Application of biochar from vine shoots (Vitis vinifera L.) as an organic amendment in the soil is an alternative agricultural management of interest. The behavior of this type of amendment in the soil requires more information to adjust the pyrolysis conditions in order to obtain a high-quality biochar. The aim of this work is determining the influence of the application of this type of biochar on the soil-plant system. For this purpose, an agronomic test was performed in greenhouse pots. A randomized tri-factorial block design was adopted with the following factors: final pyrolysis temperature (400 and 600 °C), application rate (0 wt. % as a control, 1.5 and 3 wt. %) and texture of the growing media (sandy-loam and clay-loam origin). The selected crop was sorghum (Sorghum bicolor L. Moench), the development and production of which was evaluated during two complete growing cycles under greenhouse conditions. Application of biochar produced at 400 °C significantly increased plants roots dry weight in the sandy-loam growing substrate (52% compared to the control). Grain production was also significantly affected by biochar application, showing better results after addition of biochar produced at 400 °C. Water holding capacity and K, Ca, and Mg contents were enhanced by biochar addition, with evident effects of the application ratios for some of these variables. The effect on the pH of substrates in the sandy-loam texture was weak; however, a significant decrease was observed after the addition of biochar produced at 600 °C.

HIGHLIGHTS Higher pressure led to higher devolatilization rates in a narrower period of time  Using a mixture of CO2 and N2 at 0.1 MPa favored the thermal cracking of volatiles  Under CO2/N2 an increased pressure led to a decrease in the yields of CO and CH4 Biochar produced at 0.1 MPa under CO2/N2 had the highest specific surface area ABSTRACT In the present study, the effects of the absolute pressure (0.1 or 0.5 MPa) and the reactor atmosphere (pure N2 or a mixture of CO2/N2) on the pyrolysis behavior of wheat straw pellets (at 500 °C) were investigated. The most interesting aspect of this work was the use of a weighing platform (with a maximum capacity of 100 kg and a resolution of 0.5 g) to monitor the real-time mass-loss data for the biomass sample (with an initial mass of 400 g). It was observed that an increased pressure considerably affects the mass-loss profiles during the pyrolysis process, leading to higher devolatilization rates in a shorter period of time. Regardless of the pyrolysis atmosphere, an increase in the absolute pressure led to higher yields of gas at the expense of produced water and condensable organic compounds. This finding could be due to the fact that an increased pressure favors the exothermic secondary reactions of the intermediate volatile organic compounds in both liquid and vapor phases. The switch from pure N2 to a mixture of CO2 and N2 at 0.1 MPa also led to a remarkable increase in the yield of produced gas at the expense of the total liquid. This could be mainly due to the promotion of the thermal cracking of the volatile organic compounds at a high partial pressure of CO2, which is also consistent with the measured higher yields of CH4 and CO. The increased yield of CO can also be seen as a direct result of the enhanced reverse Boudouard reaction, which can also explain the much higher specific surface area (and ultra-micropore volume) measured for the biochar produced under the same operating conditions (0.1 MPa and a mixture CO2/N2 as pyrolysis medium).3

No abstract

No abstract

The combustion performance of chars derived from vine shoots, wheat straw, and corn stover was investigated to assess the influence of both the biomass precursor and pyrolysis operating conditions. Chars were produced through slow pyrolysis at different peak temperatures (350 and 500 °C), pressures (0.1 and 0.5 MPa), and residence times of the vapor phase (50 and 150 s). From the thermogravimetric curves obtained under air, the combustion performance index ( S ) was calculated for each char. Apparent kinetics were also estimated using the Coats–Redfern method and assuming an F3/2 reaction model. Results show that the combustion patterns of chars were more influenced by the type of feedstock than by the pyrolysis conditions. Corn stover appeared to be the most interesting feedstock in order to produce chars with tuned reactivity. Results from partial least-squares (PLS) regression revealed that the most important factors affecting S were the contents of potassium (negative effect) and cellulose (positive effect) in the original biomass.

