CELLULOSIC MATERIALS

Cellulosic Materials



Cellulosic Materials

Introduction

In view of continuously rising petroleum costs and dependence upon fossil fuel resources, considerable attention has been focused on alternative energy resources. Production of ethanol or ethyl alcohol (CH3CH2OH) from biomass is one way to reduce both the consumption of crude oil and environmental pollution (Lang et al., 2001a).

Primary consideration involves the production of ethyl alcohol from renewable resources and determination of the economic and technical feasibility of using alcohol as an automotive fuel blended with gasoline (Goldstein, 1981), Ethanol represents an important, renewable liquid fuel for motor vehicles (Lewis, 1996). The use of gasohol (ethanol and gasoline mixture) as an alternative motor fuel has been steadily increasing around the world for a number of reasons. Domestic production and use of ethanol for fuel can decrease dependence on foreign oil, reduce trade deficits, create jobs in rural areas, reduce air pollution, and reduce global climate change carbon dioxide buildup.

Ethanol, unlike gasoline, is an oxygenated fuel that contains 35% oxygen, which reduces particulate and NOx emissions from combustion. When burned, ethanol derived from fermentation produces no net increase in carbon dioxide in the atmosphere. It is an octane enhancing additive and removes free water which can plug fuel lines in cold climates (Lang et al., 2001 fc Ethanol is the most widely used liquid biofuel. It is an alcohol and is fermented from sugars, starches or from cellulosic biomass. Most commercial production of ethanol is from sugar cane or sugar beet, as starches and cellulosic biomass usually require expensive pretreatment.

It is used as a renewable energy fuel source as well as for manufacture of cosmetics, Pharmaceuticals and also for the production of alcoholic beverages. Ethyl alcohol is not only the oldest synthetic organic chemical used by man, but it is also one of the most important. In an earlier study (Taherzadeh, 1999), physiological effects of inhibitors on ethanol from lignocellulosic materials and fermentation strategies was comprehensively investigated. Yeast based fermentation, for example, has yielded ethanol from sugar or crops. The production of ethanol by fermentation of sugar has already been commercially established but innovative studies could bring improvements to reactors and separation systems. To produce ethanol from lignocellosic materials, it is essential to hydrolyse it before fermentation at the demonstration and industrial level. Enzymatic hydrolysis is still at an early stage, requiring substantial fundamental research (e.g., for increased yields) (Ku9uk and Demirba§, 1997). Conversion technologies for producing bioethanol from cellulosic biomass resources such as forest materials, agricultural residues and urban wastes are under development and have not yet been demonstrated commercially. Uncertainties regarding commercial scale performance and profitability combined with unclear market outlook in the longer term constrain private investment in such facilities. The estimated world ethanol production in 1998 was 33.3 billion liters (Berg, 1998). Approximately 9% of the ethanol is produced synthetically, and consequently, fermentation is responsible for 91% of global ethanol production (Wheeler et al., 1991). Brazil is the dominant producer of alcohol with a production of ...