Characterization of diffuse odorous emissions from lignocellulosic biomass storage

The use of lignocellulosic biomass for green energy production is increasing, but the wood storage may lead to ambient odor related issues. This study aims to assess the odor potential and to investigate the mechanisms that promote odorous emissions from wood chip heaps. To achieve this goal, four experimental campaigns were conducted in an Italian thermal power plant. During these campaigns, odor concentration and chemical-physical parameters, that should theoretically affect the odor potential of biomass heaps, were investigated. The first important outcome revealed a strong heterogeneity on the heaps surface, classified as dry or smoking according to the superficial humidity and smoke. Smoking areas proved to be much more emissive and at self-ignition risk than dry regions. Indeed, odor concentration on smoking regions reached values in the order of 10^5 ouE/m^3, significantly higher than dry region ones (10^2 ouE/m^3). In addition, the highest values of odor concentration have been detected in the first days of storage, when fatty acids are oxidized and terpenes are released. Again, after 30 ÷ 80 days, i.e. about 20 days after the temperature peak caused by biological activity, odor concentration increases, suggesting a possible cause-effect mechanism between biological processes and odor release. Unexpectedly, odor emissions decreased during summer, reasonably due to the high ambient temperature which reduces the moisture content limiting biological activity. However, after about 100 days of storage, smoking regions extent and odor emissions can be considered negligible.