of pumice and biochar (produced from willow wood chips at a highest heating temperature of 350 °C) on the mobile-water content when added to a sandy soil were investigated. Pumice and biochar (of 1.5-, 3-, and 6-cm Ø) were characterised using Scanning Electron Microscope (SEM) technology. The fraction of mobile-water present in these amendments, previously added to a sandy soil at different application rates and particle sizes, was determined using a tracer (Na+) technique. The results showed that the overall larger contribution of pumice to the water mobility than that of biochar under near-saturated conditions could be related to its relatively higher levels of macro-scale plus meso-scale porosity, and this increased as the pumice particle size increased. Both pumice and biochar had a predominance of pores with a Ø < 30 μm and relatively high total porosity, which are expected to contribute to water retention dilution of salinity when these amendments are added to salt-affected sandy soils. In order to evaluate the effects of pumice and biochar amendments on water retention and salinity of a sandy soil under simulated arid conditions, pumice and biochar of different particle sizes (1.5-, 3-, and 6-cm Ø) were separately added at different rates (3, 6, and 12%, v/v basis) to the soil. This was drip irrigated with an artificial saline water under non-draining conditions. Pebbles applied at identical rates and sizes as pumice and biochar, were used as positive controls, whereas no amendment was the negative control. Treatments underwent 10 wetting and drying cycles at 35 ℃ at the end of which, the residual soil was separated from the amendments. We found that (i) the EC of the residual soil followed the order pumice < biochar < positive control = negative control, with differences where existing, being significant at p < 0.05; (ii) the smallest EC and sodium adsorption ratio (SAR) values of the residual soil were achieved when applying 12% pumice, regardless of the particle size; the opposite pattern (12% > 6% > 3%) was observed in the pumice when analysed separately from residual soil; (iii) pumice and biochar treatments retained an increasing amount of water in the soil after each drying cycle (significant at p < 0.05); and (iv) at the end of the experiment, the EC values of the leachates indicated that salts retained in pumice were more slowly mobilised than those in the biochar. The application of either pumice or biochar can contribute to a decrease soil salinity, but pumice could additionally serve as a tool to remove salts from salt-affected soils. In order to investigate whether individual or combined additions of either pumice (PU) and/or algae (AL) to a sandy soil could alleviate the impact of irrigation with saline water on the growth of lucerne (Medicago sativa L.) under simulated semi-arid conditions. A plant growth chamber study was conducted that included six treatments that received saline water (6.4 dS m-1): T1 (sand – positive control), T2 (sand + 3% (v/v basis) PU), T3 (sand + 12% PU), T4 (sand + 3% PU + 2% AL), T5 (sand + 12% PU + 2% AL), T6 (sand + 2% AL). A seventh treatment was T7 (sand – negative control), to which deionised water was added. All treatments underwent 14 cycles of irrigation wetting and drying events (at 27 ± 1 ℃/ 16 ± 1 ℃ day/night). Results showed that, at the end of the experiment and compared with the positive control (T1), the two treatments with the largest application rate of PU (T5 and T3) showed the largest (significant at p < 0.05) reduction in soil EC, SAR, and water-extractable ions among those treatments receiving saline water (T1-T6). Lucerne in treatments T1-T6 always had a smaller (p < 0.05) biomass, leaf dry weight (DW), and relative growth rate than the treatment receiving deionised water (T7) (DW: 2.3 g m-2), but values for treatment T5 (DW: 1.7 g m-2) were significantly larger (p < 0.05) than for treatments T1-T4 and T6 (DW < 1.1 g m-2). Overall, the results obtained suggest that, if proven feasible at a field scale, the combined addition of PU (12%), by reducing salinity and contributing to water retention, and AL (2%), by adding nutrients and/or bioactive compounds, could be used to mitigate salt stress and improve plant growth in sandy soils under arid conditions. The information obtained in this thesis supports the use of pumice and algal amendments as ingredients of Technosols designed to reduce salinity and water-stress of crops growing under arid conditions. Both materials are easily available (if to be used in areas close to a volcanic region and at the seaside), low cost, and their use in agriculture may open new doors to deal with the current problems faced in dry regions.Item An investigation on the stability of biochar-C in soils and its potential use to mitigate non-CO₂ greenhouse gases using near-infrared (NIR) spectroscopy : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Manawatu, New Zealand(Massey University, 2020) Mahmud, Ainul FaizahThe global interest in using biochar for C sequestration-climate mitigation and soil improvement has driven rapid expansion in biochar research to understand its properties and application impacts. The potential for biochar application to increase soil organic carbon (SOC) stocks and its potential agronomic and additional environmental benefits, such as reducing soil nitrous oxide (N₂O) emission, are determined by its stability in the soil, which is dependent on its intrinsic properties and the soil conditions. The inherent properties of biochar are highly influenced by feedstock type and pyrolysis temperature hence, the use of various types of feedstock and pyrolysis technologies leads to uncertainties in predicting the effect of biochar addition to soils. Previous research has established a general assumption that biochar stability is strongly influenced by the type of feedstock used and maximum pyrolysis temperature. Research is required, however, to produce practical and reliable techniques that can be used to verify the reported maximum pyrolysis temperature, regardless of the type of feedstock used and predict the likely stability of the biochar. In addition to the pyrolysis process, the final particle size of the biochar and the