The potential of agroforestry in the provision of sustainable woodfuel in sub-Saharan Africa

Abstract

Woodfuel plays a critical role in energy provision in sub-Saharan Africa (SSA), and is predicted to remain dominant within the energy portfolio of the population in the coming decades. Although current inefficient technologies of production and consumption are associated with negative socio-economic and environmental outcomes, projected charcoal intensive pathways along with urbanization may further accelerate pressures on tree covers. This paper reviews the status of the woodfuel sector in SSA, and estimates the magnitude of impacts of increasing wood demand for charcoal production on tree cover, which will be obviously unsustainable under business-as-usual scenarios. Agroforestry, if widely adopted as an integrated strategy together with improved kilns and stoves, can have a significant impact to reduce wood harvest pressures in forests through sustainably supplying trees on farm. A systematic approach is required to promote multi-purpose agroforestry systems compatible with farmers’ needs under local farming systems and current dryland socio-economic contexts.

Full text

The
potential
of
agroforestry
in
the
provision
of
sustainable
woodfuel
in
sub-Saharan
Africa
§
Miyuki
Iiyama
1
,
Henry
Neufeldt
1
,
Philip
Dobie
1
,
Mary
Njenga
1,2
,
Geoffrey
Ndegwa
1,3
and
Ramni
Jamnadass
1
Woodfuel
plays
a
critical
role
in
energy
provision
in
sub-Saharan
Africa
(SSA),
and
is
predicted
to
remain
dominant
within
the
energy
portfolio
of
the
population
in
the
coming
decades.
Although
current
inefficient
technologies
of
production
and
consumption
are
associated
with
negative
socio-economic
and
environmental
outcomes,
projected
charcoal
intensive
pathways
along
with
urbanization
may
further
accelerate
pressures
on
tree
covers.
This
paper
reviews
the
status
of
the
woodfuel
sector
in
SSA,
and
estimates
the
magnitude
of
impacts
of
increasing
wood
demand
for
charcoal
production
on
tree
cover,
which
will
be
obviously
unsustainable
under
business-as-
usual
scenarios.
Agroforestry,
if
widely
adopted
as
an
integrated
strategy
together
with
improved
kilns
and
stoves,
can
have
a
significant
impact
to
reduce
wood
harvest
pressures
in
forests
through
sustainably
supplying
trees
on
farm.
A
systematic
approach
is
required
to
promote
multi-purpose
agroforestry
systems
compatible
with
farmers’
needs
under
local
farming
systems
and
current
dryland
socio-economic
contexts.
Addresses
1
World
Agroforestry
Centre,
United
Nations
Avenue,
Gigiri,
Nairobi,
Kenya
2
University
of
Nairobi,
Nairobi,
Kenya
3
University
of
Passau,
Passau,
Germany
Corresponding
author:
Iiyama,
Miyuki
(m.iiyama@cgiar.org)
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147
This
review
comes
from
a
themed
issue
on
Terrestrial
systems
Edited
by
Cheikh
Mbow,
Henry
Neufeldt,
Peter
Akong
Minang,
Eike
Luedeling
and
Godwin
Kowero
Received
08
June
2013;
Accepted
17
December
2013
S1877-3435/$
–
see
front
matter,
#
2013
The
Authors.
Published
by
Elsevier
B.V.
All
rights
reserved.
http://dx.doi.org/10.1016/j.cosust.2013.12.003
Introduction
Although
solid
biomass
accounts
for
only
10%
of
primary
energy
supply
globally,
woodfuels
continue
to
have
a
crucial
and
sometimes
dominant
role
in
energy
provision
in
the
developing
world.
Woodfuels
account
for
>80%
of
primary
energy
supply
in
sub-Saharan
Africa
(SSA),
a
where
>90%
of
the
population
rely
on
firewood
and
charcoal
for
energy,
especially
for
cooking
(Figure
1)
[1,2

].
Indeed,
SSA
had
the
world’s
highest
regional
per
capita
woodfuel
consumption
in
2011
at
an
average
of
0.69
m
3
/year,
com-
pared
with
a
global
average
of
0.27
m
3
/year
(Figure
2).
Although
woodfuels
dominate
in
the
SSA
region,
the
technologies
of
production
and
consumption
are
generally
rudimentary
and
inefficient
in
wood
use,
leading
to
nega-
tive
health,
socio-economic,
and
the
environmental
out-
comes
[3

].
Indoor
pollution
caused
by
woodfuels
burnt
in
inefficient
stoves
in
badly
ventilated
cooking
areas
is
a
major
cause
of
mortality
from
respiratory
infections,
with
women
and
children
suffering
most,
thus
often
labeled
as
the
‘killer
in
the
kitchen’
[4

,5,6,7].
The
scarcity
of
appropriate
energy
sources
has
led
poor
households
to
spend
considerable
time
in
woodfuel
collection,
time
that
otherwise
could
have
been
spent
on
more
productive
activities
[8].
Lack
of
ready
availability
of
other
energy
sources
has
also
led
to
the
burning
of
cow
dung
and/or
crop
residues
that
would
be
better
used
as
fertilizers
to
support
food
production
[9],
to
the
burning
of
wood
from
tree
species
that
were
traditionally
avoided
because
of
their
more
harmful
smoke
[10],
to
the
use
of
more
polluting
alternative
fuels
such
as
plastic
[11]
and
to
the
giving
up
of
cooking
food
properly
altogether.
Wide
dependence
on
woodfuels
harvested
from
forests
and
woodlands
could
significantly
deplete
these
resources
in
SSA
[2

