Ramboll carried out a risk assessment on biomass fly ash for Eco 2 Ltd in 2016. Our client operates a biomass renewable energy facility that combusts straw and clean wood and produces a potash-rich fly ash. We supported their End of Waste submission and established that the fly ash can be used as a fertiliser substitute when applied to agricultural land with no significant risks to human health or the environment.
End of Waste test criteria
To demonstrate that waste material can be considered a product and therefore outside waste regulatory control, the Environment Agency developed the End of Waste test criteria, including a range of requirements that must be met. One of these requirements is an assurance that there are no properties in the waste-derived product, including trace components or contaminants, that could lead to a worse environmental impact than if you were to use an equivalent non-waste product.
Our approach to risk assessment
In response to the Environment Agency’s concerns about potential risks associated with dioxins and furans contained in fly ash and the effects of bioaccumulation, we developed a conceptual model for the site and assessed human health and environmental risks. In line with current UK practice for assessing risk from contaminated land, we used statistical analysis to establish a representative dioxin and furan concentration within the fly ash.
Ramboll assessed the following:
• Major sources of dioxin in the human diet
• Deposition to land
• Entry into the food chain
• Exposure pathway for livestock
• Exposure pathway for arable land
• The bioaccumulation effects
The toxic equivalency (TEQ) was calculated and assessed against rural and urban background soil concentrations.
What we discovered
Results showed that dioxin concentrations in the fly ash did not exceed the dioxin guideline values. The application of fly ash to agricultural soils did not appear to significantly contribute to net dioxin loading and is unlikely to pose a significant risk to human health through dietary exposure.
Our team will continue to carry out assessments on potential impacts over a prolonged period.