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This paper assesses and compares existing and new technologies for space heating in Germany (e.g., heat pumps, and solar thermal and wood pellet systems) in terms of their environmental impacts. The various technologies were analyzed within the context of the new German legislation. The assessment was carried out on three levels: 1. Global emissions: a life cycle assessment was carried out in order to find the global environmental footprint of the various technologies; 2. Local emissions: the effects of local emissions on human health were analyzed; and 3. Immissions: the immissions were evaluated for the various technologies using a dispersion calculation. A special feature of this study is the substitution of frequently used database emission values by values obtained from field studies and our own measurements. The results show large differences between the different technologies: while electric heat pumps performed quite well in most categories, wood pellet systems performed the best with respect to climate change. The latter, however, are associated with high impacts in other environmental impact categories and on a local scale. The promotion of some technologies (especially systems based on fuel oil, a mixture of fuel oil and rapeseed oil, or a mixture of natural gas and biomethane) by the newly introduced German legislation is doubtful. In terms of the immissions of wood pellet systems, it can be concluded that, even for extremely unfavorable meteorological conditions, the regulatory limits are not exceeded and the heating systems have a negligible influence on the total PM load in the ambient air

The sections in this article are Introduction and Summary Biomass Fuels Biomass Combustion Techniques Combustion Process Manually Operated Systems Log Wood Combustor Systems Log Wood Fired Heating Systems Automatically Fed Combustors Combustion Concepts for Automatically Fed Firing Systems Automatically Operated Wood Chip and Pellet Heating Systems Emissions Electricity Production and Combined Heat and Power

Various methods are available to investigate the particular emissions of combustion processes, and a brief survey of these is presented in this chapter. Within the flue gas of combustion, particle numbers may be measured continuously using either nucleus counters or light‐scattering instruments. The particle mass concentration is typically measured discontinuously by using filtering systems. Particle size distributions may be determined by applying fractionation to the aforementioned concentrations. On this basis, size‐classified particle number distributions or mass distributions may be measured. Typical fractionation methods can distinguish between aerodynamic separation on the basis of inertia (impactor, cyclone) and the electrical mobility of the particles. By comparing size distributions based on aerodynamic diameter with mobility diameter, the effective density of a particle collective can be calculated. A dilution system is normally required for the continuous measurement of particle concentrations in combustion flue gases, to reduce the dew point (avoiding condensation), and to adapting the concentrations to the instrument range. Ejector diluters, porous tubes and dilution tunnels are typically used to investigate stationary combustion processes. When analyzing the particle collective, it is essential to draw a representative sample; thus, in order to avoid sampling errors, certain criteria such as isokinetic sampling or transport losses must be respected.

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