method of incorporation into the soil may also influence the ability of the biochar to moderate soil properties and function. With previous research, there is general lack of attention given to these potentially influential parameters when assessing the impact of biochar application to soil. Therefore this thesis evaluates (i) the use of near-infrared (NIR) spectroscopy technique for predicting the maximum pyrolysis temperature of biochar as it is a well-known, non-destructive, and rapid technique for analyzing organic material; (ii) the effect of biochar application, with special attention to biochar particle size and depth of placement, on N₂O soil emission and SOC stocks; and (iii) the integrated use of NIR spectroscopy for SOC measurement. In the first study, we hypothesized that NIR spectroscopy can be used to predict the maximum pyrolysis temperature achieved during biochar production. Eighty-two carbonized materials produced from various feedstock types and pyrolysis conditions with the reported pyrolysis temperature ranged between 220 to 800 °C, were scanned using NIR spectrometer and were used as the calibration set. The NIR calibration model was built by correlating the NIR spectral data with the reported pyrolysis temperature using partial least squares regression (PLSR). A separate sample set (n=20) was compiled using laboratory-produced biochar made from pine wood at pyrolysis temperature ranged from 325 to 723 °C. The calibration model validated using (i) leave-one-out cross-validation (LOO-CV) and (ii) the prediction set, yielded good accuracy (LOO-CV: r²=0.80 and RMSECV:48.8 °C; prediction: r²=0.82 and RMSEP: 57.7 °C). Results obtained in this study have shown that NIR spectroscopy can be used to predict the maximum pyrolysis temperature of biochar and has the potential to be used as a monitoring tool for biochar production. In addition to the first study, the predictive ability of the NIR model was evaluated further. We hypothesized that the variation in feedstock types and pyrolysis processes may affect the predictive performance of the NIR model in predicting the maximum pyrolysis temperature of biochar. Therefore, three sample sets were generated from a total of 82 carbonized materials and its subsets (Set A: n=82; Set B: n=68; Set C: n= 48) and were used for developing three calibration models. The selection of samples for Set B and C was made by reducing the variability associated with production conditions and feedstock type i.e. Set B consist of samples produced by slow pyrolysis and using the same pyrolyzer unit, while for Set C (a subset of Set B), samples produced from “processed feedstocks” were excluded. A separate sample set (n=18) consists of samples produced from animal manure, crop residue, and woody materials were used as the prediction set. This biochar was produced using the slow pyrolysis technique in a laboratory or under relatively high production controlled conditions at temperature ranged from 250 to 550 °C. These calibration models were validated using (i) leave-one-out cross-validation (LOO-CV) and (ii) a prediction set, with the model based on set C gave the best prediction (R2: 0.941; RMSEP: 27.3 °C), followed by the model based on set A (R2: 0.896; RMSEP: 35.6 °C), and set B (R2: 0.928; RMSEP: 37.3 °C). These results indicate that feedstock types have a considerable effect on the performance of the NIR model while the effect of pyrolysis conditions was less pronounced. Thus, data variability from samples needs to be taken into account in developing the NIR calibration model for predicting the maximum pyrolysis temperature of biochar. Before studying the effect of biochar on N₂O soil emission and SOC stocks, the maximum pyrolysis temperature of biochar to be used in the experiment was predicted using the NIR spectroscopy technique. The estimated pyrolysis temperature – after scanning the 3-year old pine wood biochar and using the NIR model developed – was 500 °C, while the reported temperature was 550 °C. A controlled glasshouse study was conducted to investigate the effect of biochar particle size and the impact of soil inversion (through simulated mouldboard ploughing) on N₂O emissions from soils to which cattle urine was applied. We hypothesized that the application of biochar may (i) affect N₂O emissions through changes in soil physical properties, specifically soil aeration and water retention; and (ii) the effects of biochar addition on these properties may differ depending on their particle size (e.g., a larger particle size may increase soil aeration whereas a smaller particle size may clog pores), and their placement in soil (e.g., the incorporation of a large particle size-biochar at depth may promote water movement from the top layer and increase the overall drainage of the soil). Pine biochar (550 °C) with two different particle sizes (<2 mm and >4 mm) was mixed either into the top soil layer at the original 0–10 cm depth in the soil column or at 10–20 cm depth by inverting the top soil to simulate ploughing. Nitrous oxide emissions were monitored every two to three days, up to seven weeks during the summer trial, and measurements were repeated during the autumn trial. The use of large particle size biochar in the inverted soil had a significant impact on increasing the cumulative N₂O emissions in the autumn trial, possibly through changes in the water hydraulic conductivity of the soil column and increased water retention at the boundary between soil layers. Thus, the importance of the role of biochar particle size and the method of biochar placement on soil physical properties and the implications of these on N₂O emissions was highlighted. In the same glasshouse study, the effect of biochar particle size and depth of placement was further evaluated in relation to soil organic C. We hypothesized that (i) the large-particle size biochar may affect soil aeration and accelerate soil C decomposition rate with increased oxygen availability, and this effect is greater when biochar is incorporated at depth due to the more compacted soil at deeper layer with poorer aeration compared to the surface layer; and (ii) the NIR spectroscopy technique can be used to predict the SOC concentration and SOC