Teruhito Miyamoto

INFLUENCE OF SUGARCANE BAGASSE-DERIVED BIOCHAR APPLICATION ON NITRATE LEACHING IN CALCARIC DARK RED SOIL

Application of biochar has been suggested to improve water- and fertilizer-retaining capacity of agricultural soil. The objective of this study was to evaluate the effects of bagasse charcoal (sugarcane [ L.] bagasse-derived biochar) on nitrate (NO) leaching from Shimajiri Maji soil, which has low water- and fertilizer-retaining capacity. The nitrate adsorption properties of bagasse charcoal formed at five pyrolysis temperatures (400-800° C) were investigated to select the most suitable bagasse charcoal for NO adsorption. Nitrate was able to adsorb onto the bagasse charcoal formed at pyrolysis temperatures of 700 to 800° C. Nitrate adsorption by bagasse charcoal (formed at 800° C) that passed through a 2-mm sieve was in a state of nonequilibrium even at 20 h after the addition of 20 mg N L KNO solution. Measurements suggested that the saturated and unsaturated hydraulic conductivity of bagasse charcoal (800° C)-amended soils are affected by changes in soil tortuosity and porosity and the presence of meso- and micropores in the bagasse charcoal, which did not contribute to soil water transfer. In NO leaching studies using bagasse charcoal (800° C)-amended soils with different charcoal contents (0-10% [w/w]), the maximum concentration of NO in effluents from bagasse charcoal-amended soil columns was approximately 5% less than that from a nonamended soil column because of NO adsorption by bagasse charcoal (800° C). We conclude that application of bagasse charcoal (800°C) to the soil will increase the residence time of NO in the root zone of crops and provide greater opportunity for crops to absorb NO.

Estimation of net carbon sequestration potential with farmland application of bagasse charcoal: Life cycle inventory analysis through a pilot sugarcane bagasse carbonisation plant

Enriching soil carbon storage is regarded as a viable option for mitigating greenhouse gas (GHG) emissions in the agricultural sector. Carbon sequestration by applying biomass into the soil can be an effective sequestration pathway for agriculture. Biochar, charcoal produced from biomass pyrolysis, is highly stable against microbial decomposition, and applying this to farmland has the potential to mitigate GHG emissions. However, CO2 is emitted throughout the biochar life cycle, including pyrolysis, transportation, and farmland application. Therefore, estimating the net carbon sequestration potential by considering these CO2 emissions is important. To this end, operational data from a pilot sugarcane bagasse carbonisation plant were collected, and the net carbon sequestration potential with farmland application of bagasse charcoal was calculated using inventory data from the pilot plant. The results were as follows: (i) kerosene consumption during the carbonisation process was the greatest contributor to CO2 emissions within the life cycle of applying bagasse charcoal to farmland; (ii) the initial dryness of the feedstock was an important factor in estimating net carbon sequestration potentials; (iii) the CO2 mitigation potential with farmland application of bagasse charcoal on Miyako Island would be 1200–1800 t CO2/year.

Influences of feedstock and pyrolysis temperature on the nitrate adsorption of biochar

ABSTRACT Biochar (BC), charcoal produced through the pyrolysis of biomass, is reported to adsorb dissolved nitrate-nitrogen (NO3-N). The NO3-N adsorption properties of BC differ depending on the feedstock and the pyrolysis conditions, and the influences have not been systematically clarified. Therefore, we evaluated the dependence of feedstock and pyrolysis temperature on the NO3-N adsorption properties of BC. Wood chips [Japanese cedar [Cryptomeria japonica] (CE) and Japanese cypress [Chamaecyparis obtusa] (CY)], moso bamboo [Phyllostachys edulis] chips (MB), rice [Oryza sativa] husks (RH), sugarcane [Saccharum officinarum] bagasse (SB), poultry manure (PM) and domestic wastewater sludge (WS) were air-dried and heated in a batch-type carbonization furnace at pyrolysis temperatures of 400, 600 and 800°C, with a hold time of 2 h. Among the BC produced from each feedstock, the one produced at 800°C had the greatest NO3-N adsorption. The NO3-N adsorption by BC produced from wood-based biomass at 800°C was significantly higher than that of the BC produced from non-wood-based biomass at 800°C. Therefore, BC made from wood-based biomass at higher temperature can be adequate as soil amendment material for adsorption of NO3-N.

