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Aerobic respirometry, which involves measuring the carbon dioxide (CO 2) evolved during decomposition, is an invaluable metric for evaluating biomass decomposability, characterising compost feedstocks, and studying decomposition dynamics over time. However, respirometric systems and CO 2 sampling methods can be expensive, operationally cumbersome, and produce temporally low-resolution data. This paper details the technical development and validation of an automated, multi-vessel respirometric system using off-the-shelf microcontrollers and miniature non-dispersive infrared (NDIR) CO 2 sensors to produce temporally high-resolution and accurate CO 2 data generated from decomposing biomass. The accuracy of the NDIR CO 2 sensors, as given by the cumulative CO 2 (g), was validated through an acetic acid-sodium bicarbonate reaction test. In this test, a mean cumulative CO 2 evolution of 0.99 g (n = 8) was measured with the sensors from an expected stoichiometric yield of 1 g CO 2 , with a standard deviation of ±0.137 g. The operation, reliability, and reproducibility of the system were tested through a series of biomass decomposition experiments. Through these experiments, an airflow rate of 0.25 L min−1 was found to be most effective at preventing the excessive drying of biomass at an initial moisture content of 50%. The system sensed, per 5-s sampling event, a peak CO 2 concentration of ∼28,000 ppm at a temperature of 35 °C, which resulted in the largest mean cumulative CO 2 evolution of 27.93 g from 200 g dry biomass. As indicated by the CO 2 curves, the system can produce reliable and high-resolution CO 2 datasets on an individual vessel basis, making it a useful tool for respirometric studies. • An aerobic respirometric system with high-resolution CO 2 sampling was developed. • The reproducibility of the data in organic matter decomposition trials was high. • Accuracy of the CO 2 sensors was shown through acetic acid-sodium bicarbonate test. • The system produced reliable CO 2 data for aerobic decomposition of organic waste. [ABSTRACT FROM AUTHOR]

Agricultural tractors may idle from 10 to 43% of their entire operating life and this inoperative time must be minimised because it is detrimental to the environment, public health, fuel economy, and engine lifespan (Perozzi et al., 2016). On passenger cars, start and stop (SS) systems have been extensively used, but they are not currently installed in any commercial tractor. Studies show that for very short idling stops SS systems might be ineffective for the additional energy required for re-starting the engine. This study aims to investigate the potential advantages of SS systems on agricultural tractors. To this aim, the energy required for engine start-up and the subsequent emissions were measured and then compared with the energy and the emissions during idling. Moreover, a predefined control strategy of the SS system was developed, and its potential fuel and emission savings were estimated using real-world data. In terms of fuel consumption and CO emission, turning off the engine is recommended for stops longer than 4 s and 134 s, respectively. From the collected real-world data, the tractor was run on idle for 21.7% of the entire operating duration. The results obtained with the SS control strategy developed in this paper applied to the US area, where there are 1.2 million tractors of the same power level of the tractor used in this study with a yearly usage up to 850 h, would permit to save 285.6 million litres of fuel, and, respectively of 16.5 and 754 tons of CO and CO 2. • Turning off the engine for idling stops longer than 4 s leads to fuel savings. • Turning off the engine for idling stops longer than 134 s leads to CO savings. • 45% of idling time could be avoided by farmers. • Start and Stop systems are an effective way for saving fuel and emissions. [ABSTRACT FROM AUTHOR]

Greenhouses constitute a proven solution for coping with environmental degradation and for increasing both the quantity and quality of agricultural products. Appropriate carbon dioxide (CO 2 ) control not only improves crop yield and quality but also reduces the carbon footprint of greenhouses. However, CO 2 enrichment control in greenhouses is a dynamic, interactive and time-delayed process. In practice, optimal CO 2 concentrations in the greenhouse are difficult to maintain because CO 2 is confounded with temperature, humidity, light intensity, etc.; therefore, ambient CO 2 concentrations in greenhouses are often suboptimal or excessive. This paper is a review of the current theoretical and applied studies of CO 2 enrichment in greenhouses and discusses the advantages and limitations of various methods. The major points addressed are as follows: 1) the five sources of CO 2 enrichment in greenhouses; 2) the monitoring and data processing of CO 2 concentrations; and 3) the various methods for controlling automatic CO 2 enrichment. This paper discusses new challenges and perspectives and suggests future studies and methods for a greenhouse CO 2 enrichment system. A new symbiotic greenhouse system requiring sensible CO 2 balance is also presented. Highlights • Different sources of carbon dioxide (CO 2 ) for greenhouse enrichment are discussed. • Control strategies for greenhouse CO 2 enrichment are reviewed. • Research Challenges of CO 2 control in the greenhouse are presented. • A new symbiosis greenhouse system requiring sensible CO 2 balance is described. [ABSTRACT FROM AUTHOR]