,12].
Global
policy
debates
on
energy
supply
have
mostly
ignored
woodfuels,
but
instead
emphasized
the
need
for
the
poor
to
gain
access
to
‘modern’
energy
sources
such
as
kerosene,
liquefied
petroleum
gas
(LPG)
and
electricity
[13].
The
reality
is,
however,
that
modern
energy
sources
are
unlikely
to
provide
primary
household
energy
needs
for
most
of
the
poor
in
SSA
for
some
decades
yet,
due
to
the
fiscally
unsustainable
magnitude
of
the
subsidies
and
infrastructure
required
to
do
so,
and
households’
low
incomes
for
fuel
purchases
[14,15

].
In
§
This
is
an
open-access
article
distributed
under
the
terms
of
the
Creative
Commons
Attribution
License,
which
permits
unrestricted
use,
distribution
and
reproduction
in
any
medium,
provided
the
original
author
and
source
are
credited.
a
In
this
paper,
sub-Saharan
Africa
excludes
South
Africa,
which
for
the
region
has
an
exceptionally
high
electrification
rate.
The
following
42
countries
in
sub-Saharan
Africa
are
covered:
Angola,
Benin,
Botswana,
Burkina
Faso,
Burundi,
Cameroon,
Central
African
Republic,
Chad,
Congo,
Co
ˆte
d’Ivoire,
Democratic
Republic
of
the
Congo,
Djibouti,
Equatorial
Guinea,
Eritrea,
Ethiopia,
Gabon,
Gambia,
Ghana,
Guinea,
Guinea-Bissau,
Kenya,
Lesotho,
Liberia,
Malawi,
Mali,
Mauritania,
Mozambique,
Namibia,
Niger,
Nigeria,
Rwanda,
Senegal,
Sierra
Leone,
Somalia,
Sudan
(former),
Swaziland,
Togo,
Uganda,
Uni-
ted
Republic
of
Tanzania,
Zambia,
Zimbabwe.
Available
online
at
www.sciencedirect.com
ScienceDirect
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147
www.sciencedirect.com

the
coming
twenty
years
or
more,
charcoal
will
be
con-
sumed
by
a
wide
range
of
socio-economic
groups
in
SSA
while
firewood
will
remain
important
for
the
poorest
who
cannot
afford
charcoal
[16

,17

].
Current
trends
may
accelerate
forest
degradation
[18].
Efforts
to
provide
energy
for
all
communities
in
SSA,
at
an
acceptable
environmental
cost,
mean
little
without
recog-
nizing
the
reality
of
the
continued
importance
of
wood-
fuels,
and
should
support
reform
of
the
sector
to
make
it
more
efficient
and
sustainable,
rather
than
just
discounting
it
in
future
planning
[16

,17

].
Woodfuel
production
in
agroforestry
systems
may
provide
a
more
sustainable
alternative
to
collection
from
natural
forest
and
woodlands,
and
could
provide
multiple
benefits
for
small-
holders,
while
limiting
land
degradation
and
deforestation,
with
possible
net
sequestration,
raising
incomes,
and
improving
health
and
nutrition
[18,19].
Few
harmonized
estimates
exist
on
the
future
of
the
woodfuel
sector
in
SSA
to
guide
policy
debates.
The
current
review
addresses
how
the
woodfuel
sector
in
SSA
can
meet
the
energy
demands
of
the
poor
who
will
not
benefit
from
modern
energy
supplies
in
the
near
future
in
ways
that
are
sustainable
and
avoid
serious
health
risks,
and
assesses
the
potential
role
of
agrofor-
estry.
First,
the
current
status
of
the
woodfuel
sector
in
the
region
with
a
particular
focus
on
charcoal
is
con-
sidered,
followed
by
the
review
on
past
unsuccessful
approaches
to
promote
woodfuel
supply.
Then
a
simple
model
to
project
wood
demand
for
charcoal
production
and
its
impacts
on
tree
cover
under
scenarios
of
the
Agroforestry
potential
for
sustainable
woodfuel
in
SSA
Iiyama
et
al.
139
Figure
1
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
World
(12,149,8
45 M
toe)
Asia
(3,
731,223 Mt
oe)
Latin America
(540,0
17
Mto
e)
Africa
(673,5
00
Mto
e)
sub-Saharan
Africa -
South Afric
a
(290,7
58
Mto
e)
heat
electricity
biof
uels and wa
ste
geothermal, solar etc,
hydro
nuclear
natural g
as
oil prod
ucts
crude oil
coa
l and pea
t
Current Opinion in Environmental Sustainability
Regional
comparison
of
contributions
of
different
primary
sources
to
energy
supply
in
2009.
Source:
IEA
Statistics
(www.iea.org/stats/).
Figure
2
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
World
Asia
Latin Ameri
ca
Africa
sub-Saharan
Africa-
South
Africa
m
3
/year/person
Current Opinion in Environmental Sustainability
Regional
comparison
of
per
capita
woodfuel
consumption
in
2011.
Source:
FAOSTAT
(http://faostat3.fao.org/).
www.sciencedirect.com
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147

adoption
and
non-adoption
of
appropriate
practices
is
presented.
The
review
concludes
by
calling
for
a
sys-
tematic
approach
for
supply
management
interventions,
and
outlining
critical
information
gaps
for
guiding
policies
and
promoting
wider-scale
adoption
of
improved
methods.
The
woodfuel
sector
in
SSA
The
status
In
SSA,
firewood
is
widely
used
in
rural
areas
[17

