Use of dispersion modelling for Environmental Impact Assessment of biological air pollution from composting: Progress, problems and prospects.

With the increase in composting asa sustainable waste management option, biological air pollution (bioaerosols) from composting facilities have become a cause of increasing concern due to their potential health impacts. Estimating community exposure to bioaerosols is problematic due to limitations in current monitoring methods. Atmospheric dispersion modelling can be used to estimate exposure concentrations, however several issues arise from the lack of appropriate bioaerosol data to use as inputs into models, and the complexity of the emission sources at composting facilities. This paper analyses current progress in using dispersion models for bioaerosols, examines the remaining problems and provides recommendations for future prospects in this area. A key finding is the urgent need for guidance for model users to ensure consistent bioaerosol modelling practices.

Delivering organisational adaptation through legislative mechanisms: Evidence from the Adaptation Reporting Power (Climate Change Act 2008).

There is increasing recognition that organisations, particularly in key infrastructure sectors, are potentially vulnerable to climate change and extreme weather events, and require organisational responses to ensure they are resilient and adaptive. However, detailed evidence of how adaptation is facilitated, implemented and reported, particularly through legislative mechanisms is lacking. The United Kingdom Climate Change Act (2008), introduced the Adaptation Reporting Power, enabling the Government to direct so-called reporting authorities to report their climate change risks and adaptation plans. We describe the authors' unique role and experience supporting the Department for Environment, Food and Rural Affairs (Defra) during the Adaptation Reporting Power's first round. An evaluation framework, used to review the adaptation reports, is presented alongside evidence on how the process provides new insights into adaptation activities and triggered organisational change in 78% of reporting authorities, including the embedding of climate risk and adaptation issues. The role of legislative mechanisms and risk-based approaches in driving and delivering adaptation is discussed alongside future research needs, including the development of organisational maturity models to determine resilient and well adapting organisations. The Adaptation Reporting Power process provides a basis for similar initiatives in other countries, although a clear engagement strategy to ensure buy-in to the process and research on its long-term legacy, including the potential merits of voluntary approaches, is required.

Sensitivity of predicted bioaerosol exposure from open windrow composting facilities to ADMS dispersion model parameters.

Bioaerosols are released in elevated quantities from composting facilities and are associated with negative health effects, although dose-response relationships are not well understood, and require improved exposure classification. Dispersion modelling has great potential to improve exposure classification, but has not yet been extensively used or validated in this context. We present a sensitivity analysis of the ADMS dispersion model specific to input parameter ranges relevant to bioaerosol emissions from open windrow composting. This analysis provides an aid for model calibration by prioritising parameter adjustment and targeting independent parameter estimation. Results showed that predicted exposure was most sensitive to the wet and dry deposition modules and the majority of parameters relating to emission source characteristics, including pollutant emission velocity, source geometry and source height. This research improves understanding of the accuracy of model input data required to provide more reliable exposure predictions.

Integrating horizon scanning and strategic risk prioritisation using a weight of evidence framework to inform policy decisions.

Poor connection between data on emerging issues and credible policy decisions continues to challenge governments, and is only likely to grow as demands on time and resources increase. Here we summarise recent efforts to integrate horizon scanning and risk prioritisation approaches to better connect emerging issues to the political discourse on environmental and food-related issues. Our categorisation of insights including potential future risks and opportunities to inform policy discussions has emerged from a structured three-year programme of horizon scanning for a UK pan-governmental futures partnership led by the Department for Environment, Food and Rural Affairs (Defra). Our efforts to integrate horizon scanning and risk prioritisation, utilising a qualitative weight of evidence framework, has created a systematic process for identifying all signals of potential future change with significant impact for the strategic mission and underlying values of policy actors. Our approach encourages an exploration of factors out of the control of organisations, recognising that resilience depends on the flexibility of management strategies and the preparedness to deal with a variety of unexpected outcomes. We discuss how this approach addresses key cultural and evaluative challenges that policy actors have had in embedding horizon scanning in evidence-based policy processes, and suggest further developments to build confidence in the use of horizon scanning for strategic planning.

Morphological classification of bioaerosols from composting using scanning electron microscopy.

This research classifies the physical morphology (form and structure) of bioaerosols emitted from open windrow composting. Aggregation state, shape and size of the particles captured are reported alongside the implications for bioaerosol dispersal after release. Bioaerosol sampling took place at a composting facility using personal air filter samplers. Samples were analysed using scanning electron microscopy. Particles were released mainly as small (<1 µm) single, spherical cells, followed by larger (>1 µm) single cells, with aggregates occurring in smaller proportions. Most aggregates consisted of clusters of 2-3 particles as opposed to chains, and were <10 µm in size. No cells were attached to soil debris or wood particles. These small single cells or small aggregates are more likely to disperse further downwind from source, and cell viability may be reduced due to increased exposure to environmental factors.

