Witold Stępniewski

The effect of bed properties on methane removal in an aerated biofilter--model studies.

The capacity of laboratory-scale aerated biofilters to oxidize methane was investigated. Four types of organic and mineral-organic materials were flushed with a mixture of CH(4), CO(2) and air (1:1:8 by volume) during a six-month period. The filter bed materials were as follows: (1) municipal waste compost, (2) an organic horticultural substrate, (3) a composite of expanded perlite and compost amended with zeolite, and (4) the same mixture of perlite and compost amended with bentonite. Methanotrophic capacity during the six months of the experiment reached maximum values of between 889 and 1036 gm(-2)d(-1). Batch incubation tests were carried out in order to determine the influence of methane and oxygen concentrations, as well as the addition of sewage sludge, on methanotrophic activity. Michaelis constants K(M) for CH(4) and O(2) were 4.6-14.9%, and 0.7-12.3%, respectively. Maximum methanotrophic activities V(max) were between 1.3 and 11.6 cm(3)g(-1)d(-1). The activity significantly increased when sewage sludge was added. The main conclusion is that the type of filter bed material (differing significantly in organic matter content, water-holding capacity, or gas diffusion coefficient) was not an important factor in determining methanotrophic capacity when oxygen was supplied to the biofilter.

The influence of soil oxygen availability on yield and nutrient uptake (N, P, K, Ca, Mg, Na) by winter rye (Secale cereale)

The influence of soil oxygen diffusion rate (ODR) on winter rye (Secale cereale cv Dańkowskie Nowe) growth, yield, and mineral composition was studied in the greenhouse. A range of soil ODR values was created by manipulating soil water tension and soil bulk density. The soil bulk densities used during the experiment were: 1.20, 1.35 and 1.50 Mg m-3. The soil water tensions used were 15–80 kPa (control), 2–5 kPa and 0 kPa (2–5 mm of water ponded on the soil surface). The 2–5 and 0 kPa water tensions were applied for 15 days beginning at 3 growth stages (stress I at two-three leaves, stress II at shooting, stress III at heading). Yield at full maturity decreased to as little as 30–50% of the controls when ODR dropped below 20 μg m-2 s-1. When soil hypoxia occurred early (2–3 leaves, or shooting), straw weight decreased for ODR<20 μg m-2 s-1 and root potassium content increased for ODR below 10 μg m-2 s-1. The uptake of all measured macroelements was decreased at low oxygen availability. Oxygen diffusion rates of >30 μg m-2 s-1 were needed for adequate nutrient uptake.

A Possibility to Reduce Methane Emission from Landfills by Its Oxidation in the Soil Cover

Landfills of municipal wastes are considered to be a source of total methane emission to the atmosphere estimated at 20 to 70 Tg annually which is an important contribution (6–20%) to total anthropogenic emission (about 360 Tg). Atmospheric concentration of this very radiatively active gas (about 30 times more than CO2) is increasing at a rate of approximately 1% per year. One of the possibilities to reduce the ongoing methane concentration growth in the atmosphere is the reduction of anthropogenic emission by about 10%, which corresponds to the oxidation of 3/4 of methane emitted from landfills. According to some authors the cheapest and the most feasible way of decreasing methane emission from municipal wastes is increasing the degree of methane oxidation in the landfill cover soil.

Hydraulic Conductivity and Landfill Construction

Landfills are important engineered constructions spread all over the world. Their number is calculated in thousands as the production of wastes in Europe only, reaches each year 3000 million tones of which 14% (about 415kg per capita) is municipal waste (EEA, 2004). Of this in 1999 about 57% was landfilled, 16% was incinerated, 20% recycled and composted and 7% was treated in other way. There are numerous types of landfills from simple dumping sites to rather sophisticated constructions constituting real bioreactors. Due to uncountable biochemical reactions occurring within the waste body, landfills produce biogas and leachates which threaten the pollution of air, water and soil. The environmental impact of landfills depends, to a high extent, on a bottom liner and top capping isolating the landfill from the surrounding. The quality of this isolation is determined by the water permeability as, in fact, no constructions are completely impermeable. There are two essential types of liners i.e. mineral clay liners and synthetic liners of different geomembranes (or combination of both). As durability of synthetic liners is limited in time the mineral clay liners, which can persist thousands of years, if managed in a sophisticated way as it was proved by the countless layered natural soils worldwide, are preferred as a long term impermeable and rigid system. It is necessary to emphasize that landfill should preferably have a bottom liner and top capping. The function of bottom liner is to prevent the deeper soil layers and the groundwater from contamination with soluble substrates and irreversible pollution of the future drinking water reservoirs. The function of the top capping is to avoid infiltration of the precipitation water (from rain and from snow melting) and migration of methane and odors from the biogas to the atmosphere. However, the top capping system also has to guarantee optimal (or at least satisfactory) conditions for plant growth while the deep rooting of plants must be prevented. Thus, these conflicting requirements can be only fulfilled by special mineral soil systems which, if they are adjust, will preserve their properties for ever.