stocks in biochar-amended soil. Carbon stocks were estimated using NIR spectroscopy coupled with partial least-squares regression analysis (NIR/PLSR) and direct organic C measurements using an elemental analyzer. The NIR spectra of the soil were acquired by scanning intact soil cores using the NIR spectrometer. By the end of the glasshouse trial (327 days), the large-particle size biochar applied at depth had induced significant soil C loss (9.20 Mg C ha⁻¹ (P < 0.05), possibly through the combination of enhanced soil aeration, and the interrupted C supply from new plant inputs at that depth due to soil inversion. This C loss did not occur in the treatment with the small-particle size biochar. Near-infrared (NIR) spectroscopy was able to predict the SOC concentration, however, the prediction accuracy may be negatively affected by an increasing biochar particle size and soil inversion, thus may affect the subsequent SOC estimates. The information obtained in this thesis will inform the future use of biochar and contribute to the knowledge of possible factors affecting soil N₂O emission from biochar-amended soil, the mineralization of native SOC, and the changes in SOC stocks over time, particularly in the pastoral soils of New Zealand. Also, based on this study, the use of NIR spectroscopy technique may potentially be integrated as part of the methodology for SOC estimation.Item Linking soil functional biodiversity and processes to soil ecosystem services : biochar application on two New Zealand pasture soils : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatu, New Zealand(Massey University, 2020) Garbuz, StanislavSheep and beef farming and dairying are an important part of the New Zealand economy, occupying about 40% of land area used for the livestock. Maintenance of that land is an essential part of sustainable agriculture. For a long time, biochar has been used and considered as a multifunctional soil amendment adding to the natural capital stocks of the soils and contributing to a wide range of soil ecosystem services, provision of nutrients (soil fertility) through the increasing nutrient availability, neutralising acidity through liming, and mitigating climate change through carbon (C) storage. In this thesis I investigate the effects of biochar, made from willow at 350°С and added as an amendment, on soil ecology and biochemistry-based processes within an ecosystem services modelling framework. In the literature review (Chapter 2) I draw links between the importance of soil ecosystem services, including soil biodiversity and human needs. The potential role of biochar application in improving soil productivity and mitigating the negative impact of land management are also discussed. To evaluate the impact of biochar, added as an amendment, on the chemical and biological properties and processes in soil as it influences soil processes underpinning ecosystem services, and to explore any synergistic interactions between biochar, soil, functional groups of soil fauna and plants, two experiments were conducted: (i) a six-month mesocosm experiment in the glasshouse and (ii) a field-based mesocosm experiment that ran for 12 months. In both experiments two contrasting soils were used – an Andosol (Allophanic) and a Cambisol (Brown). Both soils cover extensive areas of New Zealand. In the mesocosm experiment in the glasshouse (Chapter 3) biochar had a significant positive effect on clover growth and biomass, and this effect was more pronounced in the presence of earthworms and in one soil type. On their own, biochar and earthworms increased clover growth more in the Cambisol, while the positive synergistic effect of biochar and earthworms on soil biochemical processes and clover growth was more evident in the Andosol The synergistic effect of biochar and earthworms was also observed in an increase in the abundance of Collembola and in soil fungal biomass. The field mesocosm experiment investigated how adding biochar as an amendment to a grazed pasture affects the soils biological and physico-chemical properties. The experiment was conducted at four locations with different livestock systems (dairy and sheep) and soils (Andosol and Cambisol) under contrasting management practices (two pastures, with or without dairy shed effluent addition on the Andosol, and two pastures with either low or high phosphorus (P) fertilizer input in the Cambisol) over 12 months. The three treatments were: (i) willow biochar produced at 350 °C (1% w/w); (ii) lime, added at the liming equivalence of the biochar application (positive control); (iii) no amendments (negative control). Results of the field experiment are reported in three chapters. Chapter 4 reports how adding biochar affected biological and physico-chemical properties and the plant root biomass at each of the four grazed pasture locations on Andosol and Cambisol. Biochar addition had a positive (P<0.005) effect on total nitrogen (N), organic C, Olsen P contents, bacterial (Cb) and fungal (Cf) C biomass, and Collembola abundance, compared with the control and lime treatments 12 months after addition. At all four locations, the increases in N, C and P in the biochar treatment were greater than the amount of N, C or P added in the biochar. On average, root biomass was 6.9 Mg ha-1 higher (P<0.005) in all four soils to which biochar was added, when compared with the other two than the other two treatments. Biochar addition also lowered (P<0.005) the bulk density of the soil, on average by 7% across the four sites, compared with the control. Earthworm abundance in lime-treated soils was higher (P<0.01) than in the negative control. In the presence of biochar, earthworm abundance was only higher (P<0.05) than the control in the Andosol without effluent. In biochar-amended soils, Collembola abundance was higher (P<0.005) than the controls in all soils, while there was no effect on Oribatida and Gamasina populations. Chapter 5 investigated the effect biochar addition had on the biochemical activity (soil enzymes) in the soils after 12-months. Dehydrogenase activity, which is strongly correlated with soil microbial biomass, was higher in the soils to which biochar had been added. Cellulase activity was also higher