]
and
sometimes
in
cities
[20],
although
it
is
often
regarded
as
an
inferior
energy
source
for
use
by
the
poor
[17

].
Firewood
is
also
used
by
industries
and
estates
such
as
tea,
coffee
and
tobacco
[20].
The
use
of
charcoal
is
preferred
by
many
consumers
especially
in
urban
areas
due
to
its
higher
energy
density
per
unit
weight,
cheaper
transport
costs
and
relative
cleanness
(producing
less
smoke)
than
firewood[4

,17

,21],
although
it
emits
more
carbon
monoxide
[15

].
Since
the
1980s,
with
urbaniz-
ation,
the
share
of
the
energy
market
taken
by
charcoal
compared
to
firewood
has
steadily
grown
[17

,22].
The
potential
of
woodfuel,
particularly
charcoal,
for
economic
development
is
enormous
[3

,20].
The
charcoal
market
in
SSA
provides
significant
employment
and
involves
many
benefiting
stakeholders,
including
collec-
tors,
harvesters,
producers,
transporters,
wholesalers
and
retailers
[20].
In
2007,
the
charcoal
industry
in
the
region
was
estimated
to
be
worth
>US$
8
billion,
involving
>seven
million
people
in
production
and
delivery.
By
2030,
the
market
is
predicted
to
exceed
US$
12
billion,
employing
12
million
people
[3

].
Despite
its
economic
significance,
the
charcoal
market
is
generally
viewed
negatively
and
is
often
an
informal
and
sometimes
illegal
business,
with
a
complex
and
multi-layered
regulatory
context,
which
results
in
an
unclear
framework
for
sta-
keholders
[3

,17

,23].
Sustainability
of
the
sector
Firewood
supply
for
domestic
use
may
involve
collecting
dead
wood
from
non-forest
sources
[10].
Charcoal
pro-
duction
generally
relies
on
cutting
of
live
trees
[10,24,25,26

]
from
natural
rather
than
planted
tree
stands
[2

].
Harvested
wood
is
converted
to
charcoal
in
rudimentary
earth
kilns
with
an
efficiency
ranging
from
8
to
20%
[10,26

].
Displacement
for
agriculture
appears
to
be
the
most
important
driver
for
deforestation
in
humid
forest
areas,
with
permanent
losses
of
carbon
stocks,
and
charcoal
often
a
byproduct
of
forest
clearance
[17

,26

,27].
Pro-
duction
of
charcoal,
in
turn,
can
have
a
significant
land-
scape-level
impact
on
land
degradation
due
to
multitudes
of
tree
cuttings
at
production
site
level
even
when
not
driving
overall
forest
cover
loss
[26

].
With
rapid
urban-
ization
and
population
growth
in
SSA,
the
negative
impacts
of
charcoal
production
on
forests
and
woodlands,
such
as
reducing
natural
regeneration,
will
increase
mark-
edly
[4

,17

,25,28].
Options
to
improve
sustainability
Although
regarding
a
complete
switch
from
woodfuels
to
modern
energy
as
the
most
desirable
intervention,
along
with
other
experts
[15

],
we
strongly
advocate
for
improv-
ing
the
sustainability
of
the
existing
woodfuel
sector
as
a
practical
solution,
realizing
the
former
will
not
be
feasible
in
the
near
future
in
SSA.
To
improve
sustainability,
woodfuel
policies
need
to
be
harmonized
and
the
effi-
ciency
of
charcoal
production
and
consumption
improved
[15

].
Major
components
of
an
integrated
strategy
for
a
sustain-
able
charcoal
industry
are
improved
kilns,
improved
cooking
stoves
and
sustainable
supply
in
the
framework
of
enabling
policies.
More
efficient
kilns
will
reduce
the
amount
of
wood
required
per
unit
of
charcoal
produced,
which
(all
else
being
equal)
should
reduce
overall
wood
demand
for
charcoal
production
[4

,29

].
Improved
cooking
stoves
that
burn
charcoal
and
firewood
more
efficiently
should
have
the
same
effect
[30],
and
also
reduce
air
pollution
provided
stoves
are
installed
and
maintained
properly
[6].
Changes
in
land
management
are
also
required
to
create
sustainable
charcoal
supply
systems
rather
than
the
‘one-off’
harvesting
of
wood
[29

].
With
relevant
management,
carbon
stocks
in
for-
ests
can
recover
and
be
maintained
along
with
charcoal
production
[26

,31].
The
changing
views
and
approaches
to
address
the
woodfuel
problem
Low
adoption
of
agroforestry
for
charcoal
production
Agroforestry
may
play
an
important
role
in
making
char-
coal
supply
more
sustainable
by
reducing
pressure
on
harvesting
wood
from
natural
tree
stands
through
increas-
ing
wood
supply
on
farm.
b
To
date,
however,
adoption
rates
of
agroforestry
practices
especially
focused
for
char-
coal
production
in
SSA
and
elsewhere
are
in
general
disappointing
[22,24].
It
is
worth
learning
from
the
past
approaches
for
the
failure.
Lessons
from
earlier
approaches
In
the
1970s,
the
woodfuel
crisis
was
a
hot
issue
not
only
for
Africa
but
for
Asia.
The
common
approach
then
was
a
so-
called
a
supply-demand
gap
theory.
Projecting
the
demand
for
woodfuels
excessive
of
the
supply
capacity
of
forests,
it
generally
advocated
massive
aforestation
and
reforestation
to
close
a
widening
gap,
especially
targeting
high
agricul-
tural
potential
zones
whose
forests
were
perceived
most
threatened
by
local
woodfuel
demand
driven
by
high
140
Terrestrial
systems
b
On-farm
production
of
resources
can
also
result
in
market
and
infrastructure
development
that
‘pulls
in’
wild
resources
as
well
as
planted
stock,
and
which
result
in
forest
clearance
for
further
planting
and
the
relegation
of
natural
stands
to
‘stop-gap’
supplies
[32].
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147
www.sciencedirect.com

