The changes in the domestic solid fuel market (including forecasted increases in the fuel prices) and the growing requirements related to actual environmental standards, result in increased interest in renewable energy sources, such as biomass, wind and solar energy. These sources will allow to achieve reduction in the CO2 emission, and consequently – avoid environmental costs after 2020. Therefore, the development of distributed energy systems, based on the use of biomass boilers, gas boilers and high efficiency combined heat and power units, will enable the fulfillment of current standards in the field of energy efficiency and emission of pollutants to the atmosphere. It should be emphasized that the actions taken to reduce emissions (e.g. anti-smog act) will contribute to reducing coal consumption in the municipal and housing sector (households, agriculture and other customers) in favor of biomass and other renewable energy sources. The article reviews selected biomass technologies: - fluidized, dust and grate boilers, - straw-fired boilers, - cogeneration systems powered by biomass, - torrefaction and biomass carbonisation. The mentioned technologies are characterized by a high potential of in the field of dynamic development and practical application in the coming years. Thus, they can improve difficult situation in the distributed energy sector with a capacity up to 50 MW.
The influence of sewage sludge torrefaction temperature on fuel properties was investigated. Non-lignocellulosic waste thermal treatment experiment was conducted within 1 h residence time, under the following temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as lignocellulosic reference material. The following parameters of biochar have been measured: moisture, higher heating value, ash content, volatile compounds and sulfur content. Sawdust biochar has been confirmed to be a good quality solid fuel. High ash and sulfur content may be an obstacle for biochar energy reuse. The best temperature profile for sawdust torrefaction and fuel production for 1 h residence time was 220°C. At this temperature the product contained 84% of initial energy while decreased the mass by 25%. The best temperature profile for sewage sludge was 240°C. The energy residue was 91% and the mass residue was 85%. Higher temperatures in both cases caused excessive mass and energy losses.