Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Biomassa voor de energievoorziening van tuinbouwclusters
    Zwart, H.F. de; Ruijs, M.N.A. ; Visser, H.J.M. - \ 2016
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1393) - 34
    bio-energie - glastuinbouw - haalbaarheidsstudies - economische haalbaarheid - warmte - kooldioxide - elektriciteit - biomassa - biobased economy - biochar - verbranding - opwekking van elektriciteit - warmteproductie - bioenergy - greenhouse horticulture - feasibility studies - economic viability - heat - carbon dioxide - electricity - biomass - biobased economy - biochar - combustion - electricity generation - heat production
    Biomass combustion in combination with a cluster of greenhouses to provide heat, CO2 and electricity can provide a partly solution to the sustainability of the horticultural sector. A biomass gasification plant could also provide valuable biochar, the result of partial combustion of biocarbon. This was shown to have attractive characteristics to be used in high quality potting soil. Despite the high value of the biochar (contributing for 16% of the income from the plant), the economic feasibility of a biomass combustion plant depends heavily on governmental subsidies (SDE +). When the developed technology is used on a practical scale, a biomass plant of 8 MW thermal power and 1.4 MW of electrical power is a sound size. Such a plant fits well with a horticultural cluster of 15 hectares, consisting of 6 ha Tomato, 6 ha Pepper and 3 hectares of Chrysanthemum. The biomass plant produces over 91% of the heating and 95% of the CO2 requirement and 67% of the electricity counsumed. However during winter a lot of electricity will have to be bought, which is compensated with selling to the public grid in summer. The biomass combustion plant will mainly run on biomass is supplied from elsewhere. The biomass from the local cluster covers only 0.3% of the combusted amount. If all available biomass from Netherlands territory would be used to heat greenhouses about 20% of greenhouse industry could make use of system like described in this report.
    Harvesting, logistics and upgrading of herbaceous biomass from verges and natural areas for use in thermal conversion : TKI BBE Park Cuijk
    Elbersen, H.W. ; Keijsers, E.R.P. ; Bakker, R. ; Kamp, R.G.M. op den; Holshof, G. ; Spijker, J.H. ; Ree, R. van; Arkestijn, Karlijn ; Schijndel, Daan van; Haasnoot, Kees ; Remmelink, Bert-Erik ; Bakker, P. ; Massop, Hans ; Quik, Jan - \ 2015
    Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research 1552) - ISBN 9789462575110 - 83
    biobased economy - biomass - grass clippings - bioenergy - cogeneration - netherlands - sustainability - combustion - biobased economy - biomassa - grasmaaisel - bio-energie - warmtekrachtkoppeling - nederland - duurzaamheid (sustainability) - verbranding
    The main goal of this project was to analyse if it is technically possible, environmentally favourable and economically profitable to use herbaceous biomass from verges (roadsides) and natural areas as raw material for combustion in the Cuijk facility of Essent for the production of CHP (combined heat and power).
    Post combustion CO2 capture with substituted ethanolamines and piperazines : Ab initio and DFT studies
    Gangarapu, S. - \ 2014
    Wageningen University. Promotor(en): Han Zuilhof, co-promotor(en): Ton Marcelis. - Wageningen : Wageningen University - ISBN 9789462570320 - 170
    kooldioxide - ethanolamine - piperazinen - verbranding - oplosmiddelen - computationele chemie - carbon dioxide - ethanolamine - piperazines - combustion - solvents - computational chemistry

    The emission of greenhouse gases in the atmosphere, particularly carbon dioxide, caused by fossil fuel combustion, has been claimed to be responsible for global warming. Capturing of carbon dioxide from exhaust gases by using aqueous amine solutions is an important process for the reduction of the emission of these gases from power plants. Monoethanolamine (MEA) is used as an industrial solvent for carbon dioxide capture from exhaust gases. However, the use of MEA for CO2 capture from power plants is expensive. Therefore, finding the cheaper solvent for CO2 capture is needed to reduce the CO2 emissions into the atmosphere and thereby saving the biodiversity in the world.

