Disposal of Cake of Jatropha Seed is one of the major problems being faced by BioDiesel Producers across the world. Seed cake is not a problem but it is a big asset. There are two ways of processing these to produce Organic Fertilizer.

1. Bio Gas Plant : Here the Biomass is digested in a simple plant and Bio Gas produced is stored and used. The area required for plant is very small.

2. Composting : Here the Biomass is digested underground but Bio Gas produced is wasted. Needs large area of land.

A 1 ton per day biodiesel plant, produces 2.5 to 3 tons of seed cake. If we carefully analyze this waste, we will realize that majority of it is biodegradable. Oil seed cake is a by-product obtained from the oil extraction process and can be converted to valuable organic fertilizer. Generally a slurry of 8 to 10% solids is used in Bio Gas plant, and one can get 350 Kilo Calories per Kg of cake. The cake has the following properties and nutrients:

1. Moisture : 4.58%
2. Nitrogen : 3.2 - 6.0% (N₂)
3. Phosphorus : 1.4 - 2.75 (P₂O₅)
4. Potassium : 0.94 - 1.68% (K₂O)
5. Crude Protein : 58%

When compared with other organic sources, (manures, seed and oil cakes), oil seed cake from Jatropha provides essential nutrients at comparable levels. The seed cake is unusable as feed for livestock due to its toxicity. This biodegradable waste, if handled properly would maintain the natural balance of essential elements and thereby promote more harvests from nature.
Disposal of Seed Cake of Jatropha, can be achieved by several other means like incineration, landfills, dumping in the sea or other water bodies etc. These methods have their own hazards. Incineration can lead to respiratory illnesses. Moreover, it may lead to disruption of biogeochemical cycles of several elements and will have long term effects on biosphere. Landfill and dumping can pollute water bodies.

Bio Gas Plant would serve many purposes such as :

1. Environment friendly disposal of waste, which is need of hour considering mass pollution everywhere.

2. Generation of fairly good amount of fuel gas, which will definitely support the dwindling energy resources.

3. Generation of high quality manure, which would be weed less and an excellent soil conditioner. This is very important for replenishing fast decreasing resources of productive soils. It must be noted that need for replenishing the soil with high quality organic manure has been identified in plan documents.

4. Biogas is a colour less, odour less and inflammable gas. The gas generated in this plant can also be used as a source of natural gas. The production is about 0.25 to 0.35 cubic meters per kg of cake with following composition of biogas

   • Methane (CH₄) : 70-75%
   • Carbon Dioxide (CO₂) : 10-15%
   • Water vapours : 5-10%

OPERATION
The material to be processed is brought to the plant site every day. Two workers are needed for the operation of the plant. The important tasks to be done are :

• Transport of waste materials
• Processing the waste in mixer
• Routine operations for pre-digester and digester tanks
• Manure pits

INFRASTRUCTURE REQUIRED
Infrastructures required to set-up a Bio gas plant of a capacity of 1 ton/day of Oil Cake

• Area of Plot : 300 m²
• Manpower : Two unskilled persons
• Power supply : 1 KW
• Water Supply : 1200 liters
• Cost : Rupees 500,000

Feeding Chamber

Overflow Pit

Homogenization Chamber

Digestor

Sludge Overflow

Sludge Drying