Strategies for Converting Biomass Materials to Generate Energy and Power in Nigeria

blusharmenianManagement

Nov 9, 2013 (3 years and 8 months ago)

197 views




Strategies for Converting Biomass Materials to Generate Energy and
Power in Nigeria

P.

A. Ogwo
1 *
L.O. Obasi
1

and D.S.Okoroigwe
2

1
Department of
Environmental Resource Management, Abia State University
, Uturu,Nigeria

(*Corresponding author:
pfaikon78@yahoo.com
)

2
Department of Geography and Planning
, Abia State University
,
P.M.B. 2000 Uturu, Abia State,
Nigeria


ARTICLE INFO

Article history

Received 20 November

2012

Received in revised form 4
December 2012

Accepted 23rd December
2012

Available online 10 February, 2013









Keywords
:

Biomass, Nigeria,
Sources, Conversion
technology





Abstract

A survey of biomass resource
materials was
carried out in Ab
ia State, South Eastern Nigeria. The
aim
of the survey was to examine various sources and
availability of biomass materials that could provide
feedstock for convers
ion to energy and power
. Results
show that biomass materials are highly available from
agriculture, forestry and municipal source
s that can form
a substantial part of future energy sources and biomass
-

derived energy generation systems for developing
countries such as Nigeria.
The major sources are listed
and could yield a total potential of nearly
159 million dry
tons of biomass ann
ually. Observation
shows that only a
fraction

of available biomass is currently utilized in
fuel
wood

for cooking an
d charcoal for heating ovens.

The
pa
per provides a demonstration of biogas

energy
conve
rsion technology using perennial grasses
that could
re
duce the cons
traints of energy shortage, env
ironmental
pollution, and emission of green house gases.

copyright@ 2012 cepa


1
INTRODUCTION

Biomass resources of Nigeria
consist of wood, forage grasses and
shrubs, wastes from timber, forestry,
agriculture, municipal and industrial
activities
.

The Energy Commission of
Nigeria (
ECN)

estimates that
biomass
energy resource materials of Nigeria are

157 million tons per year, available in
79.4 million hectares of woodland and
ISSN 2141-1824
Vol. 3, No 6
C
J
Contents lists available at

Journal of Environmental Management and Safety

Journal homepage:
www.cepajournal.com

Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


158


grassland out of a total 92.4 million
hectares of land

area
in Nigeria
. Biomass
resources are also available from
discarded plant parts after harvesting
useful parts like
roots,l
eaves,stalks,straws,
and
chaff.
This vast amount of biomass resources
are denuded due to man
-
made factors
including the slash
-
and burn agriculture
and indiscriminate bush burning leaving
a big gap between energy supply and
demand.

Nigeria, like

most countr
ies of
the world continues to meet her energy
needs
by burning oil and gas (fossil fuel)
because knowledge of alternative energy
sources has not been applied in Nigeria.
Biomass conversion into fuels is an
attractive option to supplement and later
replace
petroleum
-
based economy with
the concomitant environmentally benign
alternative energy sources.

As the world
faces the formidable challenge of
containing

Greenhouse
gases (GHGs
)

to
manageable levels, biomass material
c
onversion
technologies have

received
considerable attention in recent
years
.Biomass and biomass
-
based
materials can be converted to energy
through th
e following technologies:
thermo
chemical,biochemical,mechanical,chemi
cal,and electro
-
chemical
devices
(Mckendry, 2002; Demirbas and
Ar
in, 2002; Boyle, 2004 and Lin, 2007)
In spite of these technologies available
for biomass conversion, Nigeria
continues to destroy her biomass
resources through open bush burning in
fallow and uncultivated lands.This
practice destroys the ecosystem,produce
s
har
mful air pollutants
and net

greenhouse
emissions.

1.1
Overview of biomass materials
and conversion technologies

It is estimated that about 159
million dry tons of biomass are available
annually in Nigeria.
(ECN,2005)

Only a
fraction of these enormous resources are
converted through direct burning of
fuel
wood

for domestic use. Another small
fraction is converted to charcoal for
heating and bakery industries.A part
from the fraction that is utilized, the rest
is destroyed through open burning of
biomass in fallow and uncultivated
lands. This practice destroys t
he
ecosystem, produces harmful air
pollutants and produces net green house
emissions.