    Comparing the social costs of biofuels and fossil fuels: A case study of Vietnam
    Thanh, L. le; Ierland, E.C. van; Zhu, X. ; Wesseler, J.H.H. ; Ngo, G. - \ 2013
    Biomass and Bioenergy 54 (2013). - ISSN 0961-9534 - p. 227 - 238.
    diesel-engine - methyl-ester - performance - emissions - biodiesel - blends - combustion
    Biofuel substitution for fossil fuels has been recommended in the literature and promoted in many countries; however, there are concerns about its economic viability. In this paper we focus on the cost-effectiveness of fuels, i.e., we compare the social costs of biofuels and fossil fuels for a functional unit defined as 1 km of vehicle transportation. We base our empirical results on a case study in Vietnam and compare two biofuels and their alternative fossil fuels: ethanol and gasoline, and biodiesel and diesel with a focus on the blends of E5 and E10 for ethanol, and B5 and B10 for biodiesel. At the discount rate of 4%, ethanol substitution for gasoline in form of E5 or E10 saves 33% of the social cost of gasoline if the fuel consumption of E5 and E10 is the same as gasoline. The ethanol substitution will be cost-effective if the fuel consumption of E5 and E10, in terms of L km-1, is not exceeding the consumption of gasoline by more than 1.7% and 3.5% for E5 and E10 respectively. The biodiesel substitution would be cost-effective if the fuel consumption of B5 and B10, in terms of L km-1 compared to diesel, would decrease by more than 1.4% and 2.8% for B5 and B10 respectively at the discount rate of 4%.
    Hout verstoken toch niet zo klimaatneutraal
    Arets, Eric - \ 2013
    wood - combustion - sustainability - environmental impact - carbon dioxide - emission - biobased economy
    Rural residential CO2 emissions in China: Where is the major mitigation potential?
    Liu Wenling, Wenling ; Wang Can, ; Mol, A.P.J. - \ 2012
    Energy Policy 51 (2012). - ISSN 0301-4215 - p. 223 - 232.
    biomass - combustion - gases
    Despite high-speed economic growth in recent decades, rural China is still confronted with persisting poverty, alongside energy shortages and environmental degradation. In tackling climate change, carbon emissions from rural energy use have been given little attention up till now. This paper provides an analysis of rural residential CO2 emissions in China based on diverse accounting methods, and employs the geographic information system (GIS) to map emissions of each province. Identifying the major emission sources could provide a basis for understanding the potential for greenhouse gas emission reduction and proposing related policy recommendations. The results showed that the largest GHG mitigation potential can be found at traditional biomass use among residents. Four emission reduction policy strategies are identified: (i) shifting to commercial energy; (ii) furthering the use of decentralized renewable energy options; (iii) commercializing biomass energy via biomass power generation, biomass briquettes and biogas production; (iv) improving the combustion efficiency of traditional biomass use in household appliances. Differences in resource endowment and local economic conditions created varied levels of rural residential greenhouse gas emission, the related mitigation potential, and the kinds of strategies and policies that need to be developed in the Chinese provinces.
    Verbranding : duurzame warmte door verbranding houtsnippers
    Dubbeldam, R. ; Louis Bolk, - \ 2012
    Wageningen UR etc.
    bio-energie - kachels - houtspaanders - warmte - verbranding - energieproductie in de landbouw - biobased economy - bioenergy - stoves - wood chips - heat - combustion - agricultural energy production - biobased economy
    Vooral in Duitsland, Zwitserland en Oostenrijk waar veel hout voorhanden is, vind je biomassaketels. Ook in Nederland schaffen agrariërs ze aan. Stallen en het woonhuis met hout verwarmen bespaart kosten en spaart het milieu. Het gebruik van fossiele brandstoffen en daarmee de CO2-uitstoot nemen sterk af.
    Comparison of woody pellets, straw pellets, and delayed harvest system herbaceous biomass (switchgrass and miscanthus): analysis of current combustion techniques determining the value of biomass
    Hui, Y. - \ 2011
    [S.l.] : S.n.
    bio-energie - bolletjes - energiegehalte - hout - strobrokken - stro - verbranding - miscanthus - panicum virgatum - biobased economy - bioenergy - pellets - energy content - wood - straw pellets - straw - combustion - miscanthus - panicum virgatum - biobased economy
    Since the energy consumption is growing fast, it is important to find alternative resources for the future generation energy supply. This study is going to compare the woody pellets, straw pellets and delayed harvest system biomass (switchgrass and miscanthus) from the combustion technique perspective. What problems during the thermal conversion will determine the value of herbaceous pellets lower than wood pellets? Both literature review and consulting with experts are used in the research. Although at this moment, application of herbaceous biomass will cause problems like corrosion, slagging and fouling, many solutions have already in their experimental stage. As the need of energy increase, the market for herbaceous biomass is bright.
    Modeling global N2O emissions from aquatic systems
    Ivens, W.P.M.F. ; Tysmans, D.J.J. ; Kroeze, C. ; Löhr, A.J. ; Wijnen, J. van - \ 2011
    Current Opinion in Environmental Sustainability 3 (2011)5. - ISSN 1877-3435 - p. 350 - 358.
    nitrous-oxide emissions - fresh-water - rivers - future - budget - inputs - ocean - combustion - trends - impact
    Human activities on land have increased the N inputs to rivers and coastal waters worldwide. This increased aquatic emissions of nitrous oxide (N2O). Global, spatially explicit modeling of N flows from land to sea and associated N2O emissions have been developed for a number of decades. During the 1990s, global N2O studies focused to a large extent on closing the global budget. Since then, aquatic emissions of N2O have been subject of scientific discussions. Although it is widely recognized that human activities on land increase aquatic N2O emissions, quantification is difficult because of lack of experimental data. In order to reduce uncertainties, additional long-term studies are required measuring N and N2O concentrations in aquatic systems. More explicit modeling of N2O formation and the underlying biogeochemical cycling in aquatic systems would improve our understanding of aquatic N2O emissions. Global models preferably include both N cycling, N2O production, and river transport in a spatially explicit way, as well as biogeochemical cycling in coastal seas and oceans. Integrative studies are needed that account for the interactions between different impacts of increased levels of reactive N in the environment. We argue that it is still difficult to close the global N2O budget.
