Biomass Energy Resources in Kenya
As of 2007, biomass energy, i.e. firewood, charcoal and agricultural wastes contributes approx. up to 70% of Kenya’s final energy demand and provides for almost 90% of rural household energy needs, about one third in the form of charcoal and the rest from firewood. It is estimated that 80% of urban households’ wood-fuel demand is met by charcoal.
Biomass Energy Potential and Distribution in Kenya
Biomass comes from various forest formations such as closed forests, woodlands, bush lands, wooded grasslands, farms with natural vegetation and mixtures of native and exotic trees, industrial and fuel wood plantations, and residues from agricultural crops and wood-based industries. These sources contribute to Kenya's national biomass resource as follows:
- Indigenous vegetation mainly from closed forests, woodlands, bush lands and wooded grasslands – 16 million m3
- Farmlands consisting of exotic tree species such as grevillea, eucalyptus and remnant natural vegetation – 14 million m3
- Plantations, mainly of eucalyptus –2 million m3 and
- Residues from agriculture and wood based industries – 3 million m3.
Closed forest denotes woody vegetation that forms a continuous stand of at least 10m in height with interlocking crowns. Closed forest formations cover approximately 1,247,400ha and have an average annual productivity of 1.3m3/ha/yr. The total potential volume available is approximately 1.60 million m3 annually. Most closed forests are gazetted (legally recorded) and are on public lands managed by the Kenya Forest Department. Others are located in protected areas (national parks and national reserves managed by the Kenya Wildlife Service).
Closed forest ecosystems dominate the central highland mass with the Rift Valley (Mau/Transmara/Olposimoru forest complex, Kaptagat and Kiptaberr forests) and Central Provinces (Mt. Kenya and Aberdare forests) controlling 50% and 20% respectively of the closed forest cover in Kenya. Some closed canopy forests are also found in the Eastern, Western, and Coast provinces, and scattered patches are encountered in the marginal districts.
Woodlands are open stands of trees at least 8 m tall with a canopy cover of 40% or more and a ground layer dominated by grasses. They cover an area of about 2,092,600 ha, about 4% of the total woody vegetation cover. Average productivity is 0.64 m3/ha/yr yielding a total of 1.3 million m3 annually. Woodlands are the natural vegetation in areas with marginal rainfall and are the transition between semi-humid and semi-arid zones. Most occur in the Coast and Rift Valley Provinces with an equal amount in the North Eastern and Eastern Provinces. Central, Nyanza and Western Provinces have limited woodland vegetation. Various County Councils own most of the woodland vegetation under powers vested in them by the Trust Lands Act. Communities and individuals who keep cattle, sheep and goats own the balance.
Bushland vegetation consists of short shrubs 3-7 m in height and climbers occurring in open stands, with a canopy cover of 40% or more. They cover about 24,629,400 ha with an average growth rate of 0.44 m3/ha/yr and contribute 10.84 million m3 annually. Bush lands are in the North Eastern, Coast, Rift Valley and Eastern Provinces in order of decreasing coverage. This vegetation also occurs in openings of disturbed closed forests and woodlands and in most highland forests due to human disturbance (tree poaching and encroachment). Their productivity in the high potential areas is remarkably high but much less in arid and semi-arid areas.
Wooded grasslands are extensive, they cover an estimated 10.6 million hectares in Kenya and are characterized by grasslands and scrub vegetation with a 10-40% woody vegetation cover. Wooded grasslands are found in the arid and semi-arid areas of the Rift Valley, North Eastern and Eastern Provinces in the order of importance. County councils own most of the wooded grasslands under the Trust Land Act. The annual increment rate of wooded grasslands is 0.25 m3/ha/yr with a potential gross yield of 2.60 million m3 annually.
Grasslands have scattered, short, small-diameter tree species, comprising mainly Acacias. They cover an area of 1,203,500 ha with an average productivity of 0.08 m3/ha/yr. for an annual total of 0.096 million m3.
Grassland vegetation occurs in the Eastern, North Eastern, Coast and Rift Valley Provinces in order of importance. Western and Central Provinces have no grasslands and there is only a small area in Nyanza Province.
