Gliricidia – Biomass has huge potential for Clean Development Mechanism

Power and energy crisis in the global scenario, aggravated further by steep rises in price of crude oil and it’s rapid increase in consumption, has been compelling Sri Lanka to focus on developing alternate sources of energy for industrial, commercial and household sectors. Solar power, wind power, bio-gas and firewood have been known to be the main alternate sources of energy

N.Yogaratnam. B.Sc.Agric,Ph. D (London) Tree Crops Specialist
Clean Development Mechanism (CDM) or Carbon Trading, is an arrangement under the Kyoto Protocol (UNFCCC1997) that allows Sri Lanka, that has no legal commitments under the Kyoto Protocol, to assist 39 developed countries to reduce Green House Gas (GHG) emissions by implementing emission reduction projects in Sri Lanka and trade their emission reduction with developed countries.

Two types of projects have been recognised, (1) Emission avoidance and (2) Green House Gas removal. Gliricidia biomass power generation has been identified as one with huge potential for carbon trading under the Kyoto Protocol.
Establishment of biomass plantations for energy production and the substitution of fossil fuels is also an eligible forest CDM project under the Bonn agreement.

Background
Power and energy crisis in the global scenario, aggravated further by steep rises in price of crude oil and it’s rapid increase in consumption, has been compelling Sri Lanka to focus on developing alternate sources of energy for industrial, commercial and household sectors. Solar power, wind power, bio-gas and firewood have been known to be the main alternate sources of energy.

The technological advancement and inadequate facilities in Sri Lanka had been the major constraint for the use of such alternate sources. Bio-gas offers a possibility but non-availability in commercial quantities for the industrial sector is a discouraging factor. It therefore appears that firewood may be the most suitable source in terms of technological acceptance and for economy reasons as indicated below:-

4 kg. of firewood = 2 kg of coal = 1 kg of diesel.
Biomass energy had been a dominant factor in the economic development of the country for many years. Apart from the household sector, the industrial and commercial sectors have also been using biomass fuel to meet their thermal energy requirements eg. brick, bakery, tea, rubber industries etc.

Traditionally, forests have been providing the firewood requirement of the country. These resources are now in the stage of depletion due to frequent harvesting. Moreover, such practices have also resulted in adverse impact on the environment. The crops that are cultivated for such purposes; should therefore possess characteristics that would enable them to withstand frequent harvesting and cause no adverse effects in the environment, besides providing some additional benefits, other than as a prime source of biomass energy and in CO2 sequestration and N20 abatement.

Such system of cultivation should combine policies, technologies and activities aimed at integrating socio-economic principles with environmental concerns so as to simultaneously, enhance production and productivity, protect the potential of natural resources, reduce level of production risks, be economically viable, socially acceptable and politically supportable. ‘Gliricidia’ is likely to meet all these requirements

This article analyses and provides strategies for the use of Gliricidia as a source of biomass energy at least to partly meet the energy requirement of the industrial commercial sectors and seek carbon credits under the CDM.

Biomass power generation
Gliricidia sepium, a very promising source of biomass energy for power generation was introduced into this country from Mexico, a south American country, by the missionaries; about 300 years ago. Subsequently, it has become popular as a shade tree in tea plantations, a supportive tree for pepper plants and as a fencing crop in coconut plantations and in most other parts of the country.

Although this tree is scientifically known as Gliricidia sepium, it is popularly referred to as Wetamara, Makulata, Wetahiniya, Giniseeriya and Ladappa in different parts of the country Among the several fuel wood trees viz. Gliricidia, Acacia, Ipil, Eucalyptus, Calliandra etc., that were evaluated for use in coconut growing areas, Gliricidia has been identified as the most acceptable tree for commercial use.

Productivity potential
Box 1 indicates an estimated productivity potential of Gliricidia under rain-fed conditions in Sri Lanka. An average yield of 200 tonnes (20% moisture) of fuel wood per hectare per year and 16 tonnes (fresh weight) of foliage per hectare per year has been confirmed in field trials.