    Stoken op olifantsgras: energie en milieueffecten
    Kasper, G.J. - \ 2011
    V-focus 8 (2011)4. - ISSN 1574-1575 - p. 23 - 25.
    brandstofgewassen - miscanthus - bio-energie - verbranding - milieufactoren - emissie - biobased economy - fuel crops - miscanthus - bioenergy - combustion - environmental factors - emission - biobased economy
    In V-focus van februari 2011 zijn de resultaten van teelt, oogst en opslag van olifantsgras bij witvleeskalverhouder Henken in Rhenen besproken. Warmteopwekking door verbranding in een biomassaketel is het uiteindelijke doel van deze grasteelt. De resultaten van verbranding en de milieu- en energievoordelen voor de hele keten worden in dit artikel besproken.
    Color encoded microbeads-based flow cytometric immunoassay for polycyclic aromatic hydrocarbons in food
    Meimaridou, A. ; Haasnoot, W. ; Noteboom, L. ; Mintzas, D. ; Pulkrabova, J. ; Hajslová, J. ; Nielen, M.W.F. - \ 2010
    Analytica Chimica Acta 672 (2010)1-2. - ISSN 0003-2670 - p. 9 - 14.
    monoclonal-antibody - pahs - milk - combustion - particles - exposure - luminex - samples - salmon - pyrene
    Food contamination caused by chemical hazards such as persistent organic pollutants (POPs) is a worldwide public health concern and requires continuous monitoring. The chromatography-based analysis methods for POPs are accurate and quite sensitive but they are time-consuming, laborious and expensive. Thus, there is a need for validated simplified screening tools, which are inexpensive, rapid, have automation potential and can detect multiple POPs simultaneously. In this study we developed a flow cytometry-based immunoassay (FCIA) using a color-encoded microbeads technology to detect benzo[a]pyrene (BaP) and other polycyclic aromatic hydrocarbons (PAHs) in buffer and food extracts as a starting point for the future development of rapid multiplex assays including other POPs in food, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). A highly sensitive assay for BaP was obtained with an IC50 of 0.3 µg L-1 using a monoclonal antibody (Mab22F12) against BaP, similar to the IC50 of a previously described enzyme-linked immunosorbent assay (ELISA) using the same Mab. Moreover, the FCIA was 8 times more sensitive for BaP compared to a surface plasmon resonance (SPR)-based biosensor immunoassay (BIA) using the same reagents. The selectivity of the FCIAs was tested, with two Mabs against BaP for 25 other PAHs, including two hydroxyl PAH metabolites. Apart from BaP, the FCIAs can detect PAHs such as indenol[1,2,3-cd]pyrene (IP), benz[a]anthracene (BaA), and chrysene (CHR) which are also appointed by the European Food Safety Authority (EFSA) as suitable indicators of PAH contamination in food. The FCIAs results were in agreement with those obtained with gas chromatography–mass spectrometry (GC–MS) for the detection of PAHs in real food samples of smoked carp and wheat flour and has great potential for the future routine application of this assay in a simplex or multiplex format in combination with simplified extraction procedure which are under development.
    CO2-doseren met gereinigde rookgassen: overmaat schaadt
    Staalduinen, J. van; Dueck, T.A. - \ 2010
    Onder Glas 7 (2010)1. - p. 54 - 55.
    tuinbouw - teelt onder bescherming - kassen - capsicum annuum - vruchtgroenten - ethyleen - kooldioxide - verontreiniging - elektrische energie - verbranding - paprika - glastuinbouw - rookgassen - warmtekrachtkoppeling - groenten - horticulture - protected cultivation - greenhouses - capsicum annuum - fruit vegetables - ethylene - carbon dioxide - pollution - electrical energy - combustion - sweet peppers - greenhouse horticulture - flue gases - cogeneration - vegetables
    Anders dan NOx kan etheen in paprika al bij zeer lage concentraties ernstige schade en productiederving veroorzaken. Onderzoekers achten het daarom niet verantwoord om fors hogere CO2-concentraties na te streven dan 800 ppm bij gebruik van gereinigde rookgassen. Voorts raden zij aan etheenconcentraties in de kas te meten (bij voorkeur op lage hoogte) en niet te doseren vlak na het in- of terugschakelen van WKK of ketel. Op die momenten vindt er geen optimale verbranding plaats en ontstaat er extra verontreiniging
    Landschapsbeheer en biomassa : een gelukkig huwelijk
    Stobbelaar, D.J. ; Groningen, E. van - \ 2009
    Groen : vakblad voor groen in stad en landschap 65 (2009)12. - ISSN 0166-3534 - p. 6 - 9.
    biomassa - hout - verbranding - energiebronnen - landschapsbeheer - houtwallen - friese wouden - biomass - wood - combustion - energy sources - landscape management - hedgerows - friese wouden
    Beetsterzwaag ligt in het coulissenlandschap van het Westerkwartier in Friesland, een landschap van weiden die worden omzoomd door houtwallen en elzensingels. Niet vreemd dus dat hier één van de eerste grotere houtgestookte energiecentrales van Nederland staat. Deze biomassa-installatie verwarmt water door houtsnippers te verbranden. Om het gehele jaar rond warmte te kunnen leven, heeft de energie-installatie vierhonderd kilometer houtwal en elzensingels nodig, die in een vijftienjarige rotatie afgezet worden.
    Bioplastic is niet afbreekbaar
    Have, H. D'; Bolck, C.H. - \ 2009
    EOS magazine: actueel maandblad voor wetenschap en technologie 2009 (2009)oktober. - p. 30 - 31.
    afvalverwerking - verbranding - milieueffect - afvalverwijdering - bioplastics - biobased economy - biopolymeren - vlaanderen - waste treatment - combustion - environmental impact - waste disposal - bioplastics - biobased economy - biopolymers - flanders
    Bioplastic is biologisch afbreekbaar of zelfs volledig composteerbaar, zeggen de producenten. Maar dat klopt niet. In de praktijk gaat het bioplastic in Vlaanderen gewoon de verbrandingsoven in
    Verwaarding reststroom uienbewerking
    Meeusen-van Onna, M.J.G. ; Schroot, J.H. ; Mulder, W.J. ; Elbersen, H.W. - \ 2008
    Wageningen : Agrotechnology & Food Sciences Group (ASFG nr. 886) - ISBN 9789085048503 - 155
    uien - oogstresten - verwerking - extractie - industriële toepassingen - compostering - verbranding - fermentatie - kleurstoffen in voedsel - antioxidanten - scheidingstechnologie - bioethanol - biobased economy - onions - crop residues - processing - extraction - industrial applications - composting - combustion - fermentation - food colourants - antioxidants - separation technology - bioethanol - biobased economy
