Gas emissions from biodegradable waste in United Kingdom landfills.

The aim of this research was to predict the effect that the biodegradable municipal waste (BMW) diversion targets in the European Union landfill directive (99/31/EC) would have on landfill gas emissions. This is important for continued mitigation of these emissions. Work was undertaken in three stages using the GasSim model (v1.03) developed by the Environment Agency (England and Wales). The first stage considered the contribution to gas emissions made by each biodegradable component of the waste stream. The second stage considered how gas emissions from a landfill accepting biodegradable wastes with reduced biodegradable content would be affected. The third stage looked at the contribution to gas emissions from real samples of biologically pretreated BMW. For the first two stages, data on the waste components were available in the model. For the third stage samples were obtained from four different biological treatment facilities and the required parameters determined experimentally. The results of stage 1 indicated that in the first 15 years of the landfill the putrescible fraction makes the most significant contribution, after which paper/card becomes the most significant. The second stage found that biodegradability must be reduced by at least 60% to achieve a reduction in overall methane generation. The third stage found that emissions from samples of biologically pretreated BMW would result in a significant reduction in gas emissions over untreated waste, particularly in the early stage of the landfill lifetime; however, low level emissions would continue to occur for the long term.

Characterization of compost-like outputs from mechanical biological treatment of municipal solid waste.

Throughout the world, most municipal solid waste consists of biodegradable components. The most abundant biological component is cellulose, followed by hemicellulose and lignin. Recycling of these components is important for the carbon cycle. In an attempt to reduce the environmental impacts of biodegradable wastes, mechanical biological treatments (MBTs) are being used as a waste management process in many countries. MBT plants attempt to mechanically separate the biodegradable and nonbiodegradable components. The nonbiodegradable components are then sent for reprocessing or landfilled, whereas the biodegradable components are reduced in biological content through composting or anaerobic digestion, leaving a compost-like output (CLO). The further use of these partially degraded residues is uncertain, and in many cases it is likely that they will be landfilled. The implications of this for the future of landfill management are causing some concern because there is little evidence that the long-term emissions tail will be reduced. In this study, the CLOs from four different biological treatment processes were characterized for physical contamination through visual inspection and for biological content using a sequential digestion analysis. The results indicate that the composition of the incoming waste, dependent on the way the waste was collected/segregated, was the factor that influenced biological content most, with length of treatment process the second most important.

Household hazardous waste disposal to landfill: using LandSim to model leachate migration.

Municipal solid waste (MSW) landfill leachate contains a number of aquatic pollutants. A specific MSW stream often referred to as household hazardous waste (HHW) can be considered to contribute a large proportion of these pollutants. This paper describes the use of the LandSim (Landfill Performance Simulation) modelling program to assess the environmental consequences of leachate release from a generic MSW landfill in receipt of co-disposed HHW. Heavy metals and organic pollutants were found to migrate into the zones beneath a model landfill site over a 20,000-year period. Arsenic and chromium were found to exceed European Union and US-EPA drinking water standards at the unsaturated zone/aquifer interface, with levels of mercury and cadmium exceeding minimum reporting values (MRVs). The findings demonstrate the pollution potential arising from HHW disposal with MSW.

Spray irrigation of landfill leachate: estimating potential exposures to workers and bystanders using a modified air box model and generalised source term.

Generalised source term data from UK leachates and a probabilistic exposure model (BPRISC(4)) were used to evaluate key routes of exposure from chemicals of concern during the spraying irrigation of landfill leachate. Risk estimates secured using a modified air box model are reported for a hypothetical worker exposed to selected chemicals within a generalised conceptual exposure model of spray irrigation. Consistent with pesticide spray exposure studies, the key risk driver is dermal exposure to the more toxic components of leachate. Changes in spray droplet diameter (0.02-0.2 cm) and in spray flow rate (50-1000 l/min) have little influence on dermal exposure, although the lesser routes of aerosol ingestion and inhalation are markedly affected. The risk estimates modelled using this conservative worst case exposure scenario are not of sufficient magnitude to warrant major concerns about chemical risks to workers or bystanders from this practice in the general sense. However, the modelling made use of generic concentration data for only a limited number of potential landfill leachate contaminants, such that individual practices may require assessment on the basis of their own merits.

Household hazardous waste data for the UK by direct sampling.

The amount of household hazardous waste (HHW) disposed of in the United Kingdom (UK) requires assessment. This paper describes a direct analysis study carried out in three areas in southeast England involving over 500 households. Each participating householder was provided with a special bin in which to place items corresponding to a list of HHW. The amount of waste collected was split into nine broad categories: batteries, home maintenance (DIY), vehicle upkeep, pesticides, pet care, pharmaceuticals, photographic chemicals, household cleaners, and printer cartridges. Over 1 T of waste was collected from the sample households over a 32-week period, which would correspond to an estimated 51,000 T if extrapolated to the UK population for the same period or over 7,000 T per month. Details of likely disposal routes adopted by householders were also sought, demonstrating the different pathways selected for different waste categories. Co-disposal with residual household waste dominated for waste batteries and veterinary medicines, hence avoiding classification as hazardous waste under new UK waste regulations. The information can be used to set a baseline for the management of HHW and provides information for an environmental risk assessment of the disposal of such wastes to landfill.

Assessing quantities and disposal routes for household hazardous products in the United Kingdom.

The disposal of household products containing hazardous substances (household hazardous wastes; HHW) is of concern due to possible health and environmental effects as a consequence of environmental pollution. The potential risks of disposal are proportional to the amounts of products used and waste generated, but much of the data relating to quantities are old, inconsistent, or nonexistent. Hence, full-scale risk assessment is not yet feasible. This pilot study was aimed at an initial assessment of the amounts of hazardous products used or stored within the household and potential disposal routes. Representatives of 400 households from southeast England were interviewed about socio-demographic factors, perception of the risks associated with the use and disposal of hazardous waste generated in households, quantities of particular products currently in use or stored within the household, and times and methods of disposal of such products. The estimates of quantities obtained were compared with sales figures and waste estimates to improve understanding of product flow through to the HHW stream. The disposal routes investigated demonstrated that most householders claim to use the entire product priorto disposal in the general refuse bin. The relationship with socio-demographic factors demonstrated a difference between neighborhood size and length of residence in a household with regard to product quantities possessed and the disposal habits adopted.