Quantification of the resource recovery potential of municipal solid waste incineration bottom ashes

Municipal solid waste incineration (MSWI) plays an important role in many European waste management systems. However, increasing focus on resource criticality has raised concern regarding the possible loss of critical resources through MSWI. The primary form of solid output from waste incinerators is bottom ashes (BAs), which also have important resource potential. Based on a full-scale Danish recovery facility, detailed material and substance flow analyses (MFA and SFA) were carried out, in order to characterise the resource recovery potential of Danish BA: (i) based on historical and experimental data, all individual flows (representing different grain size fractions) within the recovery facility were quantified, (ii) the resource potential of ferrous (Fe) and non-ferrous (NFe) metals as well as rare earth elements (REE) was determined, (iii) recovery efficiencies were quantified for scrap metal and (iv) resource potential variability and recovery efficiencies were quantified based on a range of ashes from different incinerators. Recovery efficiencies for Fe and NFe reached 85% and 61%, respectively, with the resource potential of metals in BA before recovery being 7.2%ww for Fe and 2.2%ww for NFe. Considerable non-recovered resource potential was found in fine fraction (below 2 mm), where approximately 12% of the total NFe potential in the BA were left. REEs were detected in the ashes, but the levels were two or three orders of magnitude lower than typical ore concentrations. The lack of REE enrichment in BAs indicated that the post-incineration recovery of these resources may not be a likely option with current technology. Based on these results, it is recommended to focus on limiting REE-containing products in waste for incineration and improving pre-incineration sorting initiatives for these elements.     

Invertebrate introductions in marine habitats: two species of hydromedusae (Cnidaria) native to the Black Sea,Maeotias inexspectata and Blackfordia virginica,invade San Francisco Bay

The hydrozoans Maeotias inexspectata Ostroumoff, 1896 and Blackfordia virginica Mayer, 1910, believed to be native to the Black Sea (i.e. Sarmatic) and resident in a variety of estuarine habitats worldwide, were found as introduced species in the Petaluma River and Napa River, California, in 1992 and 1993. These rivers are mostly-estuarine tributaries that flow into north San Francisco Bay. Both species appeared to be well-established in this brackishwater habitat. Salinities at the collection sites were about 11 during the summer, rising to nearly 20 in the early autumn and falling to near 0 in the winter. Large numbers of all sizes of both species of medusae were observed and collected, indicating that the hydroid stages of the life cycles of the two are also well-established in these rivers. In the Petaluma River, populations of both species were at maximum in late July, with numbers of individuals declining through August and into September; the Napa River was sampled only in October, and at that time only B. virginica was found. Examination of full guts of M. inexspectata and B. virginica medusae revealed that both species had fed nearly exclusively on small crustaceans, principally barnacle nauplii, copepods and their eggs and nauplii, and crab zoea larvae (M. inexspectata only). All the M. inexspectata medusae were males, indicating that the population has probably developed from the introduction of perhaps only a single male polyp or polyp bud. In spite of its inability to reproduce sexually, this population appears to be maintained by the prodigious ability of the polyp to bud and reproduce asexually, and is fully capable of invading additional low-salinity habitats from its present Petaluma River site. Male and female B. virginica medusae were collected in both the Petaluma River and the Napa River, indicating that B. virginica may have been introduced by either the polyp or medusa stage (or both), but that multiple individuals (of both sexes) must have arrived from another port in one or more invasions. As indicated for M. inexspectata, the B. virginica population will also probably seed new populations in San Francisco Bay and elsewhere. Based on its cnidome as well as the morphology of both medusa and polyp, M. inexspectata has been reclassified by moving it from the family Olindiidae, Limnomedusae, to the family Moerisiidae, Anthomedusae.     

Warming induces shifts in microzooplankton phenology and reduces time-lags between phytoplankton and protozoan production

Indoor mesocosm experiments were conducted to test for potential climate change effects on the spring succession of Baltic Sea plankton. Two different temperature (Δ0?°C and Δ6?°C) and three light scenarios (62, 57 and 49?% of the natural surface light intensity on sunny days), mimicking increasing cloudiness as predicted for warmer winters in the Baltic Sea region, were simulated. By combining experimental and modeling approaches, we were able to test for a potential dietary mismatch between phytoplankton and zooplankton. Two general predator–prey models, one representing the community as a tri-trophic food chain and one as a 5-guild food web were applied to test for the consequences of different temperature sensitivities of heterotrophic components of the plankton. During the experiments, we observed reduced time-lags between the peaks of phytoplankton and protozoan biomass in response to warming. Microzooplankton peak biomass was reached by 2.5 day °C^?1 earlier and occurred almost synchronously with biomass peaks of phytoplankton in the warm mesocosms (Δ6?°C). The peak magnitudes of microzooplankton biomass remained unaffected by temperature, and growth rates of microzooplankton were higher at Δ6?°C (μ_?0?°C?=?0.12 day^?1 and μ_?6?°C?=?0.25 day^?1). Furthermore, warming induced a shift in microzooplankton phenology leading to a faster species turnover and a shorter window of microzooplankton occurrence. Moderate differences in the light levels had no significant effect on the time-lags between autotrophic and heterotrophic biomass and on the timing, biomass maxima and growth rate of microzooplankton biomass. Both models predicted reduced time-lags between the biomass peaks of phytoplankton and its predators (both microzooplankton and copepods) with warming. The reduction of time-lags increased with increasing Q₁₀ values of copepods and protozoans in the tritrophic food chain. Indirect trophic effects modified this pattern in the 5-guild food web. Our study shows that instead of a mismatch, warming might lead to a stronger match between protist grazers and their prey altering in turn the transfer of matter and energy toward higher trophic levels.     