    In opdracht van ZUVER heeft Wageningen Universiteit en Research Centre de mogelijkheden bekeken voor verwaarding van de reststroom die bij de uienbewerking vrijkomt. Tijdens het uienbewerkingsproces komt een continue reststroom vrij. Deze reststroom bedraagt voor alle uienbewerkingsbedrijven tezamen jaarlijks 16.800 tot 18.900 ton. De reststroom komt vrij tijdens drie verschillende deelprocessen: lossen, afstaarten en sorteren/verpakken. De samenstelling van de reststroom is bij ieder proces anders. De drie deelprocessen geven qua omvang de volgende reststromen: ¿ Lossen: 4.800 ton tot 5.400 ton ¿ Afstaarten: 9.600 ton tot 10.800 ton ¿ Sorteren: 2.400 ton tot 2.700 ton Op dit moment 2008 wordt de reststroom gecomposteerd en over het land uitgereden. Tegelijkertijd willen de uienbewerkingsbedrijven ook kijken naar afzetmogelijkheden met meer toegevoegde waarde. De reststroom bevat interessante componenten die mogelijk interessant zijn voor hoogwaardiger toepassingen. De droge bruine pellen zijn rijk aan onoplosbare vezels en ze bevatten relatief veel quercitine. De wortels en bolstoel bevatten relatief veel zwavelcomponenten die als geur- of smaakstof herkenbaar zijn. Mogelijk kan een mengsel van quercitine en de zwavelcomponenten toegepast worden als insecticide of herbicide. Dit zal afhangen van werkzaamheid, dosering en benodigde zuiverheid. Wanneer de reststroom wordt gescheiden in een grondfractie en een overige fractie zijn er meer mogelijkheden voor de reststroom in beeld. Er zijn dus voordelen van scheiding van de grond- en niet-grondfractie. Het scheiden net na het lossen gebeurt al op dit moment: dat is de losstroom. Voor een aanvullende scheidingsstap is vooral de droge scheidingstechnologie in beeld. Het gaat dan bijvoorbeeld om windziften. Immers op elk bedrijf staan al afzuiginstallaties . ZUVER wil via mechanische stappen de scheiding verder optimaliseren . Om deze scheidingstechnieken te implementeren is nog wel een kort onderzoekstraject noodzakelijk waarin de technische en economische haalbaarheid van een scheiding van grond en uienpellen (inclusief staarten) uitgezocht wordt. Op basis van de samenstelling van de reststroom uit de uienbewerking is een groot aantal toepassingen bedacht. Deze toepassingen zijn gegroepeerd Verwaarding reststroom uienbewerking naar toegevoegde waarde, waarbij het onderscheid in fertilizer (compost, bodemverbeteraar), fuel (energie), fibre (vezel), feed (veevoer), food (humane voeding), farma en other (overig) is gehanteerd. De potentiële toepassingen omvatten een groot scala aan producten, die sterk uiteenlopen waar het gaat om de toegevoegde waarde. Daarvan lijkt een aantal toepassingen aantrekkelijk voor de uienbewerkingsbedrijven. Deze opties zijn nader uitgewerkt. Het gaat daarbij om opties die al binnen handbereik liggen, zoals compostering. Daarnaast zijn er toepassingen waar enig aanvullend onderzoek noodzakelijk is zoals verbranding. De meer hoogwaardiger toepassingen als kleurstof, antioxidant fungicide en insecticide vergen ook verdere ontwikkeling (met partners). Voor deze meer hoogwaardiger toepassingen geldt dat bedrijven die actief zijn in deze markt interesse hebben in de producten die de uienbewerkingsbedrijven kunnen aanleveren. In een samenwerkingsverband kunnen de mogelijkheden voor de verdere productontwikkeling worden verkend.
    Chromium-incorporated TUD-1 as a new visible light-sensitive photo-catalyst for selective oxidation of propane
    Hamdy Mohamed Saad, M.S. ; Berg, O. ; Jansen, J.C. ; Maschmeyer, T. ; Arafat, A. ; Moulijn, J.A. ; Mul, G. - \ 2006
    Catalysis today 117 (2006)1-3. - ISSN 0920-5861 - p. 337 - 342.
    containing mesoporous silica - metal-oxide surfaces - photocatalytic reaction - irradiation - combustion - no - dehydrogenation - hydrocarbons - reduction - zeolite
    Chromium was incorporated in the framework of TUD-1 mesoporous silica by a one-pot synthesis procedure, using triethanolamine as a bi-functional template. The Cr-TUD-1 catalyst was characterized by means of X-ray diffraction, high-resolution transmission electron microscopy, UV¿vis and Raman spectroscopy, as well as elemental analysis and N2 sorption measurements. The results indicate that chromium is incorporated as tetrahedrally co-ordinated Cr6+ in the framework of TUD-1. When tested as a catalyst for the photo-oxidation of propane, Cr-TUD-1 showed high activity and high selectivity towards acetone under visible light irradiation (¿ = 435 nm).
    Mixed Conifer Forest Duff Consumption during Prescribed Fires: Tree Crown Impacts
    Hille, M.G. ; Stephens, S.L. - \ 2005
    Forest Science 51 (2005)5. - ISSN 0015-749X - p. 417 - 424.
    sierra-nevada - spatial-patterns - plot-scale - soil - pine - growth - throughfall - combustion - severity - moisture
    Fire suppression has produced large forest floor fuel loads in many coniferous forests in western North America. This study describes spatial patterns of duff consumption in a mixed-conifer forest in the north-central Sierra Nevada, California. Overstory crown coverage was correlated to spatial patterns of duff depth after prescribed fire. On one site that was burned under dry conditions, almost all duff was consumed, with some remaining in overstory gaps. On a second site that was burned under moist conditions a few days after the first annual precipitation, strong spatial patterns of duff consumption were recorded with increasing distance from the base of the nearest overstory tree, the probability of duff remaining after prescribed fire increased significantly. There is strong evidence that spatial variation of precipitation throughfall resulted in higher duff moisture in gaps, whereas duff beneath crown cover was drier, and therefore, totally consumed. This study demonstrates that including a spatial component in a process-based duff consumption model would improve the accuracy of fire-effect predictions.
    Onderzoek naar de emissies van de brand bij ATF in Drachten
    Bruggen, M. van; Baars, A.J. ; Traag, W.A. - \ 2001
    Bilthoven etc. : RIVM [etc.] (Rapport RIKILT 2001.010) - 42
    verbranding - bemonsteren - luchtverontreinigende stoffen - gezondheidsgevaren - risicoschatting - melk - grassen - nederland - combustion - sampling - air pollutants - health hazards - risk assessment - milk - grasses - netherlands
    Assessment of ecotoxicological risks of element leaching from pulverized coal ashes
    Jenner, H.A. - \ 1995
    Agricultural University. Promotor(en): J.H. Koeman. - S.l. : Jenner - 230
    rook - sintels - verbranding - as - vliegas - brandstoffen - steenkool - bodem - uitspoelen - ecosystemen - toxicologie - chemicaliën - ecotoxicologie - bioaccumulatie - smoke - slags - combustion - ash - fly ash - fuels - coal - soil - leaching - ecosystems - toxicology - chemicals - ecotoxicology - bioaccumulation

