According to Directive 2008/98/EC (EU, 2008), the operation of an incinerator for Municipal Solid Waste (MSW) is classified either as energy recovery (R1) or as disposal (D10) depending on the result achieved by applying the R1 formula.
R1 = (Ep - (Ef + Ei) / (0.97 x (Ew + Ef)In which:
- Ep stands for annual energy produced as either heat or electricity. It is calculated with energy in the form of electricity being multiplied by 2.6 and heat produced for commercial use multiplied by 1.1 (GJ/year);
- Ef stands for annual energy input to the system from fuels contributing to the production of steam (GJ/year);
- Ew stands for annual energy contained in the treated waste calculated using the net calorific value of the waste (GJ/year);
- Ei stands for annual energy imported excluding Ew and Ef (GJ/year);
- 0,97 is a factor accounting for energy losses due to bottom ash and radiation.
The directive gives concise definitions of the various terms, leaving room for arbitrary interpretations. Therefore, in 2011, the DG Environment of the European Commission issued some non-binding guidelines on the interpretation of such a formula (EC, 2011). Many operative aspects were clarified, although only conceptual specifications were given for the quantification of the EW term (the energy contained in the treated waste). In fact, for the determination of the EW term, reference is made to the indirect method for the calculation of boiler thermal efficiency, as defined by the standard EN 12952-15 (CEN, 2003).
In the process of calculating the R1 formula for waste-to-energy initiatives in which UNIVASTUM participates, we identified various difficulties that hinder the accuracy of such calculations.
The main difficulty was the instability of the calorific value of waste used as fuel for gasification, which is most typical for municipal solid waste.
Municipal solid waste is characterized by its intrinsic instability, which arises from the significant dependence of its composition on the geographical location of the facility, the particular characteristics of the regional population, and even the variations associated with specific days of the week and seasonal changes. As a result, the determination of the R1 coefficient prior to the project's implementation is not adequately precise.
Meanwhile, when working with mono-waste, this index for UNIVASTUM solutions can be calculated quite accurately, which is what we propose in this article.
In accordance with our established procedures, we will present a calculation of the P1 index pertaining to the operation of a waste-to-energy facility that utilizes the gasification of WARP, employing used tires as its fuel source.
We calculate for the standard solution waste to energy UNIVASTUM the following:- Electric power (net to the grid) - 4 MW
- Heat supplied to the consumer - 4 MW
- Waste disposal (used tires) - 16,000 tons per year
- Number of working hours per year - 8,000
- Waste tires LHV is considered as 32 to 34 MJ/kg, which is comparable to that of one ton of coal or 0.7 tons of petroleum-based fuel. For the calculation, we used 33 MJ/kg.
- 1 kW-h is equal to 3,6 MJ