Agro – characteristics
Gliricidia is adapted to wide-ranging agro-climatic and soil conditions and can be cultivated all over Sri Lanka except in coastal areas, on mountain tops and in arid areas.
Tolerant to poor soils: Apart from water logged and rocky soils, it can be cultivated in all other types of soil including degraded marginal lands.

Tolerant to fire: If Gliricidia sepium is planted at a spacing of 1 metre x 1 metre or with higher density, the canopy of these trees closes within a few months of planting and within a few months of each harvest thus suppressing the growth of weeds. The absence of large extents of it has a deep root system, trees will not be destroyed totally by fire. With the first rainfall after the incidence of fire, new shoots would grow from the roots emerging through the soil. These shoots grow very rapidly supported by the extensive root system thus re-establishing a healthy plantation.

Amenable for easy harvest and transport: Trees could be ‘trained’ to produce branches at a height convenient for manual harvesting. The branches are very straight and free of any side branches. The foliage is soft and does not cause any abrasion to the skin of workers while harvesting. After harvesting the branches from the tree, it is sufficient to lop the top part of each branch. As the branches of Gliricidia are straight and are free of any side branches, voids created during stacking and transport are minimal. This enables to achieve a high bulk density during storage and transport.

Easily decomposable litter with foliage, when buried in soil, lasts for about 6 weeks. The soil retains the nutrients for about 5 – 6 months. Foliage of most other trees takes much longer to decompose. The high rate of decomposition is also a desirable feature as quick release of nutrients accelerates the growth of crops when foliage is used as organic manure. Leaf litter from trees normally is a fire hazard in plantations during the drought months. This hazard is minimised with quick decomposition of leaf-litter. Nutrient recycling process in the soil is also accelerated.

Reduces Pests and Diseases to adjoining Crops (Alloepathy): Alloepathy is a natural phenomena in some trees to repel pests and suppress weeds. Gliricidia sepium, when planted in high density, maintains a closed canopy of leaves thus preventing sunlight reaching the ground. This prevents the growth of weeds. The natural faint smell of the foliage is responsible for repelling all insects and pests. Furthermore, roots of Gliricidia sepium exude some root chemical which would inhibit the survival of undesirable weeds and pests. However, goats and cattle relish on Gliricidia sepium foliage. It’s also less susceptible to pests and disease. It has been cultivated in Sri Lanka for over 100 years, and has never been affected by any major pests or disease. Like any other plants, it needs moisture at the time of establishment. Once established, from about 3 months after planting, it can even withstand severe droughts that may be experienced in certain areas.

Nitrogen fixation: It is a leguminous tree with very high rate of nitrogen fixation. Measurements carried out reveals that 1.0 hectare of plantation produces an average of 12 tonnes of fresh foliage which is equivalent to 300 kg of urea annually.

Growth rate: 1.0 hectare of Gliricidia plantation established on degraded land in the dry zone, produces annually an average of 30 tonnes of woody biomass (at 20% moisture). It coppices profusely after every harvest. Production and growth of new coppices do not decline over the years.

Ease of propagation: It could be propagated either from seeds or from stem cuttings. Stems with length varying from 1.0 meter to 2 meters could be used as planting material. Planting holes by crowbar are sufficient for rooting provided planting is carried out at a time when moisture is available in the soil. Ideally, this is done at the beginning of the monsoon rainy season. When propagated from seeds, a nursery is established and seedling is replanted at the beginning of the monsoon rain.

Its multiple uses include branch wood as fuel wood, as support for vegetable cultivation, as support tree for pepper cultivation etc. Foliage is used as nitrogenous green manure and as cattle and goat fodder. The foliage from 1 hectare of Gliricidia sepium plantation could support about 6 animals (cattle).Small growers will be able to establish units of ‘bio-gas’ by using cattle/goat dung.
Of around 15 tree species tested and identified as suitable tree crops for fuel wood plantations, Gliricidia sepium was found to be the most significant species which offer series of other complimentary benefits as far as the soil and environmental aspects are concerned. Gliricidia sepium is historically grown as a boundary fence tree which does not require any special agronomic practices, care of pest control measures due to some inherited genetic characteristics typical to it. It is a drought tolerant tree crop which has the capacity of absorbing nitrogen from the atmosphere with the least intake of soil nutrients while fixing nitrogen into the soil.

CDM potential
Gliricidia, being a perennial leguminous tree crop, would be an ideal material to establish bio-mass plantations for energy production and the substitution of fossil fuels. The baseline emissions targeted would include CO2 in the atmosphere and N2O in chemical nitrogenous fertilizers. Under a mixed cropping system with other perennial tree crops e.g. Rubber, this would lead to an annual CO2 reduction in the region of 150,000t CO2 eq.

Recycling of Gliricida foliage and other complimentary organic farm wastes as nutrients for the main and secondary crops in a mixed cropping system will minimize N2O emission and also loss of nutrients by volatilisation, denitrification, leaching etc. by about 40 to 45 percent, besides minimizing environmental pollution in the absence of chemical fertilizers.

Estimated revenue from 1.0MW Gliricida biomass power plant, with an annual emission reduction of about 7,546t CO2 eq, would be, about US $ 75,465 per year at the rate of US$ 10 per tCO2, besides the additional benefits from N2O abetment which carries a Global Warming Potential (C02 equivalents) of around 310 as against 1.0 by C02.

Cultivation of Gliricida
Gliricidia could be grown as a monocrop plantation or as a mixed crop along with other short/long term crops grown in the locality. All scrub trees should be removed but it is not necessary to plough the soil. Planting methods, include a spacing - 1 m x 1 m double rows with a density of - 8000 trees/ha.

Planting Materials (Propagation) are by seeds and stem cuttings. Seeds are collected in March-April of the year. These seeds should be laid in polybags with a planting medium of soil and organic mixture.

Matured stem cutting of 1.0 m height and 2.5-3.5 cm diameter is selected for planting during the monsoon period of May/June or October/December. October-December is ideal for planting due to rain and favourable air temperature.

The cost of field establishment increases with plant density. Moreover, high plant density would also result in difficulties in harvesting, collecting and transporting branches. Taking all these factors into consideration, a spacing of 1 meter x 1 meter has been taken as the optimum requirement. To facilitate collection and transport, a 4 meter gap should be provided for every 12 rows of trees .When planted as a mixed crop, the spacing and plant density would depend on the requirement of other crops. In such instances, flexibility is necessary with regard to spacing and plant density.

After Care operation includes, filling all vacancies due to mortality during the monsoon periods. Manual weeding or chemical weeding by application of Glyphosate could be done. Two rounds of weeding in the initial year is required and subsequently natural suppression of weeds could be seen due to over-shading.
Training of Trees, during the first year, is by removal of all side branches and allowing the plant to grow until 6-10 erect branches are formed.

Harvesting
First harvest could commence after a year of establishment. In the first harvest, the main stems of the trees are cut at chest height. All side branches are also removed to provide easy access to each tree. Within a week or so, many shoots will sprout near the cut-end, which will grow and mature. Subsequent harvests should be carried out by cutting and removing mature branches close to the base of the respective branches.

After the first harvest both, wood and foliage yields increase and reach the maximum at the fourth year of planting and then sustain the wood yield around 6.0 – 8.0 kg of wood/tree/year (at 20% moisture level).
Generally, this is eight months. This varies during the dry weather conditions and also during the peak monsoonal periods (November – December). In large Gliricidia plantations, rotational harvesting could be practiced. As an example, in a 100 acre land, this could be done on the basis of 2 acres per day for 50 days. In very large plantations, continuous employment throughout the year could be organised by scrutinising daily harvest area and number of workers engaged in harvesting.

At present harvesting is done manually, using knives. However, in large scale plantation, mechanical devices could be used to increase efficiency and to reduce cost of harvesting.