    This thesis describes the consequences of the disposal of the combustion residues of coal, especially the uptake of elements from such residues and their effects on various organisms. The effects on benthic organisms in fresh and in seawater are considered in the first two parts. The third part looks at the uptake of elements from coal residues and their effect on the growth of plants and worms.

    The central theme is the combustion residue known as pulverized fuel ash (PFA), or 'flyash'. Coal is a product of natural origin that was formed from plant remains in the period between 265 and 203 million years ago. During the coal forming process the elements from plants become 100 to 1000 times more concentrated. In all probability, further concentration occurred through airborne deposition and the salts from sea and freshwater. The elements present will be concentrated a further 10 times during combustion in a boiler. This means that following combustion, the unburned elements are re-released to the environment, whether or not they are bound to flyash particles. Some elements are released directly in the gaseous phase, other elements condense on the surfaces of the flyash spheres and another fraction is bound up in the matrix of these particles. The question is whether an adequate estimate can be made, from the ecotoxicological point of view, as to what effect on the environment PFA will have when used in unbound applications.

    The elements in PFA can be divided into macro-elements which occur in relatively high concentrations (g/kg) and trace elements which occur at concentrations of less than I mg/kg. It is largely these trace elements which reach the environment through leaching from PFA and accumulate in organisms. In The Netherlands, however, discharge of PFA in unbound form (not as cement/concrete 'stabilized' products) is not a concern at the moment. It may possibly be (re)considered as an option in the future, at which point in time, knowledge of possible environmental effects will be essential. At present, nearly all PFA is used by the cement industry. Additionally, a small quantity is used in pellet form as artificial gravel in the concrete industry.