Biomass and biomass


based
materials can be converted to energy
through the following technologies:
thermo


chemical, biochemical,
mechanical, chemical and electro


ch
emical technologies.Thermo
-

chemical
technology is a method for treating dry
biomass and includes

the following:
combustion, gasificatio
n, pyrolysis, and
liquefaction
Direct Combustion is the
oldest and most common biomass
conversion technology in which bi
omass
is burnt to produce steam, which turns
turbine
s

that produce electricity. Other
combustion technologies include: co

firing, repowering and combined heat
and power
(CHP
) systems.

2
M
ATERIALS AND METHODS

Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of
Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


159


2.1
Selection of

Potential feedstock
fo
r biogas Production.

Elephant grass (
Pennisetumpurpureum
)

Elephant grass is a cane
-

like perennial
grass species growing in many grassland
and fallow land in Nigeria. The grass
utilizes the efficient C
4

carbo
n fixation
path.
Total annual productivity of
elephant grass is estimated to be 70.2
tons per hectare.

Elephant grass can be
compacted into
briquettes

and used as
solid biofuel or co


fired with charcoal
in power plants.

Maize Stalk (
Zea mays
)

Maize is widely grown in Nig
eria. The
first rain crop is eaten as boiled or
roasted fresh ears. After harvest the stalk
is left on the farm as waste.

Paspalumnotatum

grass

Paspalum is a lawn grass widely
established in Abia State University,
Uturu. The grass forms stolons and
establi
shes excellently when
vegetatively
propagated. I
t also with stands heavy
tramplin
g and mow
ing.

Guinea grass (
Panicum maximum
)

Guinea grass
is an erect vigorously
growing tuft

grass found in most
savannah fallow land in Abia State. It
can grow up to 2 meter
s in height.


2.2
Collection of Biomass Materials

The experiment was conducted in
Abia State University, Uturu (N05
49’41.4” and E 007 23’40.7”)
Elephant
grass (
Pennisetumpurpureum
)

was
c
ollected from a fallow land in O
kigwe,
Imo State, Nigeria.Maize
stalks (
Zea
mays
) were collected from a farm in
Uturu, Abia State after the maize cobs
have been harvested

Paspalumnotatum

gras
s

cuttings were
collected from lawn mowing
s

in the
Uturu campus of Abia State University
,

while the Guinea grass (
Panicum
maximum
) was harvested from hereby
bush fallow in Uturu, Abia State,
Nigeria.

The grass and stalks were cut


up into small pieces with the aid of
cutlass and ground into paste using an
electric grinder. The essence of grinding
was to increase the surface area av
ailable
for microbial activities. 500gm each o
f
Elephant grass, maize stalk, Paspalum
and G
uinea grass paste were measured
and diluted with water in the ratio of
1:

5
(Imasuen et al, 2011). A sewage sludge
inoculum

was collected from ecologica
l
sanitation
composting pit at P
lot R3 Abia
State University Satellite Village, Uturu.
The sludge

inoculum

was added to a set
of four anaerobic digesters locally
designed and constructed for the
experiment. Anaerobic digestion of the
biomass materials was maintained at

mesophilic temperature which ranged
from

28
0
C

to35
0
C

for a period of 40 days
and agitated manually once daily. The
pH and physic


chemical propertiesof
the digester mixtures were measured
using appropriate methods.


Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


160


3
RESULTS AND DISCUSSIONS


Table 1
:

Examples of Bioenergy Resource Types in Nigeria

BIOMASS TYPE

TYPICAL EXAMPLE

Agricultural sources

Agricultural Residues e.g. Maize straw, rice straw, Energy crops
J
atropha

for biodiesel, perennial grasses such as
Penn
iset
umspp
.
Food processing residues,
e.g.

Hulls, husks, shells, pits, coc
onut

shells, groundnut husks, rice husk, maize cobs, Animal waste
(manure)

Forest Residues

Forest Residu
es ( logging, slash, brush, thinning, trimmings, etc.