Effects of Biochar Produced From Sugarcane Bagasse at Different Pyrolysis Temperatures on Water Retention of a Calcaric Dark Red Soil

Abstract Biochar (BC) is a promising soil amendment that can enhance water retention and plant-available water capacity while mitigating CO2 emissions. We investigated the effect of sugarcane bagasse–derived BC on the water retention properties of a calcaric clay soil amended with 3% (wt/wt) BC produced at three pyrolysis temperatures (400°C, 600°C, and 800°C). For BC pyrolyzed at 800°C (BC800), water retention curves of soil amended at 1%, 5%, and 10% (wt/wt) were also measured. Water retention curves were measured immediately after amending soil with BC (all types and rates) and after a 180-day incubation period for soils amended with 3% BC. The hydrophobicity of BC pyrolyzed at 400°C (B400) was the highest of the three temperatures tested, resulting in the lowest water retained in soil amended with BC400, but only for measurements done before incubation. During incubation, the hydrophobicity of B400 decreased as the aliphatic compounds became exhausted by oxidation of the BC surfaces. The available water capacity of the clay soil increased significantly by more than 60% when amended with BC at rates greater than of 3% wt/wt (P < 0.05).

Evaluation of strips of centipede grass for sediment load reduction

Reddish sediment runoff from agricultural fields results in coastal environmental problems in Okinawa, Japan. Recent studies have demonstrated the effectiveness of strips of centipede grass (Eremochloa ophiuroides (Munro) Hack.), a perennial turf grass, in reducing the sediment loads from farmlands. However, sufficient information has not been provided to determine the appropriate strip specifications in the grass strip design. This study evaluated centipede grass strips for reduction of reddish sediment runoff from farmlands in Okinawa, Japan. A numerical model simulating the reddish sediment transport in the grass strip was constructed to determine the sediment removal efficiency of the strip. The model was verified using data obtained from field plot experiments with the grass strips under natural conditions. The sensitivity analysis of the model showed that the length of the grass strip (i.e. the dimension of the strip in the direction of flow) and unit inflow discharge have a great effect on sediment removal efficiency. The sediment removal efficiency obtained from the model simulation increased with the length of the strip and the increment of the efficiency decreased with the length of the strip. Therefore, these results indicate that the effective and efficient length of a centipede grass strip is 3 m for the reduction of reddish sediment loads under typical farmland conditions in Okinawa.

Effect of sensor installation on the accurate measurement of soil water content: Effects of sensor installation on soil water measurement

&NA; We evaluated the effects of different methods of installing a capacitance soil moisture sensor on the sensors output with six soil types and three methods of sensor installation. For Method 1, the sensor was first placed in a container and then buried. For Method 2, the entire sensor (including prongs and circuitry) was inserted into a prepacked soil sample. For Method 3, the sensor prongs were installed directly into a prepacked soil sample, and then soil was placed around the circuitry. The sensor outputs of Method 1 were significantly smaller for the volumetric soil water content (&thgr;) of most of the soil types compared with the sensor outputs of the other two methods. Large differences in sensor outputs were observed in relation to the installation method, which resulted in a large estimation error when using a soil moisture sensor. For example, the difference in &thgr; values calculated by the calibration equation obtained by Methods 1 and 2 was 0.076 m3 m−3, a maximum for the Andisol sample. We observed a significant linear relation between the maximum differences in &thgr; (which might result from the different sensor installation methods) and the coarse pore volume determined from soil water characteristic curves. Compaction around the sensor induced by sensor installation, which might be considerable for soil with many coarse pores, was considered the main reason for an increase in the soil moisture sensors output value. For the sensor installed by Methods 2 or 3, a second‐order polynomial equation could be used to translate sensor output to &thgr; accurately except for soils with > 40% clay content or very low bulk density. HighlightsAn appropriate calibration equation is important to monitor soil water content precisely.Effects of different sensor installation methods on calibration equations have not been determined.Method of installation considerably affected output values of a capacitance sensor.Soil compaction by sensor installation increases the sensor output: more so in coarse pore soil.