In modified atmosphere packaging (MAP), the transpiration of the fresh product and exchange of water through the polymeric packaging are often not properly considered. This paper presents a mathematical model to describe the evolution in water vapour, O 2 and CO 2 concentrations in the packaging headspace, the weight loss of the product and the condensation of water in a MAP system with perforations. Transpiration was considered as the sum of water transferred out from the product due to the gain of energy from its respiration process and the difference in water activities between the product and the surrounding atmosphere. Respiration was represented using Michaelis–Menten enzyme kinetics. The gas transfer through the packaging and the perforations was described with Fick equations. The temperature influence on these processes was considered to follow the Arrhenius' law. To experimentally determine the model parameters, feijoa fruits ( Acca sellowiana Berg) were stored under different storage conditions: packaging type, relative humidity and temperature. The completed model was subsequently validated in a MAP test by packaging fruits in perforated polypropylene (PP) and polylactic acid (PLA) bags for 13 days at 12 °C and 75% RH. Inside the PP bags, a saturated atmosphere (100% RH) was reached and 1.48% of the initial weight in the packed fruit was lost by day 13, while in the PLA bags, an equilibrium RH of 83% and a fruit weight loss of 3.29% were measured. The prediction capacity of the model was satisfactory, with coefficients of determination (R 2 ) between 0.88 and 0.99 for the different tests. [ABSTRACT FROM AUTHOR]

Livestock production is a source of numerous environmental problems caused by pollutant gas emissions. In naturally ventilated buildings, estimating air flow rate is complicated due to changing climatic conditions and the difficulties in identifying inlets and outlets. To date no undisputed reference measurement method has been identified. The objective of this paper was to compare CO 2 - and SF 6 -based tracer gas methods for the estimation of ventilation rates ( V R C O 2 vs. V R S F 6 ) in naturally ventilated dairy barns both under conventional and very open ventilation situations with different spatial sampling strategies. Measurements were carried out in a commercial dairy barn, equipped with an injection system for the controlled release of SF 6 , and measurement points for the monitoring of SF 6 and CO 2 concentrations to consider both horizontal and vertical variability. Methods were compared by analysing daily mean V R C O 2 / V R S F 6 ratios. Using the average gas concentration over the barn length led to more accurate ventilation rates than using one single point in the middle of the barn. For conventional ventilation situations, measurements in the ridge seem to be more representative of the barn average than in the middle axis. For more open situations, both V R C O 2 and V R S F 6 were increased, V R C O 2 / V R S F 6 ratios being also more variable. Generally, both methods for the estimation of ventilation rates gave similar results, being 10–12% lower with the CO 2 mass balance method compared to SF 6 based measurements. The difference might be attributed to potential bias in both methods. [ABSTRACT FROM AUTHOR]

Adaptation of a greenhouse climate management strategy to local climate conditions is important for the improvement of resource use efficiency of greenhouse crop production. In this paper the optimal greenhouse climate management under hot, humid, subtropical summer conditions was investigated through simulation analysis based on the Greenhouse Process (KASPRO) model, previously validated under this particular conditions. The study was limited to affordable means of greenhouse design, crop and climate management such as ventilation capacity, canopy size and whitewashing, in a greenhouse without injection of carbon dioxide. Obviously, the increase of greenhouse ventilation capacity leads to an increase of carbon dioxide concentration in the greenhouse air, canopy transpiration, and thus evaporative cooling of the greenhouse air and crop canopy, and in turn to an increase of crop biomass production. The results show, however, that there is a rather sharp ceiling beyond which there is little gain in increasing ventilation capacity. For a cucumber crop under the summer conditions typical of Shanghai, the ventilation capacity of the greenhouse should be about 40 volume changes per hour. The balance of assimilation, respiration and evaporative cooling ensure that crop biomass production is maximal at a canopy leaf area index of 4. [Copyright &y& Elsevier]

Present municipal solid waste landfills generate biogas and leachate. Biogas is flared on site to destroy noxious contaminants and water is extracted from leachate to be drained away. However, biogas could alternatively be a cheap fuel for winter heating and could provide horticultural greenhouses with abundant carbon dioxide to boost plant growth all year long. The paper describes how this idea was tested in a full-scale experiment through a partnership between French Institut National de la Recherche Agronomique (INRA) and a pool of private industries. A commercial boiler was converted to biogas and combustion exhaust gases rich in carbon dioxide were purified to remove phytotoxic residues. A CO2 supplementation technique using these purified exhaust gases was tested. Two soilless rose crops were grown under two identical 300 m2 plastic greenhouses, one equipped with exhaust gas injection and the other one, kept under normal atmosphere, being the control. Crop yields and cut rose quality were compared during 24 months. It was found that the high crop productivity gains allowed by exhaust gas injection bring the major contribution to greenhouse economics, much more important than the reduction of heating costs brought by burning biogas. This underlines the potential for new efficient horticultural greenhouses locating near modern landfill sites in France and elsewhere in developed countries. [Copyright &y& Elsevier]