A Review of Life Cycle of Ethanol Produced from Biosyngas

Abstract

This review compiled the life cycle (LC) studies on ethanol produced via gasification of biomass centering on greenhouse gas (GHG) emission and production cost to discuss their potential environmental and socioeconomic impacts. Numerous efforts have been made to evaluate the LC of ethanol produced with biosynthesis (gasification-microbial fermentation) and chemical synthesis (gasification-catalytic synthesis) of syngas produced from biomass (hereafter referred to biosyngas), and deals with system boundary, feedstock, energy paths and utilization of by-products to determine the environmental impacts as well as the production cost. It seems that most of the LC studies were conducted based on different research targets. Most of the reviewed studies support the environmental and economic viability of ethanol except for a few examples. A wide variation was observed in the reported GHG emission and production cost of ethanol which are dependent on the system boundary and assumptions, feedstock, conversion technologies and plant sizes. Consequently, in-depth studies are needed for each stage of the LC of ethanol from biosyngas for any future investment, commercial production, and sustainability. Moreover, a careful consideration has to be placed on the land use change and soil quality and their rebound effects if lignocellulosic biomass is to be put to use in the ethanol industry. LCA MethodologyLife cycle assessment (LCA) is a tool for evaluating environmental effects of a product, process, or activity throughout its life cycle Inventory analysisThe inventory analysis involves data collection on raw materials and energy consumption, emissions to air, water and soil, and solid waste generation. The inventory analysis is the most work intensive and time consuming phase in an LCA, mainly because of data collection. The data collection can be less time consuming if good databases are available and customers and suppliers are willing to help. Nowadays, many LCA databases are exists and can normally be bought together with LCA software. Data from databases can be used for processes that are not product specific, such as general data on the production of electricity, coal or packaging. However, site-specific data are required for product specific data. Inputs are energy (renewable and non-renewable), water, raw materials etc. Outputs are the products and co-products, and emission to air, water and soil and solid waste generation.

Single-Step Conversion of Ethanol to n-Butene over Ag-ZrO2/SiO2 Catalysts

“…Liquid samples collected from the knockout pot were analyzed separately ex situ using liquid chromatography. The ethanol conversion and the product selectivities were calculated as presented in equations [1] and [2] below. The carbon balance was typically within 10%.…”

“…Nonedible cellulosic feedstocks are attractive, because they are widely available, abundant, and relatively inexpensive; however, they currently represent a more costly option for producing ethanol . Ethanol also can be produced by enzymatic or thermocatalytic upgrading of syngas derived from biomass, municipal solid waste, or industrial waste gases (e.g., from steel mills). − Taken together, the ethanol “blend wall” coupled with advancements in production efficiency and feedstock diversification may potentially lead to excess ethanol at competitive prices available for production of a wide range of fuels and commodity chemicals …”

Production and Use of Sustainable C2‐C4 Alcohols – An Industrial Perspective

“…Several parameters need to be considered in analyzing the sustainability of ethanol produced by gas fermentations. System boundaries, carbon accounting, by‐product use and feedstock choice are of major significance and standardized methods are needed, especially when comparing results with conventional or other advanced approaches , . It is obvious that energy demands for downstream processes are higher than with conventional bioethanol processes as ethanol concentrations in the fermentation broth are lower in gas fermentations.…”

Energy Potential of Natural, Synthetic Polymers and Waste Materials - A Review

“…If the pyrolysis temperature is above 500 °C, a decrease in the yield of charcoal is observed. Slow pyrolysis of biomass at high temperatures, 800 to 1000 °C in the inert or steam atmosphere causes the formation mainly gaseous product containing CO 2 , CO, H 2 , CH 4 and some other gases with calorific value 10-12MJ/Nm 3 or 14-16MJ/kg [104].…”