Mill Residues: (
sawdust, woodchips, shavings, etc.

Municipal Wastes

Organic fractions of municipal solid wastes, urban wood waste,
sludge , waste oils, fats, greases


From the data presented in Table 1, it
can be seen that biomass materials are
very much available in Nigeria from
Agricultural, Forestry and municipal
sources, Agricultural residues such as
maize straw, rice straw, Perennial grass
like
Paspalumnotat
um
,
Pan
icu
mmaximum

and
Penniset
umpurpureum

are available
from uncultivated farm
s
and bush fallow
systems. Biomass from forestry residues
are usually from logging, commercial
deforestation
,

trimmings and mill
residues such as saw dust, wood clips
and shavings. Municipal wastes sources
are very much available from organic
solid wastes and human wastes. There is
therefore the n
eed to harness biomass
from thes
e source
s for biomass energy
produc
tion in Nigeria.


Table 2: Biomass


Energy Conversion Systems and their Products

BIOMASS CONVERSION

TYPICAL EXAMPLES

PRODUCTS

Thermo


Chemical

Combustion

Gasification

Pyrolysis

Liquefaction

Carbonization

Thermal heat

Producer
gas

Char, bio


oil

Liquid diluted fuel

Biochemical Conversion

Fermentation

Anaerobic digestion

Ethanol

Biogas


Mechanical Extraction

Oil seeds crops

eg. Cotton, groundnut rape

Oil

Physical

Briquetting

Densified fuel

Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of
Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


161


Chemical

Esterification

Biodiesel

Methyl ester

glycerine


Data presented in Table 2 are
potential biomass energy conversion
system accessed from literature review.
Apart from the use of biomass as fuel
wood in domestic cooking and lighting
in the rural areas of

Nige
ria, m
ost of the
conversion technologies already

available in most countries are alien
to
Nigeria, indicating little awareness of
the potential of biomass sources for
energy and power generation in Nigeria.
This might probably be the reason vast
majority of

biomass are wasted in open
bush burning which has become an
annual ritual.


Table
3
: Characteristics of selected feedstock mixed with sludge

PARAMETER

UNIT

ELEPHANT

GRASS

MAIZE

STALK

PASPALUM

NOTATUM

GUINEA

GRASS

Total Solids

%

20.3

21.2

19.8

18.9

Organic Solids

%

18.6

19.4

18.5

18.2

Organic
carbon

%

44.4

44.3

40.8

41.5

Nitrogen

g/Kg

16.7

14.5

9.2

9.8

C:N ratio


26.6

30.5

16.2

20.5


Data presented in Table 3
indicate that total solids, organic solids
were highest in maize stalk (21.2and
19.4%) and least in Guinea grass (18.9
and 18.2%).Organic Carbons in maize
stalk was compara
ble with that of
elephant grassw
hile
organic solids in
E
lephant grass were

similar to that of
P
aspalumnotatum
.
The carbon:
nitrogen
ratio varied from 16.2 in Paspalum to
30.5 in maize stalk. The relat
ively higher
C.N ratio in maize stalk
could be
responsible for the high
rate of

biogas
production.
FAO (
1996) recommends a
C/N ratio ranging from 20 to 30 as
optimum for anaerobic
digestion. High
C/N ratio would lead to rapid
consu
mption of nitrogen by
methanogen
s for meeting

their protein
requirement while low C/N ratio would
lead to liberation and accumulation of
nitrogen in form of ammonia which
would increase the pH value of the

content in the digester.

.



Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


162




Table
4:

Time Lag, Cumulative Biogas Production, Biomethane Potential and
Biodegradability of different Feedstock
.

PARAMETER

ELEPHANT

GRASS

MAIZE

STALK

PASPALUM

NOTATUM

GUINEA

GRASS

Time lag
(days)

24

4

6

7

Cumulative gas
yield

70

240

154

230

Mean vol. of gas
production

2.27

2.95

3.68

3.78

Biomethane
potential ml d
-
1

36.85

45.27

38.48

32.86

Biodegra
da
bility

%

66

60

76

70


Table 4 shows the results of the
experiment

carried out for 40
days.Results indicate that total biogas
yield and on set of gas flammability
varied with different feedstocks. Daily
biogas production from maize stalk


sludge mixture, elephant grass


sludge
mixture and Guinea grass


sludge
mixture
commenced within 48 hours of
charging the respective digesters, while
gas production started on the 4
th

day for
the Paspalum grass


sludge mixture.The
production of flammable biogas took
different time lags.
Time lag varied from
4 to 24 days.


