Production of Biofuels and Biochemicals from Lignocellulosic Biomass: Estimation of Maximum Theoretical Yields and Efficiencies Using Matrix Algebra

摘要

The dependence on fossil fuels in developed countries is causing increasing concern. Global warming, issues related to peak oil, sustainability issues, and mounting concern for national energy security are the main drivers for a worldwide effort toward a reduction in fossil fuel consumption. The challenge is substantial, because fossil resources are such an integral part of our economy. However, there are many efforts to address this challenge. Development of conversion technologies fed by renewable resources is seen as a promising option. Many technologies for renewable energy are already well-developed and competitive in the market. Emerging technologies include biorefinery complexes, where biomass is used as a renewable carbon-based source for the production of bioenergy and biochemicals. The latter is perceived as a promising alternative to oil-based chemicals. Given the constraints on availability for renewable biomass supply, the importance of efficient use of biomass with a maximization of useful final products is well-acknowledged. Assessing the potentials for biochemicals can be achieved with an a priori cstimation of the maximum theoretical yields, as well as a prediction of the conversion efficiencies (in terms of mass, carbon, and energy efficiency) of selected biorefinery production chains. This paper addresses this issue, providing a calculation procedure with which the theoretical yields and efficiencies of some biorefinery systems are estimated. Among the possible biomass sources, lignocellulosic biomass is selected as the raw material, because it is the most-widespread renewable source available in the world, it is locally available in many countries, and it does not compete with food and feed industries. The conversion of biomass to biofuels and chemicals requires conversion of the feedstock from a solid to a liquid state, but also the addition of hydrogen and rejection of excess oxygen, together with other undesired elements. The carbon contents of lignocellulosic biomass components (cellulose, hemicellulose, and lignin) and products are calculated with the help of mathematical equations, and then the chemical reactions for the conversion of feedstock to products are modeled using matrix algebra: the maximum amount of biofuels and/or biochemicals from biomass and the maximum mass, energy, and carbon conversion efficiency of the biorefinery pathway are determined. Following this calculation procedure, an application to some biorefinery systems is performed and discussed. Combining the best feedstock with the most promising final products, results show that up to 0.33 kg of bioethanol, 0.06 kg of furfural, and 0.17 kg of FT-diesel per kg of softwood can be produced and mass, carbon, and energy conversion efficiencies of 56%, 70%, and 82%, respectively, are achieved.