Waste-to-Energy (WtE) plants generate electricity and heat through the thermal treatment of municipal solid waste (MSW). In 2003, the European Court of Justice stated that a particular WtE plant was a disposal operation because its main purpose was to treat waste, not taking into account the energy produced and exported by WtE plants, their contribution to the national energy supply, to resource economising (primary fuel savings) and the corresponding reduction of CO2 emissions (greenhouse gases, climate relevance).
Waste Framework Directive (WFD) 2008/98/EC introduced a calculation formula for determining the energy efficiency of incineration installations. The R1 formula aims to distinguish a recovery operation (R1 - Use principally as a fuel or other means to generate energy) from a disposal operation (D10 - Incineration on land), when it does not meet the R1 efficiency criteria threshold.
The "R1 criterion" or the "R1 formula" is a non-dimensional figure based on the 1st law of thermodynamics (energy input = energy output) combined with political objectives (minimizing demand for primary fuels). The R1 formula is the following:
- the threshold value is 0.6 for plants that began to be operational before 31/12/2008 and 0.65 for newer plants.
- Ep: annual energy produced as 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;
- Ef: annual energy input to the system from fuels contributing to the production of steam;
- Ei: annual energy imported excluding Ew and Ef;
- Ew: annual energy contained in the treated waste.
The main objective of the R1 formula is to promote the efficient use of energy from waste in Waste to Energy (WtE) plants. It takes into account the plant’s effectiveness in recovering the energy contained in waste, as well as the effective uses of energy as electricity, heating and cooling, or processing steam for industry.
Annex II of the WFD restricts the scope of the formula to "incineration facilities dedicated to the processing of Municipal Solid Waste", so it does not apply to plants that are dedicated to incineration or co-incineration of hazardous waste, hospital waste, sewage sludge or industrial waste.
It is also crucial that the formula be applied to the correct parts of the EfW process and that the “system boundaries” are set correctly. The system boundaries used will have considerable implications on the energy streams that are calculated as Ef, Ew and Ei in the efficiency calculation. Therefore, the 'system boundaries' are clearly defined in the guidance as the 'functional incineration unit' and not the installation according to the IPPC permit. The functional incineration unit is set as the incineration oven(s), the boiler(s), and the incineration flue gas cleaning system. Often, energy transformation and recovery equipment such as heat exchangers feeding a district heating or cooling network and/or turbine generator are also taken into account.
The most significant issues regarding the R1 Formula are the following:
However, the Article 38.1 of the Waste Framework Directive provides that regarding the R1 formula, local climatic conditions may be taken into account, such as the severity of the cold and the need for heating insofar as they influence the amounts of energy that can technically be used or produced in the form of electricity, heating, cooling or processing steam.
The advantages of introducing the R1 formula are that Waste-to-Energy plants are classified as recovery rather than disposal; thus the R1 formula will facilitate WtE moving up the waste hierarchy. The R1 formula is applicable only in European countries, while it should not be mixed with the efficiency ratio (η) of the plant.