Household solid waste characteristics and management in Chittagong, Bangladesh

Solid waste management (SWM) is a multidimensional challenge faced by urban authorities, especially in developing countries like Bangladesh. We investigated per capita waste generation by residents, its composition, and the households' attitudes towards waste management at Rahman Nagar Residential Area, Chittagong, Bangladesh. The study involved a structured questionnaire and encompassed 75 households from five different socioeconomic groups (SEGs): low (LSEG), lower middle (LMSEG), middle (MSEG), upper middle (UMSEG) and high (HSEG). Wastes, collected from all of the groups of households, were segregated and weighed. Waste generation was 1.3kg/household/day and 0.25kg/person/day. Household solid waste (HSW) was comprised of nine categories of wastes with vegetable/food waste being the largest component (62%). Vegetable/food waste generation increased from the HSEG (47%) to the LSEG (88%). By weight, 66% of the waste was compostable in nature. The generation of HSW was positively correlated with family size (r(xy)=0.236, p<0.05), education level (r(xy)=0.244, p<0.05) and monthly income (r(xy)=0.671, p<0.01) of the households. Municipal authorities are usually the responsible agencies for solid waste collection and disposal, but the magnitude of the problem is well beyond the ability of any municipal government to tackle. Hence dwellers were found to take the service from the local waste management initiative. Of the respondents, an impressive 44% were willing to pay US$0.3 to US$0.4 per month to waste collectors and it is recommended that service charge be based on the volume of waste generated by households. Almost a quarter (22.7%) of the respondents preferred 12-1pm as the time period for their waste to be collected. This study adequately shows that household solid waste can be converted from burden to resource through segregation at the source, since people are aware of their role in this direction provided a mechanism to assist them in this pursuit exists and the burden is distributed according to the amount of waste generated.     

Control of GHG emission at the microbial community level

All organic material eventually is decomposed by microorganisms, and considerable amounts of C and N end up as gaseous metabolites. The emissions of greenhouse relevant gases like carbon dioxide, methane and nitrous oxides largely depend on physico-chemical conditions like substrate quality or the redox potential of the habitat. Manipulating these conditions has a great potential for reducing greenhouse gas emissions. Such options are known from farm and waste management, as well as from wastewater treatment. In this paper examples are given how greenhouse gas production might be reduced by regulating microbial processes. Biogas production from manure, organic wastes, and landfills are given as examples how methanisation may be used to save fossil fuel. Methane oxidation, on the other hand, might alleviate the problem of methane already produced, or the conversion of aerobic wastewater treatment to anaerobic nitrogen elimination through the anaerobic ammonium oxidation process might reduce N2O release to the atmosphere. Changing the diet of ruminants, altering soil water potentials or a change of waste collection systems are other measures that affect microbial activities and that might contribute to a reduction of carbon dioxide equivalents being emitted to the atmosphere.     

Characterizing effects of uncertainties in MSW composting process through a coupled fuzzy vertex and factorial-analysis approach

A coupled fuzzy vertex and factorial-analysis approach was developed in this study for systematically characterizing effects of uncertainties in a municipal solid waste composting process. A comprehensive composting process model was also embedded into the system framework and used to address substrate decomposition and biomass growth, as well as the interactions between moisture contents, temperatures, and oxygen concentrations. The applicability of the proposed method was verified through a custom-made pilot-scale composting system. Results from fuzzy simulation indicated that the fuzzy vertex method could effectively communicate implicit knowledge into dynamic simulations and thus provide valuable information for enhancing composting process control under uncertainty. The factorial analysis was effective in quantifying the proportion to which the uncertainty of each single or interactive effect of model parameters contributes to the overall uncertainty of the system outcomes. Thus, sensitive parameters that may lead to errors or unreasonable predictions can be determined. The proposed study system could not only be used in characterizing combined effects of uncertainties for composting processes, but was also applicable to many other environmental modelling systems.     

Natterer’s bat (Myotis nattereri Kuhl, 1818) hawks for prey close to vegetation using echolocation signals of very broad bandwidth

We present a hitherto unknown prey perception strategy in bats: Myotis nattereri (Vespertilionidae, Chiroptera) is able to perceive prey by echolocation within a few centimeters of echo-cluttering vegetation, by using frequency-modulated search signals of very large bandwidth (up to 135 kHz). We describe the species’ search behavior and echolocation repertoire from the field and from experiments in a flight tent. In the field, bats varied signal parameters in relation to their distance from vegetation and usually flew close to vegetation. In the flight tent, M. nattereri detected and localized prey by echolocation alone as close as 5 cm from vegetation. Apparently, the bats were able to tolerate some overlap between prey and clutter echoes. Passive prey cues (vision, olfaction, prey-generated sounds) were not used in prey perception. The bats selected prey by size. The animals performed aerial catches and produced approach sequences typical for aerial hawking bats, but were able to do so within a few centimeters of the substrate. M. nattereri thus has access to silent, suspended prey very close to vegetation (e.g., spiders, and caterpillars on threads). Received: 29 September 1999 / Received in revised form: 12 February 2000 / Accepted: 12 February 2000     

Aggression and resource sharing among foundresses in the social wasp Polistes dominulus: testing transactional theories of conflict