in the soil to which biochar had been added, reflecting the increased amounts of plant detritus entering the soil, from the greater root biomass following biochar application. When the geometric mean of all the enzyme activities was summed, biochar had a more pronounced effect than lime. An exception was peroxidase, which in contrast to dehydrogenase and cellulase, had higher activity in the soil treated with lime (positive control) and was positively correlated with earthworm abundance, which also was higher in the lime-treated soil. Biochar had less of an effect on both pH and earthworm abundance. There was a positive correlation between nitrate reductase and earthworm abundance, as earthworms increase nitrate concentration in soil. In Chapter 6 I attempted to assess the long-term impact of biochar on soil potential to provide ecosystem services and investigated the influence of the biochar application on the time dynamics of physicochemical and biological properties. Soil samples were collected at 6 and 12 months after the start of the field experiment. Except for mineral N (NO3--N and NH4+-N), the effect of sampling time was similar across sites. Biochar had a long-term positive effect on OC, TN and Olsen P in all sites. Reduced by biochar, soil acidity and BD remained at the same level after 6 and 12 months in all four sites. The effect of biochar on mineral N was not constant in time, and mostly depended on the soil order and management practices rather than on treatments. Soil biological and biochemical properties had patterns which can be interpreted as seasonal. Biochar increased bacterial and fungal biomass as well as abundance of arthropods and earthworms; these changes in soil biota were reflected in soil enzymatic activities. It was shown that biochar has a persistent effect on soil natural capital stocks and functions and showed itself as an effective amendment able to enhance the soil over time. In the Chapter 7 the results of the analysis of the effects of biochar and lime addition on soil physicochemical and biological properties (Chapter 4) and enzymatic activity (Chapter 5) were used to semi-quantify the effects and potential benefits of biochar and lime amendments application for the delivery of specific soil ecosystem services. In comparison with the control treatments, there was a significant positive impact of biochar on soil properties, including soil microflora, earthworms, OC, soil BD, pH and overall soil enzyme activity, associated with C sequestration. In comparison with control and lime, biochar increased components of soil natural capital stocks responsible for food and fibre production ecosystem service. There was also significant positive impact of biochar on soil properties associated with fertility maintenance. Biochar and lime had similar positive effect on water regulation and disease and pest control services. The thesis shows that application of willow wood biochar produced at low temperature has a significant positive effect on a number of the chemical and biological properties and processes in soils (up to 12 months) that extend to the rooting characteristics of the plant, and this might contribute to the productivity of pasture land, while increasing health and resilience to the impact of land management. Biochar, through its effect on soil properties contributes to dynamic interactions between soil, plant and functional groups of soil biota. As a result, biochar positively impacts on the dynamical links between components of soil natural capital and ecosystem services provided by the soil. In summary, biochar produced from willow wood at low temperature may be an effective tool in the pasture systems/soils investigated here as a part of sustainable farming practices, which can increase plant productivity, improve soil physical properties and fertility, reduce disease and pest risks, and at the same time might be used as an instrument to mitigate climate change.Item Guidelines for small scale biochar production system to optimise carbon sequestration outcome : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Bioprocessing Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2019) Cortez Pires de Campos, ArthurBiochar is made in a 60 kg batch pyrolysis reactor developed by Massey University in both prior work and during this project. This thesis details the design and control features necessary to produce biochar (charcoal) at temperatures ranging from 400-700°C. It also examines the emissions abatement necessary to achieve the best possible carbon footprint by combusting the gases to avoid release to the atmosphere. The feedstock for this work was Pinus radiata without bark. The biochar reactor is a vertical drum mounted on top of a combustion chamber containing two forced draft LPG burners. The combustion gases pass through an outer annular drum and so heat the biomass through the external wall. Evolving pyrolysis gases then move toward a central perforated core inside the drum, then descend into the combustion chamber where they are partially combusted. The range of highest treatment temperatures (400-700°C) was extended by controlling the partial combustion by varying a secondary air supply into the combustion chamber (previously only 700°C was achievable). Effective emissions abatement requires complete combustion. This work reveals that the flammability of the pyrolysis gases is not high enough to self-combust and so does not remove soot and other products of incomplete combustion, such as CO and CH4. Therefore, supplementary fuel is always needed. Here, this was achieved using modulated LPG burners at the flare. This system has the problem of batch pyrolysis reactors, where the release of volatiles from the reactor is uncontrolled, making the design of a variable rate flare system a non-trivial matter. Modifications made to the reactor design in this project include insulating the flare chimney, extending it to provide sufficient residence time, and installing adjustable vents to ensure sufficient air entrainment for complete combustion. This achieved emissions of CO and CxHy (hydrocarbon, mostly CH4) of 32 and 51 ppm respectively, which were well within the US EPA limits for both suspension