Sustainable Development and Application of Bio-Energy in Coconut Plantations

One hectare of coconut land (156 palms ha"') planted with gliricidia (2 ,250 trees ha' into double rows in avenues o f coconut) and available natural pasture and outside supplied paddy straw coupled with six buffaloes were mixed into a farming model to examine the total productivity and potential o f green energy production by wood and biogas. Six buffaloes were maintained in a shed and the manure was collected for biogas generation. Biogas was purified from H 2 S and used to run a 0.75 hp engine. Wood o f gliricidia was used to energize a 3.5 kW gassifire for generating electricity. Productivity o f gliricidia in the 3 r d year was 4.5 kg wood (at 2 0 % moisture) and 3.5 kg o f fresh foliage per tree/year. Each buffalo produced an average o f 622 liters o f milk at the first lactation (for a period of 10 months) and value o f a calf was Rs. 41,244.00 at the age o f 17 months. Soils of the model were enriched by adding the effluent of biogas. The fertility o f soil (N, P, K, Mg, moisture holding capacity) improved significantly over soils sampled outside the model. The effluent of biogas was more fertile than dried buffalo dung. As a result, nut yield o f a coconut palm increased from 30 to 60 nuts pa lm'year 1 over a period of two years. In green energy production, the dung of six buffaloes passed thorough a biogas generator produced electricity per day equivalent to 3 liters o f diesel. On the other hand gliricidia wood o f one hectare o f coconut land was sufficient to energize 3.5 kW gassifire-engine-generator set for 1,600 hours/ year and this was equivalent to 5,000 units of electricity (kWh). Thus one hectare o f coconut/ gliricidia/natural pasture/paddy straw with six buffaloes was able to produce green energy equivalent to 5,700 units o f electricity (kWh) or 8,550 liters o f diesel, in addition to farm income derived from coconut, buffalo milk and other benefits o f buffalo farming. The total return (coconut, selling o f calves, buffalo milk and bio fertilizer) added up to Rs. 1,379,520 ha'year"'. The applicability of this model for small farmer o f the coconut triangle is evident from this study.


INTRODUCTION
Along with the price increases of fossil fuels and electricity, there is also an increased realization in the country that traditional energy is going to be more expensive with time.Therefore, a greater utilization of alternatives has to be actively promoted by the state to sustain the economic growth of the country.Further, self reliance is now viewed as an importanant aspect in both food and energy in view of global political and economic developments.
Sri Lanka is fortunate to enjoy a major share of energy obtained from indigenous sources.However, the share of indigenous sources is shrinking rapidly, in view of the ever growing energy demand due to rapid economic development of the country.At present, the share of imported energy is 43% and is increasing steadily.Fossil fuel derived energy sources world over are undergoing serious market upheavals at present and there is no hope of stability in the foreseeable future.In year 2008, the sharp increase of world oil prices saw Sri Lanka's oil imports consuming more than one third of all export earnings.Hence, development of alternative energy production systems within the plantation/agriculture sector is vital for national energy security and sustainable agricultural production.The objectives of this study were to maximize farm income through an integrated (Coconut/ Gliricidia/ Paddy straw / Cattle) farming system using the theoretical model given below (Fig. 1) and to develop a sustainable bio energy system to meet energy requirement of household.
Institute from January, 2007 to August, 2008.The mean annual rainfall of the location is around 1,400 mm distributed over two seasons in a year.Mean annual temperature is 30°C The soil is the Boralu series and land suitability for coconut is S 5 (Somasiri et al, 1994).Transmission of photosynthetically active radiation at the site under coconut palms was over 90 % at mid day on a cloudless day.

a). Coconut Plantation
One hectare of coconut land was selected to establish this fanning model.General maintenance was carried out and palms were fertilized without urea and P, K and Mg were incorporated to soil as practiced in organic farming.

c). Cattle Shed
The cattle shed was designed to accommodate 12 buffaloes however, only six buffaloes were maintained in this study.The construction cost was Rs. 185,000.00.Water pipe lines were placed above the animals to moisten buffaloes by spraying water during very warm periods of the day.

Productivity of Gliricidia
At the initial stage the productivity of a gliricidia tree was 1.9 kg of foliage and 1.0 kg of wood (Table 1).It was observed that both outputs increased with the present tree management system.Gliricidia produced more wood weight than foliage.

