CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Lignocellulosic biomass
(e.g. sawdust obtained from wood) provides a unique and sustainable
resource for environmentally safe organic fuels and chemicals.
Furthermore, due to the abundance of lignocellulosic materials, its
conversion to ethanol (a biofuel) is considered one of the most
important uses of biomass as an energy source in the modern world
especially in the United States, Europe and Asia (Kheshgi, 2000).
Sawdust is produced as a
small discontinuous chips or small fragments of wood during sawing of
logs of timber into marketable sizes. The chips flow from the cutting
edges of the saw blade to the floor during sawing operation, hence its
name sawdust has hitherto been classified as a waste and a nuisance to
man and its environment, but in recent years, researches have shown that
sawdusts can be used in the production of biogas, packaging fillers,
and lagging materials etc. The ethanol produced from the food crops were
called first generation bio ethanol, whereas the ethanol produced from
lignocellulosic biomass were called second generation biomass (Naik et
al., 2009). But there were some concerns related to the first
generation bio ethanol. Some of them were food security in which there
was an issue that the use of food crops will increase the food prices.
Greenhouse gases balance also seems to shift as the production of bio
ethanol involves more and more food crops. Some environmental concern
shows that bio ethanol production from crops might affect the
biodiversity and water preservation. The quest for alternative energies
has provided many ways to produce electricity, such as wind farms,
hydropower, or solar cells. However, about 40% of the total energy
consumption is dedicated to transports and in practice requires liquid
fuels such as gasoline, diesel fuel, or kerosene. These fuels are all
obtained by refining petroleum. This dependency on oil has two major
drawbacks, burning fossil fuels such as oil contributes to global
warming and importing oil creates a dependency on oil producing
countries(Sadler,
2004).
Again, ethanol produced
from biomass would be of great benefit to the transportation sector
where it is assumed that two-third of Nigeria’s gasoline is consumed.
Globally, fossil fuels are being threatened out of dominance over other
fuels by the negative effects of fossil fuels products on the
environment e.g. the release of greenhouse gases like carbon dioxide
that contribute to global warming.
The pollution of air,
water, and soil by fossil fuels products (carbon dioxide from fossil
fuel combustion accounted for nearly 80% of global warming in the 1990s)
(Hileman, 1999). The greatest proportion of the world’s energy
requirements comes from petroleum exports especially in the Middle East,
a region of high political tension, the reasons that necessitate
efforts at finding alternatives to fossil fuels. Lignocellulose wastes
refer to plant biomass wastes that are composed of cellulose,
hemicellulose, and lignin as well as other minor components. Both the
cellulose and hemicellulose fractions are polymers of sugars, and are
thereby potential sources of fermentable sugars, which can be converted
into other products (Ndukwe et al., 2013). Hemicellulose can be readily
hydrolyzed under mild acid or alkaline conditions. The cellulose
fraction is more resistant and therefore requires more rigorous
treatment than the hemicellulose fraction. Currently, the second
generation bio-products from lignocellulosic biomass such as bioethanol,
biodiesel, and methane are increasingly being produced from wastes
(residues) rather than from energy crops (jatropha, Swtich grass, and
willow) because the latter competes for land and water with food crops
that are already in high demand. The use of food crops such as corn and
sugarcane to produce biofuels is increasingly being discouraged due to
the current worldwide rise in food prices. In order to minimize
food-feed-fuel conflicts, it is necessary to integrate all kinds of
bio-waste into a biomass economy (Mahro and Timm, 2007). Furthermore,
the use of lignocellulosic waste offers a possibility of geographically
distributed and greenhouse-gas-Favourable sources of products (Rubin,
2008). The Energy Commission of Nigeria reported that the fuel-wood
resource constitutes 2.8% of the total renewable energy resources in
Nigeria. Biomass reserve in Nigeria is put at 80 %, which equals to an
equivalence of 1.645 billion tonnes of energy which is predicted to be
potentially available for the next 100 years (Umar et al., 2000).
Nigeria started the importation of ethanol from Brazil, and thereafter
there was a call to mass produce cassava as a raw material for
cellulosic ethanol production. The argument was that Nigeria has not
properly produced enough cassava for its populace, it seems as if the
push has died down .thus, the focus at establishing the fact that
sawdust (hardwood) can be used as a veritable resource for bio-ethanol
production (Nwakaire, 2013). Most importantly the greatest reason for
research and development of alternative energy is the environmental
consequences emanating from exploitation of fossil fuel the goal is to
achieve zero net carbon (iv) oxide balance and improvement in urban air
quality.
1.2 Statement of the Problem
In order to provide an
alternative source of energy, fuels and chemicals from traditional
fossil fuel, the project aims at considering how to generate energy in a
systematic approach of utilizing wood wastes or residues (sawdust)
generated from Nigerian forest reserves. Ethanol produced from sawdust
can provide a cleaner environment, environmentally friendly fuel and
stimulate community based jobs for our teeming youths and economic
growth. Lignocellulosic biomass such as sawdust, poplar wood, sugar cane
bagasse, herbaceous grasses, and municipal wastes provide a unique and
sustainable resource for environmentally safe organic fuels and
chemicals.
1.3 Aim and Objectives
Aim: To produce ethanol
through the fermentation of reducing sugars resulting from the
hydrolysis of pretreated sawdust (Hardwood). The objectives are as
follows:
1. To characterize the sawdust
2. To assess the yield of bioethanol produced
3. To characterize the bioethanol produced
4. To evaluate the effects of process parameters on the yield of bioethanol.
1.4 Scope of the Study
This research work is
restricted to the use of hardwood sawdust (Danta) as the substrate for
the production of bioethanol. The extraction will be done by hydrolysis
of sawdust to breakdown the cellulose and hemicelluloses to simple
sugar.
1.5 Significance of the Study
Most African countries
manage a large area of forest lands (reserves) from which timber is
harvested. The sub-Saharan African population depends mainly on wood
(Ceceski et al., 1979). However, due to lack of technical know-how
needed for using wood and wood wastes (residues) for renewable energy
and the huge finances involved (Walker, 2006). There has been general
motivation towards the exploitation of wood and wood wastes as important
sources for renewable energy (bio-energy). Biofuel sources are
geographically more evenly distributed than fossil fuels.
Lignocellulosic raw materials (biomass materials that have cellulose,
hemicellulose binded together with an insoluble substance known as
lignin) minimize the potential conflict between land use for food (and
feed) production and energy feedstock production. Presently, ethanol is
produced from food reserve crops like cassava, beet or carrots (Momoh,
1997). These are meant for human consumption. The raw material is less
expensive and can be produced with lower input of fertilizers,
pesticides and energy.
The production of
bioethanol from sawdust (lignocllulosic) is attracting interest due to
the relative availability and less expensive nature of the raw material.
Biofuels might also produce employment in rural areas. Wood and wood
wastes as energy sources on an industrial scale in African countries
have not been sufficiently looked into. Industries are more interested
in the more convenient and high energy content fossil fuels (Momoh,
1997). In the field of research it is well known that there has been
very little input of experimental data from African countries into the
global development of wood and wood residues for the production of
solid, liquid or gaseous fuels. For environmental reasons, ethanol, a
clean burning fuel, constitutes the most important approach for using
lignocellulosic residues. Ethanol is a better fuel than gasoline because
of its excellent physiochemical characteristics (Bailey, 1996). Adding
10 percent ethanol (v/v) to gasoline increases the octane number,
improves engine efficiencies through excellent anti-knocking properties
and gasoline oxygenation.