Regulators as agents: modelling personality and power as evidence is brokered to support decisions on environmental risk.

Complex regulatory decisions about risk rely on the brokering of evidence between providers and recipients, and involve personality and power relationships that influence the confidence that recipients may place in the sufficiency of evidence and, therefore, the decision outcome. We explore these relationships in an agent-based model; drawing on concepts from environmental risk science, decision psychology and computer simulation. A two-agent model that accounts for the sufficiency of evidence is applied to decisions about salt intake, animal carcass disposal and radioactive waste. A dynamic version of the model assigned personality traits to agents, to explore their receptivity to evidence. Agents with 'aggressor' personality sets were most able to imbue fellow agents with enhanced receptivity (with 'avoider' personality sets less so) and clear confidence in the sufficiency of evidence. In a dynamic version of the model, when both recipient and provider were assigned the 'aggressor' personality set, this resulted in 10 successful evidence submissions in 71 days, compared with 96 days when both agents were assigned the 'avoider' personality set. These insights suggest implications for improving the efficiency and quality of regulatory decision making by understanding the role of personality and power.

Effective drinking water collaborations are not accidental: interagency relationships in the international water utility sector.

The role that deficient institutional relationships have played in aggravating drinking water incidents over the last 30 years has been identified in several inquiries of high profile drinking water safety events, peer-reviewed articles and media reports. These indicate that collaboration between water utilities and public health agencies (PHAs) during normal operations, and in emergencies, needs improvement. Here, critical elements of these interagency collaborations, that can be integrated within the corporate risk management structures of water utilities and PHAs alike, were identified using a grounded theory approach and 51 semi-structured interviews with utility and PHA staff. Core determinants of effective interagency relationships are discussed. Intentionally maintained functional relationships represent a key ingredient in assuring the delivery of safe, high quality drinking water.

Scientific commentary: Strategic analysis of environmental policy risks--heat maps, risk futures and the character of environmental harm.

We summarise our recent efforts on the policy-level risk appraisal of environmental risks. These have necessitated working closely with policy teams and a requirement to maintain crisp and accessible messages for policy audiences. Our comparative analysis uses heat maps, supplemented with risk narratives, and employs the multidimensional character of risks to inform debates on the management of current residual risk and future threats. The policy research and ensuing analysis raises core issues about how comparative risk analyses are used by policy audiences, their validation and future developments that are discussed in the commentary below.

Better by design: rethinking interventions for better environmental regulation.

Better regulation seeks to extend existing policy and regulatory outcomes at less burden for the actors involved. No single intervention will deliver all environmental outcomes. There is a paucity of evidence on what works why, when and with whom. We examine how a sample (n=33) of policy makers select policy and regulatory instruments, through a case study of the Department for Environment, Food and Rural Affairs (Defra), UK. Policy makers have a wide range of instruments at their disposal and are seeking ways to harness the influence of non-governmental resources to encourage good environmental behaviour. The relevance of each influence varies as risk and industry characteristics vary between policy areas. A recent typology of policy and regulatory instruments has been refined. Direct regulation is considered necessary in many areas, to reduce environmental risks with confidence and to tackle poor environmental performance. Co-regulatory approaches may provide important advantages to help accommodate uncertainty for emerging policy problems, providing a mechanism to develop trusted evidence and to refine objectives as problems are better understood.

Spatial variations in airborne microorganism and endotoxin concentrations at green waste composting facilities.

The emission and dispersal of bioaerosols from open-air commercial composting facilities continues to be contentious. A meta-dataset enumerating cultivable microorganism emission and downwind concentrations is not yet available. A dataset derived from repeated and replicated field studies over a period of two years at two commercial composting facilities is presented. The data characterises patterns in Aspergillus fumigatus, actinomycetes, Gram-negative bacteria and endotoxin emission and downwind concentrations. For all bioaerosols, compost agitation activities had a significant impact on concentrations; levels were variable up to 600 m downwind from site. Bioaerosols declined rapidly from source and exhibited a secondary peak 100-150 m from site boundary. All bioaerosols were found downwind from site in elevated concentrations. Compared to those found 100 m upwind, levels were significantly higher at 180 m downwind for A. fumigatus; at 300-400 m for actinomycetes and Gram negative bacteria, and at 100 m for endotoxins. Periodically, elevated concentrations could be found for all bioaerosols at distances further downwind. The evidence provided by this data set provides operators and regulators of facilities with reliable data to inform the location, risk assessment and bioaerosol sampling strategies of commercial composting facilities.

