Influence of Temperature Fields on the Quality of Dried Wood Products

The reasons of white spots appearance in the middle of oak timber are determined. These white spots reduce the cost of the lamina made of oak timbers - the front covering of floorboards. It is proposed to intensify the drying process by using oscillating drying schedules to avoid this defect. A method for calculating the duration of such drying is proposed. This method includes the peculiarities of heating and cooling periods kinetics of oak timbers with 25 mm and 30 mm thickness. The inexpediency of using the oscillation of the drying agent parameters in the range of wood moisture content below 20% has been established. An adequate model for calculating wood temperature and air humidity during wood heating and cooling periods has been developed using heat and mass transfer criteria and experimentally determined oak wood moisture conductivity coefficient. Based on the results of theoretical and experimental studies oscillating drying schedules of different thickness oak timbers are offered. Tests of the proposed schedules in industrial conditions showed no discoloration of the central layers of European oak (Quercus robur) timbers. The drying process duration was reduced by 1.5–2.4 times and energy consumption were reduced by 1.53 times.

Research activation energy in thermal modification of wood

The analysis of the process of thermal modification of wood, which was modified by a controlled process of pyrolysis of wood heating (> 180 ° C) in the absence of oxygen, which causes some chemical changes in the chemical structures of cell wall components (lignin, cellulose and hemicellulose), durability. It is proved that in the process of thermal modification the decomposition of hemicelluloses and the amorphous part of cellulose occurs, and therefore the amount of substances that are the environment for the development of fungi in wood significantly decreases. In addition, lignin and the formed pseudolignin undergo a process of polymerization and redistribution of cell volume and give cell walls greater density, hardness, increase hydrophobicity (water repellency), thereby reducing their ability to absorb moisture and edema. Polymerized lignin fills the inner cavity of the cell, forming a closed porous structure with a low ability to bind water. It was found that the most effective parameter for reducing such substances is the temperature and exposure time. The results of thermogravimetric researches are given, the dependence of weight loss on temperature of researches on the basis of which activation energy is calculated is defined. The results of determining the activation energy show that for hardwood species this value exceeds more than 1.5 times compared to softwood.

Exposure to household air pollution over 10 years is related to asthma and lung function decline

The question addressed by the studyAre long-term Household Air Pollutions (HAPs) associated with asthma and lung function decline in middle-aged adults, and whether these associations were modified by GST gene variants, ventilation and atopy.Materials and MethodsProspective data on HAPs (heating, cooking, mould, smoking) and asthma were collected in the Tasmanian Longitudinal Health Study (TAHS) at mean ages 43 and 53 years (n=3314). Subsamples had data on lung function (n=897) and GST gene polymorphisms (n=928). Latent class analysis was used to characterise longitudinal patterns of exposure. Regression models assessed associations and interactions.ResultsWe identified seven longitudinal HAP profiles. Of these, 3 were associated with persistent asthma, greater lung function decline and %reversibility by age 53 years, compared to “least exposed” profile, for who used reverse cycle air conditioning, electric cooking and without smoking. “All gas”(OR:2.64, 95%CI 1.22–5.70), “wood heating/smoking” (2.71, 1.21–6.05) and “wood heating/gas cooking” (2.60, 1.11–6.11) were associated with persistent asthma, greater lung function decline and %reversibility. Participants with GSTP1 Ile/Ile genotypes were at a higher risk of asthma or greater lung function decline when exposed compared to other genotypes. Exhaust fan use and opening windows frequently could reduce the adverse effects of HAP produced by combustion heating and cooking on current asthma presumably through increasing ventilation.Answer to the questionExposures to wood heating, gas cooking and heating, and tobacco smoke over 10 years increased the risks of persistent asthma, lung function decline and %reversibility, with evidence of interaction by GST genes and ventilation.

Accurate, Low Cost PM2.5 Measurements Demonstrate the Large Spatial Variation in Wood Smoke Pollution in Regional Australia and Improve Modeling and Estimates of Health Costs

The accuracy and utility of low-cost PM2.5 sensors was evaluated for measuring spatial variation and modeling population exposure to PM2.5 pollution from domestic wood-heating (DWH) in Armidale, a regional town in New South Wales (NSW), Australia, to obtain estimates of health costs and mortality. Eleven ‘PurpleAir’ (PA) monitors were deployed, including five located part of the time at the NSW government station (NSWGov) to derive calibration equations. Calibrated PA PM2.5 were almost identical to the NSWGov tapered element oscillating microbalance (TEOM) and Armidale Regional Council’s 2017 DustTrak measurements. Spatial variation was substantial. National air quality standards were exceeded 32 times from May–August 2018 at NSWGov and 63 times in one residential area. Wood heater use by about 50% of households increased estimated annual PM2.5 exposure by over eight micrograms per cubic meter, suggesting increased mortality of about 10% and health costs of thousands of dollars per wood heater per year. Accurate real-time community-based monitoring can improve estimates of exposure and avoid bias in estimating dose-response relationships. Efforts over the past decade to reduce wood smoke pollution proved ineffective, perhaps partly because some residents do not understand the health impacts or costs of wood-heating. Real-time Internet displays can increase awareness of DWH and bushfire pollution and encourage governments to develop effective policies to protect public health, as recommended by several recent studies in which wood smoke was identified as a major source of health-hazardous air pollution.

CO2 Efficiency Break Points for Processes Associated to Wood and Coal Transport and Heating

This paper aims to deal with CO2 emissions in energy production process in an original way, based on calculations of total specific CO2 emissions, depending on the type of fuel and the transport distance. This paper has ambition to set a break point from where it is not worthwhile to use wood as an energy carrier as the alternative to coal. The reason for our study is the social urgency of selected problem. For example, in the area of public sector decision-making, wood heating is promoted regardless of the availability within the reasonable distance. From the current state of the research, it is also clear that none of the studies compare coal and biomass fuel transportation from the point of view of CO2 production. For this purpose, an original methodology has been proposed. It is based on a modified life cycle assessment (LCA), supplemented with a system of equations. The proposed methodology has a generalizable nature, and therefore, it can be applied to different regions. However, calculation inputs and modelling are based on specific site data. Based on the presented numerical analysis, the key finding is the break point for associated processes at a distance of 1779.64 km, since when that it is better to burn brown coal than wood in terms of total CO2 emissions. We can conclude that, in some cases, it is more efficient to use coal instead of wood as fuel in terms of CO2 emissions, particularly in regard to transport distance and type of transport.

Air Quality Impacts of Smoke from Hazard Reduction Burns and Domestic Wood Heating in Western Sydney

Air quality was measured in Auburn, a western suburb of Sydney, Australia, for approximately eighteen months during 2016 and 2017. A long open-path infrared spectrometer sampled path-averaged concentrations of several gaseous species, while other pollutants such as PM 2.5 and PM 10 were sampled by a mobile air quality station. The measurement site was impacted by a number of indoor wood-heating smoke events during cold winter nights as well as some major smoke events from hazard reduction burning in the spring of 2017. In this paper we compare the atmospheric composition during these different smoke pollution events and assess the relative overall impact on air quality from domestic wood-heaters and prescribed forest fires during the campaign. No significant differences in the composition of smoke from these two sources were identified in this study. Despite the hazard reduction burning events causing worse peak pollution levels, we find that the overall exposure to air toxins was greater from domestic wood-heaters due to their higher frequency and total duration. Our results suggest that policy-makers should place a greater focus on reducing wood-smoke pollution in Sydney and on communicating the issue to the public.