population
density
[33,34].
By
the
late
1980s,
however,
the
gap
approach
turned
out
to
be
not
effective
in
achieving
the
desired
outcomes
[34,35].
Recommended
woodlot
for
woodfuel
supply
was
not
undertaken
by
farm
households
who
were
instead
interested
in
planting
trees
for
com-
mercial
poles/timbers
which
fetched
higher
unit
values
[34,36,37].
Indeed,
detailed
studies
revealed
that
farms
in
high
potential
areas
frequently
had
sufficient
tree
covers
thus
abundant
woody
biomass,
yet
women
had
reported
increasing
difficulty
in
obtaining
domestic
supplies
of
woodfuels
[35,38–40].
The
failure
of
the
gap
approach
called
for
placing
wood-
fuels
within
the
wider
context
of
local
faming
systems
and
social
and
economic
environments
[35,37].
Dewees
[41

]
critically
argued
that
the
gap
approach
only
focused
physical
scarcity
of
woodfuels,
and
ignored
the
economic
scarcity,
that
is,
farm
households’
cost
and
time
to
obtain
woodfuels
in
a
dynamically
changing
society.
Even
if
wood
becomes
physically
scarce,
as
long
as
labour
is
abundant
—
the
lack
of
economic
scarcity,
woodfuel
supply
remains
cheap.
In
turn,
woodfuel
supply
becomes
problematic
even
without
the
physical
scarcity
of
trees.
For
example,
in
high
potential
areas
opportunity
costs
of
labour
are
high
due
to
the
presence
of
economically
attractive
enterprises,
or
migration
makes
labour
chroni-
cally
scarce.
In
such
a
situation,
farm
households’
reaction
includes
either
managing
multi-purpose
trees
on
farm
to
save
labour
to
collect
woodfuels,
or
purchasing
woodfuels
while
specialized
in
on-farm/off-farm
enterprises.
Factors
masking
the
magnitude
of
the
problem
After
the
counter-arguments,
many
woodfuel
related
projects
were
scaled
down
by
the
1990s
[22].
A
prevalent
view
was
that
the
widely
predicted
woodfuel
crisis,
with
rising
prices
for
urban
consumers,
has
not
taken
place
at
the
scale
predicted.
In
India,
for
example,
despite
the
population
growth
and
urbanization,
the
quantities
of
woodfuels
used
by
households
fell
drastically
due
to
huge
shift
in
the
choice
of
household
cooking
fuels
to
fossil
fuel
[24,34].
In
contrast,
in
SSA,
the
importance
of
woodfuels,
especially
charcoal,
has
grown
since
the
1980s
[22],
while
drylands
have
emerged
as
major
charcoal
supply
areas
to
urban
areas.
For
example,
roughly
75%
of
all
the
charcoal
utilized
in
Kenya
is
considered
to
come
from
the
drylands
[42].
Interestingly,
the
charcoal
supply
in
SSA
has
been
regarded
highly
‘efficient’
at
meeting
demand
in
the
word
of
some
experts
[17

]
while
anecdotal
evidences
indicate
the
shifting
of
charcoal
‘hotspots’,
often
into
drier
conditions
[43],
accompanied
by
extensive
degradation
leading
to
downgrading
of
woodland
to
bush,
and
bush
to
scrub,
over
very
large
areas
[24].
The
apparent
lack
of
crisis
could
be
explained
by
the
lack
of
economic
scarcity
in
the
context
of
drylands
where
opportunity
costs
of
labour
remain
relatively
low
due
to
the
lack
of
alternative
economic
opportunities
due
to
low
agricultural
and
mar-
ket
potentials,
while
infrastructure
development
may
keep
transport
costs
from
rising
as
hotspots
shift
into
further
hinterlands.
Projecting
the
impacts
of
charcoal
demand
under
different
intervention
scenarios
Data
and
methodologies
There
is
lack
of
reliable
data
and
consistent
method-
ologies
to
assess
the
magnitude
of
the
impacts
of
charcoal
demand-supply
on
tree
covers
in
SSA.
National
estimates
on
charcoal
consumption
levels
tend
to
be
higher
than
the
charcoal
demand
reported
by
FAO
c
[2

