(196b) Green House Gas Emissions from Lignocellulosics USED As Raw Material for Biorefineries
Green house gas (GHG) emissions reduction is one of the main drivers of the replacement of oil with biomass as raw material for fuels and chemicals under an overall concept of biorefineries (Panichelli and Gnansounou 2008). Biorefineries have recently attracted the attention from researchers since this concept implies the effective and sustainable use of biomass resources for ensuring food and energy security, mitigating climate change and meeting the demand for renewable based chemicals and materials. The beneficial biomass resources to be used into a biorefinery as feedstock can be classified into three main categories: First, second and third generation feedstocks.
Feedstocks included into the first generation type are not only renewable, but also have feed/food uses. Its advantages lie on the high productivity of the crops. However, the population increment has resulted in concerns about competition with food needs (Hughes, Gibbons et al. 2013; Quintero, Moncada et al. 2013). The second generation feedstocks are more available and are not directly used as food, although some of them are used as livestock feed. Here agro-industrial residues from the harvesting and processing of the first generation feedstocks and crops that neither need special treatment nor threat with food security (e.g. Jatropha Curcas, Castorbean), are included. The Second generation feedstocks are more beneficial than the first generation feedstocks in terms of efficient use of land and proper environmental management. Furthermore, these raw materials are leading the way to sustainably meeting energy needs while also supplying materials for chemical and manufacturing industries. Besides, the use of organic wastes as raw material is especially beneficial: When these residues are disposed of in a landfill, it decomposes and releases methane, which is a potent global warming gas. Thus, processing these wastes to obtain value-added products reduces landfill volume as well as methane emissions (Hughes, Gibbons et al. 2013). The third generation feedstocks are considered as a viable energy resource without the disadvantages associated to the first and second generation feedstocks. Furthermore, microalgae have a very high photosynthetic efficiency, contributing to the sequestration of atmospheric carbon dioxide. However, deep analysis of separation and purification of the oils from microalgae can demonstrate that the energy consumed can affect negatively the carbon dioxide assimilation.
The aim of this work was to estimate the GHG emissions of a biorefinery system based on three second generation feedstocks to produce ethanol, poly-3-hydroxybutyrate (PHB) and electricity integrated into a biorefinery using the Life Cycle Assessment (LCA) methodology. For this study, the harvesting residues from three Colombian crops: Sugarcane, oil palm and plantain, were selected as raw materials. The raw materials were characterized by measuring moisture content (AOAC 928.09 method), klason lignin content (TAPPI 222 om-83 method), acid-soluble lignin content (TAPPI 250UM-85 method) holocellulose content (ASTM Standard D1104 method), cellulose content (TAPPI 203 os-74 method), ash content (TAPPI Standard T211 om-93 method), total nitrogen content (kjeldahl method), potash content (colorimetric method) and phosphorous content (colorimetric method). All the experiments were carried out in the Biotechnology and Agrobusiness Institute at the Universidad Nacional de Colombia at Manizales.
In Colombia, one of the harvesting practices is to leave a part of the harvested residues on the field providing to the soil a percentage of the nutrients and organic matter required by the plant growth (Serna Cock and Rodríguez de Stouvenel 2007). The remaining nutrient requirements should be supplied externally by the addition of chemical fertilizers and amendments. In this work, two scenarios have been proposed for each raw material: The first one considered the base case above described, where part of the harvesting residues are left on the field. The second scenario considered the case where all the harvesting residues are retired from the field and all the nutrients required by the crop should be externally supplied. For both scenarios, the GHG emissions for the biorerineries have been calculated. Besides, the results have been compared to the gasification of the residues to produce electricity.
The results lead to conclude that for the second scenario the GHG emissions increase, due to the increasing on the fertilizer requirements together with the decreasing on the CO2 capture by the crop.
Hughes, S. R., W. R. Gibbons, et al. (2013). Sustainable Multipurpose Biorefineries for Third-Generation Biofuels and Value-Added Co-Products, Biofuels - Economy, Environment and Sustainability. Z. Fang.
Panichelli, L. and E. Gnansounou (2008). "Estimating greenhouse gas emissions from indirect land-use change in biofuels production: concepts and exploratory analysis for soybean-based biodiesel production." Journal of Scientific & Industrial Research 67: 1017-1030.
Quintero, J. A., J. Moncada, et al. (2013). "Techno-economic analysis of bioethanol production from lignocellulosic residues in Colombia: A process simulation approach." Bioresource Technology 139(0): 300-307.
Serna Cock, L. and A. Rodríguez de Stouvenel (2007). "Lactic acid fermentative production using waste from the harvest of green sugar cane as a substrate." Interciencia 32: 328-332.
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