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Waste to bio-CNG: The role of sugar mills in the transition

Bio-CNG, a renewable source of transport fuel from sugarcane waste, is increasingly being produced in sugar mills in sugarcane-growing states around India. Thirteen Indian states currently have 44 bio-CNG plants with a total production capacity of 218,000 kilograms per day, of this renewable fuel. Experts claim that although the production of bio-CNG from sugar mills is in its nascent stage, with a demand for CNG in the transport sector, rising petrol/diesel prices and an established distribution network, there is potential for the growth of bio-CNG production. Manish Kumar provides a comprehensivereport

Sugar mills in the sugarcane-growing state of Maharashtra are experimenting with using press mud, a by-product of sugarcane, in producing bio-CNG, a renewable source of transport fuel.

One of the earliest attempts at doing this is a 2012 collaborative project in the Kolhapur District of the state in which a bio-CNG processing unit, has been using press mud supplied by the Warana Sugar Mill, to produce bio-CNG. Press mud is the compressed waste that remains after crushing sugarcane.

“Around a decade ago with the help of researchers from the Agharkar Research Institute, Pune, we first tried to analyse the potential of press mud to produce bio-CNG in labs and it was successful. We collaborated with the Warana sugar mill for the supply of press mud. Later, we started producing bio-CNG from press mud on a commercial scale. Initially, we started with one tonne (1000 kg) of press mud per day and then we went up to 100 tonnes (100,000 kg) of press mud per day,” Mohan Rao, chairman of Spectrum Renewable, the processing unit producing bio-CNG at Warana, told Mongabay-India. The unit produces four tonnes of bio-CNG per day and has the capacity to go up to a daily production of eight tonnes of bio-CNG.

The bio-CNG produced through this collaborative approach is now bought by Indian Oil, one of the leading Indian Oil Marketing Companies (OMCs). It is sold at the two outlets of the OMC near Warana and its outskirts at Amrutnagar, situated close to the highway.

Truckloads of sugarcane from farmers entering into a sugar mill at Baramati in Maharashtra.

Besides the plant at Warana, currently, in Maharashtra alone, there are two other sugar mills – one in Pune and one in Osmanabad – which are producing bio-CNG (biological compressed natural gas) from sugarcane by-products, mainly press mud and filter cake, Shekhar Gaikwad, Maharashtra’s sugar commissioner, told Mongabay-India. There is another standalone bio-CNG plant in Pune which uses municipal waste to produce bio-CNG. Gaikwad said that these sugar mills and other bio-CNG plants get financial and other incentives from the Union government under the Sustainable Alternative Towards Affordable Transport (SATAT) Scheme. The scheme, launched in 2018, supports the establishment and expansion of bio-CNG plants that use waste to produce biofuel. Under the scheme, the Union government plans to establish a total of 5,000 bio-CNG plants in India by the end of 2023-24.

According to government data, Maharashtra is the third largest producer of bio-CNG in India with a daily production capacity of 28,690 kilograms per day across its four operational plants. Gujarat leads the country with its 12 bio-CNG plants and a daily production potential of 49,028 kgs/day, followed by Punjab (35,000 kgs/day).

Bio-CNG is considered a renewable fuel and has also been proven to reduce the emission of greenhouse gasses when used as a transport fuel. Bio-CNG, derived from the filtration of biogas, is also referred to as Compressed Biogas (CBG) and bio-methane. It is derived from biogas after removing impurities like carbon dioxide and hydrogen sulphide. Studies have shown that bio-CNG offers better environmental benefits compared to other clean transport biofuels like ethanol and biodiesel, as it has the lowest greenhouse gas emissions of any vehicle fuel.

Potential and expansion
In India, around 70 per cent of the sugarcane is produced by three major states – Uttar Pradesh, Maharashtra, and Karnataka. Experts working in the sector suggested that these states can help in scaling up bio-CNG production, which is currently at a nascent stage. Narendra Mohan, director of National Sugar Institute, Kanpur, told Mongabay-India that India produces, on an average, over 300 million metric tonnes of sugarcane per year. Around 3.5 per cent of this, can be the amount of press mud produced. At this rate, he said, India has the potential to produce around 10 million metric tonnes of press mud/filter cake per year, that could be diverted for producing bio-CNG.

Mojan noted that producing bio-CNG from press mud is set to be a successful proposition in states where there is a good density of sugar mills, such as in Maharashtra, Uttar Pradesh, and Karnataka, because of the easy availability of raw material, which saves transportation and procurement issues. In the last few years, mills in these states have started producing bio-CNG from the sugarcane waste and this is likely to increase in the future, he said.

But round-the-year availability of raw materials still remains a challenge, said Mohan. “Even if it is stored, it (sugarcane waste) slowly starts decomposing and the organic compound in it starts deteriorating. This makes long-term storage a challenge and also increases the cost of production. Also, in case there is a lack of supply of sugarcane-based raw material, you will need other feedstock to keep your bio-CNG plant running,” Mohan added.

Benefits sugarcane mills offer for bio-CNG
Rohit Pathania, an expert on biofuels working as a Lead (Energy and Mobility) at OMI Foundation told Mongabay-India that press mud, the main waste released in sugar mills during sugar production, is one of the best sources for bio-CNG production, even better than municipal waste. He said that as it contains 100 per cent organic material, there is no need for segregation like what is needed in municipal waste. However, if it is not used, it would decompose and release greenhouse gases (GHG).

Several sugar mills in India are now producing biofuels like ethanol and bio-CNG from sugarcane wastes.

“There is an established market for bio-CNG/CNG and a good network of distribution which can help in the prosperity of bio-CNG in India,” Pathania said. He added that earlier the market was not very well developed because of the lack of government support. “However, after SATAT, there are incentives for setting up such plants and the biggest advantage is the assured buyer in the form of OMCs which have a strong robust distribution network,” he said.

Pathania also added that to resolve the issue of round-the-year supply of raw materials, some standalone bio-CNG plants or sugar mills can consider using mixed feedstock, like using press mud with municipal or other waste. “There is no compatibility or other issues of even mixing segregated organic wastes with press mud and produce bio-CNG. This can help in managing urban wastes as well as take care of the wastes from sugar mills too, converting both to bio-CNG to pave a way for a cleaner transport regime,” he added.

In the recent past, fuel from some waste-to-bio-CNG plants in Indian cities has been used to run government-owned buses. Asha Rout, deputy commissioner from Pune Municipal Corporation (PMC) told Mongabay-India that they are using bio-CNG produced in the city to run a portion of the city buses. Similarly in Indore, the Indore Municipal Corporation (IMC) is using bio-CNG produced in a city-based bio-CNG plant to run buses.

Promit Mookherjee, a researcher on biofuels at think-tank Observer Research Foundation (ORF), told Mongabay-India that if the scale needs to expand, the production of bio-CNG needs to align with the demand in the market to make it economically more viable. “The penetration of CNG vehicles and CNG stations in India, is mostly confined to certain regions like Delhi NCR, Gujarat, and other leading Indian cities. As the imports of LNG usually come via sea route in Gujarat, its distribution network is more developed. So, if bio-CNG plants come up in such areas first, which offer the best distribution facilities, it could be a more economically viable plan for the developers, rather than choosing Tier II and Tier III cities,” he said.

Mookherjee also said that more research and development on technologies for bio-CNG production is needed to scale up the production to cater to the demands of OMCs and make the use of bio-CNG more commercially viable for all stakeholders.

A recent study by researchers at the Indian Institute of Technology (IIT-Bombay), Queen’s University Belfast (UK), and the University of Limerick (Ireland), analysed the potential of using bagasse instead of press mud to produce bio-CNG in sugar mills. It found that for 10 tonnes per day production of bio-CNG from bagasse the cost was around Rs 87 per kg. The study  estimated that the cost can come down to Rs 37 per kg if the bagasse and electricity are given free. The study also said that if bio-CNG is used as a transport fuel compared to conventional fossil fuel, it could lead to net reduced emission of carbon dioxide up to 3.96 kgs on each kg use of bio-CNG.

Union Minister for New and Renewable Energy told the Indian Parliament in December 2022 that the government had been supporting new bio-CNG plants under the waste-to-energy programme and SATAT scheme while it has also included it under the priority sector lending for better financing. He also said that concessions on customs duty are also offered for the import of machinery and other parts for setting up bio-CNG plants.

(Courtesy: Mongabay India)