Anaerobic digesters and P recovery
This past summer I visited India to explore organic waste management operations that contributed to nutrient cycling. In today’s post I will discuss Jain Irrigation Systems Ltd (JISL). Founded on a philosophy that we should leave the world better than we found it, JISL pays close attention to environmental issues, farmer livelihoods, and the well being of both employees and customers. The company has a variety of operations, ranging from manufacturing solar panels and irrigation equipment, to propagating bananas and processing fruits and vegetables. While they appear to be on the leading edge of many different agricultural practices, it’s their industrial food processing and waste management that caught my attention.
As the food processing side of the company grew, management recognized they couldn’t rely on composting as their sole organic waste management approach. While they had significant amounts of land on which to dump the food waste, increasing volumes would create smell and insect problems, which could get them in trouble with local regulatory agencies. After a number of experiments with various types of composting failed to meet their requirements, they partnered with a German company to design and build an anaerobic digester on site in 2012- the first of its kind in India.
During Mango season, processing into mango puree results in 300 tons of waste every day. The pit is mechanically sorted from the waste to be dried to be burned for energy, while the rest of the waste (~150 tons/day) is stockpiled for feeding the digester. Processing bananas, tomatoes, and onions provides additional feedstocks for the digester throughout the year, and a nearby sugar factory also sends its waste to JISL.
Not only does the digester create enough methane to run generators producing 1.7 Megawatts of power each hour, the exhaust from the generators is sent to a boiler where it makes steam, which is sent through a condenser where it creates 400 tons of refrigeration per hour for the food warehouse. Finally, the residuals from the digestion process are sent through a belt press to extract water (which is reused for irrigation, or in the digester) and the solids are sent to composting where they are mixed with other organic waste and sold back to the farmers supplying food to the factory.
Recovering and recycling P from the organic waste may have been an afterthought, but through this integrated systems approach, JISL has found an economical way to turn a waste product into energy and nutrient resources, while protecting the environment and their bottom line.