,17

,29

].
On
the
other
hand,
there
is
a
tendency
that
national
figures
of
deforestation
reported
by
FAO
statistics
are
higher
than
the
estimates
derived
from
high
resolution
satellite
images
[45–47].
The
latter
analyses
also
reported
the
magnitude
of
forest
degradation
but
did
not
present
how
much
of
it
was
driven
by
wood
demand
for
charcoal
against
agricultural
land
expansion
[47].
Therefore,
though
being
one
of
the
most
extensive
coverage
on
the
woodfuels,
FAO
data
may
tend
to
underestimate
charcoal
demand
compared
to
country
surveys
on
one
hand,
and
overestimate
deforestation
trends
compared
to
satellite
data
analyses
on
the
other
hand.
A
few
studies
have
tried
to
estimate
and/or
project
the
impacts
of
charcoal
demand
on
tree
covers,
by
converting
wood
required
to
produce
charcoal
into
forest/woodland
areas,
principally
using
the
following
formula:
the
area
needed
to
meet
wood
demand
for
charcoalðhaÞ
¼
the
volume
of
wood
demand
for
charcoalðtonneÞ
with
different
kiln&
stove
efficiencies
biomass
stock
rateðtonne=haÞ
with
or
without
agroforestry
The
biomass
stock
rates
year
,
defined
as
(biomass
stock
[tonne]
year
/forest
area
[ha]
year
),
vary
considerably
be-
tween
time
and
across
SSA
countries,
even
within
a
country,
with
humid
regions
having
higher
stocking
rates
than
drier
regions.
FAO’s
WISDOM
(Woodfuel
Inte-
grated
Supply/Demand
Overview
Mapping)
project
[48]
has
attempted
to
develop
a
dynamic
spatial
model
and
applied
it
to
selected
eastern
African
countries.
It
uses
biomass
stock
rates
across
all
the
landscape
categories
derived
from
FAO’s
LANDCOVER
maps
to
estimate
supply
in
terms
of
land
areas.
But
for
most
SSA
countries,
charcoal
demand
estimates
are
often
only
available
at
national-scale,
while
biomass
stock
rates
are
available
for
forest
areas
only
and
often
reported
for
a
national
average.
In
applying
the
formula
to
the
forest
Agroforestry
potential
for
sustainable
woodfuel
in
SSA
Iiyama
et
al.
141
c
For
example,
Kenyan
national
charcoal
survey
estimated
1.6
million
tons
of
charcoal
in
2004
[44]
and
2.5
million
tons
in
2013
[43],
while
that
of
FAOSTAT
showed
640,501
in
2000,
and
16,500–17,700
t/year
for
2001–2011.
www.sciencedirect.com
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147

biomass
stock,
Chidumayo
and
Gumbo
[26

]
noted
the
possibilities
of
overestimating
the
impact
of
charcoal
demand
on
forest
covers
as
charcoal
is
rather
a
by-product
of
agricultural
land
expansion.
Acknowledging
the
pro-
blem,
they
used
the
FAO
data,
and
concluded
that
charcoal-induced
deforestation
contributes
to
a
fraction
of
the
total
forest
cover
loss
reported
in
Africa
(14

5%)
and
in
the
tropical
countries
on
average
(7

2%)
[26

].
Interestingly,
using
a
similar
formula
with
different
data
and
assumptions
would
lead
to
contrasting
conclusions.
For
example,
Mwampamba
[49]
extrapolated
urban
char-
coal
demand
in
Tanzania
derived
from
the
244
household
data
under
different
scenarios
of
kiln
efficiencies
and
biomass
stock
rates,
and
predicted
forests
would
deplete
in
next
few
decades
in
extreme
scenarios.
Assumptions
Acknowledging
the
constraints,
we
use
FAO
data
and
the
formula
above
to
make
tentative
projections
of
the
impacts
of
the
adoption
of
improved
kilns,
improved
cooking
stoves
and
agroforestry
as
an
integrated
sustainable
charcoal
strategy
on
tree
covers
to
guide
policy
debates.
The
rationales
behind
key
assumptions
are
given
below.
In
African
drylands,
hard-wood
tree
species
such
as
Acacia
spp.
are
considered
to
produce
a
good
quality
charcoal
[50].
Commonly,
trees
with
diameters
>4
cm
can
be
used
for
charcoal
production,
while
the
remainder
is
used
as
fuel
for
kilns,
kiln
spacers,
and
firewood
(<2
cm
diameter)
[51].
The
efficiency
or
recovery
rate
of
charcoal
kilns
depends
on
the
kiln
specifications
and
skills
to
control
carbonization
processes
to
minimize
unnecessary
combustion
of
wood
that
would
have
otherwise
been
carbonized.
Table
1
summarizes
the
specifications
of
different
charcoal
kiln
types.
Retort
kilns
with
carbonization
chambers
can
achieve
the
yield
of
30–40%
while
half
orange
kilns
also
present
high
recovery
rates
of
25–35%
[52].
They
present
a
potential
compatibility
with
simple
tree
management
such
as
coppicing
and
agroforestry
practices
with
shrubs
as
small
branches
and
twigs
can
be
carbonized
rather
than
mature
large
stems.
But
high
investment
requirement,
limited
field
experiences
(Adam
retort,
meko)
and
no
durability
(half
orange)
may
prevent
the
uptakes
by
poor
charcoal
producers
in
the
near
future.
In
turn,
earth
kilns,
whose
rudimentary
forms
are
currently
most
adopted
in
SSA,
have
also
potentials
to
improve
their
recovery
rates
from
10%
to
30%
with
relatively
low
investment
costs
(in
metal
nets
or
sheets/chimneys),
while
requiring
skills
for
stack
arrange-
ment
in
precision
[42,52,53].
In
our
model,
a
scenario
with
a
constant
kiln
efficiency
of
10%
are
compared
with
a
scenario
with
a
gradual
improvement
of
kiln
efficiency
from
10%
at
the
base
year
of
2015
to
30%
by
2050
assuming
a
gradual
dissemination
of
improved
technologies.
One
of
the
main
motivations
for
improved
cookstove
interventions
has
been
to
reduce
household
demand
for
woodfuel
thus
to
reduce
pressures
on
deforestation
[30,54].
Improved
cooking
stoves
potentially
reduce
average
daily
per
capita
fuel
use
by
19–67%,
but
the
outcomes
vary
depending
on
the
operating
conditions
[30].
A
recent
study
in
turn
reported
kitchen
performance
tests
in
rural
Kenya,
where
the
use
of
rocket
mud
stoves
in
place
of
traditional
three-stone
stoves
reduced
daily
fuel
uses
by
19%
(from
6.7
kg/day
to
5.4
kg/day,
a
cross-sec-
tional
result)
and
by
29%
(from
6.5
kg/day
to
4.6
kg/day,
a
longitudinal
result)
[55].
Based
on
it,
our
model
assumes
that
a
gradual
uptake
of
improved
cookstoves
by
house-
holds
will
reduce
the
wood
demand
by
20%
between
2015
and
2050.
Very
few
studies
are
available
on
wood
yields
of
agrofor-
estry
systems
under
smallholder
conditions
in
SSA.
In
turn,
there
are
some
experimental
studies
on
woodfuel
yields
on
multi-purpose
agroforestry
systems,
for
example,
different
species
of
Leucaena,
Crotalaria,
Tephrosia,
as
well
as
Sesbania
sesban,
Caliandra
calothyrsus,
Alnus
acuminata
in
humid/sub-
humid
conditions
[56–58]
and
different
species
of
Acacia,
Leucaena,
and
Gliricidia
sepium
in
semi-arid
conditions
[36,59].
Experimental
studies
from
Tanzanian
drylands
reported
that
rotational
woodlot
systems
using
fast
growing
N
2
-fixing
tree
species
have
the
potential
to
produce
20–
50
t/ha
of
wood
in
five
years
[36,59].
Their
mean
annual
increment
(MAI)
of
4–10
t/ha/year
are
far
higher
than
reported
MAIs
of
natural
or
minimally
managed
veg-
etation:
2.8
t/ha/year
(calculated
from
the
reported
carbon
stock
of
1.4
t/ha/year)
after
land
clearance
for
charcoal
in
Miombo
dry
forests
in
Zambia
with
1,200
mm
rainfall
per
annum
[31];
0.04–2.9
t/ha/year
of
wood
from
natural
Miombo
vegetation
in
Mozambique
[59],
and
1.3
t/ha/year
estimated
for
indigenous
acacia
species
under
a
14-year
coppicing
stands
in
arid
Laikipia
in
Kenya
with
500–
550
mm
annual
rainfall
[51].
At
the
same
time,
while
charcoal
production
with
conventional
earth
kilns
requires
wood
with
diameters
>4
cm
[51],
rotational
woodlot
sys-
tems
can
produce
wood
with
4–15
cm
diameter
at
breast
height
(DBH)
in
five
years
[36,59].
For
our
model,
we
assume
that
the
adoption
of
producing
woodfuel
on
farm
reduces
the
pressure
of
harvesting
wood
in
forests,
thus
reduce
the
rate
of
biomass
stock
change
in
forests.
The
biomass
stock
change
between
2000
and
2010
was
estimated
for
each
country
using
the
FAOSTAT
FRA
2010.
d
They
were
then
divided
by
10
to
derive
a
mean
annual
biomass
stock
change
rate
for
the
scenario
without
agroforestry
on
one
hand,
and
on
the
other
hand
divided
by
30
to
derive
a
reduced
rate
of
142
Terrestrial
systems
d
In
FAOSTAT
FRA2010,
the
data
for
growing
stock
[the
volume,
m
3
]
and
carbon
stock
[the
weight,
tonne]
was
reported
for
each
country’s
forest
area,
while
the
data
for
biomass
stock
[the
weight,
tonne]
was
not
reported
unlike
FRA2005.
Relatively
more
consistent
data
for
SSA
countries
between
FRA
2005
and
FRA
2010
was
available
in
terms
of
carbon
stock
than
growing
stock,
thus
the
carbon
stock
data
was
used
to
estimate
the
biomass
stock
using
a
factor
of
2
(FRA
estimates
carbon
in
living
biomass
as
50%
of
biomass
stock
figures).
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147
www.sciencedirect.com

