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  Dendro
 
   
   Introduction
 

Dendro power is the generation of electricity from sustainably grown biomass (fuel wood). It is particularly well suited to tropical countries such as Sri Lanka as the fuel wood can be grown rapidly and coppiced once or twice a month. Dendro using sustainably grown fuel wood can be effectively used to replace the use of fossil fuels for electricity generation and it can also deliver many other socioeconomic and environmental benefits.
   Dendro Power
 


Dendro power has great potential as a long term power generation option, both for grid-connected generation and for off-grid communities. Solar and village hydro power only have the potential to meet the energy needs of around 15-20% of the off-grid population in the country and Village Dendro Schemes can be constructed to serve off-grid communities that do not have the hydro potential and are unable to afford solar. Dendro power is a community-based electricity generating technology that includes all households in a village irrespective of their income level.


Dendro power could also be an option to replace government plans for fossil fuel power plants with sustainable renewable energy options. As the first step Energy Forum is keen to establish a grid connected dendro power plant with an out-grower system for fuel wood supply.

   
 
In Sri Lanka, nitrogen-fixing Gliricidia trees can be used as fuel wood as they are fast growing and therefore available in large volumes. Fuel wood plantations for dendro can be established as a multicrop in home gardens, as an under growth in coconut plantations, as shade for tea plantations and as a multi crop for reforestation. This means that the biomass plantations do not need to replace vital food crops. All off-grid villages in Sri Lanka have enough barren land to establish fuel wood plantations in order to the generate electricity throughout the year from Village Dendro Schemes without interfering with food crop production.
   
 
While the industry is in its infancy in Sri Lanka, there are structures and systems in place that provide an enabling environment for biomass energy production. An additional advantage to pursuing the village-based approach for biomass is that community or village based power plants have a well-established history in Sri Lanka. What has been firmly established in connection with village-based systems in the country and elsewhere is the importance of strong leadership within the community, the participation of and sustained dialogue with participants, and a well-managed Electricity Consumers’ Society (ECS).
   The Process
 

The dendro power generation process consists of three steps:

1. Growth of dedicated forests with fast growing tree species, having high energy yield.

2. Regular harvesting of biomass from the forest using coppicing techniques i.e. the tree as a whole is not cut down, but pruned systematically.

3. Biomass is transported and fed into the furnace of the conventional steam turbine/generator or fed into a gasifier to produce a combustible gas that could be burnt in a diesel engine coupled to an electrical generator.
   Dendro Technologies - Direct Combustion
 

Direct combustion of raw biomass is the simplest method of extracting energy with lowest cost, and therefore is the most common method of conversion. To generate heat (and electricity), combustion of biomass has been widely used in the past. At present, it is making a comeback in many industrial applications. This can range from simple systems such as stoves, furnaces and boilers to more advanced systems like fluidized bed combustion technology. However, straightforward conversion of thermal energy into mechanical or electric power results in considerable losses: it is not possible to raise the ratio of thermal to mechanical power above 60%. However, if the low temperature waste heat can be used productively, for instance for drying or heating purposes, much higher overall efficiencies can be obtained.
   Dendro Technologies - Gasification
 

The production of a combustible gas from solid biomass fuels has become very popular and this is achieved through a device known as “Gasifier”. In gasification, solid biomass is systematically combusted under controlled conditions to produce a combustible gas mixture. The use of a wood gasifier to generate producer gas can directly replace oil in thermal applications.


In addition, by adopting combined heat and power systems, considerable savings can be achieved through generation of thermal and electrical energy and perhaps even exporting some electrical energy to the national grid. These systems are viable for tea and rubber industries as well as for any other industry requiring thermal and electrical energy.
   Socioeconomic Benefits of Dendro Power
 

• Every Megawatt of dendro power installed creates employment for 300 people in rural communities

• Unused land and agricultural smallholds are ideal locations for the establishment of biomass plantations and people can enhance their earnings by selling fuel wood to dendro plants

• Employment opportunities are also generated out of the need to establish and manage fuel wood plantations and for plant construction and maintenance work
   Environmental Benefits of Dendro Power
 

• Biomass is a renewable energy source which is almost carbon neutral as the carbon emissions released during combustion are recaptured during re-growth. However in practice not all biomass generation will be carbon neutral as transportation to the generation plant will generate carbon emissions. Nevertheless, with the rising importance of reducing carbon emissions and addressing climate change, biomass is becoming recognised as a feasible fuel substitute for conventional energy sources.

• The leaves of the Gliricidia Sepium tree can also be used as cattle feed or as a substitute for urea as a soil nutrient.
 
   
 
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