Factors influencing availability of biomass resources and efficiency of its procurement for energy generation. A regional study for the Banská Bystrica Region, Slovakia

Abstract

The paper presents results of the study analysing the whole chain from methodology of overall and available biomass resources calculations in the region, the most efficient technologies and procurement methods, logistics and economy of biomass supply to the consumer, up to the economic and ecological gains from the conversion of boilers for co-firing wood and brown coal. The study was conducted for the Banská Bystrica region, Slovakia. There is a combined heat and power plant (CHP) in town Zvolen. CHP, originally commissioned in 1954. Overall installed output is 311 MW in heat production and 44, 3 MW in power. Annual supply to the consumers was some 790.000 GJ of heat and 103.000 GJ of electricity during the last few years. Some 60 % of heat production was used for heat and hot water supply to more than 9.000 houses and apartments and 40 % to industrial consumers. It has been using pulverized lignite with up to 1 % of sulphur content as fuel. The content of sulphur in emitted flue gas was as high as 3.500 4.000 mg SO<sub2</sub>/m³. It causes serious environmental problems in the region. New national limits for greenhouse gases emissions are 1.700 mg SO₂ /m³ and 600 mg NO_x/m³ with the effect from 1 January 2007. CHP has not been able to achieve them without substantial improvement of technology. Shift from lignite to low-sulphur content brown coal with co-firing of biomass has been identified economically the most feasible and environmentally acceptable solution. Two boilers, each of them with the output of 108 MWt, will be reconstructed for co-firing of pulverized low sulphur content brown coal and biomass. Biomass will share up to 30% of the combusted fuel. The first part of the study was focused on identification of biomass resources for energy use from forestry, wood processing industry and agriculture in the region, with the use of GIS tools. Ecological, economic and operational factors limiting utilization of potential biomass resources were identified and factored into calculations. Logistics of wood supply have been precisely analysed. Costs of wood chips supply from forest residues for three different supply chains have been calculated taking into account ecological, economic and technical limiting factors and transport distances. Also environmental issues have been analyzed. Emissions of greenhouse gases after the reconstruction of boilers will be within the limits in force after 1 January 2008, i.e. 1.400 mg SO₂/m³, 600 mg NO_x/m³, 250 mg CO/m³ and 50 mg fly ash/m³.