and fluidised bed biomass burners(2.400 and 240 ppm respectively). The net environmental impact was determined for char made at 700°C, through carbon footprint analysis. An efficient system is needed to achieve a net sequestration benefit. Here, even with emissions abatement and the above mentioned very low CO and CxHy emissions, no net benefit was achieved. With the flare working, the net fractional sequestration was -0,14 (kg C sequestered)/(kg C in biomass). Then, when the flare is turned OFF, the net fractional sequestration was -1,2401 (kg C sequestered)/(kg C in biomass). Therefore, another frame of reference for well-operated systems is that the permissible emission should be less than 0.001 (kg C emitted as CO)/(kg C biomass), without considering methane or other GHGs.Item Pilot scale pyrolyser : compliance and mechanistic modeling : a thesis presented in partial fulfillment of the requirement for the degree of Master of Engineering in Chemical and Process Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2017) Caco, Nadeem Salahaddin Abdul"A pyrolysis reactor was built in a previous project by Bridges et al (2013).The reactor is cylindrical in geometry, with a height of 1000 mm and an internal diameter of 750 mm, it stands vertically. There is a 900 mm tall and 100 mm in diameter perforated core in the center of the reactor. At the base, a combustion chamber provides the hot gases required for heating. The hot gases produced travel up and around the reactor through an annulus region of 11 mm. Heat from the gases is transferred to the reactor wall and then to the wood-chips inside. As drying and pyrolysis reactions occur, gases flow in the same direction as the heat towards the perforated core at the center. Hot pyrolysis gases then flow downwards towards the combustion chamber where they are partially combusted before flowing around the reactor and out the flue stack. This project aimed at mathematically modeling this reactor and also improving the way emissions are released so that it complies with EPA air quality standards. A mathematical model of an ‘open source’ pilot-scale pyrolysis reactor was produced to predict the product yield, carbon foot-print, biochar quality and the time taken to achieve complete pyrolysis. A non-equilibrium thermodynamic approach was used which allowed for the use of COMSOL Multi-Physics to solve the model. The Finite Element Method (FEM) was used to solve the system of equations. Pyrolysis kinetics are complex and no single model has yet been widely accepted, therefore simplifications were necessary in this model so that a reasonable solution time could be achieved while producing acceptable results. The model profile of the centre temperature closely followed that of the experimental results and thus the model was considered valid. In addition, modifications were made to the original design of the pyrolyser in order to improve emissions compliance and improve operations of the pyrolysis. It was important to manage fugitive emissions and completely combust any volatile vapours that would be released into the atmosphere while controlling the operating parameters. In order to achieve this, the following were implemented: 1) The combustion chamber was sealed completely so that no fugitive emissions can escape while limiting the ingress of oxygen. 2) A secondary blower was installed in order to better control the oxygen supply to the burners. 3) The original steel lid, which warped during pyrolysis runs resulting in gaseous leaks, was replaced with a more rigid ceramic lid that doesn’t effectively expand when heated. 4) Two 3.4 kW burners were added to the single 3.4 kW burner flare. This gives a total power of 10.2 kW, which is estimated to be enough to completely burn all gaseous products leaving the system"--PrefaceItem A study of the importance of secondary reactions in char formation and pyrolysis : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process Engineering at Massey University, Manawatū, New Zealand(Massey University, 2016) Ripberger, Georg DietrichAnthropogenic climate change, caused primarily by excessive emissions of carbon dioxide, has led to a renewed interest in char, the solid product of pyrolysis. When applied to soil as biochar it can both sequester carbon and improve soil function. To make its manufacture environmentally friendly and economically viable it is important to maximise char yield, which can be done by promoting secondary reactions. This research shows that secondary reactions, which are enhanced by prolonged vapour-phase residence time and concentration, not only increase the char yield but are the source of the majority of the char formed. All four biomass constituents (extractives, cellulose, hemicellulose and lignin) undergo secondary reactions concurrent with primary reactions over the entire pyrolysis range ≈ 140 to 500 °C, which makes it practically impossible to separate them. Secondary char formation was confirmed to be exothermic which affects the overall heat of pyrolysis. Impregnating the feedstock with the elements K, Mg and P, which are plant macro-nutrients naturally present in biomass, resulted in the catalysis of secondary char formation. The results reveal that a first order reaction model does not describe pyrolysis accurately when char formation is enhanced by catalysis and secondary reactions. Secondary char can be enhanced by increasing the particle size but there is a limit due to increased cracking and fracturing of the pyrolysing solid. This limitation is overcome by pyrolysis in an enclosed vessel, termed autogenous pressure pyrolysis, which was discovered to cause significant changes in the volatile pyrolysis products; indicating the co-production of a high quality liquid. This process, however, negatively affects the char properties relevant for biochar like the surface area, similar to self-charring and co-carbonisation of condensed volatile pyrolysis products. To increase research capabilities a unique high temperature/ high pressure reactor (600 °C at 20 MPa) was designed to allow the detailed characterisation of all three pyrolysis product classes under extreme pyrolysis conditions. This was demonstrated to be invaluable for understanding