Biomass Briquetting can address waste problems, reduce air
pollution from direct open air burning and also reduce dependance on fossil
fuels for heat generation. Dry leaves have been shown to have high calorific
values; therefore the purpose of this study is to determine the effects of some
binders on the physical and combustion properties of dried leaves briquettes.
Dried leaves were mixed with binders such as clay, starch and Arabic gum
separately at different ratios of 10%, 20%, 30% and 40%, and made into
briquettes using a manual press with a hydraulic jack of 20 tons. Physical and
combustion properties of these briquettes were obtained using different methods
prescribed by other researchers. From the results of the properties tested,
briquettes made from dried leaves and gum at 40% of binder was most resistant
to water. Dried leaves and clay at 40% had the highest relative density of
0.7977g/cm3. Dried leaves and starch had a relative density at 40%,
0.4640g/cm3 while briquettes with gum binder had 30%,
0.4030g/cm3. Dried leaves and gum at 40% had the highest volatile
matter of 84.110% and the highest heating value of 30.5118MJ/kg at 10%.
Briquettes at this ratio failed to hold, because of its low durability. The
high ash content of briquettes bonded with clay 16.353% to 34.487% made it
difficult to ignite, due to the presence of non combustible matter. Dried
leaves bonded with starch at 20% had high heating value of 30.2189, and was
able to withstand shattering with durability of 81.752% and high relaxation
ratio of 1.7427. It can then be considered as the best binder in this study.
1.1 BACKGROUND INFORMATION
Energy generated from biomass is categorized as sustainable and
renewable energy. During the plant life cycle, plant biomass materials derived
from plant adsorb carbon dioxide (CO2) through photosynthesis at
same rate as they release the gas in the combustion process, thus leading to no
net increase in atmospheric CO2 quantity. Due to the lower
contents of sulfur and nitrogen in biomass, its application also creates less
environmental pollution and health risk than fossil fuel combustion. This is
the reason why utilization of biomass is eco-friendly. Compared to fossil fuel,
however, most of agricultural wastes have higher moisture content and lower
density, thus making them technically unsuitable for direct use due to
combustion and handling problems. Conversion of biomass wastes to briquettes is
a solution for such problems. It improves biomass handling characteristics,
increases the volumetric calorific values, and reduces transportation,
collection, and storage costs (Grover and Mishra,1996).
The potential agro residues which do not pose collection and
drying problems, normally associated with biomass are dried leaves, rice husk,
groundnut shells, coffee husk and coir waste (obtained by drying process: Sybil
1958). If these agricultural waste products can be properly recycled, into
useful products, more goods will be made available to our society,
environmental pollution and other disease attack would be greatly reduced.
Solid waste can be of importance when properly used or processed, among the
uses of agricultural waste are products from rice mills, trees, etc utilized as
solid fuel (Grover and Mishra, 1996). These are wastes from trees and plants
that are usually gathered and burnt or left to decompose., e.g. stalks, leaves.
Burning a ton of leaves and agro forest residues produce 526N of
carbon monoxide, 184N of particulates which are very tiny and easily absorbed
in the lungs, and at least seven carcinogenic hydrocarbons which are all
dangerous to health (Luke Cutis, 2002). Briquetting of these residues are
found very useful because it reduces its volumetric value, increases thermal
efficiency, better transportation and handling.
Dry leaves briquettes have higher calorific values than its raw
material (Madhava et al., 2011)
Fuel is defined as natural or artificial organic substance used
as source of energy and raw material for industries. All kinds of fuel as
regards their state of aggregation are divided into solid, liquid and gaseous
and as regards their origin into natural and artificial fuels (Francis and
Peters, 1965). Solid fuels for which bound or compressed rice husk (Briquettes)
belong to group under the natural fuel origin. Briquetting is defined as the
compaction of loose combustible material for fuel making purpose. The products
obtained from the process of briquetting are known as briquettes. Briquetting
is a technology, which uses either a dry or a wet process to compress solid
waste (rice husk) into different shapes.
Briquetting of biomass can be considered for its economics,
reliability and ease of operation. Hence briquetting of rice husk for solid
fuel is used for domestic heating in cooking stove, fireplace and furnace. They
also have the advantage of cleanliness, ease of handling and igniting, produce
a small volume of smoke and its ash content is rich in potash and phosphate.
This ash can be used as fertilizer on an unfertile soil. With briquetting of
rice husk a new fuel source is found which will help in reducing wild dumping
of rice husk in the rice growing regions of Nigeria.
Renewable energy sources are being sought for domestic
cooking in developing countries due to the fact that their non-renewable
counterpart such as kerosene, LPG, etc., are not meeting the peoples’ demand.
Also the high cost of non-renewable energy sources has made people to start
deviating to the use of renewable energy sources for domestic cooking. For
renewable energy resources utilization, the briquetting technology is used.
Biomass-based fuels are utilized in many countries. Briquettes are produced not
only from biomass, but also from different type of wastes like milled paper,
plastic and other combustible wastes. Different types of briquetting equipment
and its modifications are under development. Alternative fuels like biomass are
making breakthrough to energy sector for production of green energy.