    The anion forming elements are especially important from the point of view of environmental protection. In order of leaching potential, these elements are in order of highest to lowest: selenium>molybdenum>>wolfram>vanadium>antimony>arsenic>chrome. Accumulation of these elements by organisms in excessive concentrations can lead to undesirable effects. Such effects can be increased (biornagnification) in organisms which are higher in the food-chain.

    Part 1
    In the first part of this thesis research in the marine environment is described with organisms which are indigenous to intertidal sedimentary biotopes, i.e. the lugworm Arenicola marina , the ragworm Nereis virens , the baltic tellin Macoma balthica and the cockle Cerastodermaedule. The accumulation of such elements is described in the above species and their survival during a 90- days exposure to 100% PFA and a 50% PFA mixture with sand. A sand control and a reference of moderately contaminated harbour dredged sediment from Rotterdam harbour were also used. In addition, the effect of a daily dose of PFA was examined in an effort to simulate regular disposal. At the end of this period, the organisms were sampled and the elements zinc, arsenic, chrome copper, nickel, cadmium antimony and selenium were determined in animal tissue and sediment. In the ragworm experiment, young worms were used to examine the colonisation of disposed PFA. Moreover, the effects of a 230-days exposure to a PFA substrate is described in the cockle. Alteration in the reproductive processes, tissues and organs was assessed in these animals. Parasites were also examined, as organisms living in sub-optimal conditions are often more strongly parasitised.

    The concentration of the elements measured in the PFA substrates appeared to have been reduced by 10% during the test period. However, it was clear that the arsenic and selenium concentrations had not been reduced to the extent expected (<5% only), as R is known that both elements are easily leached. The accumulation patterns in the lugworm demonstrate that arsenic in particular is accumulated (a factor of 15 in 50% PFA 150% sand and a factor of 5 in 100% PFA on basis of tissue concentrations). This is probably caused by the binding of arsenic to sediment particles which are eaten by the lugworm in its sedimentary diet. Accumulation in the cockle was only a factor of 2 above the sedimentary levels. The small accumulation levels in the cockles from the 230-days experiment were unexpected. The accumulation factor for arsenic was a factor of 3 in the baltic tellin. The concentration of zinc in the baltic tellin was remarkably high in animals exposed to all sediment types, including the control, at>550 mg/kg (dry weight). However, these concentrations do not appear to be abnormal and existed at the start of the experiments. From this it can be seen that the 'lifestyle' of the organisms used in bioassays can strongly determine the accumulation of the anionic elements. Where the cationic elements copper, chrome and nickel are concerned, no unexpected accumulation patterns were found; only zinc was accumulated. Several elements were analyzed after 4, 8 and 12 weeks exposure in the ragworm experiment. Here also, the arsenic concentration increased up to week 8 (from 23 to 76 μg/g in 100% PFA, on basis of tissue concentrations), after which a decrease was observed after12 weeks. It is interesting to note that in the ragworm, selenium was slowly but steadily accumulated and no equilibrium was reached after 12 weeks exposure. The copper concentration in ragworms increased by a factor of three. The other cation forming elements zinc, chrome and nickel did not however accumulate.

    With the lugworm, a high mortality was found in all substrates, i.e. 96% in the 100% PFA and 55.5% in the control. The lugworm appears sensitive to transplantation and 100% PFA is absolutely unacceptable as a substrate in which to burrow. By contrast, the baltic tellin showed a low mortality (20% in 100% PFA) and a wild population existed in the substrate, originating from the Wadden Sea. Cockle mortality reached 40% in the 100% PFA exposure and 15% in the control. Unexpectedly, only slight microscopic changes in the reproductive tissues were observed. In the experiment with the ragworms young animals with an average weight of 200 mg (ca. 2 cm in length) were used and an appreciable mortality of 50 - 60% was seen in the first weeks of the experiment. This mortality was to be expected as the delicate young animals were placed in the tanks by hand at the start of the experiment.

    The general conclusion concerning the leaching of elements from PFA and subsequent uptake in the benthic fauna is that a species dependent differential situation occurs. Arsenic and selenium are the most prominent elements. A second conclusion is that PFA caused a physical effect which was reflected in an altered behaviour of the organisms examined. Even in a substrate of 50% PFA / 50% sand after 60 days none of the burried worms came to the surface, indicating severe stress. The consequences of this are that, a radical change in the species composition of the benthic fauna will take place upon dumping PFA in the marine environment and recovery will take years. A lesser sedimentation through deposition over larger areas will reduce the mortality of species or populations, but effects on species composition will still occur.

    Part 2
    The experiments described in Part 2 were carried out in flow chambers with the painters mussel Unio pictorum. This mussel species was chosen because R crawls freely in the upper layers of sediment unlike other sessile bivalve species such as the Zebra mussel (Dreissena polymorpha). The painters mussel moves by sticking out their foot, which then changes shape to form an anchor with which the mussel then pulls itself along. The mussels are rather active in summer and remain permanently open, but during the winter, dig themselves in.