the underlying pyrolysis mechanism and physical processes at play.Item Can biochar ameliorate phosphorus deficiency and aluminium phytotoxicity in acid soils? : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy of Applied Science in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2015) Shen, QinhuaThe use of biochar as soil amendment to enhance soil functionality is being increasingly investigated, with particular attention given to its effects on the sustainable increase of crop production and carbon (C) sequestration. To date, however, limited research has attempted to unravel the effect of biochar on either the chemical and/or biological mobilization of the residual fraction of phosphorus (P) in soil. This fraction tends to accumulate as a result of long–term P fertilization in soils rich in aluminium (Al) and iron (Fe) oxy–hydroxides and short–range ordered aluminosilicates (i.e. allophane). There is also scant information on (i) how the speciation of soluble Al changes when biochar is applied to acid soils, and (ii) whether this application alleviates Al toxicity on plant roots. My objective in this study is therefore to determine the effect of different biochars with contrasting fertilizer and liming values on the chemistry, biology and nutrient fertility of acid mineral soils. Before studying the effect of different biochars on soil properties, several methodologies for measuring the liming properties and available nitrogen (N) in biochar were evaluated and modified where needed. For this, 19 biochars produced by pyrolysing a wide range of feedstocks under various production temperatures were used. Different pH–buffering capacity (pH–BC) methodologies – originally developed for soils (single vs multiple acid additions, short vs long equilibration times) – were tested, along with the methodology used to measure the liming equivalence. The methodologies were then validated by incubating over 10 d two acid soils (an Haplic Cambisol and an Andic Umbrisol) to which separated amendments of the 19 biochars were made at the rates estimated using both methodologies to target a final pH of 6.5 The results indicated that the relationship established between the pH–BC of the 19 biochars under study after 30–min equilibration (pH–BC30min) with a single addition of acid and that obtained after a 5–d equilibration (pH–BC5d) (predicted pH–BC5d = 2.2 × pH–BC30min + 20.4) allowed an adequate estimate of the liming potential of biochars. Similar results were found with the liming equivalent, and both methods were considered suitable to make the recommendation of the application rate. Acid hydrolysis using 6 M HCl has been proved adequate to determine available N in biochar. For this, hydrolysates of biochar are oxidized using potassium peroxodisulfate with a dilution factor of 600 so that chloride interferences are overcome and nitrate–N is then measured. This methodology, originally developed using biochars rich in N, proved not suitable for biochars with low N concentrations. Results obtained in this study have shown that a smaller dilution factor (242) is sufficiently adequate to overcome the chloride interferences while avoiding over–diluting the sample. In this study, we hypothesized that biochar can increase P availability to plant by stimulating the growth of arbuscular mycorrhizal fungi (AMF) hyphae. Therefore, methodologies to (i) estimate the length of fungal hyphae in soil and (ii) evaluate the transfer of P by AMF hyphae needed to be tested and modified where necessary. In this part of the study, three different biochars and two soil types were used. Two biochars were produced from chipped pine (Pinus radiata D. Don) branches at 450oC and 550°C (referred to as BP450 and BP550, respectively); and a third one from chipped weeping willow (Salix matsudana L.) branches at 550°C (referred to as BW550). The soils were two sil–andic Andosols of contrasting P status (Olsen P of 4.3 vs 33.3 mg kg–1, referred to as LP and HP soil, respectively). The traditional visual gridline intersection (VGI) method commonly used to measure the length of AMF hyphae distribution in soil was modified by (i) using a digital photomicrography technique (referred to as “digital gridline intersection” (DGI) method), and (ii) processing the images using ImageJ software (referred to as the “photomicrography–ImageJ processing” (PIP) method). These methods were first tested with known lengths of possum fur and then applied to measuring the hyphal length in the LP and HP soils after a 32 wk experiment growing Lotus pedunculatus cv barsille. The study confirmed that the use of digital photomicrography in conjunction with either the grid–line intersection principle or image processing (with ImageJ software) is a suitable method for the measurement of AMF hyphal lengths in soils. In addition, the traditional root study container that divides the plant growth medium into two sections – (i) a root zone to which both root and AMF hyphae have access and (ii) an hyphal zone to which only AMF hyphae have access – by a layer of nylon mesh was further modified by including a 3–mm thickness of tephra under the nylon mesh between two sections. This layer of tephra was found to be adequate to halt P diffusion from the HP soil to the LP soil for a plant growth period of 32 wk. Under such circumstances, the increase in P uptake by plant growth in a combination of a root zone of LP soil and a hyphal zone of HP soil compared with that in which both root and hyphal zones were filled with LP soil was only ascribed to the transfer of P from HP soil to LP soil by AMF hyphae. This novel root study container allows the biochar to be added to either the root zone or the hyphal zone and separates the effect of biochar on AMF hyphae development and P uptake from that on P content and availability (i.e., biochar rich in P; changes in soil pH). This device can contribute to discern whether biochar can influence AMF development and enhance P bioavailability. In order to investigate the feasibility of adding biochar to soils with high residual P so that this can become bioavailable, Lotus pedunculatus cv barsille was grown in LP and HP soils separately amended with BP450, BP550 and BW550 biochars at