Calving and milk yield of buffaloes
Out of the six female buffalo herd, five females delivered 4 males and one female calves.Body weight of all calves after sixteen months of calving exceeded 270 kg (Table 2).Average selling price of a calf was Rs. 41,244.00based on a formula given by the National Livestock Development Board.The person who looked after the project was a casual labourer employed in the Ratmalagara  At the 15 cm soil depth levels of nitrogen in system has elevated by 30% over soils outside the system.
Similarly improvement of phosphorous and potassium were one and three-fold respectively.Mg also showed a 66 % increase in soils of the system (Table 5).At a depth of 30 cm N, P, K and Mg were higher than those at a depth of 15 cm.
For example, N and P recorded a two-fold and K recorded a 4.7 fold increase.Soil pH was slightly lowered in the soil within the system.

Analysis of buffaloe dung and biogas effluent
N, P, K, Mg, pH and electrical conductivity were measured in the manure collected from the dairy and passed through the biogas unit as effluent (Table 6).N and P levels were doubled in the effluent.The K level of effluent was also higher than in the dung.Mg was slightly lower in samples of effluent.(kWh).This is equivalent to three liters of Diesel, as 5.2 m 3 volume of bio gas was generated per day.

Energy generation by wood
In the third year, average wood production of a gliricidia tree was 4.5 kg tree'year 1 (at 20% moisture level).Hence, total wood productivity of one ha system was 10,125 kg and this was sufficient to run a 3.5 kW gassifire -engine -generator set for 1,600 hours generating 5,000 units (kWh) of electrical energy.

Total energy output of the model
Applicable bio energy was by biogas and wood.In the third year of the system, this was equivalent 5,700 electricity units (kWh) or 8,550 liters of diesel per year.

Nut yield improvement
At the commencement of the experiment the average yield of a coconut palm was below 30 nuts palnr'year 1 .After 2 years of field activities, the average yield was estimated as 60 nuts palm"'year 1 and button nut count indicated that the potential yield of 2009 (3 rd year) would be over 80 nuts palnr'year'.

Biogas generation
Biogas generated from the unit was sufficient to energize a 0.75 hp capacity engine for three hours

Gross return of the model
As presented in the Table 7, the direct outturn of the model were coconuts, buffalo milk, calves and energy (biogas and gliricidia wood).On the other hand, biogas effluent was the fertilizer for coconut; hence it saved costs of chemical fertilizer, annual estimate of Rs. 45,000.00 per hectare of coconut.
As estimated, the largest income (Rs.855,000.00year 1 ) was the energy generated from biogas and wood.This shows that value of energy was approximately 2/3 of total gross income of the model.hence profit maximization of unit area of land is the main constraint (Maheswarappa et al., 1998).
Integrated farming combines crop production with livestock.The livestock enterprise is complementary to crop production programs so as to provide a balanced and productive system of farming (Liyanage and Fernando, 1991).In a hectare of coconut land five to six cows can be maintained.
On an average, 15-25 kg of fresh manure can be obtained per day from each animal (Maheswarappa etal, 1998).
In tropical agriculture there are two key issues; In energy usage, the most convenient and popular is electricity or liquid fuel.
It is important to note that in this model, the endenergy product was electricity and it was evident that it is possible to generate 5,700 electricity units (kWh) or equivalent to 8,550 liters of diesel from a hectare of coconut land.Therefore, any coconut grower will be able to make his own energy plan depending on his coconut extent and his choice of coconut based industry.Such enterprises, undoubtly reduce energy dependence of the country by increasing national energy security.
A significant development in the model is the selection of buffalo as the animal component.
Buffaloes are identified as good ruminants to feed roughage, as they are able to convert many cellulose feeds into valuable items such as milk, meat etc. (Liyanage and Fernando, 1991).However, their body temperature is above normal cows and hence wallowing is needed.This was overcome byimodifying the shed and moisting animals frequently.As a result, animal health and facility to produce milk was observed to be excellent.It could be stated that buffaloes could be moved from muddy fields to highly convenient sheds by artificial drizzling.
Gliricidia is now popular as the 4 th plantation crop due to its multiple uses (Gunathilake and Wasantha, 2004).It has the ability to fix aerial N and enrich soils by green manuring.On the other hand, it is a valuable animal feed for protein.In this model leaves of gliricidia mixed with paddy straw, was the main feed for buffaloes, and it seems to be an ideal animal feed.Therefore it was evident that good animal feed can be blended locally for high production of milk and meat in-addition to additional benefits of riianure and its recycling chain in agriculture.
Management of soil fertility in coconut plantations is now being addressed to sustain coconut yields economically.As at present, soil degradation is obvious.Application of chemical fertilizers is not the answer for management of sustainable soil fertility.Hence, the application of organic fertilizers for coconut as well as other crops is becoming a popular feature.On many occasions, cattle dung 'and other similar sources are called as organic fertilizers, however, it seems to be incorrect and 'these are virtually natural fertilizers.Today's need is not natural fertilizers, but fertilizers with easily !available nutrients.Therefore, all natural fertilizers i should be processed into chemical forms if possible , ' by normal processes.In this model, gliricidia and paddy straw were fed to buffaloes to make manure and the manure was passed through a biogas digester which gave biogas slurry /effluent.The plant chemical parameters of effluent are higher than in pure manure (Table 6) and further analysis showed that plant nutrients in effluent are easily available forms of nutrients such as N, P,-K.
Microorganisms were not analyzed in this study but it is obvious that their association with effluent should be more over dry manure.Therefore, further studies are suggested on the role of micro-organisms in effluent and cow dung (biogas benefits).There is no doubt that, this would be the reason for doubling nut yield in a short period.Therefore, it is now worthy to consider recommendations for the application of cattle dung as a natural fertilizer for coconut, which seems to be inefficient compared to its process from biogas effluent.Studies show that 2/3 of N is lost by improper compost application to soil, but the process of biogass in vitro would minimize N losses.Due to continuous activities of the model, all chemical and physical parameters of soil were improved (Table 4 and 5).Soil of the model is classified in the Land Suitability Class 5 (Somasiri et al., 1994) and potential yield of this soil is stated as 30 nuts palnr'year' or below.
However, in the model, nut yield of palm could be increased up to 60 nuts palm"' year' and then to 80 nuts or more.It is evident that marginally suitable soils could be elevated by improved coconut land management systems as practiced in this model by adopting in integrated systems with combinations of livestock and crop.

