Powering Anröchte with biogas: Hitachi Zosen Inova

A new Kompogas plant in Anröchte, Germany is generating carbon-neutral biogas to inject electricity into the grid. Hitachi Zosen Inova’s Raiko Kolar explains.

On the site of an old quarry in Anröchte, Germany, a state-of-the-art composting facility and Kompogas biodigester plant now sits.

In February this year, electricity from the plant started being fed into the grid, marking an important milestone for green energy transition in the North Rhine-Westphalia municipality.

In 2018, facility operators ESG Soest awarded the tender to construct a plug-flow digester with gas conditioning at its composting facility to international dry anaerobic digestion pioneers Hitachi Zosen Inova (HZI).

HZI’s Kompogas technology converts organic waste from municipal, commercial and industrial sources into electricity and heat or biomethane.

Synonymous with continuous dry anaerobic digestion technology, the Anröchte facility is the 25th Kompogas plant delivered by HZI in Germany.

According to Raiko Kolar, HZI Sales Manager, before developing the facility, ESG evaluated all types of technology on the market, including batch technology.

He explains that after extensive investigations, ESG recognised plug-flow technology presented the best business case.

“The tender evaluation was based on capital investment, and HZI had the best price performance ratio, as well as being able to meet all the regulations, guarantees and requirements set in the tender documents,” Kolar says.

Prior to the construction of HZI’s Kompogas plant, ESG operated two small composting facilities at the site.

“They wanted to develop a new modern plant in line with emissions standards and regulations, as the composting plants were 15-20 years old and not in line with current regulations,” Kolar says.

He explains that minimal losses of biogas, a greenhouse gas if released into the atmosphere, are integral to current regulations and can only be met by continuous technologies.

“The district also has a plan in place to contribute to the Regional Climate Protection Plan, so it was important for them to begin producing renewable energy.”

Furthermore, Kolar explains that ESG wanted to be prepared for future challenges, such as changing waste volumes and quality.

The project has a range of specificities, he adds, with plants of this kind typically producing compost and liquid digestate for application on agricultural fields.

“In this region, however, the agricultural fields left to spread the liquid is limited, so HZI developed a plant that would produce no liquid digestate, which is an important speciality of the project,” Kolar says.

The plug-flow digester has a capacity of 15,000 tonnes per annum, which will produce 1.5 million kilowatt-hours of energy from digested-source-segregated organic waste.

HZI has been working on the project for seven years, from first contact with ESG to the plant’s 2020 commissioning.

Incoming waste at the facility is shredded and screened, with the smaller post-screening fraction possessing the highest biogas potential.

The smaller faction is then feed to the digester in small portions 24 hours a day, at 30-minute intervals.

“By feeding a small amount of organic waste into the digester at regular intervals, you ensure a stable biological process. And because the bacteria are being feed continuously, the digester creates an uninterrupted biogas flow rate and quality,” Kolar says.

The digester features an internal agitator, which turns at a rate of one round per minute.

“The agitator turns very slowly, which helps the gas to be released from the porridge-like material and avoids sedimentation inside the digester,” Kolar says.

After drying and desulphurisation, the raw biogas from the Kompogas digester is either upgraded to up to 99.9 per cent methane content and fed into the gas grid, or in the case of the Anröchte facility, used directly to generate electricity.

The Kompogas plant was finished on time, Kolar says, with HZI now beyond the halfway mark of its 20-week facility trail-run.

Within the 20-week trial, HZI were required to show a three-week performance test, which Kolar says produced positive results.

“Within the test we demonstrated the efficiency, availability, throughput capacity and compliance with emissions standards required. More importantly, the customer is very satisfied with the plant,” he says.

Kompogas plants are extremely reliable, Kolar explains, with the robust design ensuring they continue to work at their original rate throughout the plant’s lifecycle.

“Kompogas has been on the market for 25 years, and we have built more than 100 plants. In total, there are 200 digesters modules currently installed, and all of them are performing and running well,” he says.

“The reliability also applies to the biological stability of the plant. With this technology, operators can be flexible when it comes to changing waste material volumes and quality, which will shift throughout the life of the plant.”

Additionally, Kolar highlights that organic input material often changes, meaning the flexibility offered by the Kompogas system is crucial.

“Plus, all of the investigations from universities in Europe show plug-flow technology has the best carbon footprint compared to other technologies,” he says.

With Australia’s waste-to-biogas market still somewhat in its infancy, Kolar stresses that operators should learn from Europe’s mistakes.

He explains that when the market was first developing in Europe 25 years ago, many operators looked towards cheaper technologies.

“These plants were not able to cope with the wood, stones and glass that comes in with the food and green waste and therefore failed to achieve throughput capacity and were shut down in 5-8 years,” Kolar says.

“It’s also important not to go with technologies that have a low biogas production efficiency. To facilitate purchasing of the produced energy, it is critical to have high biogas yields, and anaerobic-dry-continuous-plug-flow technology provides the highest biogas yields on the market.”

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