    The growth of mussels in PFA substrates was compared with data from Rhine sediment. Additionally, growth was compared with tagged mussels which were followed for several years in the River Linge, a tributary of the Rhine. Behaviour was examined with a laboratory version of the Mussel Monitor r, where activity was measured as the opening and closing actions of the valves. In a simultaneous research project at the University of Utrecht with a similar mussel species in aquaria without any substrate, the mussels remained closed and only opened for short periods. The specific question examined during these experiments was whether the mussels showed an abnormal behavioural pattern in PFA substrates and did this influence the accumulation of metals.

    The accumulation of the metal cadmium is examined in a separate study. Although cadmium only occurs in very small amounts in PFA, it was none the less chosen for this accumulation experiment, because much experience had already been gained with cadmium in laboratory experiments at the University of Utrecht. The expectation was that accumulation would be considerably different in the laboratory than in semi-field experiments due to the large difference in opening 1 closure behaviour.

    The accumulation of selenium and the occurrence of effects on the development of eggs in U. pictorum was examined. Arsenic and selenium leach readily from PFA, whereby arsenic can be strongly accumulated in contrast to selenium. Selenium (Se) is taken up only very slowly, but bioaccumulation and biornagnification does occur. Selenium is concentrated in proteins and especially in the developing oocytes which form a target organ. The literature indicates that some fish species in selenium rich waters in California die out at concentrations of 15 μg/l Se. An important fact is that Se can occur as different forms or 'species', e.g. selenite [Se( IV)], selenate [Se (VI)] and organo-selenium compounds. It is usually the Se (IV) form which occurs in PFA leachates, ie. this species which accumulates more rapidly than Se (VI). The accumulation of Se was examined in three experiments with dosed Se (IV).

    The growth of mussels in PFA was somewhat retarded when compared to growth in river sediment (Rhine and Linge). The mussels had initial difficulties in burrowing into the PFA and were only comparable with the Rhine situation after 5 days. The individual mussels nearly always stood open and showed a high level of activity interspersed with short periods when the valves were closed.

    In the cadmium experiment, mussels were exposed to four separate dosages of 50 ug/l. The accumulation of cadmium appeared to progress rapidly, and a plateau was reached after 3 weeks with kidney concentrations of ca. 400 μg/g (freeze dried weight); which means a bioconcentration factor (BCF) of 8000. No elimination of cadmium was observed during a consecutive depuration period of 29 weeks. The lack of any difference in accumulation in the presence or absence of a substrate was unexpected.

    At the selenium experiments the effect of enriching PFA and Rhine sediment with selenium was examined. The highest concentrations were observed in animals exposed to the enriched Rhine sediment. Mussels were continuously exposed for 11 weeks to 50 μg/l of Se (IV) in order to examine the possible effect on the development of oocytes and embryos. Selenium accumulation had not reached a steady state after 11 weeks of exposure. Differences (not significant) were found in the synchronisation of glochidia production (larvae on the gills of female mussels) as well as in the average size of the oocytes at the end of the exposure period. Following exposures of 22 and 11 weeks to concentrations of 50 and 250 μg/l, an accumulation of 5 and 15 μg/g was observed, with BCFs of 100 and 60 respectively (freeze dried weight). The most unexpected result was that no differences were observed in the numbers of glochidia and that no deformations were found. This implies that no demonstrable (significant) effects were found in the chosen experimental setup. Se resembles sulphur in uptake behaviour and is built in proteins (eggs). The element is an essential nurient, but can be toxic at slightly higher concentrations than ambient. On the basis of literature data for the development of eggs in a perch species during a 32 week experiment, the expectation was that effects would indeed be found.

    The accumulation of cadmium in U. pictorum occurred rapidly. The kidneys formed the the main target organ and a steady state is apparently reached after three weeks of exposure. Elimination of cadmium hardly occurr over a period of 28 weeks whithout dosing. No mortality was found during the exposure and during the elimination period. An important finding is that the presence or absence of substrate, which has a dear effect on behaviour (valve movement), did not influence the uptake of cadmium.

    One apparent effect of selenium on oocytes, embryos and larval development is that the timing of the appearance of larvae in the gills of the females is altered. The consequence of this is that the mussels retain the larvae longer on the gills and release them later. Such longer retention might have consequences for the life cycle of this species through a delay in the settlement on fish and the ditribution of the larvae.

    Main conclusion from this section is that PFA has a marked influence on the quality as a sediment by physical changes leading to abnormal behaviour and secondly through the leaching of elements.