Energy Use and CO2 Production in Tropical Agriculture and Means and Strategies for Reduction or Mitigation

Carbon dioxide emissions due to fossil fuel consumption are well recognized as a major contributor to climate change. In the debate on dealing with this threat, expectations are high that agriculture based economies of the developing world can help alleviate this problem. But, the contribution of agricultural operations to these emissions is fairly small. It is the clearing of native ecosystems for agricultural use in the tropics that is the largest non-fossil fuel source of CO₂ input to the atmosphere. Our calculation show that the use of fossil energy and the concomitant emission of CO₂ in the agricultural operational sector - i.e. the use of farm machinery, irrigation, fertilization and chemical pesticides - amounts to merely 3.9% of the commercial energy use in that part of the world. Of this, 70% is associated with the production and use of chemical fertilizers. In the absence of fertilizer use, the developing world would have converted even more land for cultivation, most of which is completely unsuitable for cultivation. Current expectations are that reforestation in these countries can sequester large quantities of carbon in order to mitigate excessive emissions elsewhere. But, any program that aims to set aside land for the purpose of sequestering carbon must do so without threatening food security in the region. The sole option to liberate the necessary land for carbon sequestration would be the intensification of agricultural production on some of the better lands by increased fertilizer inputs. As our calculations show, the sequestration of carbon far outweighs the emissions that are associated with the production of the extra fertilizer needed. Increasing the fertilizer use in the developing world (without China) by 20%, we calculated an overall net benefit in the carbon budget of between 80 and 206 Mt yr^?1 dependent on the carbon sequestration rate assumed for the regrowing forest. In those regions, where current fertilizer use is low, the relative benefits are the highest as responding yield increases are highest and thus more land can be set aside without harming food security. In Sub-Saharan Africa a 20% fertilizer increase, which amounts to 0.14 Mt of extra fertilizer, can tie up somewhere between 8 and 19 Mt of CO₂ per year (average: 96 t CO₂ per 1 t fertilizer). In the Near East and North Africa with a 20%-increased fertilizer use of 0.4 Mt yr^-1 between 10 and 24 Mt of CO₂ could be sequestered on the land set aside (40 t CO₂ per 1 t fertilizer). In South Asia this is 22–61 Mt CO₂ yr?1 with an annual additional input of 2.15 Mt fertilizer (19 t CO₂ per 1 t fertilizer). In fact, carbon credits may be the only way for some of the farmers in these regions to afford the costly inputs. Additionally, in regions with already relatively high fertilizer inputs such as in South Asia, an efficient use of the extra fertilizer must be warranted. Nevertheless, the net CO₂ benefit through implementation of this measure in the developing world is insignificant compared to the worldwide CO₂ output by human activity. Thus, reforestation is only one mitigating measure and not the solution to unconstrained fossil fuel CO₂ emissions. Carbon emissions should, therefore, first of all be reduced by the avoidance of deforestation in the developing world and moreover by higher energy efficiency and the use of alternative energy sources.     

Use of earth observation satellite data for land degradation mapping and monitoring in Mediterranean ecosystems: Towards a satellite-observatory

The degradation of the permanent seminatural vegetation and the resulting acceleration of soil degradation and erosion processes constitute major elements of land degradation in the Mediterranean basin. Given the European Commission's interest in mapping and controlling desertification phenomena in the Mediterranean member states, the Environmental Mapping and Modelling Unit (EMAP) of the Joint Research Centre is investigating possibilities for using operational earth observation satellites for mapping and repeated monitoring of vegetation and soil characteristics. In the context of previous experiments, approaches have been developed that can already be routinely applied to large regions. This paper discusses the problems of standardized retrieval of remotely sensed primary parameters (such as reflectance), concepts relating to the thematic interpretation of reflectance data, and the definition of satellite-derived degradation indices. In addition, this paper presents requirements for designing an operational satellite observatory for monitoring Mediterranean land degradation.     