Comparison of coal/solid recovered fuel (SRF) with coal/refuse derived fuel (RDF) in a fluidized bed reactor.

An experimental study was undertaken to compare the differences between municipal solid waste (MSW) derived solid recovered fuel (SRF) (complying with CEN standards) and refuse derived fuel (RDF). Both fuels were co-combusted with coal in a 50 kW fluidized bed combustor and the metal emissions were compared. Synthetic SRF was prepared in the laboratory by grinding major constituents of MSW such as paper, plastic, textile and wood. RDF was obtained from a local mechanical treatment plant. Heavy metal emissions in flue gas and ash samples from the (coal+10% SRF) fuel mixture were found to be within the acceptable range and were generally lower than that obtained for coal+10% RDF fuel mixture. The relative distribution of heavy metals in ash components and the flue gas stream shows the presence of a large fraction (up to 98%) of most of the metals in the ash (except Hg and As). Thermo-gravimetric (TG) analysis of SRF constituents was performed to understand the behaviour of fuel mixtures in the absence and presence of air. The results obtained from the experimental study will enhance the confidence of fuel users towards using MSW-derived SRF as an alternative fuel.

The 'bankability' of the new waste technologies: an econometric method for risk sharing in private finance waste contracts.

The identification of risk and its appropriate allocation to partners in project consortia is essential for minimizing overall project risks, ensuring timely delivery and maximizing benefit for money invested. Risk management guidance available from government bodies, especially in the UK, does not specify methodologies for quantitative risk assessment, nor does it offer a procedure for allocating risk among project partners. Here, a methodology to quantify project risk and potential approaches to allocating risk and their implications are discussed. Construction and operation of a waste management facility through a public-private finance contract are discussed. Public-private partnership contracts are special purpose vehicle (SPV) financing methods promoted by the UK government to boost private sector investment in facilities for public service enhancement. Our findings question the appropriateness of using standard deviation as a measure for project risk and confirm the concept of portfolio theory, suggesting the pooling of risk can reduce total risk and its impact.

Residues characterisation from the fluidised bed combustion of East London's solid recovered fuel.

Waste thermal treatment in Europe is moving towards the utilisation of the combustible output of mechanical, biological treatment (MBT) plants. The standardisation of solid recovered fuels (SRF) is expected to support this trend and increase the amount of the generated combustion residues. In this work, the residues and especially the fly ashes from the fluidised bed combustion (FBC) of East London's NCV 3, Cl 2, and Hg 1 class SRF, are characterised. The following toxicity indicators have been studied: leachable chlorine, organochlorides expressed as pentachlorobenzene and hexachlorobenzene, and the heavy metals Cu, Cr, Cd, Zn, Ni, and Pb. Furthermore the mineralogical pattern of the ashes has been studied by means of XRD and SEM-EDS. The results suggest that these SRF derived ashes have significantly lower quantities of Cu, Cd, Pb, Zn, leachable Cl, and organochlorides when compared to other literature values from traditional waste thermal treatment applications. This fact highlights the importance of modern separation technologies employed in MBT plants for the removal of components rich in metals and chlorine from the combustible output fraction of SRF resulting to less hazardous residues.

Hidden flows and waste processing--an analysis of illustrative futures.

An existing materials flow model is adapted (using Excel and AMBER model platforms) to account for waste and hidden material flows within a domestic environment. Supported by national waste data, the implications of legislative change, domestic resource depletion and waste technology advances are explored. The revised methodology offers additional functionality for economic parameters that influence waste generation and disposal. We explore this accounting system under hypothetical future waste and resource management scenarios, illustrating the utility of the model. A sensitivity analysis confirms that imports, domestic extraction and their associated hidden flows impact mostly on waste generation. The model offers enhanced utility for policy and decision makers with regard to economic mass balance and strategic waste flows, and may promote further discussion about waste technology choice in the context of reducing carbon budgets.

Better environmental regulation--contributions from risk-based decision-making.

Internationally, pressure is being exerted on governments and regulators to develop modern forms of regulation that deliver more for less, and in better ways. We discuss the ways in which one large regulator, the Environment Agency for England and Wales, has responded to such pressures by implementing risk-based approaches to regulation. After exploring the context for key elements of risk-based environmental regulation, we consider the evolving influence of such approaches. We discuss the impacts against the UK Government's principles for better regulation and the key criteria for policy evaluation, before considering some of the challenges: the need to i) understand the best practice and promote consistency in risk-based regulation; ii) develop reliable, responsive forms of risk assessment and monitoring; iii) build capacities for responsive risk regulation; iv) evaluate the influence of different regulatory styles; and v) better understand the potential role of the private sector.