an application rate of 10 t ha–1 using the novel root study container for 32 wk without any further P and N fertilization. We found that (i) none of the tested biochars conferred any specific advantage to the HP soil; (ii) the addition of BW550 biochar to the LP soil increased plant growth by 59% and P uptake by 73%, while the pine–based biochar (e.g., BP450 and BP550) provided no extra nutrient uptake and no plant growth increase. This was ascribed to supplemental nutrients (especially P) from the BW550 biochar along with its liming effect and associated increase in P availability; (iii) biochar produced from BP450 biochar caused a 70% P uptake increase (and 40% plant growth increase) by stimulating AMF growth and accessing a high–P area (HP soil) to which the plant root had no access. More research is needed to discern the underlying mechanism. The liming effects of BW550 and BP550 biochars were further compared with those of lime chemicals (e.g., Ca(OH)2 and NaOH) in a short–term (10–d) incubation using two soils with contrasting pH–BC (an Haplic Cambisol and an Andic Umbrisol) to which these amendments were added. The two soils were first amended with BW550, BP550, Ca(OH)2 or NaOH at specific rates so that pH values of 5.4, 5.6, 5.8 and 6.4 were targeted and incubated at room temperature (25 oC) for 10 d. At the end of the incubation, a radical elongation bioassay using alfalfa (Medicago sativa L.) was carried out. Thereafter, soils were characterized with special attention to the Al chemistry, i.e. aqueous reactive Al fractionation and inorganic monomeric Al speciation. The final objective was to reveal the mechanisms through which these biochars alleviate Al toxicity on roots. Results showed that, for a specific soil, a smaller amount of BW550 biochar was required to increase the same unit of pH and reduce a similar amount of exchangeable Al compared with the amount required of BP550 biochar. The addition of BW550 biochar (at application rates < 9.1 %) and Ca(OH)2 stimulated alfalfa (Medicago sativa L.) seedling growth, whereas that of BP550 (at application rates > 2.4 %) and NaOH caused inhibition. The distinct responses of the root growth to the presence of Ca(OH)2 and BW550 biochar and to that of NaOH and BP550 biochar were explained by (i) a decrease in both inorganic monomeric Al (mainly in AlF2+ and Al3+) and colloidal Al, and (ii) an increase in aqueous Ca2+, in the former, as expected. In the latter there was (i) an increase in aqueous colloidal Al and Na+, and (ii) a decrease in soluble Ca2+. Thus, BW550 biochar was shown to be a more effective liming agent than was BP550 biochar. The information obtained in this thesis supports the use of biochar to manage high P affinity Andosols and acid soils, which are abundant in New Zealand. The technology of producing biochar from willow woodchips or feedstock alike with resultant solid products of high nutrient status and liming potential may contribute to the recycle of nutrients while increasing soil pH. Pine woodchips produced at relatively low temperature (e.g., 450oC) have been shown to enhance AMF abundance and functionality. Thus, biochar with specific environmental and agricultural purposes should be tailored accordingly. The root study container with a layer of “P diffusion break” and the measurement of AMF hyphal length using the photomicrography in conjunction with image software analysis (e.g., ImageJ) will advance studies of the responses of AMF to soil additives (e.g., biochar or green waste) and their associated enhancement of soil functions.Item Investigation on the effect of biochar addition and the use of pasture species with different rooting systems on soil fertility and carbon storage : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy (MPhil) in Soil Science at the Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand(Massey University, 2015) Wisnubroto, Erwin IsmuThere is a potential to increase soil carbon (C) sequestration in New Zealand pastoral soils, especially in the subsoils where the soil C stocks have been reported to have a greater C saturation deficit than the topsoils. Selecting pasture species with deeper root systems will enhance soil formation at depth and mineral weathering, thus enhancing the potential for soils to stabilize organic matter (OM). Moreover, the addition of biochar may increase the stable C pool of soils and provide other additional benefits. Up to the present time few studies have investigated the potential of biochar to promote root growth and allocation of plant C to the subsoil. A glasshouse study was carried out to examine the effect of adding a nutrient-rich biochar at various dose (0, 1.5, 5 and 10 Mg ha–1 without nitrogen (N) fertiliser; 0, 1.5, 10 and 20 Mg ha–1 with N fertiliser at a dose of 113 kg N ha–1) to a sandy soil on plant growth (aboveand below-ground). The results indicated that, in the absence of N limiting conditions, biosolids-derived biochar could improve plant biomass yield as a result of the addition of available P and K. This amendment also caused an increase in plant root length. Subsequently, a 2-year lysimeter trial was set up to compare changes in C stocks of soils under deep- or shallow-growing pastures as well as to investigate whether biochar addition below the top 10 cm could promote root growth at depth. For this: i) soil ploughing at cultivation for pasture establishment was simulated in two different soils (a silt loam soil and a sandy soil) by inverting the 0–10 and 10–20 cm depth soil layers, and biochar was mixed at a rate of 10 Mg ha–1 in the buried soil layer, where appropriate; and ii) three pasture types with contrasting root systems were grown. Distinctive biochars were selected for these two soils so that soilspecific plant growth limitations could be overcome. In the silt loam, soil inversion resulted in a net loss of native organic C in the buried horizon under shallow-rooted species, but not under deep-rooted species. The addition of a C-rich pine biochar (equivalent to 7.6 Mg C ha–1) to this soil resulted in a net C gain (6–16% over the non-biochar treatment, calculated up to 30 cm; P < 0.05) in the buried soil layer under all pasture treatments; this overcame the net loss of