Functional diversity of mesograzers in an eelgrass–epiphyte system

Historically, small invertebrate grazers in marine plant communities have been considered to be a relatively homogeneous group in their impact on ecosystem processes. However, recent studies propose that species composition is an important agent in determining grazer effects. We used four mesocosm experiments to test the biomass-specific and density-dependent effects of common mesograzers in temperate regions (Littorina littorea, Rissoa membranacea, Idotea baltica and Gammarus oceanicus) on epiphyte and eelgrass biomass and productivity. Mesograzer species identity strongly influenced epiphyte accumulation and eelgrass growth, where Rissoa was the most efficient mesograzer (per biomass) and Gammarus had the weakest impact. Density-dependent effects varied considerably among species. Both gastropod species reduced epiphyte accumulation in direct proportion to their density, and Littorina had the strongest negative effect on epiphyte biomass. The impact of Idotea seemed to level off to a threshold value and Gammarus had no density-dependent effect on epiphyte accumulation at all. Rissoa and Idotea increased eelgrass productivity in accordance with their effect on epiphyte accumulation, whereas Littorina showed a less positive effect than could be expected by its strong impact on epiphyte biomass. Gammarus had no significant impact on eelgrass growth. Our results show that the different functional traits of superficially similar mesograzers can have important consequences for ecosystem processes in macrophyte systems.     

The dance language of the honeybee mutant diminutive wings

Summary The dance communication of honeybees was studied using the short-winged mutant diminutive wings. The wing area of the mutant is reduced to 67% that of the wild type. This reduction in wing area leads to increases in both the wing beat frequency and the frequency of the sounds emitted during the dances. At the same time the amplitude of the sound signals is reduced. These changes have a strong effect on the recruitment success of the dances, which is reduced to less than 50%. Thus, the acoustical signals emitted by dancing bees play an essential role in the bees' dance communication.     

Biological degradation and greenhouse gas emissions during pre-storage of liquid animal manure

Storage of manure makes a significant contribution to global methane (CH4) emissions. Anaerobic digestion of pig and cattle manure in biogas reactors before outside storage might reduce the potential for CH4 emissions. However, manure pre-stored at 15 to 20 degrees C in buildings before anaerobic digestion may be a significant source of CH4 and could reduce the potential CH4 production in the biogas reactor. Degradation of energy-rich organic components in slurry and emissions of CH4 and carbon dioxide (CO2) from aerobic and anaerobic degradation processes during pre-storage were examined in the laboratory. Newly mixed slurry was added to vessels and stored at 15 and 20 degrees C for 100 to 220 d. During storage, CH4 and CO2 emissions were measured with a dynamic chamber technique. The ratio of decomposition in the subsurface to that at the surface indicated that the aerobic surface processes contributed significantly to CO2 emission. The measured CH4 emission was used to calculate the methane conversion factor (MCF) in relation to storage time and temperature, and the total carbon-C emission was used to calculate the decrease in potential CH4 production by anaerobic digestion following pre-storage. The results show substantial methane and carbon dioxide production from animal manure in an open fed-batch system kept at 15 to 20 degrees C, even for short storage times, but the influence of temperature was not significant at storage times of <30 d. During long-term storage (90 d), a strong influence of temperature on the MCF value, especially for pig manure, was observed.     

Spatial variability of fallout-90Sr in soil and vegetation of an alpine pasture

According to the soil-to-plant transfer concept generally used in dose assessment modeling, the plant uptake of a radionuclide should depend linearly on its concentration in the soil. In order to validate this concept for (90)Sr in a semi-natural ecosystem, plant and soil samples were taken at 100 plots of a 100 x 100 m(2) area within an alpine pasture near Berchtesgaden, Germany. At three plots, the vertical distribution of (90)Sr in the soil was determined in addition. A statistically significant correlation between the soil and plant concentration of (90)Sr was not detectable (Spearman correlation coefficient R=-0.116, p>0.05) within the range of the Sr-concentration covered (15-548 Bq kg(-1) dry soil and 17-253 Bq kg(-1) dry plant material). Thus, the prerequisite of the soil-to-plant transfer concept was not fulfilled for (90)Sr at this site. Organic carbon and total nitrogen were also determined in the soil samples. Both elements were highly correlated (R=0.912, p<0.001), their ratio being C/N=10.9+/-0.7. While C was positively correlated with the (90)Sr concentrations in the soil (R=0.342, p<0.001), negative correlations were observed for the plant concentrations (R=-0.286, p<0.01) and the concentration ratios (R=-0.444, p<0.001) of (90)Sr. These results are compared with those recently obtained for (137)Cs by Bunzl et al. (J Environ Radioactiv 48 (2000) 145).