    Part 3
    Part 3 is concerned with research carried out with plants and earthworms. Phytomonitoring as illustrated here with duckweed, is still a rather uncommon monitoring technique but admirably suited to the purpose of testing leachates from PFA. Experiments with the duckweed Lemna minor are described where the effects of conventional PFA, PFA from low NOx burners, bottom ash and coal gasification ash were examined. In order to be able to compare the observed effects properly, sediments from a canal and a river were sampled and tested also. At the same time different methods of producing leacheates were examined. A distinction is made between natural leacheates; and artificially produced leacheates, where element concentrations were in agreement with the 'cascade' leachate technique (successive leaching of 5 times). An image analysis technique was developed to measure the growth of duckweed in a simple and effective manner, in the various experiments. The effects of coal gasification slag (a type of bottom ash) were also examined. In the coal gasification process, the flammable gaseous components are first removed from the powdered coal with the aid of steam under high pressure and reducing conditions. The gas mixture thus produced is burned by conventional means. During this process, only a relatively small fraction of flyash is produced and is removed. The bulk of the residue is formed by coal gasification slag (CG slag) which remains after the gasification process. The growth of yellow nut sedge (Cyperus esculentus) and the elements which accumulate in the plant were examined in the laboratory. The effects on the earthworm Eisenia fetida were examined in a similar manner.

    Duckweed appeared to be very suitable organism to monitor leacheates from PFA. It appears from the experiments that the anion forming elements cause the effects in the conventional PFA and the low NOx leacheates, while the cations cause the effects in the sediments from the Apeldoornsch Kanaal and the Rhine. The toxicity of PFA is considerably lower when compared to that of the Apeldoornsch Kanaal. This difference is mainly caused by zinc (>4000 μg/l which occurs in the leachate from the Apeldoornsch Kanaal; the 'no effect concentration' for duckweed is about 160 μg/l.

    The order of toxicity for elements such as those found in separately executed tests with duckweed was: cadmium>copper>zinc,>arsenic (111)>seleniurn (IV)>boron>molybdenum.

    The leaching of elements from coal gasification slag appeared to be minimal. The growth of the yellow nut sedge decreases with increasing concentration of coal gasification slag through lack of nutrients and not as a result of the toxic elements from CG slag. Addition of nutrients resulted in a marked improvement in growth. Growth in PFA was equally retarded, in this case because the fresh PFA contained boron which shows growth effects on plants above 60 μg/g. Accumulation was found to be restricted to boron and molybdenum. The physical effect of compaction of the PFA, through which the substrate becomes so hard as to prevent proper root growth, should also be considered as a serious effect. A clearly negative effect on the growth and mortality of the worm E. fetida was found in PFA and CG slag. The mortality was especially high (32%) in PFA; growth was only found in potting soil. Accumulation was only observed for arsenic. The availability of the anion forming elements from PFA was greater that from CG slag.

    The contention that PFA in general should be evaluated as a chemical waste needs to be reconsidered in the light of the results presented here. At present, The Government of The Netherlands is considering a revision of this standpoint, through which PFA will be placed in a category with raw materials. The effects of conventional and low NOx PFA are related to the anion forming elements. The leaching of elements from CG slag appears to be very small. The sediments from the Apeldoornsch Kanaal show a far higher toxicity than PFA, which is caused by the high zinc concentrations. The effects of the sediments from the Rhine and the Apeldoornsch Kanaal are associated with the cation forming elements.

    Final Conclusions
    The main conclusion is that through the disposal of PFA, the greatest changes are caused by physical effects, as appears from the marine and freshwater studies. The acceptability of PFA as a substrate for benthic organisms is far worse that expected. Within the relatively short time period of the tests, accumulation of elements and acute effects appears to be far less important than expected. A reduction in number of oocytes in U. pictorurn was found prior to spawning. The later appearance of the larvae of U. pictorum point to possible effects at the population level. Where accumulation of elements is concerned, the anions arsenic and selenium are the most important elements in leacheates.

    Phyto-monitoring of PFA leacheates and sediments from the Apeldoornsch Kanaal and Rhine with the duckweed (L. minor) shows that PFA has but a comparatively low toxicity. The leaching of elements from CG slag is minimal and the observed effects can be accounted for by a lack of nutrients. The main thrust of the "Bouwstoffenbesluit" which is in preparation at present and aims at preventing soil pollution, is the leaching of unbound and stabilized residues. For PFA in unbound form, this means that the leaching characteristics must be measured in a column test and the composition determined following Aqua Regia digestion. During digestion, the matrix is broken open and a composition spectrum arises which is far removed from the natural situation as illustrated by the duckweed experiments, for example. For the elements antimony, chrome, fluorine, molybdenum, selenium, vanadium and the sulphate component, the threshold value of the "Bouwstoffenbesluit" will in all probability not be achievable when based on the proposed column test. More knowledge is needed concerning the leaching of PFA in unbound and stabilized form under natural conditions, when considering the biologically available fraction. This means that more information is needed on the speciation of the elements in bioassay studies. In unbound form, the physical effects on the aquatic environment (substrate) and thereby on species and populations is an area where as yet, little is known. The possibilities for stabilized applications of non-usable wastes such as bottom ashes, and flyash from coal- and waste combustion, in 'artificial waste blocks' requires more attention. Applications can certainly be found in the form of artificial reefs, aimed at biotope improvement for sessile organisms and young fish.

    In general, toxicological risks of unbound PFA deposition show to be less severe as initially assumed. However, physical effects for benthic organisms will be severe.

    Effecten van verstrooien van crematie-as : betreffende het asverstrooiingsveld nabij de Kampdwarsweg te Zeist
    Molenaar, J.G. de - \ 1994
    Wageningen : IBN-DLO (IBN - rapport 095) - 39
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