native organic C in this horizon under shallow-rooted pastures. In the sandy soil all pasture species were able to maintain soil C stocks at 10–20 cm depth over time. In this soil, the exposure of a skeletal and nutrient-depleted soil layer at the surface may have fostered root growth at depth. The addition of a nutrient-rich biosolids biochar (equivalent to 3.6 Mg C ha–1) to this soil had no apparent effect on total C stocks. In this 2-year study, none of the biochar amendments affected either pasture yield or root growth. More research is needed to understand the mechanisms through which soil C stocks at depth are preserved.Item Biochar systems for carbon finance -- an evaluation based on Life Cycle Assessment studies in New Zealand : a thesis presented in partial fulfilment of the requirements of Doctor of Philosophy in Science at Massey University, Wellington, New Zealand(Massey University, 2013) Anaya de la Rosa, Ruy KorschaChar produced from the pyrolysis of biomass and applied into soils (biochar) can, under some conditions, improve soil functions and sequester carbon (C) over millennia. In New Zealand, if 80% of the available biomass residues were converted into biochar, about 1.7 Mt CO2 could be sequestered annually. This represents ~2.4% of NZ’s total annual greenhouse gas (GHG) emissions. However, the trade-offs associated with alternative uses of biomass need to be assessed from a life cycle perspective, particularly when considering policymaking. The biomass feedstocks evaluated using Life Cycle Assessment were orchard prunings, logging residues, and wheat straw. The goals were i) to compare alternative management scenarios and ii) to determine the use of biomass that can achieve the largest amount of carbon credits in order to support policymaking. The biomass for heat-only (HO) scenario could mitigate 276 – 1,064 kg CO2-eq per t biomass; the combined heat and power (CHP) scenario could reduce 410 – 1,608 kg CO2-eq per t biomass; and the biochar scenario could abate 271 – 792 kg CO2-eq per t biomass. Ranges vary according to the type of feedstock assessed and the type of fossil fuel (coal or natural gas) displaced. The assessment of the HO and CHP systems giving greater GHG emission reductions than the biochar system can be misleading as these only involve fossil-fuel offsetting whereas the biochar system would sequester some carbon irrespective of the other activities assumed to be displaced. The biochar carbon stability factor is the key component that affects its capacity to mitigate climate change. A distinctive C accounting, reporting and crediting approach should be developed for biochar to have high economic potential in carbon-pricing mechanisms. Several approaches for incentivising biochar carbon sequestration were explored. These include using conservative carbon-accounting estimates, issuing temporary credits, establishing buffer funds, creating carbon credit multipliers, and inventing a new unit such as ppm CO2 reductions for recognising atmospheric CO2 removals as opposed to avoiding GHG emissions. While biochar technology is currently facing numerous barriers for acceptance in carbon markets, its future is promising since biochar production also offers potential in the agriculture, energy and waste management sectors.Item Design and characterisation of an 'open source' pyrolyser for biochar production : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Chemical and Bioprocess Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2013) Bridges, RhondaAn 'open source' field-scale batch pyrolyser was designed and constructed to produce biochar, which is the solid residue formed when biomass thermally decomposes in the absence of oxygen. The design approach was focused on simplicity for the intended target user, a hobby farmer. This is achieved in a batch process, where temperature ramp rates, gas flows and the end-point are controlled. Solids handling is only required at either end of the process. LPG is used as the initial heating source and later as the ignition source when pyrolysis gases are recycled. A mathematical model formulation of the process was developed to predict the proportions of products produced as well as the time taken to achieve complete pyrolysis. Reaction kinetics are complex and not fully understood. In this model, simplifications were taken to provide guidelines for the reactor design as well as the effects of moisture on the process efficiencies. The quality performance of the 'open source' pyrolyser was determined by comparing its biochar to that produced in a lab scale gas fired drum pyrolyser. Parameters varied on the lab drum pyrolyser were highest treatment temperature in the range 300 to 700 °C, sample size, moisture content and grain direction for Pinus radiata. The properties that were investigated are elemental composition (C, H, N, S), proximate analysis (moisture, volatile matter and fixed carbon) and char yield (% wt/wt). The ash content was determined by residue on ignition. For the lab scale experiments, it was found with increasing peak temperature that yield, volatile matter and hydrogen to carbon ratio decrease. Yield was unaffected by moisture, size and grain direction. The design of the pilot reactor followed the principle observed with particle size that, in order to get maximum residence time of the vapour and tar in the reactor, the reactor was designed with a perforated core so that the vapours have a tortuous path of travel. This design also meant that heat and mass transfer occurred in the same direction, from the outer wall to the perforated core. In comparison to the lab scale pyrolyser, the same trends were observed in regards to temperature. High yields of 29.7 wt % and 28.8 wt % were obtained from wood with an initial moisture content of 21.9 wt % and 60.4 wt % respectively, confirming yield is unaffected by moisture. Mass and energy balances were conducted on both the lab scale and pilot scale pyrolysers. For every kilogram of carbon in LPG used on the lab scale pyrolyser, an average of 0.25 kilograms of carbon is produced at 700 °C. Based on the optimum run for the pilot scale, for every kilogram of carbon in LPG used, 2.6 kilograms of carbon is produced at 700 °C.