Currently in Estonia as milled plastic packaging wastes are used
in rotary cement kiln by blowing the milled compounded plastic particles (25
mm) into the combustion chamber. In the future these wastes could be grinded
and briquetted for gasification in power stations (Jaan, 2010). Before
the waste briquetting, preconditioning of the material is necessary. First step
is processing of municipal waste by disintegrator mills for the size reduction.
Smaller particle size helps to obtain better properties of the product by
drying, mixing and briquetting.
Mixing of milled plastic waste with biological materials (wood
sawdust, paper, etc.) leads to better briquette pressing as well as to greater
calorific value. Before briquetting, the moisture content of the material
should be reduced by drying process. Lower moisture content improves the
briquetting process. The technology uses mechanical and chemical properties of
materials to compress them into compact shape (briquettes) without use of
additives or binders in the high pressure compacting process. Briquetting is
mostly used for compacting of biomass (rice husk, sawdust, wood shavings, bark,
straw, cotton, paper, etc.). The biomass undergoes the process of briquetting, while
high pressure and temperature simultaneously act upon the mass, the cellular
structures within the material release lignin, which binds individual particles
into a compact unit – briquette. Briquetting, however, can also be used for
compacting of compounded plastic waste or municipal waste etc. Briquetting is
executed by briquetting presses. The material is pressed into the pressing
chamber with high compacting pressure and high pressing temperature. For
briquette quality control, the physical parameters, such as density, moisture
content and compressive strength, were found to be the best indicators of the
quality. (Jaan, 2010).
Studies have been carried out on different biomass briquettes
like wood, charcoal, rice husk, determining the effect of a particular binder
on the briquette. Also studies have been carried out on the development of rice
husk briquettes as fuel for water boiling test, (Yahaya and Ibrahim, 2012).
Also on Rice husk production using molasses, cowdung and clay as binder, after
carbonizing the rice husk and bagasse in a muffle furnace (Jaan, 2010).
It has therefore become necessary to consider dried leaves for
briquetting because of its high calorific value. The binders to be used are
readily available and cheap. They are starch gel, clay and Arabic gum. They are
grouped into organic and inorganic binders. The organic binder is the Starch
gel, while the inorganic are the Clay and Arabic gum. The reason for this
choice is that they are more readily available in the South Eastern part of Nigeria,
than the other binders and also less expensive. Also they have been tested and
do not contain toxic materials when burnt.
1.2 PROBLEM STATEMENT
Dried leaves can be seen lying waste in most houses, industries,
schools, markets, walk ways, gardens, fields, etc. Most times these leaves are
left to litter the entire surroundings, other times they could be gathered and
burnt openly. Open burning of leaves has been proven to cause health hazards
(Luke Cutis, 2002). Most of these agricultural wastes have been highly
promoted to be used in various heating systems, during the past decades.
Compared to fossil fuel, however, most of agricultural wastes have higher
moisture content and lower density, thus making them technically unsuitable for
direct use due to combustion and handling problems (Grover and Mishra, 1996).
Conversion of wastes to briquettes is a solution for such problems. It improves
biomass handling characteristics, increases the volumetric calorific values,
and reduces transportation, collection, and storage costs (Grover and Mishra,
Briquetting of dried leaves is relatively new. The effect of a
binder on the heating properties of dried leaves briquettes amongst other
briquettes like rice husk, saw dust and groundnut shell was studied (Madhava et
el., 2011) but no detailed study has been carried out on the effect of the
organic and inorganic binders which will be used in this study on the physical
and combustion properties of briquettes. These binders to be used are readily
accessible and available.
This search will enable briquette producers to produce the best
quality dried leaves briquettes bearing in mind which binders that are locally
accessible to use for best results.
1.3 OBJECTIVES OF THE STUDY
The general objective of the study is to produce dried leaves
briquettes using some specific organic and inorganic binders, then to determine
the effect of these binders on the physical and combustion properties of the
briquette. The specific objectives are:
produce dried leaves briquettes using three different binders
determine the effect of the binders on the physical and combustion properties
of the dried leaves briquette.
1.4 JUSTIFICATION OF THE WORK
Briquetting technology is being encouraged in developing
countries as it serves as a cheaper alternative to cooking gas and kerosene
used in most homes which are on the high side in terms of cost. It also serves
as a cleaner, more presentable, less stressful and safer alternative to the use
of firewood and charcoal for cooking. Therefore, there is a necessity to invest
in briquetting and achieve the best results.
The result of this study will thereby help in understanding how
binders affect the combustion properties of briquettes and also help
researchers and producers choose type of binder to be used in dried leaves
1.5 LIMITATION OF THIS STUDY
This study is limited to dried leaves briquettes production.
Other biomass could have different effects when mixed with the binders. The
interest in this study is dried leaves because it burns well and most times are
lying waste and causing pollution in our environment.
Also only three binders are used, one organic binders which are
starch gel, and two inorganic binders which are Arabic gum and clay. There
exists a number of other binders whose effects could also be determined.