Waste Derived Fuel
Prior to energy recovery, the combustion of waste was commonly used as a way to reduce the large volumes being sent to landfill, but was considered to be below landfill in the Waste Hierarchy.
Today, energy recovery is seen as a preferable alternative since landfill generates carbon dioxide and methane gasses, whereas combustion generates only carbon dioxide. A report issued by DEFRA estimates that methane is around 25 times more damaging to the atmosphere than carbon dioxide.
As a general definition, a Waste Derived Fuel is a form of Municipal Solid Waste, which may have undergone a variety of different processes and treatments in order to make it suitable for use as a fuel. Very often, the compositional quality and the environmental parameters are not well described which can pose a risk for both producers and end users. This prompted the European Commission to introduce a new term for waste being converted to fuel – Solid Recovered Fuel (SRF).
What is SRF?
SRF is distinguishable from other waste derived fuels as it is produced in accordance with the requirements of the European standards for SRF, specifically in accordance with EN15359. Other fuels produced from waste are often called Refuse Derived Fuel (RDF).
What are the differences between SRF & RDF?
The main difference between SRF and RDF is that SRF is intentionally produced with respect to quality criteria, whereas RDF is usually the remaining fraction from waste treatment operations. Producers of SRF control the production process to ensure that their fuel meets the desired specification. RDF is a non-specified waste and so its quality and environmental features cannot be guaranteed.
To help SRF producers create the right fuel for the end user, a classification system has been put in place in the UK by the Waste and Resources Action Programme (WRAP), based on three main criteria: economic, technical and environmental. This system helps SRF producers classify their fuel, whilst also allowing the end user to analyse the associated data of the fuel to determine it’s suitability for their facility. Awareness of these characteristics are essential to the running of efficient energy from waste (EfW) incineration plants here in the UK or in Europe as well as meeting the differing regulatory requirements in Europe.
The classification system is arranged as follows:
- Economic Attributes
These determine the relative quality, and hence value of the fuel.
- Technical Attributes
A combustion facility would have to be designed to deal with these components effectively.
- Environmental Attributes
The presence of heavy metals could lead to harmful emissions to the atmosphere.
A high percentage of biomass is preferable since this is fuel from a sustainable source.
In order to classify and assess the suitability of a waste derived fuel, testing is required for a number of crucial parameters.
Chemtest undertakes all of the key tests including calorific value (gross and net), proximate/ultimate analysis, halides, metals and biomass analysis.
Upon sample receipt, basic or detailed gravimetric compositional characterisation may be undertaken such as moisture content and manual sorting into individual fractions.
Subsequent methods of sample preparation are undertaken in accordance with BS EN 15443:2011 and analysis is carried out in accordance with the relevant BS or proven in-house procedures. The key parameters undertaken are: