Date : 7 September 2023
A Game-Changer in Anaerobic Digester Operations
Distilleries produce a high volume of wastewater known by various names such as spent wash, vinasse, slop, stillage, or distillery effluent. These streams present a significant environmental challenge due to their high Chemical Oxygen Demand (COD) and other pollutants. However, they also offer an untapped potential for energy recovery through biogas production. This blog post VORTA pre-treatment that significantly enhances the biogas yield from distillery spent wash.
Distilleries, often coupled with the sugarcane industry, produce large amounts of wastewater. For example, for every cubic meter of alcohol produced, 10-15 m3 of distillery wastewater is generated. Considering the scale of ethanol production globally—greater than 40 billion liters in India and over 300 billion liters in Brazil—the associated wastewater is immense. Current treatment methods range from fert-irrigation and bio-composting to incineration and anaerobic digestion (AD), each with its own limitations.
Although AD is an attractive option due to its low operating costs and potential for energy recovery in biogas, its efficiency is limited. For instance, the conversion of COD rarely exceeds 70% in spent wash, and even lesser for more difficult-to-digest streams. This gap led researchers to explore pre-treatment methods to make the organic matter in wastewater more bioavailable for anaerobic bacteria. VORTA pretreatment is a method that involves the formation and subsequent collapse of vaporous microbubbles in a flowing liquid. This process creates localized hot spots, intense shear, and highly reactive oxygen species, facilitating the breakdown of complex organic matter.
A recent study [1] using VORTA pre-treatment has shown promising gains. The main conclusions from the study are:
- For Spent Wash (COD 120,000 ppm): A 14% enhancement in Biochemical Methanation Potential (BMP) was observed, translating into a net energy gain of ~1 GJ/ton COD.
- For Vinasse (COD 27,000 ppm): Overall improvements in digester operations were noticed.
- Industrial-Scale Validation: A 10-22% increase in biogas yields was confirmed in large-scale industrial spent wash digesters, corroborating the lab findings.
In an era where sustainable waste management is not just ideal but essential, VORTA pretreatment emerges as a scalable and energy-efficient solution. It not only addresses the wastewater management crisis but also supports the bioenergy sector by enhancing biogas yields. With confirmed laboratory and industrial-scale results, this technology could well be the linchpin in constructing a more circular and sustainable bioeconomy, especially for the sugarcane and distillery industries.
References
[1] Nagarajan, Sanjay, and Vivek Vinayak Ranade. 2020. ‘Pre-Treatment of Distillery Spent Wash (Vinasse) with Vortex Based Cavitation and Its Influence on Biogas Generation’. Bioresource Technology Reports 11 (September): 100480. https://doi.org/10.1016/j.biteb.2020.100480.