annual
mean
biomass
stock
change
under
the
agrofor-
estry
scenario.
Then
we
used
the
derived
‘‘annual’’
biomass
stock
change
rates
for
each
country
to
project
levels
of
biomass
stock
annually
for
the
period
from
2015
to
2050,
respectively
for
the
scenarios
without
or
with
agroforestry.
Under
the
agroforestry
scenario,
the
bio-
mass
stock
rate
in
forests
could
improve
by
0.65
t/ha/
year,
compared
to
0.19
t/ha/year
under
the
scenario
without
agroforestry,
on
average
for
all
the
SSA
countries
in
the
same
period.
Variously
reported
wood
productivity
of
MAI
of
4–10
t/ha/year
in
agroforestry
systems
is
far
larger
than
this
assumed
biomass
stock
change
rate
in
forests
under
the
agroforestry
scenario
(0.65
t/ha/year
on
average),
thus
it
may
be
a
rather
conservative
assumption.
Projections
of
wood
demand
for
charcoal
The
average
annual
growth
rates
of
charcoal
consumption
in
SSA
between
2000
and
2010
were
1.01%
for
firewood
and
2.96%
for
charcoal,
and
the
latter
was
higher
than
the
average
population
growth
rate
of
2.58%
of
the
same
period.
Using
these
incremental
increases
to
project
the
Agroforestry
potential
for
sustainable
woodfuel
in
SSA
Iiyama
et
al.
143
Table
1
Comparison
of
charcoal
kiln
specifications.
Kiln
type
Recovery
rate
Wood
size
Notes
on
scales/skills/
investment
Earth
Pit
kiln
11.8%
(a)
–
The
pit
kiln
is
more
commonly
used
in
Asia.
America
(a)
Traditional
earth
mound
kiln
8–10%
(c)–15–20%
(b)–20–30%
(d)
Wood
chopped
into
sizeable
pieces
(b)
No
need
of
transport
as
to
construct
close
to
the
wood
supply
site,
are
flexible
in
size
and
shape,
well-matched
to
the
dispersed
nature
of
the
charcoal
trade,
little
capital
yet,
requires
skill
to
achieve
high
efficiency
(b),
(d),
(e),
(f)
Improved
earth
kiln
25.7%
(a)–27%
(e)
Workable
pieces,
1–1.5
m
(e)
Casamance
kiln
16.8%
(a)
to
26–30%
(e)
0.5
m
length
wood
with
different
diameters,
mainly
larger
pieces
(e)
Masonry
Dome
kiln
28–30%
(b)
Tree
stumps
(b)
Immobile,
transport
costly
(b)
Half
orange
kiln
25–35%
(g)
(50–60%
(b)*)
Twigs
and
branches
(b)
Uses
small
materials
(b)
Metal
Drum
kiln
28–30%
(e)–32–38%
(f)
Stems
or
tree
branches
of
6–
10
cm
diameter
with
80
cm
length
(e)
Suitable
for
household
domestic
production
(e)
Portable
steel
kiln
About
25–30%
(e)
A
max
diameter
of
20
cm,
45–
60
cm
long
(e)
Designed
to
be
easily
transported,
high
capital
costs
(e)
Meko
(Mekko)
kiln
(50–75%
(b)*)
1.5
cm
diameter
(b),
0.8
m
long
pieces
(e)
Consisting
of
two
chambers
—
the
inner,
basically
a
modified
drum,
for
carbonization
and
the
outer
for
firing,
designed
to
cause
pyrolysis
of
dry
wood
to
take
place
in
an
inner
chamber
to
facilitate
complete
carbonization.
Easy
to
assemble,
mobile,
but
still
prototype/costly
(b)
Retort
Adam
retort
kiln
30–40%
(g)
Can
utilize
branches
of
shrubs
and
small
trees
such
as
Tarconanthus
camphorates
(b)
The
kiln
returns
the
wood
gases
and
heat
back
to
the
carbonisation
chamber,
burns
a
higher
proportion
of
the
tar
components,
leading
to
higher
efficiency
and
reduced
noxious
emissions.
High
investment
costs,
suitable
for
semi-industrial/industrial
use,
yet
limited
field
experience
(g)
Source:
(a)
Chidumayo
and
Gumbo
2013
[26];
(b)
Kalenda
et
al.
[42]*
(these
figures
on
half
orange
kilns
and
meko
kilns
can
be
overestimated,
as
normally
it
is
not
possible
to
get
recovery
rates
of
more
than
50%
from
wood
carbonization);
(c)
ESDA
[44];
(d)
Bailis
2009
[29];
(e)
Oduor
et
al.
2006
[53];
(f)
Oduor
et
al.
2012
[50];
(g)
Vis
2013
[52].
www.sciencedirect.com
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147

future
trend,
the
demand
for
charcoal
will
increase
by
2.8
times
and
that
for
firewood
by
1.4
times
between
2015
and
2050.
Projections
of
wood
demand
for
charcoal
and
fire-
wood
under
different
kiln
and
stove
efficiency
scenarios
are
given
in
Figure
3.
A
gradual
improvement
in
kiln
efficiency
from
10%
to
30%
would
result
in
massive
savings
in
wood
requirements.
The
gradual
adoption
of
charcoal
cooking
stoves
with
an
improvement
in
efficiency
of
20%
would
also
result
in
significant
savings.
Impacts
of
wood
demand
for
charcoal
on
tree
cover
and
a
potential
role
of
agroforestry
Figure
4
integrates
the
impacts
of
kiln/stove
efficiencies
on
wood
demand
and
the
impacts
of
agroforestry
adoption
144
Terrestrial
systems
Figure
4
0
500
1000
1500
2000
2500
3000
3500
4000
4500
2015
2020
2025
2030
2035
2040
2045
2050
forest areas required to meet charcoal demand
(000 ha/year)
kiln @10
%
kiln @10
% + i
mprov
ed s
tove
kiln @10
% + i
mprov
ed s
tove + AF
kiln @10→@30
%
kiln @10→@30
% + i
mpro
ved
st
ove
kiln @10→@30
% + i
mpro
ved
st
ove +
AF
Current Opinion in Environmental Sustainability
Projected
areas
of
natural
forested
and
woodlands
cut
to
meet
charcoal
requirement
in
sub-Saharan
Africa
based
on
different
intervention
scenarios.
Notes:
Data
are
based
on
the
same
countries
as
in
this
figure,
except
Djibouti,
Eritoria,
Mauritania,
Sudan
(former)
and
Togo.
Figure
3
0
200
400
600
800
1000
1200
2015
2020
2025
2030
2035
2040
2045
2050
million m
3
/year
firewo
od demand
wood for charco
al ki
ln@10%
wood for charco
al ki
ln@10% + i
mprov
ed
stove
wood for charco
al ki
ln@10%
to @30
%
gra
dually
wood for charco
al ki
ln@10%
to @30
%
gra
dually
+ i
mprov
ed s
tove
Current Opinion in Environmental Sustainability
Projected
woodfuel
demand
under
different
kiln
and
stove
efficiency
scenarios
in
sub-Saharan
Africa.
Notes:
Where
there
were
obvious
reporting
errors
on
charcoal
demand
in
FAOSTAT
for
individual
countries,
figures
were
adjusted
when
other
national
data
on
consumption
were
available.
Current
Opinion
in
Environmental
Sustainability
2014,
6:138–147
www.sciencedirect.com

