A sweet way to transform biomass into renewable energy

There is little doubt that the bioenergy industry will continue to grow in momentum as the global appetite for sustainable and more environmentally-friendly energy alternatives becomes entrenched. Governments across the world are turning away from fossil fuels like coal and oil and urgently looking for replacements. Consequently, the use of biomass to produce energy has increased significantly in recent years, supporting a growing bioeconomy across the world.

For example, bagasse is a biomass produced as a by-product biowaste during sugar manufacturing processes. Simply explained, during the sugar-making process, sugarcane is cut from the farm, the juice is extracted and it is crystalised into raw sugar. Bagasse is the residual fibre left over from the sugarcane extraction process. Instead of diverting bagasse to landfill or selling it as fertiliser, sugar mills can repurpose it to produce heat and electricity, in turn boosting independence and profit without creating more greenhouse gases. In most production processes, around 30% of the total mass of sugarcane is left over bagasse and 70% of the total mass of input sugarcane is raw sugar juice; meaning to say the average sugar mill with capacity of 6,000 tons of sugarcane crushed per day can produce maximum of 49MW of electricity; and generate the process steam (heat) needed to cook the extracted sugar juice.

Producing steam from bagasse to produce electricity is not new, yet more and more of these owners across the world are taking the opportunity to do this. They are not only generating power for their own mills, but getting support from their governments in the form of tariffs to feed surplus energy into their national grids.

Lew Bent Fei, Sales Manager Asia Pacific at technology giant Siemens Energy, says that governments in Asia and Southeast Asia have been recently pushing ahead with support for biomass-to-energy plants as these continents try to reduce their dependency on fossil fuel power generation and thus reduce greenhouse gas emissions and promote renewable energy. For example, Lew says that the Japanese government is offering high biomass power generation tariff of €20cent/kwh. It is encouraging developers to build biomass plant for power generation as it turns away from coal. The Philippines has also recently launched biomass portfolio standards to boost the country’s renewable energy use. In Thailand, the government has also introduced what it calls a ‘Small Power Producer’ and ‘Very Small Power Producer’ initiative to also support biomass power by giving some form of compensation to power producers using biowaste as fuel.

Siemens Energy has helped drive this power generation trend through long-standing production and research on technologies and equipment. A key objective has been to improve the efficiency and bring down the cost of recovering biomass. Additionally, every single industrial steam turbine manufactured is tailor-made for individual customer’s needs. This highly customised modular design capability enable Siemens Energy to insert design elements needed by individual customers into each steam turbine. As a market leader for industrial steam turbines, Siemens Energy offers a comprehensive range of reliable and versatile steam turbines for the power output range from <1 to 250MW.

With this technology, its steam turbines can convert not only sugar, but a wide range of biomass products and waste into useful heat and power.

So, can Siemens Energy’s technology help mill owners make more money from their waste? Saurabh Maniyar, Regional Sales Manager Asia Pacific at Siemens Energy, seems to think so.

He says: “Sugarcane grows for around 12 to 16 months before being harvested between June and December each year. Of course, this depends on the country and the climate. As soon as it is cut, it needs to be used immediately. This means that the waste produced can only be used by mill owners and turned into energy for around six months of the year.

“Hence, sugar mill owners need highly-efficient turbines to help their plants become more fuel efficient. This can lead to increased revenue. Sometimes, they use biomass other than bagasse to allow their plants to run for the other six months of the year. This allows them to sell the power all year round and make more money. This is attractive because in many countries, sugar prices are regulated by their governments and sugar production is prominent in most countries. So in some countries mill owners do not actually get a lot of revenue from raw sugar production per se. In essence, sugar prices are currently low. However, they can make extra money by using bagasse for power generation and using molasses (another by-product of the sugar-making process) and turning it into bioethanol. Demand for bioethanol is also growing strongly across the world, especially in the US, Africa and the Asia Pacific region.”

Mitr Phol runs two Siemens Energy’s SST-300 steam turbines

Case study

Mitr Phol, which describes itself as Thailand’s largest sugar producer, is a customer of Siemens Energy and is using its steam turbines.

Sugar production at Mitr Phol forms a complete cycle: Crushed cane is turned into refined sugar, leftovers are used as fertilisers for the field, and bagasse is used to feed the boilers. Mitr Phol has also signed an agreement with the Electricity Generating Authority of Thailand (EGAT) to sell its excess power.

Running a big operation like this is not easy. To consistently produce electricity, Mitr Phol says it needs reliable and high-performance steam turbines and generators. In order to become a high-performance sugar producer, it says it needed to introduce technology from Siemens Energy. In two of its six sugar mills in Thailand, Mitr Phol runs two Siemens Energy’s SST-300 steam turbines. Mitr Phol’s ‘Phu Khieo 1’ sugar mill has been using an 11.4-MW condensing SST-300 since 2007. Its ‘Phu Khieo 2’ mill started operating its 26-MW backpressure turbine SST-300 after a plant modernisation in 2014. Together the two factories Phu Khieo 1 and 2 crush 40,000 tons sugar per day. The result: 1,500 tons of refined sugar per day and roughly 502 gigawatts of produced electricity per year.

The use of waste products as new resources to produce energy has increased the profitability of the sugar production process for Mitr Phol. Its sugar mills have also become energy independent and so this has led it to stabilise its production process and increase its economic competitiveness on the market.

“With the new Siemens Energy equipment, we’ve achieved a very high level of stability and performance and are able to produce more electricity using the same amount of bagasse,” says Arnut Yospanya, Managing Director of Bio Power Business at Mitr Phol Group.

Siemens Energy also offers a servicing network to help maintain the steam turbines, which customers want to keep for a long period (at least 20-years plus). The company also specialises in producing dual casing steam turbines, which are in high demand in Asia.

Maniyar says that these turbines feature a generator within its centre and high-pressure (HP) and low pressure (LP) turbines by their sides. Due to these features, Maniyar says its dual casing steam turbines can offer higher efficiency compared with their competitors. Conventional dual casing steam turbines tend to offer a generator at one end and HP and LP turbines “one after the other”, which makes the turbines less efficient, Maniyar adds.

All in all, it seems like a lot of mill owners are looking to make use of more efficient technologies like the ones that Siemens Energy provide. As demand for renewable energy grows, many of these owners are utilising bagasse in high-performance, biomass-to-energy plants in order to help drive profitability and build a sustainable, ‘sweet’, self-supplying energy production industry.

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