Eemeli Tsupari

Estimation of annual CH4 and N2O emissions from fluidised bed combustion: An advanced measurement-based method and its application to Finland

Abstract The aim of this study was to develop and apply an advanced, measurement based method for the estimation of annual CH 4 and N 2 O emissions and thus gain improved understanding on the actual greenhouse gas (GHG) balances of combustion of fossil fuels, peat, biofuels and REF. CH 4 and N 2 O emissions depend strongly on combustion conditions, and therefore the emission factors used in the calculation of annual emissions contain significant uncertainties. Fluidised bed combustion (FBC) has many good properties for combustion of different types of fuels and fuels of varying quality, e.g., biofuels and wastes. Therefore, it is currently increasing its market share. In this study, long term measurements (up to 50 days) were carried out at seven FBC boilers representing different size classes, loadings and fuel mixes. Both decreasing load and increasing share of coal in fuel mix increased N 2 O emissions. Measurement results from different loading levels were combined with the common loading curves of similar plants in Finland to estimate annual emissions. Based on the results, recommendations for emission factors for the Finnish GHG emission inventory are given. The role of FBC as a potential technology for the utilisation of biofuels and wastes with future GHG reduction requirements is discussed.

Comparing the greenhouse gas emissions from three alternative waste combustion concepts

Three alternative condensing mode power and combined heat and power (CHP) waste-to-energy concepts were compared in terms of their impacts on the greenhouse gas (GHG) emissions from a heat and power generation system. The concepts included (i) grate, (ii) bubbling fluidised bed (BFB) and (iii) circulating fluidised bed (CFB) combustion of waste. The BFB and CFB take advantage of advanced combustion technology which enabled them to reach electric efficiency up to 35% and 41% in condensing mode, respectively, whereas 28% (based on the lower heating value) was applied for the grate fired unit. A simple energy system model was applied in calculating the GHG emissions in different scenarios where coal or natural gas was substituted in power generation and mix of fuel oil and natural gas in heat generation by waste combustion. Landfilling and waste transportation were not considered in the model. GHG emissions were reduced significantly in all of the considered scenarios where the waste combustion concepts substituted coal based power generation. With the exception of condensing mode grate incinerator the different waste combustion scenarios resulted approximately in 1 Mton of fossil CO(2)-eq. emission reduction per 1 Mton of municipal solid waste (MSW) incinerated. When natural gas based power generation was substituted by electricity from the waste combustion significant GHG emission reductions were not achieved.