The Effect of Texture on Methane Oxidation Capacity in a Sand Layer — a Model Laboratory Study

The microbiological process of methane oxidation in soils has been recognised as an important component of the global budget of atmospheric methane, contributing in 6% to its removal from the atmosphere. However, this process plays an important role in decreasing methane emission from these sources which are isolated from the atmosphere by a soil layer e.g. recultivated municipal landfills. The consumption of methane in aerated soils is affected by many factors; one of them being the gas transport resistance within the soil. Four sand and gravel fractions characterised by different gas diffusion properties viz. 0.25–0.5 mm, 0.5–1.0 mm, 1.0–2.0 mm, 2.0–4.0 mm, were used in our study. Each of the fractions placed in columns (1m by 0.15 m in diameter) was purged from the bottom with methane with a constant rate. The difference between the amount of CH entering and leaving the column was a measure of the capacity for methane oxidation. The highest methane oxidation capacity (9.47±0.44 dm3m-2h-1) was observed in the case of 0.51.0mm fraction.

Shrink-swell potential, hydraulic conductivity and geotechnical properties of clay materials for landfill liner construction

Abstract This paper presents studies concerning the applicability of two clay materials for the construction of a sustainable landfill liner. The studies consisted in determination of basic characteristics of the materials, eg particle size distribution, bulk density, particle density, total porosity, pore size, mineralogy, specific surface area, nanoparticle size, and Atterberg limits, as well as measurements of their geotechnical and hydraulic parameters, such as in situ saturated hydraulic conductivity, modules of primary and secondary compression, cohesion, and angle of internal friction. Furthermore, the effects of compaction performed by the Proctor method at various water contents on swelling and shrinkage characteristics and saturated hydraulic conductivity were investigated in order to determine the compliance with the national requirements for selection of material for landfill liner construction. The determined characteristics and geotechnical parameters of the tested clay materials allowed qualifying them as suitable for municipal landfill construction. The shrinkage potential of the tested clays observed was rated as moderate to very high. The cyclic drying and rewetting of the clay materials performed resulted in a significant increase in saturated hydraulic conductivity. Thus, the clay sealing layers, as part of a multilayer liner, should be very carefully operated, preventing the drying out of the clay sealing and assuring the possibility of its constant saturation.

Stress responses of spring rape plants to soil flooding

Abstract Stress responses of spring rape to soil hypoxia were investigated during 8-days flooding. Soil air-filled porosity decreased from 25-30% to 0%, oxygen diffusion rate - from 2.6-3.5 to 0.34 μmol O2 m-2 s-1, and redox potential - from 460 to 150mVwithin few hours. Alcohol dehydrogenase activity in roots increased up to 7-fold after one day of flooding and then decreased to 170% of control. Superoxide dismutase activity in roots increased by 27% during first 3 days and then dropped to 60% of control; in the leaves superoxide dismutase activity increased in average by 44%. Ascorbate peroxidase activity in leaves increased by 37% during first 3 days and then decreased to control value. Glutathione reductase activity increased by 45% in roots of flooded plants but did not change in leaves. Proline concentration in leaves increased up to 4-fold on the 3d day of flooding and then decreased to control value. Thus soil flooding induces increase of alcohol dehydrogenase activity and subsequent increase of superoxide dismutase and glutathione reductase activities in roots while the leaves display a few days increase of free proline concentration and ascorbate peroxidase activity, and a long-term increase of superoxide dismutase activity.

Effect of starch binder on charcoal briquette properties

Abstract The paper shows the results of a study on the effect of starch binder on the mechanical, physical and burning properties of charcoal briquettes. Two types of binders were repeatedly used to make briquettes of native wheat starch and modified wheat starch, at 8% of the whole. Briquetting was performed in a roller press unit, and pillow-shaped briquettes were made. The moisture of the mixed material ranged from 28 to 32%. The product, whether the former or the latter, was characterized by very good mechanical properties and satisfactory physical properties. Moreover, the type of starch binder had no effect on toughness, calorific heating value, volatiles, fixed carbon content and ash content. However, the combustion test showed quite different burning properties. As briquettes should have short firing up time and lower smokiness, as well as high maximum temperature and long burning time, we have concluded that briquettes with native wheat starch as a binder are more appropriate for burning in the grill.

Environmental Oxygenology and Related Thresholds and Standards

Oxygenology has been defined as the scientific discipline related to the presence and the role of oxygen in nature on earth (Stepniewski and Stepniewska 1998; Stepniewski et al. 2005). It is a branch of environmental sciences comprising issues of oxygen generation, absorption, turnover, storage, transport, functions and measurement in the environment.