Effective Disposal

Utilising distillery waste to generate power

While 2017-18 saw record production of sugarcane and sugar, 2018-19 is likely to witness even higher peaks, thus increasing the need for handling molasses and other by-products. In this scenario, the diversification of the sugar industry into distillery (producing alcohol and ethanol) and cogeneration (producing steam and power) industries is inevitable. Further, with the growing environmental concerns in India and globally, proper disposal of waste, or rather its “alternative usage”, has gained immense importance.

Spent wash – the effluent generated during ethanol production – could be used as a key source of bioenergy either by transforming it into biogas (methane), to be used as boiler fuel, or by concentrating it in multiple effect evaporators and then incinerating it, along with bagasse, coal and other biomass sources, in an incineration boiler to integrate it with a turbine to produce bio-electricity.

The benefits are several. Besides meeting captive power requirements, the resulting potash-rich ash could be sold to generate additional revenue and eliminate the disposal problem. Overall, the process reduces the production cost per litre of alcohol and generates steam to meet the process requirement of the distillery. Today, India is a net importer of potassic fertiliser, and this process of utilising distillery waste could help, in a small way, to reduce the quantum of these imports.

Environmental concerns

India is one of the largest producers of ethanol in the world and possibly the second largest in Asia. According to the Indian Sugar Mills Association (ISMA), ethanol supply to oil marketing companies (OMCs) for blending with petrol is expected to rise 71 per cent in the 2017-18 season to touch a record 1,130 million litres, helping sugar mills generate a revenue of Rs 45,000 million. In contrast, around 660 million litres of ethanol was procured by OMCs under the ethanol blending programme during the December 2016 – November 2017 season. The ISMA attributed the potential jump in ethanol supply during 2017-18 to a 5 per cent improvement in the ethanol procurement price over the previous year and the increase in sugarcane availability, resulting in a higher production of molasses.

Most of the Indian distilleries use sugarcane molasses as raw material for the production of alcohol. Unfortunately, these industries rank high on the list of the top 17 heavily polluting industries identified by the Ministry of Environment, Forest and Climate Change. Spent wash generated from the distillation process has a very high pollution potential. It is not only high in organic and inorganic loading, but also has a dark brown colour even after biomethanation. In those parts of the country where land application of distillery wastewater is practised, the colour problem in groundwater is so acute that distilleries have to provide potable water to surrounding villages.

Many physico-chemical and biological methods have been tried to treat this problem, but a cost-effective and efficient treatment method is still awaited. The application of untreated wastewater to land reduces the alkalinity of the soil and destroys crops. It behaves much more hazardously when disposed of in waterbodies, leading to depletion of dissolved oxygen and endangering aquatic life.

To address the growing environmental concerns due to the liquid waste generated from molasses-based distilleries, the central and state pollution control boards released the zero liquid discharge (ZLD) norms. In line with this, the Cogeneration Association of India (Cogen India), in association with the National Sugar Institute (NSI) and the All India Distillers’ Association, organised a business meet in Lucknow on March 15, 2018 to promote distillery/ethanol projects, along with incineration boiler-based cogeneration power plants at sugar factories in India. Interesting insights into issues concerning all stakeholders were shared and discussed.

A particularly interesting case study by Balrampur Chini Mills on its distillery waste incineration experience was presented. Three years ago, the company had pondered the decision to opt for the incineration of distillery spent wash generated from its three ethanol producing units. A team visited a few installations in southern India and Kenya, and found that the units were operating with coal as support fuel with a very high downtime and inefficient operations. But since Balrampur Chini had plenty of surplus bagasse, it decided to use it as support fuel. Since then, its 60 kilolitre per day distillery with a 40 tonne per hour incineration boiler has been operating successfully.

Such projects will give a new impetus to sugar factories to improve their financial sustainability. This is crucial given the downward trend in revenues from the sale of sugar and cogeneration power surplus, as well as the expected fall in sugar prices in the domestic and international markets in light of the abundant sugar crop.

Alcohol industry: Issues and remedies

The present requirement of ethanol for 10 per cent ethanol-blended petrol is estimated at 3,000 million litres per annum (requirement as per the latest tender floated by the oil companies is 3,130 million litres), which is expected to grow with increase in vehicle population.

As per Narendra Mohan, director, NSI, Ministry of Consumer Affairs, Food and Public Distribution, the blending targets have not yet been achieved despite consistent efforts being made in this direction. Earlier, when record sugar production of around 29 million tonnes had been projected for the year 2017-18, alcohol production from molasses was estimated at 2,800 million litres, and that from grains at 1,500 million litres. Thus, after considering the alcohol demand from other sectors, such as the potable and chemical sectors, to the extent of 3,250 million litres, the shortfall in alcohol demand is estimated at about 2,000 million litres per annum, indicating an increase in demand in the coming years.

The government’s fuel import bill continued to rise to reach $140 billion in 2016-17, from $100 billion in the previous year, resulting in 82 per cent of its crude oil requirement being imported. Thus, there is a need to harness other feedstock to produce power – not only to provide clean and green energy and replace fossil fuels, but also to reduce dependency on crude oil imports and preserve foreign exchange.

Over the past few years, there have been significant advancements in fermentation and distillation technologies. This has not only helped the distillation industry enhance the alcohol yield per unit of molasses, but has also reduced spent wash generation, and steam and power requirements of the industry. The treatment of spent wash and other effluents from molasses-based distilleries has assumed greater significance, in view of the ZLD requirement. The two routes for ZLD – bio-composting and incineration – need to be followed in letter and spirit as per the directions of the pollution control boards. Besides ZLD, the installation of incineration boilers will help harness the fuel value potential of spent wash to produce/export power.

Further, the drawal of fresh water from natural sources needs to be reduced by maximising the recirculation of condensates and other streams after due treatment. The industry may avail of financial assistance being provided by the Indian government through the Sugar Development Fund for setting up new distillation/cogeneration units and upgrading the existing units.

Sustainable energy complexes

In light of the above factors, the sugar industry in India has realised the importance of diversification for sustainability. It is moving from stand-alone sugar factories towards the concept of integrated energy complexes, comprising sugar, power and ethanol units. The government has set ambitious targets of 10 per cent blending of ethanol in petroleum fuels, creating an opportunity for the sugar industry.

The case study presentation by Balrampur Chini Mills and further inputs by Dalmia Sugars and Hindustan Petroleum Corporation Limited at Lucknow raised awareness  regarding the difficulties faced in implementing such projects. But ultimately, these projects have been successful, primarily due to the teamwork of vendors and other stakeholders.

According to Sanjay Khatal, executive director, Cogen India, and managing director, Maharashtra State Federation of Cooperative Sugar Factories, “The sugar industry continues to be a strong backbone for rural India, being perhaps the only industry in India with a strong supply chain management in place. It has therefore continued to remain contemporary, both in terms of diversification and technological upgradation, which is why sugar factories are no longer stand-alone sugar-producing units and pollutants as they once used to be in the 1950s and 1960s.”

In conclusion, all the participants and Cogen India expressed the need to work together in pursuing a favourable policy and regulatory framework, particularly in terms of tariffs, etc. This will enable sugar factories/distilleries to implement and operate these projects profitably.

India has committed to reduce the country’s energy intensity in the Paris climate agreement. The challenge now lies in balancing our ever-growing energy requirements with the equally important issues of protecting the environment.

With inputs from Cogen India and NSI

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