The cumulative methane
production was calculated using the
modified Gompertz equation:







{


[





(



)



]
}

Where M = cumulative methane
production (ml)

e = exp (1)

Rm = maximum specific
methane production
rates (mld
-
1
)

P = methane producti
on
potential (ml)











(

)

Maize stalk had the highest biomethane
potential (45.27ml d
-
1
) while Guinea
grass had the lowest (32.86 ml d
-
1
).

4

CONCLUSION AND
RECOMMENDATIONS



The use of biomass material as
energy sources in Nigeria is justified
because

o

The supply of biomass is
renewable

Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of
Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


163


o

Electricity produced by biomass
reduces the threat of global
climate change

o

Using biomass waste eliminates
the need for putting them in
garbage dump and indiscriminate
open burning

o

Clearing biomass from wooded
and follow areas help prevent
annual bush fire.

o

Using by product methane gases
to produce electricity eliminates
odour in livestock production and
reduces air pollution in the
surrou
nding area

Widespread use of biomass to produce
clean, renewable transportation fuel or
electricity is good business for Nigeria
and would reduce the hardship posed on
the people as a result of the fossil fuel
subsidy removal. There is therefore the
need t
o establish a bioenergy Action
Plan for Nigeria. The objectives of the
Action Plan will include

i.

Development of sustainable
biomass and market for bio


based products

ii.

Alignment of Nigeria’s existing
regulatory requirement to
encourage production and use of

biomass resources

iii.

Facilitating market entry for new
application of bioenergy including
electricity, biogas and biofuels.

iv.

Maximizing the contribution of
bioenergy towards achieving
Nigeria’s removal of fossil fuel
subsidy, climate change, renewable
energy
and environmental goals.


REFERENCES

APHA, ANWA and WPCF (1995)
standardmethods for the
examination of water and waste
water, 19

Washington, D.C.

Boyle, G (2004) Renewal Energy: Power
for a sustainable future 2
nd

ed. 2004,
oxford University Press

x1, 452p.

Demirbas A and Arin, G (2002) an
overview of business pyrolysis:
energy sources 24(5)471
-
482.

Energy Commission of Nigeria (2005)
Renewable Energy Master Plan,
Federal Republic ofNigeria.

FAO (1996) systems approach to biogas
technology a training manual

for
extension.

Imasuen, A O, et al.
(2011) Biogas
Production from fresh maize leaves
(Zea mays): Effect of Dilution
ratios. Continental Journal of
Applied Sciences 6(1): 21


24.
ISSN: 1597


9928. Available at
http://www.wiloludjournal.com
.

Lin, J.C.M (2007) Combination of a
biomas fixed updraft gasifer and a
stirling engine for power production.
Journal of Energy Resources
Technology, Transactions of the
ASME, 2007 129(1) p66
-
70.

Mckendry, P (2002) Energy Pro
duction
from biomass (Part 1): Overview of
biomass, Bioresource Technology
83(1)37
-
46.

Paepatung, N, et al. (2009) Biomethane
Potential of biological Solid
materials and Agricultural Wastes.
Asian Journal on Energy and
Environment 10(01) 19


27. ISSN
1513


4121 available at


www.asian
-
e
nergy
-
journal.info
.

Ogwo P.A., ObasiL.O. and Okoroigwe D.S./Journal of Environmental Management and Safety Vol. 3, No. 6, (2012) 1
57



16
4


164


Uzodinma, E. O and Ofoefule, A. U.
(2009) Biogas Production from
blends of field grass (Panicum
maximum) with some animal
wastes. International Journal of
Physical Sciences Vol.

4(2) pp
091


095. Available online at
http://www.academicjournals.org

ISSN 1992


1950.