Wood Supply from Farms
Wood supply from farms comes from small woodlots interspersed with crops, from the farm boundaries and from other scattered trees within the farm. Farms cover about 10 million ha and have a highly variable wood productivity. A reasonable estimate is about 1.44 c m3/ha/yr to supply approximately 14.4 million m3/ha/yr.
Forest plantations have a mature height of over 15 m and covered an area of some 136,300 ha. Annual productivity is variable but can average 19.9 m3/ha with a possible national contribution of 2.7 million cubic m3/ha/yr . Most plantations are found in the central highlands of the Central and Rift Valley Provinces. Isolated plantations occupying small areas are located in the Coast, Eastern, Nyanza and Western Provinces. Plantations are both publicly and privately owned with a potential area of about 120,000 ha public and managed by the Forest Department; only 75,000 ha are presently planted. About 16,000 ha are privately owned by tea estate companies for the supply of fuel wood.
Although there are apparently large wood volumes available from the various vegetation types, not all of it is accessible for energy. Accessible wood depends on a number of factors such as:
- legal issues
- environmental issues
- objectives of management
- and infrastructure
Closed forests are gazetted and their use is restricted and controlled by the Forest Department under the Forests Act. Other vegetation types are also legally inaccessible due to environmental features, e.g. they form part of a water catchment, have been purposely planted to control water run-off and soil erosion, or they protect and conserve biological diversity. As such, only about 5% of the potential wood volume in closed forests is accessible for wood energy. Ownership of forested areas is also important and determines control and access.
Communities in semi-arid and arid areas freely use wood for fuel, for the production of charcoal and for construction poles. Access to woodlands, bush lands and wooded grasslands is much easier than access to closed forests. However, accessibility is made difficult by remoteness and the difficult topography of some areas, and small tree sizes (mostly less than 5 cm diameter).
Wood for charcoal production is currently obtained unsustainably from communal savannah woodlands and rangelands in the semi-arid and arid lands of Kenya or through clearing land of trees for agriculture. Charcoal is produced inefficiently using traditional earth kilns whose efficiencies range between 10–13% (ten tonnes of wood for every one ton of charcoal) yet higher recoveries of between 30-40% have been achieved using brick and metal kilns. Current kilns lead to high loss of raw material, and twigs and branches are left to decay on the ground.
Accessibility to woodland, bush lands, and wooded grasslands may be approximately 30%. Grasslands where woody vegetation is scattered are about 10% accessible to surrounding settlements. Trees on farm and private estates are 100% accessible to their owners, of which about 90% is available for fuel wood.
Forest plantations are mainly managed with the objective of meeting the industrial requirements of timber for construction. Private plantations, however, often consist of Eucalyptus species planted for fuel wood. These provide only a small portion of supply while little wood waste in public plantations contributes to energy supplies. Accessibility is therefore estimated at only 35% for all types of plantations, which are primarily planted for sawn timber and construction poles.
Farm residue is used as a source of fuel particularly in areas where energy demand exceeds supply and in certain seasons when wood supply is limited. The quantities of residues are dependent on yields of the particular crop and proportional to the area planted. Residues are 50% accessible to the farmer as a source of energy. As of the year 2000, sources of biomass residue in Kenya included; maize 1.6 million tons/yr, Sorghum 76,000 tons/yr, wheat 42,000 tons/yr, millet 46,000 tons/yr, beans 77,000 tons/yr, rice 1,000 tons/yr, cassava 12,000 tons/yr, coconut 6 tons/yr, cashew nut 2tons/yr, coffee 300,000 tons/yr, tea 60,000 tons/yr and sisal 8,000 tons/yr.
There are two major sources of industrial wood waste. Logging sites where branches and tops remain after felling, supply about 35% of log harvest which has already been considered under plantation supply. The other source is sawmilling sites where sawdust, bark and small off-cuts are available for fuel wood. The average annual production of industrial wood processed by sawmills (other wood based industries consume their waste for internal purposes) in 1999 and 2000 was about 130,000 tonnes.
- GTZ (2007): Eastern Africa Resource Base: GTZ Online Regional Energy Resource Base: Regional and Country Specific Energy Resource Database: II - Energy Resource.