Tug-of-war models of within-group conflict predict that the frequency of conflict will be positively related to the degree of reproductive sharing within the group; in contrast, a negative relationship supports transactional models, in which reproductive payments among group members limit the degree of within-group selfishness. We tested predictions of the tug-of-war and transactional models by examining cofoundress interactions during the founding (preworker) phase of colony development in 30 naturally nesting colonies of the paper wasp Polistes dominulus. We found that the mean rate of foundress aggression and the mean probability of food sharing were significantly negatively associated, which supports the prediction of the transactional, not the tug-of-war model. Further, cofoundress aggression significantly increased over the founding phase (independently of temperature), while the fraction of aggression initiated by the dominant (alpha) foundress significantly decreased over this period. We show that both of these results are predicted by the transactional model of within-group conflict. Interestingly, the alpha’s rate of aggression was significantly positively temperature dependent, while the beta’s was not. This indicates that the alpha’s aggression level may often be near her physiological maximum, while the beta’s aggression is limi- ted by other factors, contradicting the prediction of the tug-of-war model. Moreover, the alpha’s aggression was significantly positively temperature dependent only in the second half of the founding period, as predicted by the transactional model since this is when there is least reproductive sharing. Finally, our results indicate that the alpha’s level of aggression depends on the resources controlled by the beta. Received: 18 January 2000 / Revised: 19 June 2000 / Accepted: 24 June 2000     

Reproductive success of monogamous and polygynous pied flycatchers (Ficedula hypoleuca)

One of the most interesting aspects of the mating system of pied flycatchers is the regular occurrence of polygyny. Here we present data on the reproductive success of polygynously paired pied flycatcher males compared to monogamous males based on paternity analyses through DNA fingerprinting. Males paired with two females suffered a higher loss in reproductive output per female compared to monogamous males due to (1) a greater proportion of unhatched eggs in their broods, (2) greater nestling mortality and (3) a greater probability of being cuckolded. Nevertheless, the number of fledglings was significantly greater for polygynous males. Based on the number of nestlings that returned for subsequent breeding seasons, however, the reproductive success of monogamous and polygynous males did not differ significantly. These data raise the question as to why males attempt polygyny. Received: 16 August 1999 / Received in revised form: 15 March 2000 / Accepted: 18 March 2000     

Training Captive-Bred or Translocated Animals to Avoid Predators

Abstract: Animal reintroductions and translocations are potentially important interventions to save species from extinction, but most are unsuccessful. Mortality due to predation is a principal cause of failure. Animals that have been isolated from predators, either throughout their lifetime or over evolutionary time, may no longer express appropriate antipredator behavior. For this reason, conservation biologists are beginning to include antipredator training in pre-release preparation procedures. We describe the evolutionary and ontogenetic circumstances under which antipredator behavior may degenerate or be lost, and we use principles from learning theory to predict which elements can be enhanced or recovered by training. The empirical literature demonstrates that training can improve antipredator skills, but the effectiveness of such interventions is influenced by a number of constraints. We predict that it will be easier to teach animals to cope with predators if they have experienced ontogenetic isolation than if they have undergone evolutionary isolation. Similarly, animals should learn more easily if they have been evolutionarily isolated from some rather than all predators. Training to a novel predator may be more successful if a species has effective responses to similar predators. In contrast, it may be difficult to teach proper avoidance behavior, or to introduce specialized predator-specific responses, if appropriate motor patterns are not already present. We conclude that pre-release training has the potential to enhance the expression of preexisting antipredator behavior. Potential training techniques involve classical conditioning procedures in which animals learn that model predators are predictors of aversive events. However, wildlife managers should be aware that problems, such as the emergence of inappropriate responses, may arise during such training.     

Life under Arctic sea ice – reproduction strategies of two sympagic (ice-associated) amphipod species, Gammarus wilkitzkii and Apherusa glacialis

The reproductive strategies of two gammaridean amphipod species, Gammarus wilkitzkii and Apherusa glacialis, that permanently inhabit the Arctic sea ice were investigated. G. wilkitzkii reaches sexual maturity at an age of 2 years and produces 128 ± 54 eggs fem.⁻¹ yr⁻¹. Mating takes place during fall and winter, and the development of the large eggs (0.60 to 0.80 mm diam.) lasts 6 to 7 months. The sex ratio of G. wilkitzkii was dominated by males in a proportion of 1.5:1. In vivo studies showed that juveniles are released in batches from the brood pouches of the females during April and May. A. glacialis reaches sexual maturity at the age of 1 year and produces 555 ± 151 eggs fem.⁻¹ yr⁻¹. The eggs are between 0.18 and 0.23 mm in diameter, and are the smallest known for gammaridean amphipods. Eggs are kept in packages of two to eight in the brood pouches of females. The sex ratio of A. glacialis was dominated by females in a proportion of 3:1. The high fecundity of both amphipod species, the release of juveniles in batches over a period of time, a high proportion of females (A. glacialis), and an elongated life-span with multiple spawnings (G. wilkitzkii) are discussed as possible adaptations to the specific and highly variable conditions under Arctic sea ice. Received: 29 December 1999 / Accepted: 8 March 2000