Fertiliser from organic waste: A money spinner
 

by Ramani Kangaraarachchi

A Rs.7 million worth patented process for fast digestion of plant and animal waste into organic fertiliser is now under way in Sri Lanka.

The Horana Urban Council has approved the construction of a fertiliser manufacturing plant based on the above process and the Central Environmental Authority has given approval to commission the plant early next year. Plant design activities are already in progress.

Senior Lecturer and former Head of the Department of Chemical and Process Engineering, University of Moratuwa, engineer Anul Perera has developed a process by which plant waste, such as, leaves, saw dust, tea waste, straw, paddy husk, salvinia, weeds, fruit peels, seeds and animal waste, such as, offal, feathers, bones, skin, (in other words any type of organic waste) etc., can be converted into organic fertiliser, with a high content of Nitrogen (N), Phosphorous (P) and Potassium (K), within 1 to 2 days.

Since the process involves automatic heating of waste material to more than 1000C, the organic fertiliser produced will be free from various germs, such as, bacteria, virus and fungi, that can cause illnesses, to people, animals and plants. He has received two patents for this process from the Director of Intellectual Property.

This process has been tested with all types of waste material. The fertiliser obtained has been successfully tested for various crops, including, rice, coconut and vegetables. Steps have been taken to test it on tea. The process has been demonstrated at several government institutions, Perera said. This process is a solution to the urban waste problem, since, it converts all types of organic waste into fertiliser in 1 or 2 days and gives a product that can generate an income.

Since it is a 1 to 2 day process, it does not require stockpiling of waste for several months. The cost of fertiliser produced from this process will be Rs. 3-4 per kg and will be richer than traditional compost.

The fertiliser can be sold to the local market at a price of Rs. 7,000 per MT. Moreover, this process leads to automatic separation of other non-degradable material, such as plastics, glass and metal from the organic fertilizer, in a germ free condition, so that they can be recycled.

Traditional processes, such as, land filling, composting and biogas generation are extremely slow, requiring 3-4 months time to digest garbage. If these systems are adopted, large extents of land have to be allocated because, garbage have to be stockpiled for 3-4 months.

As an example, if the daily collection of garbage is 500 MT, at any given time 45,000 to 60,000 MT will be in garbage stock piles, undergoing digestion. In land filling and composting processes a leachate is produced, which has a very high BOD value and contaminates soil and water.

According to Perera this process can solve the fertiliser problem in the country very easily. The annual paddy production is around 2 million tons in the country.

With each ton of paddy, 1.5 tons of straw is produced as a result of which the total straw production in the country is around 3 million tons per year.

If the straw can be converted into NPK and mineral rich organic fertiliser and put back to the paddy field it could give back the NPK to the soil. The organic component of straw can promote the development of an eco system in the soil, thereby promoting micro and macro-organic activity beneficial to the soil.

Through the new process that Perera has developed, straw, paddy husk as well as any other plant and animal refuse can be converted into organic fertiliser in 1-3 days, whereas, traditional composting processes require more than 3 months.

Hence, if all the straw and other plant and animal wastes are converted to mineral rich organic fertiliser by this process, it can replace imported fertiliser, such as, urea by more than 50%.

This will reduce the large burden on the government due to reduced fertiliser subsidy and will provide a cheap mineral rich organic fertiliser that is produced in Sri Lanka, using local material which will be the beginning of an agricultural revolution in the country he said. Email: [email protected]