An integrated appraisal of energy recovery options in the United Kingdom using solid recovered fuel derived from municipal solid waste.

This paper reports an integrated appraisal of options for utilising solid recovered fuels (SRF) (derived from municipal solid waste, MSW) in energy intensive industries within the United Kingdom (UK). Four potential co-combustion scenarios have been identified following discussions with industry stakeholders. These scenarios have been evaluated using (a) an existing energy and mass flow framework model, (b) a semi-quantitative risk analysis, (c) an environmental assessment and (d) a financial assessment. A summary of results from these evaluations for the four different scenarios is presented. For the given ranges of assumptions; SRF co-combustion with coal in cement kilns was found to be the optimal scenario followed by co-combustion of SRF in coal-fired power plants. The biogenic fraction in SRF (ca. 70%) reduces greenhouse gas (GHG) emissions significantly ( approximately 2500 g CO(2) eqvt./kg DS SRF in co-fired cement kilns and approximately 1500 g CO(2) eqvt./kg DS SRF in co-fired power plants). Potential reductions in electricity or heat production occurred through using a lower calorific value (CV) fuel. This could be compensated for by savings in fuel costs (from SRF having a gate fee) and grants aimed at reducing GHG emission to encourage the use of fuels with high biomass fractions. Total revenues generated from coal-fired power plants appear to be the highest ( 95 pounds/t SRF) from the four scenarios. However overall, cement kilns appear to be the best option due to the low technological risks, environmental emissions and fuel cost. Additionally, cement kiln operators have good experience of handling waste derived fuels. The scenarios involving co-combustion of SRF with MSW and biomass were less favourable due to higher environmental risks and technical issues.

Biodrying for mechanical-biological treatment of wastes: a review of process science and engineering.

Biodrying is a variation of aerobic decomposition, used within mechanical-biological treatment (MBT) plants to dry and partially stabilise residual municipal waste. Biodrying MBT plants can produce a high quality solid recovered fuel (SRF), high in biomass content. Here, process objectives, operating principles, reactor designs, parameters for process monitoring and control, and their effect on biodried output quality are critically examined. Within the biodrying reactors, waste is dried by air convection, the necessary heat provided by exothermic decomposition of the readily decomposable waste fraction. Biodrying is distinct from composting in attempting to dry and preserve most of biomass content of the waste matrix, rather than fully stabilise it. Commercial process cycles are completed within 7-15 days, with mostly H(2)O((g)) and CO(2) loses of ca. 25-30% w/w, leading to moisture contents of <20% w/w. High airflow rate and dehumidifying of re-circulated process air provides for effective drying. We anticipate this review will be of value to MBT process operators, regulators and end-users of SRF.

Better environmental decision making - recent progress and future trends.

Recent trends in risk-based decision making are reviewed in relation to novel developments in comparative risk analysis, strategic risk analysis, weight of evidence frameworks, and participative decision making. Delivery of these innovations must take account of organisational capabilities in risk management and the institutional culture that implements decision on risk. We stress the importance of managing risk knowledge within organisations, and emphasise the use of core criteria for effective risk-based decisions by reference to decision process, implementation and the security of strategic added value.

A survey of green burial sites in England and Wales and an assessment of the feasibility of a groundwater vulnerability tool.

Since 1994, 200 'green' or natural burial sites have been developed in the UK and Eire, attracting regulatory attention because of perceived risks to groundwater. Here, a survey of natural burial practice in England and Wales (n=49 of 141 elicited) is presented, providing data on operational trends and supporting the design of a groundwater vulnerability assessment tool. Natural burial grounds are generally small in area (< 0.8 ha), adopt a mean single burial depth of 1.45 m bgl and a mean plot density of ca. 1480 graves ha(-1). A vulnerability screening tool is described that allows a desk-based evaluation of sites by reference to seven groundwater risk attributes. Initial feasibility is evaluated through application to 131 sites.

Estimating pollutant removal requirements for landfills in the UK: III. Policy analysis and operational implications.

The policy analysis and management implications for achieving landfill equilibrium status within a sustainable timescale (decades rather than centuries) are presented based on modelled results reported previously. Until relatively recently, timescale estimates suggested that equilibrium or landfill completion could be achieved within 40-60 years i.e. the same order of magnitude as financial provision for aftercare. However results of modelling in this study (reported in previous paper) suggest that timescales may be considerably longer (many centuries in some instances) suggesting that financial provision may be inadequate. The role of the most promising and available waste treatment technologies and strategic waste management options in contributing towards achieving equilibrium status are discussed. Results suggest that a re-examination of techniques for accelerating landfill stabilisation, including aerobic and bioreactor landfill, is warranted.