Sustainable Energy: The Biofuels
Option:
By Bishnunarine Tulsie
Biomass is
among the most precious and versatile resources on earth. It provides not only
food but also energy, building materials, paper, fabrics, medicines and
chemicals. Biomass has been used for energy purposes ever since man discovered
fire. Today, biomass fuels can be utilised for tasks ranging from heating the
house to fuelling a car and running a computer.
WHERE DOES
BIOMASS COME FROM?
Carbon
dioxide from the atmosphere and water from the earth are combined in the
photosynthetic process to produce carbohydrates (sugars) that form the building
blocks of biomass. The solar energy that drives photosynthesis is stored in the
chemical bonds of the structural components of biomass. If we burn biomass
efficiently (extract the energy stored in the chemical bonds) oxygen from the
atmosphere combines with the carbon in plants to produce carbon dioxide and
water. The process is cyclic because the carbon dioxide is then available to
produce new biomass.
Biomass is
considered to be one of the key renewable resources of the future at both small
and large-scale levels. It already supplies 14 % of the world’s primary energy.
This share is likely to increase, particularly in developing countries with
increases in population and per capita demand, and depletion of fossil-fuel
resources.
BENEFITS OF
BIOMASS AS ENERGY SOURCE
Rural
economic development in both developed and developing countries is one of the
major benefits of biomass. Increase in farm income and market diversification, reduction of agricultural commodity
surpluses and derived support payments, enhancement of international
competitiveness, revitalization of depressed rural economies, reduction of
negative environmental impacts are some of the most important issues related to
utilisation of biomass as an energy source. The new incomes for farmers and the
rural population would improve the welfare of rural communities and could
contribute to reduced urban migration. The number of jobs created (for
production, harvesting and use) and the industrial growth (from developing
conversion facilities for fuel, industrial feed stocks, and power) could be significant.
The production of biofuels could also be an activity
for farmers displaced by global market conditions for traditional agricultural
pursuits.
The use of
biomass energy has many unique qualities that provide environmental benefits
also. It can help mitigate climate change, reduce acid rain, soil erosion,
water pollution and pressure on landfills, provide wildlife habitat, and help
maintain forest health through better management. The latter has a direct
impact on potable water production in
BIOMASS FUELS
Plants are
the most common source of biomass. They have been used in the form of wood,
peat and straw for thousands of years. Today the western world is far less
reliant on this high energy fuel because of the general acceptance that coal,
oil and electricity are cleaner, more efficient and more in keeping with modernisation
and technology. However this is not really the right impression. Plants can
either be specially grown for energy production, or can be harvested from the
natural environment. Plantations of fast growing plants can produce biomass
quickly for fuel. The options for
biomass fuel production are many and varied and choices based
on assessments is needed for each country’s circumstances.
SOME BIOFUEL
OPTIONS:
Wood Residues can be, and usually is
removed sustainably from existing forests through selective harvesting.
Agricultural Residues is a
potentially huge source of biomass. Crop and animal wastes provide significant
amounts of energy, coming second only to wood as the dominant biomass fuel
world-wide.
Short Rotation Plants can be
produced by so-called short-rotation plantations of trees and other plants like
grasses. These can be used as fuels with the main
advantage being their short span between plantation
and harvesting – typically between three and eight years.
Fuelwood refers to all
types of fuels derived from forestry and plantations. Fuelwood
accounts for about 10 per cent of the total biomass used in the world.
Charcoal is carbonized wood and
is a more convenient biofuel because of its high
energy content, lower density, cleaner burning characteristics and resistance
to decay and termite infestation.
CONVERSION OPTIONS
Nearly all
types of raw biomass decompose rather quickly, so few are very good long-term
energy stores. Recent years have therefore seen considerable effort devoted to
the search for the best ways to use these potentially valuable sources of
energy. In considering the methods for extracting the energy, it is possible to
order them by the complexity of the processes involved:
o
Direct combustion of biomass.
o
Thermochemical processing
to upgrade the biofuel. Processes in this category
include pyrolysis, gasification and liquefaction.
o
Biological processes such as anaerobic digestion
and fermentation which lead to a useful gaseous or liquid fuel.
The immediate
product of some of these processes is heat - normally used at or near the place
of production. For other processes the product is a solid, liquid or gaseous
fuel with better stability, storage and transport characteritics.
SYNTHETIC
FUELS
Methanol: A gasifier
which uses oxygen rather than air can produce a gas consisting mainly of Hydrogen
(H2), Carbon Monoxide (CO) or Carbon Dioxide (CO2). The interesting potential of this lies in the
fact that removal of the C02 leaves a gas from which almost any
hydrocarbon compound may be synthesised. Reacting the
H2 and CO is one way to produce pure methane. Another possible
product is methanol (CH3 OH), a liquid hydrocarbon with a high
energy density. Methanol is a liquid fuel used as a direct substitute for
gasoline.
Ethanol: Fermentation is an anaerobic biological
process in which sugars are converted to alcohol by the action of
micro-organisms, usually yeast. The resulting alcohol is ethanol (C2
H3 OH) rather than methanol (CH3 OH), which can be used as
fuel in suitably modified engines or as a gasoline extender in gasohol -
gasoline containing up to 20% ethanol. This technology is associated with the
rum industry and is well understood in the
Boigas:
When biomass decomposes in the absence of oxygen (anaerobic
decomposition) methane (CH4) and Carbon Dioxide (CO2) are
produced. This combination of gases,
called biogas has been in production in the
Landfill gas is biogas produced from
decaying bio materials in landfills.
Production is slower that in biogas digesters, making this a longer term
source of fuel.
Wood Gasification is the production of
flammable gas products such as methane, hydrogen and hydrocarbon gases from the heating of
wood.. This is done by burning wood in a burner which restricts air intake so
that complete burning of the fuel cannot occur. A related process is the
heating of wood in a closed vessel using an outside heat source.
Fermantation is the conversion of biomass into ethanol. Alcohol can be used as a liquid fuel in
internal combustion engines either on its own or blended with petroleum.
Therefore, they have the potential to change and/or enhance the supply and use
of fuel (especially for transport).
Options and Challenges for
There are
many options for a greater contribution of biofuels
to the national energy mix, ranging from the traditional direct combustion of fuelwood to the production of solid, liquid or gaseous
hydrocarbons. The economics of the
options will need closer examination.
Such assessments must include raw material supply opportunities and
costs, opportunity costs associated with placing land under the production of
fuels, technology choice, end use possibilities and social responses to new
fuel sources. The scarcity of land will
be a major consideration and this will require a close examination of the
possibilities of sustainably using steep slopes which are generally unsuitable
for food production or physical development for energy production. These considerations must also factor in the
rising cost and diminishing supplies of traditional fuels. The outlook must be to find longer term solutions
to these challenges by beginning to plan for the nation’s energy future sooner
rather than later.
Director