Analysis of air emissions and greenhouse gases in woody biomass production chain
The whole world is trying to increase energy production from renewable energy sources. Biomass, mainly solid fuel (e.g. wood chips, sawdust, etc.), takes first place in Lithuania's efforts to increase energy production from renewables. There are a lot off studies about minimization of greenhouse gases (GHGs) during biomass combustion for energy production due to biogenic CO2. Unfortunately, such aspects as biofuel production, including biomass collection in harvesting sites, delivery to special interim sites, processing, produced biofuel transportation to combustion plants is rarely estimated in this studies. A considerable amount of diesel fuel is used within these processes by various mechanisms (e.g., skidders, tractors, crushers, chippers, etc.); therefore woody biomass production and delivery processes have significant environmental impact to air quality and climate change due to air emissions (CO, NOx, NMVOC, PM, NH3) and GHGs (CO2, N2O, NH4) from off-road and road mobile sources.
This paper presents the method of evaluation and results of analysis of material and energy flows of wood chips production from traditional raw materials – firewood and forest logging waste (residues). It was estimated that up to 0.038 toe of diesel fuel is used for one toe of produced woody biomass, incl. over 52% - for biofuel delivery to combustion plant; 0.293 kg of air emissions and over 22.5 kg of GHGs are emitted to the air during production of one tonne of wood chips. Results of comparison analysis show that in case of biofuel production from logging residues, volume of GHGs is 57% higher in comparison to wood chips are produced from firewood. Several recommendations how to minimize significant environmental impact due to usage of logging residues to energy purposes are presented in article.
Received environmental indicators can be successfully used for further detailed life-cycle assessment of woody biomass production and usage for alternative energy.