Combine harvesters are an important cause of fires worldwide. The purpose of this work has been to investigate the critical points associated with the risk of fire, identified through a survey distributed to combine owners in Aragon (Spain). Information was collected on the technical characteristics of the machines and, when appropriate, on the characteristics of the generated fires (crop, use of straw chopper, point in which the fire was originated, etc.). Based on the survey data, relationships between the characteristics of the machine and the ignition of a fire were analyzed, and the points of the harvester in which the fire originated were investigated. A statistically significant relationship of fire risk was only found with the number of hectares harvested, in such a way that the risk would be especially high for machines with more than 6000 accumulated ha. 32% of the fires were originated in the engine zone, compared with 31% in the cutting bar and 18% in the bearings and belts. The study was completed with on-site temperature measurements carried out on nine machines in 2018 and 2019, in which temperatures above 250 • C were recorded in the exhaust manifold and in the cutting bar. These temperatures exceeded the ignition thresholds obtained in the flammability studies conducted for wheat residues collected from the harvesters.Agronomy 2019, 9, 877 2 of 13 can be analyzed for the different regions. In the case of Aragon, there were 226 and 357 forest fires in 2018 and 2019, which affected a total surface of 215 and 1291 ha, respectively. The second most important cause of those fires, after negligence, was associated with agricultural machinery (including harvesters), which accounted for 8.8% of the fires that occurred in 2018 and 9.2% of those that took place in 2019.The possible causes of fire ignition in agricultural machines and specifically in harvesters are very varied. Quick [5] lists a number of potential points in which fire can start: engine and flue gas outlets, transmissions, bearings, brakes, electrical short-circuits, impact of mowing heads with stones or other elements, and introduction of foreign bodies into the machine. Of all of them, the most common cause is the accumulation of combustible material in points with high temperatures located near the engine. The surface temperatures of these elements can reach 500 • C [5], exceeding the ignition temperatures of the crop residues, which vary depending on the thickness of the sample, but which are generally above 200 • C in the case of wheat straw [6]. As for the spread of the fire, field conditions can favor or hinder the process, which would be influenced by four main factors: relative humidity, ambient temperature, wind speed, type and condition of the crop [5,7].Despite the importance of the consequences of agricultural and forest fires, there are hardly any studies focused on the causes of fires in combine harvesters. So far, the most important studies have been those carried out in the USA by Shutske et al. [8,9], in which the authors ...

The effects of biochar on soil–plant–microorganisms systems are currently being extensively investigated. Considering that arbuscular mycorrhizal fungi (AMF) play an essential role in nutrient dynamics, the present study aims at understanding vine shoot-derived biochar effects on AMF activity and the impact of their multiplication in soils on water-stress resistance of plants. Three agronomic tests were performed in greenhouse pots. The first experiment evaluated the effects of three factors: final pyrolysis temperature for biochar production (400 °C and 600 °C), application rate (0 weight-wt.- % as a control, 1.5 wt. %, and 3.0 wt. %) and texture of the growing media (sandy-loam and clay-loam origin) on AMF, microbial communities and phosphatase activity. In the second experiment, an indigenous consortium of AMF was multiplied through the solid substrate method and sorghum as a trap plant with biochar addition. This process was compared to a control treatment without biochar. Obtained inocula were tested in a third experiment with lettuce plants under different water irrigation conditions. Results from the first experiment showed a general increase in AMF activity with the addition of the biochar produced at 400 °C in the sandy-loam texture substrate. Results of the second experiment showed that the biochar addition increased AMF root colonization, the number of AMF spores and AMF infective potential. Results of the third experiment showed that biochar-derived AMF inoculum increased AMF root colonization, AMF spores, dry biomass and the SPAD index in a lettuce crop under low-water irrigation conditions.

Nine wheat straw-derived biochars were produced under different pyrolysis conditions (i.e. peak temperature, absolute pressure, and pyrolysis atmosphere) and subsequentially activated with CO2 at 800 °C in order to study the influence of the pyrolysis operating conditions on the textural properties of the resulting activated biochars.