Key outcomes:

  • Impact assessment completed
  • Government regulations satisfied
  • Stack height optimisation

Global interest in Waste-to-Energy (WtE) facilities has been growing to meet a rising need to reduce landfill usage and minimise the greenhouse gas impacts of landfill gas. A typical WtE plant combusts waste, carefully blended to account for the varying calorific value of different waste streams. The efficiency of the combustion process depends on a number of factors such as waste composition and plant design. Designs employing moving grate incinerators and gasification plants are often used to accommodate waste across a wide range of calorific value. The produced heat energy is then utilized in converting water to steam, which is then passed through turbogenerators to convert mechanical energy to electrical energy. While WtE technology benefits the environment by reducing landfill usage and increasing renewable energy generation, the combustion of waste can result in wide range of emissions that need to be understood and dispersed appropriately to ensure safe exposures for the surrounding community. Typical emissions can include a wide range of compounds including carbon monoxide, NOX, dioxins, heavy metals and particulates.

Example ground level concentration contours

Figure 1: Example pollutant ground level concentration of various pollutants emitted from a Waste-to-Energy plant (marked by the red flag) generated by AERMOD modelling.

As a consequence of these emissions, the assessment and approvals of WtE facilities are subjected to high level of scrutiny by health and environmental regulators. One of the standard key requirements for EPA approvals is a screening-level air dispersion modelling to assess both likely and worst-case emissions. Typically, a plume dispersion model, such as AERMOD, AUSPLUME, CALPUFF or TAPM, is selected in consideration of both regulatory guidelines and conversations with the local regulator. Each of these models has its limitations and results from some of these models strongly depend on its settings. Hence, strong knowledge of the sub-models and working is required to generate accurate results.

The team at Synergetics is highly experienced in conducting dispersion modelling and assessing the impacts on air quality in the surrounding areas of the proposed facility. The assessment models ground level concentration of different pollutants, as per standard guidelines set by regulatory bodies. In addition to approvals, we also conduct optimization studies on stack dimensions. For example, air quality assessment has been undertaken for multiple stack heights to optimise the stack height, ensuring that the ground level concentrations are within safe exposure limits for the local community. In hilly regions, topological data is used with meteorological data to incorporate the effect of variations in the surrounding topology. Odour assessments are also conducted for facilities, to address regulatory concerns regarding odour emissions from material handling.