Karin Granström

Emissions of hexanal and terpenes during storage of solid wood fuels

The purpose of this study was to investigate emissions during storage of solid wood fuels by measuring both the emission of monoterpenes and the formation of aldehydes during storage of undried saw...

A Method to Measure Emissions from Dryers with Diffuse Leakages 2—Sensitivity Studies

ABSTRACT Measurements of VOC emissions from dryers have several known difficulties. An earlier published method to measure emissions of VOC from dryers deals with problems associated with diffuse emissions and high moisture content of the drying medium. [1] In this article, a different calculation path are used and the influence of the main parameters are studied in more depth. For one experiment, confidence intervals for all of the parameters are calculated. Experimentally induced uncertainties are found to be more important than a theoretically important parameter. Suggestions are made on how to increase accuracy.

Volatile organic compounds emitted from hardwood drying as a function of processing parameters

During the drying of wood, volatile organic compounds are emitted. These emissions contribute, in the presence of nitrogen oxides and sunlight, to the formation of ground level ozone and other harmful photo-oxidants. Emissions of volatile organic compounds from the drying of birch sawdust in a spouted bed were analyzed with a flame ionization detector and with a gas chromatograph-mass spectrometer. A D-optimal model of the emissions showed that the emissions increased exponentially with decreasing sawdust moisture content and that the final sawdust moisture content was influencing emissions about twice as much as the inlet drying medium temperature and the month of logging. At inlet temperatures of 140–170 °C, the emissions increased steeply when the moisture content of the sawdust reached 10%, whereas an inlet temperature of 200 °C caused a surge of thermal degradation products at 15% moisture content. The results of this study should help to reduce the emissions of volatile hydrocarbons during the drying of hardwood sawdust and wood chips.

Wood processing as a source of terpene emissions compared to natural sources

The aim of this paper is to analyse the importance of terpene emissions from forestry and the wood industry and relate these anthropogenic emissions to the natural terpene emissions from undisturbed forests. Biogenic volatile organic compounds are emitted naturally from trees and other plants. Boreal forests are dominated by terpene-emitting tree species. Anthropogenic terpene emissions occur due to drying, machining and tooling of wood. This is a cause of concern with regulatory authorities faced with expanding production of biofuels, e.g. wood pellets. Anthropogenic terpene emissions are of current importance as the use of biofuels has increased considerably over the recent years. The most important environmental effects of terpene emissions are due to the formation of photo-oxidants and atmospheric aerosols. Photo-oxidants cause forest and crop damage, and are harmful to humans. Carbonaceous aerosols have an impact on climate change. Furthermore, most sesquiterpenes are used in the chemical communication systems of various insects. There are also issues concerning the working environment in the wood industry. Environmental effects of terpene emissions are analysed with focus on three key aspects: the total amount of emissions, the concentration in air and the types of terpenes emitted. The reported concentrations of monoterpenes are in most cases below the occupational exposure limits, with drum barking and pellets production from non-dried sawdust close to the limit. Anthropogenically emitted terpenes have a higher proportion of sesquiterpenes than naturally emitted terpenes have,

A method to measure emissions from dryers with diffuse leakages, using evaporated water as a tracer

Abstract This paper describes a novel method to measure emission from dryers. The method resolves the known difficulties caused by diffuse emissions, and also solves the problems associated with high moisture content of the drying medium. The basic idea is to use water vapor to determine the exhaust flow, while a dry ice trap is used both to preconcentrate emitted VOCs and to determine the moisture content of the drying medium.

Underestimation of Terpene Exposure in the Nordic Wood Industry

This study determined that emission of sesquiterpenes from processed wood warrants attention in the work environment. Currently, only the monoterpenes in the terpene group are monitored in occupational hygiene studies. Terpene emissions are a work environment issue for industries that process wood, as they are known to cause respiratory difficulties and mucous membrane irritation. Fresh sawdust of the most common boreal conifers, Norway spruce (Picea abies) and Scots pine (Pinus sylvestris), was subjected to processing (drying), and the emissions were analyzed with a gas chromatograph-mass spectrometer. The data indicate that workers are exposed to significant amounts of sesquiterpenes, an observation that has not been recorded previously at wood processing plants. On average, the proportion of sesquiterpenes to monoterpenes was 21 ± 5% (STD, n = 11) for spruce and 15 ± 5% (STD, n = 13) for pine. The composition of terpenes emitted in air from spruce wood differs from the composition in resin. The sum of monoterpenes and sesquiterpenes can exceed the occupational exposure limit for turpentine for processes where monoterpene concentrations are already close to the occupational exposure limit, and for processes involving the processing of bark. Findings suggest that future studies of health effects from terpenes in air should measure monoterpenes and sesquiterpenes to assess whether the current OELs are appropriate.

Co-digestion of manure with grass silage and pulp and paper mill sludge using nutrient additions

ABSTRACT There is an increasing worldwide demand for biogas. Anaerobic co-digestion involves the treatment of different substrates with the aim of improving the production of biogas and the stability of the process. This study evaluates how methane production is affected by the co-digestion of pig and dairy manure with grass silage and pulp and paper mill sludge and assesses whether methane production is affected by factors other than nutrient deficiency, low buffering capacity, inadequate dilution, and an insufficient activity and amount of microorganism culture. Anaerobic digestion was performed in batch reactors under mesophilic conditions for 20 days. The season of grass silage and manure collection proved to be an important factor affecting methane production. Spring grass silage produced a maximum of 250 mL/VSadded and spring manure 150 mL/VSadded, whereas autumn grass silage produced at most 140 ml/VSadded and autumn manure 45 mL/VSadded. The pulp mill sludge used is comprised of both primary and secondary sludge and produced at most 50 mL/VSadded regardless of season; this substrate benefitted most from co-digestion.

Emissions from sawdust in packed moving bed dryers and subsequent pellet production

ABSTRACT This study quantifies emissions of hydrocarbon terpenes from the drying of sawdust in packed moving bed dryers, through the production chain to the finished pellets, and determines the parameters suitable for emission control. The terpene content in softwood sawdust and pellets was analyzed using gas chromatography. The distribution of VOC emissions over the bed was measured with a flame ionization detector. After drying, 30–40% of the initial terpenes remain in the wood, 20–30% remain after grinding, and 10–15% remain after pelleting. Dryer emissions correlate with residence time and final sawdust moisture content. Pellet press emissions correlate with pellet moisture content.

Low Dosage Chemical Treatment for Improved Oxygenation of Pulp Mill Effluents

AbstractMost pulp and paper mills use aerobic biological treatment for their effluents. Aeration is the single most energy intensive process of a treatment plant. Surfactants, commonly occurring in...

Characterization of Wood-Dryer Condensate with Assessment of Toxicity to Microorganisms

Drying of wood causes airborne emissions that can be reduced by recirculating all or part of the drying medium. This favors both emission control and energy efficiency, but results in a condensate ...