Author(s)

K. J. Ptasinski

Abstract

Concerns about global climate change and depletion of fossil fuels have increased interest in biomass and other renewable energy sources. Due to shortage of clean biomass much attention is recently devoted to various biowaste streams. This paper focuses on biowaste gasification, where the produced synthesis gas can be subsequently used to produce biofuels, including Fischer- Tropsch hydrocarbons, methanol and hydrogen. The thermodynamic efficiency of biowaste gasification is evaluated for various feedstocks using energy and exergy indicators. It is shown that exergetic efficiency is lower than corresponding energetic efficiencies. Modification of biomass gasification is proposed to improve process efficiency. Finally, the conversion efficiency of overall chains biomass-to-biofuel is discussed. Keywords: renewable energy, biomass, waste gasification, exergy analysis. 1 Introduction With declining petroleum resources and concerns about climate change more attention is now being directed towards sustainable production of chemicals and transportation fuels. In this respect biomass has neutral CO2 impact and is the only current sustainable source of carbon. The most promising biomass-to biofuel route is a two-stage process involving production of syngas from biomass gasification, followed by synthesis of transportation fuels, involving Fischer- Tropsch hydrocarbons, methanol, and hydrogen. It was previously demonstrated that the gassier is one of the least-efficient unit operation in the whole biomassto- biofuels chain. Therefore, an analysis of the gasifier alone can substantially contribute to the efficiency improvement of the whole biofuel production technology.

Keywords

renewable energy, biomass, waste gasification, exergy analysis.