Just after harvesting, the bulk (sticks and leaves) should be left for about 3 – 4 days for natural shedding of leaves. This process is helpful for nutrient recycling through decomposition of leaves. Gliricidia leaves could also be used for other purposes such as green manuring, feeding animals etc.

Processing of Gliricidia wood
At the time of harvesting, moisture percentage of wood would be about 50% or more. Once wood is allowed for sun drying for easy chopping, moisture percentage decreases to app. 30%. At the storage, either in grower’s land or at the power generating site; (with 2 – 3 weeks of storage period), the moisture level of wood further decrease to 25% or less. Therefore, proper storage techniques (in bags or acceptable size of heap) should be adopted.
Gliricidia wood could be supplied in different forms in the following manner:

(a) Chopped by manual labour (individual grower) into size of 10.0 – 15.0 cm and packed in netted polyurethane bags.
(b) Chopped by a ‘chopping machine’ (individuals or group of farmers) to the above specifications and supplied in similar manner.
(c) Supplied as long sticks and chopped at the site of power plant.
Cost of a machine is around Rs. 95,000/- and such machine could be used by individuals or a group of farmers. Sometimes, middlemen may also get involved. This could be eliminated if the company arranges a net work of organised chopping facilities.

Economic benefits
Box 3 highlights the economics of establishing Gliricidia as a monoculture plantation in an extent of 1.0 ha with a plant density of 8,000 trees per ha.
The requirement for wood based steam turbine driven electricity generator 1.0 MW power plant is about 40mt of Gliricidia wood per day (at 20% moisture level). Assuming the productivity of Gliricidia to be 30mt per ha per year, an average of 1.5 ha of Gliricidia plantation (monoculture stand) would be sufficient to meet this requirement on a per day basis.

The increasing threat from climate change on environment and sustainable development, power crisis and non-profitability in corporate business, looming over the country can be turned into a boom with Gliricidia Biomass Power Generation (GBPG). Indian experience of using all forms of biomass very extensively for power generation and carbon trading is a very good example.

To summarise
1. Due to increasing concern over climate change and its consequences and cost of petroleum based Electrical and Thermal Power generation in Sri Lanka, development and application of alternative energy sources is considered urgent and necessary.
2. Use of wood biomass appears to be the most appropriate technology applicable to local conditions and necessary developments in the use of such techniques have also advanced.
3. Among the wood source, Gliricidia sepium has been identified as the most suitable source for thermal/electrical wood based power generation.
4. Gliricidia could be grown under wide – ranging agro-climatic and soil conditions.
5. Wood yield of Gliricidia is about 30.0 mt/ha/year (monoculture at 20% moisture level) at its 4th year of establishment and thereafter.
6. For 1.0MW power plant, approximately 40m.t. of Gliricidia wood per day may be required and for a year 14,400 mt., at 20% moisture level may be required. Approximately 480 ha of a Gliricidia plantation may be required to meet this wood requirement.
7. Gliricidia could be grown as a monoculture plantation at the rate of 8,000 trees/ha.
8. When growing as a mixed crop, planting density would depend on other crops grown in this system.
9. Proposed purchasing price (minimum) for chopped Gliricidia wood is Rs, 2.20 per kilo of wood ie. Rs.2,200 per mt (at 20% moisture level) at the power generation site. An incentive price scheme could be adopted on the basis of moisture content and weight of wood.
10. Chopping of wood should be done by the growers/suppliers. Cost of a machine for such purpose is app. Rs.95,000.
11. Cost and benefits of Gliricidia under monoculture situation - it is estimated that a profit of Rs.35,970/- per year could be made from year 4 and thereafter from a one – hectare plantation.
12. A field survey has to be carried out and suitable land and potential out-growers should be identified.
13. Cultivation and supply of Gliricidia should be coordinated in a manner that will strengthen the wood supply arrangement and minimise cost.
14. Other benefits of Gliricidia eg foliage for animal feeding and as fertiliser etc should be developed at farmer level.
15. Gliricidia has huge potential for CDM / Carbon Trading, a system which is still add-end under-developed and under-exploited in the country.

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