Pyrolysis of Lignocellulosic Biomass: The Case Study of Spartina Argentinensis

EMILIANO JOZAMI; SUSANA FELDMAN; MELISA BERTERO; BÁRBARA CIVIT; ULISES SEDRAN

Buenos Aires

Conferencia; 2nd RCN Conference on Pan American Biofuels & Bioenergy Sustainability; 2016

Greenhouse gases (GHG) from fossil fuel combustion are one of the main drivers of climate change (CC). Therefore, its displacement by renewable energy sources will contribute to mitigate CC impacts. Lignocellulosic biomass is recognized as a feedstock for the production of bioenergy due to the fact that cellulose is the most abundant organic compound on Earth. Spartina argentinesis (espartillo) is a C4 grass which dominates herbaceous plant communities in an extensive region of northern Santa Fe, western Santiago del Estero and southern Chaco provinces (Argentina), named "Bajos Submeridionales". The region comprises more than 3 million hectares of halohydromorphic soils poorly drained, annual rainfall ranging from 800 to 1200 mm with a high interannual variability; hence, it is prone to subsequent cycles of drought and floods. Most farmers within this region practice extensive livestock farming: large plots (circa 100 hectares) subjected to continuous grazing. Due to the low palatability of S. argentinensis, especially when it is in advanced vegetative states, prescribed fires are a common practice among farmers looking for a higher digestibility regrowth. However, this practice generates numerous negative externalities: emission of GHG, production and dispersion of particulate matter (affecting the respiratory tract), risk of uncontrolled fires, and deterioration of rural infrastructure (poles and fencing). Nevertheless, there existoptions to exploit this feedstock as a source of renewable energy through, e.g., its pyrolysis into useful fuels and/or chemicals. The biomass was obtained from rangelands nearby the town of Coronda (Santa Fe), using a forage cutter and a round baler. Bales were subjected to three consecutive transformations: icoarsely chopped; ii- chopped with a 25-50 mm mesh (density of 66.9 kg.m-3) and iii- finely grinded to obtain a particle size of 0.2-0.5 mm (density of 165 kg.m-3). Finally, biomass was successfully pelletized without adding any binding agent obtaining pellets that, considering physics parameters, fall in the Enplus-A1 category. Pellets were dried and then pyrolysed in a laboratory unit based on a stainless steel reactor heated electrically inside an oven. The experiments were performed in a fixed bed with a 20 °C min-1 heating ramp from room temperature to 500 °C, cond ition which was maintained constant during 30 min, under inert atmosphere (30 ml.min-1 N2 flow). Three main streams were obtained: liquids (bio-oil andtar), solids (char) and gases (mainly composed by carbon oxides, hydrogen and methane). Yields were 29.2 % (bio-oil), 7.4 % (tar), 33.8 % (char) and 29.7 (gases). The bio-oil contained 44.9 % of water and the rest were oxygenated organic compounds mainly derived from cellulose and hemicelullose, the major ones being acetic acid, furfural and other furanes and linear and cyclic pentenones. Moreover, compounds derived from lignin were also present, such as phenol, guaiacol and their alkylated derivatives. The alquitranous phase (tar) showed a majority of phenolic and high molecular weight compounds (acids, alcohols, esters and long chain hydrocarbons). Considering these results, both in terms of bio-oil and tar yields and their compositions, this biomass can be considered a promising renewable source of fuels and chemicals.