CONCLUSIONS
There is a significant potential in coconut lands to increase crop productivity and to generate ecologically sound green (bio) energy.In national food security, milk production is given high priority due to high cost of imported packs of milk powder.
In this regard, role of cattle/buffaloes and other ruminants play a vital role by producing natural fertilizers in addition to milk.It is now well accepted that without ruminants there is no sustainability in agricultural production.This study, proved that integration of coconut, gliricidia, pasture and paddy straw coupled with buffaloes is able to increase productivity and sustainability of coconut lands.The interesting feature is the production of a bio-energy system and the highest outturn was from the energy.
All necessary technical directions are given here to develop much bio energy when is needed among local village farming communities.In conclusion, it is suggested that "Bio-energy villages" should be developed to achieve independence not only in democracy but also in national energy security.

Fig
Fig.l.Theoretical Model prior to the trials consists of coconut, buffalo, gliricidia, paddy straw and natural grasses to produce green energy.

Fig. 2 .
Fig. 2. Updated Income from 1 ha Coconut /Gliricidia Plantation Integrated with a Buffalo Dairywith no involvement for power generation.

Table 1 :
Fresh foliage and wood yield of gliricidia in the bio-energy system at the Ratmalagara Estate

Table 2 :
Productivity of the buffalo unit at the Ratmalagara Estate

Table 3 .
Milk yield of the buffalo unit at the Soil analysis for several chemical and physical properties was carried out using soil in the system where animal movement and residues of the system w|as added and soil outside the model for comparison.The electrical conductivity, soil bulk density, moisture holding capacity of soil in the model were clearly elevated to improve the quality of the soil in the model area.This was noticed at i soil depths of 15 cm and 30 cm (Table4).

Table 4 .
Electrical Conductivity, pH, Bulk density and moisture holding capacity of soil in the model and soil outside the model at the Ratmalagara Estate 'System (IN) 27.89jis/cm 33.39[is/cm

Table 5 .
So/7 nutrient levels (TV, P ,K, Mg, Ca and Na) within the model and outside at the Ratmalagara Estate

Table 6 .
Buffaloe dung and gas unit slurry analysis at the Ratmalagara Estate

Table 7 .
Estimated gross return of the model at the Rathmalagara Estate at the end of 3 rd year