Assessment of wood chip combustion and emission behavior of different agricultural biomasses

The increased interest in using farm-grown biomass for energy production makes it necessary to expand and deepen knowledge on combustion of agricultural residues. The lack of data and studies on solid fuel quality, and combustion related emissions, represents an obstacle to the sustainable development of agricultural biomass industry. In the Mediterranean basin, large quantities of lignocellulosic biomass are obtained yearly from pruning operations carried out largely widespread in fruit plantations such as citrus, grapevine and olive orchards. The most common practice to eliminate this type of residue is the open burning, carried out directly on the field by farmers, without any emissions control or energy recovery. The aim of this study was to obtain a clear description of three different wood biomasses and their behavior during combustion. The physicochemical properties were studied to determine their influence on combustion emissions. Measurements were conducted in laboratory and subsequently carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), nitrogen oxides (NOx), sulfur dioxide (SO2), Total Organic Compounds (TOC), and particulate matter (PM) emissions were evaluated during combustion in a 30 kW boiler equipped with a multicyclone filter bags for emission abatement. Principal Component Analysis (PCA) was applied to the data of biomass properties and emissions parameters in order to elucidate which feedstock features had a more determinant influence on the combustion process. Grapevine and citrus showed high N content and consequent high NOx production. Olive highlighted the best characteristics, high energetic potential and low emissions under regulation limits; in addition, olive pruning residues is the most available woodfuel in the Mediterranean area of Europe, confirming its great potential on agricultural biomass industry sustainable development.