on
maintaining
biomass/carbon
stock
in
the
forests
to
present
their
combined
impacts
on
tree
cover.
The
scenarios
with
an
inefficient
kiln
present
an
alarming
picture.
For
example,
the
land
area
estimated
to
be
required
to
meet
the
charcoal
demand
in
the
base
year
of
2015
under
all
the
scenarios
was
about
1.6
million
ha,
over
the
half
(58%)
of
the
forest
areas
to
be
lost
during
2014–2015.
Under
the
scenario
with
10%
kiln
efficien-
cies
without
improved
stoves
and
agroforestry
(all
else
being
equal),
by
2050,
4.4
million
ha
of
forests
will
be
annually
needed
to
meet
wood
demand
for
charcoal.
The
forest
areas
under
pressures
can
be
even
larger,
if
the
real
charcoal
consumption
could
be
larger
than
the
FAO
estimates
used
here
[2

].
In
contrast,
the
gradual
adoption
of
improved
kilns
together
with
improved
cooking
stoves
and
agroforestry
can
greatly
reduce
pressures
on
forests,
as
the
forest
areas
required
annually
in
2050
could
be
even
less
than
those
at
the
base
year
(2015)
level.
Conclusions
There
can
be
serious
dryland
forest/woodland
degra-
dation
ongoing
and
projected
under
business-as-usual
scenarios,
although
the
lack
of
quality
data
and
con-
sistent
methodologies
have
prevented
from
assessing
the
magnitude
of
the
environmental
and
socio-
economic
impacts
of
increasing
wood
demand
for
char-
coal
production.
A
recent
report
[2

],
alarming
the
projected
situation
in
Africa,
called
for
an
urgent
supply-side
intervention.
Especially,
agroforestry,
if
widely
adopted
at
landscape
level
as
an
integrated
strategy
together
with
the
promotion
of
improved
kilns
and
stoves,
can
have
a
significant
impact
to
reduce
wood
harvest
pressures
in
forests
and
woodlands
through
sustainably
supplying
trees
on
farm.
These
will
support
climate
change
mitigation
and
adaption
in
the
SSA
region
through
sequestering
carbon
and
promoting
resilience
[8,60].
The
past
experiences
and
current
dryland
socio-economic
contexts,
however,
remind
us
of
the
need
for
a
systematic
approach
to
promote
multi-purpose
agroforestry
systems
compatible
with
farmers’
needs
in
the
context
of
local
farming
systems,
rather
than
giving
a
singular
focused
approach
on
woodfuel
provision.
Some
technologies
are
promising,
for
example,
rotational
woodlots
using
fast
growing
and
N
2
-fixing
tree
species
can
not
only
provide
quality
woods
for
charcoal
but
also
offer
twigs
and
branches
as
foliage
for
livestock.
At
the
same
time
they
allow
farmers
to
intercrop
without
sacrificing
yields
of
food
crops
in
the
first
2
years,
and
improving
their
yields
following
wood
harvest
[36,59].
To
promote
these
tech-
nologies,
more
research
is
needed
to
match
right
tree
species
to
right
environment,
that
is,
agroecology,
soil
conditions.
For,
tree
growth
in
terms
of
height
and
diameter
required
for
conventional
charcoal
kilns
can
differ
among
different
tree
species
due
to
the
difference
in
the
adaptation
capacity
in
any
particular
environment
[36].
In
the
meantime,
it
is
also
critical
to
promote
innovations
to
develop
affordable
and
acceptable
kiln
technologies
which
will
make
full
use
of
wood
resources
[42,51].
Key
information
gaps
that
need
to
be
addressed
to
better
support
a
woodfuel
policy
in
the
region
include:

a
better
understanding
of
future
demands
for
different
energy
sources
in
SSA
and
the
possibility
of
transfor-
mational
changes
in
energy
supply.

comparative
data
on
wood
yields
in
farm
and
forest
environments
and
the
possible
gains
through
different
agroforestry
options
(tree
species,
management)
across
different
agro-ecological
zones.

greater
knowledge
on
the
factors
affecting
the
current
limited
adoption
of
improved
kilns,
improved
cooking
stoves
as
well
as
agroforestry
practices.
For
the
latter,
a
consideration
of
options
to
encourage
farmers
to
increase
their
supply
of
woodfuels
as
a
co-product
or
bi-product
of
their
strategies
for
incorporating
and
managing
on-farm
trees
and
shrubs
for
purposes
such
as
fodders,
timbers,
soil
fertility.

best
enabling
policy
environments
for
sustainable
charcoal.
Acknowledgements
This
work
benefitted
from
the
financial
support
of
Japanese
Government
which
contributed
to
the
lead
author’s
engagement
in
bioenergy-related
projects
at
World
Agroforestry
Centre
(ICRAF).
Our
special
thanks
go
to
Ian
Dawson
for
reviewing
and
editing
this
manuscript.
We
sincerely
appreciate
the
two
anonymous
reviewers
who
provided
truly
valuable
comments
to
improve
the
manuscript.
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tion
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the
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land
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as
a
by-
product
of
land
clearance
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a
dedicated
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