• Bulker

The efficiency formula behind Navibulgar’s fleet renewal

Navibulgar has spent more than a decade building a new generation of bulk carriers designed to outperform market standards. Working with DNV, the company has combined innovative design, fuel efficiency, and operational flexibility to create one of the youngest and most efficient fleets in its segment.

• 6 Minutes
• 08 September, 2026
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Hull design optimization and lightship recalculation maximize efficiency

There is a common concept underlying the entire endeavour, which dates back to 2014: “We were looking to build vessels that are different from the market standard and would perform better than the average,” explains Kalchev. As both a naval architect and an experienced shipmaster, he has been steering the company’s fortunes since 2013, contributing his experience in both disciplines.

Seeking to benefit from innovative hull optimization technology, Navibulgar had scanned the market for a competent classification society to help develop the best designs for the programme. “We concluded that DNV offered the expertise we were looking for. The hull optimization they delivered for both vessel types has enabled us to achieve greater efficiency while lowering the environmental footprint of the vessels.”

DNV also performed complex lightship recalculations to reduce excessive material thickness in certain parts of the hulls, thereby making the ships lighter than competing designs, reports Miroslav Hristov, Senior Principal Surveyor at DNV. “We succeeded in reducing the lightweight of the vessels by several hundred tonnes, increasing the deadweight, which makes them more competitive.”

Extended cubic capacity minimizes fuel consumption and emissions per tonne-mile

“All the knowledge we have built over the years has been implemented in our newbuilds,” explains Kalchev. “In addition to the optimized hull shape and low resistance, we maximized the cubic capacity by subdividing the hull into cargo holds and shaping the cargo spaces in a precisely calculated way while minimizing the engine room and the unused forward portion of the vessel.” The resulting capacity of the new Handymaxes is actually closer to that of larger Supramaxes, he adds.

Slow-steaming strategy saves fuel

“We always try for the lowest specific fuel consumption for each voyage,” says Kalchev. “The average speed of our fleet is 11 knots; we are pretty much slow steaming all the time.” For its newbuilds, Navibulgar chose modern, electrically controlled engines that can operate at very low revolutions and are small, requiring less space, explains DNV’s Miroslav Hristov. “To ensure that they can reach optimum cruising speed faster, despite their small size, without producing excessive smoke, electric compressors were added to supply extra air to the turbochargers. DNV approved this solution, which was developed together with the engine manufacturer MAN.” With all the optimizations implemented, the vessels consume 25 to 35 per cent less fuel than the company’s older tonnage built from 2010 to 2012, confirms Kalchev.

Shallow draught and strong cranes increase flexibility

With a maximum draught of 10.5 metres, the vessels are suitable for shallow ports, Kalchev points out. “What is more, the cargo cranes are stronger, and the hatch covers larger than typical for this ship type, which makes it easier to load oversized break-bulk cargo such as long steel products. All that makes our ships more versatile, giving them an additional competitive edge.”

The first three 45,000 dwt newbuilds, delivered between 2016 and 2019, were proof that Navibulgar’s choices were spot on. “They are showing very good fuel consumption, and their other features make them especially interesting for the Atlantic trades,” says Kalchev. Navibulgar entrusted Yangzijiang Shipbuilding Group with the remainder of its orders. The yard has since delivered 25 vessels to the owner’s full satisfaction, with 11 more on order.

Taking fleet renewal to the next level with 71,000 dwt vessels

Having identified another market niche to fill, Navibulgar recently ordered eight 71,000 dwt units. “We are seeing cargo parcels going up,” reasons Kalchev. “To accommodate them, we are building a bigger Ultramax in the 60,000-plus-ten-per-cent deadweight range, which is quite unusual. As with our previous newbuilds, we want to offer the most efficient vessels that can carry more cargo while using the same quantity of fuel, resulting in a smaller ecological footprint per tonne.”

Top CII ratings confirmed by DNV

In terms of decarbonization, Kalchev says his modern ships are performing so well that he is confident they will remain compliant going into the 2030s and ’40s. “DNV provided us with a sophisticated algorithm for the calculation of the Carbon Intensity Indicator (CII) and the EU ETS,” he says. “All our vessels built since 2016 have CII ratings of A or B, most of them CII A, the highest standard. They don’t need any additional energy efficiency devices to comply. I believe that our new fleet will be one of the most efficient in this segment worldwide.”

With slow steaming and blend-in biofuels, Navibulgar can maintain these ratings, says Kalchev. “DNV is keeping a close eye on the entire fleet’s emission performance, managing our reports and verifying them using its Emissions Connect service. Furthermore, a designated person at DNV’s office in Poland is supporting us in implementing FuelEU Maritime, including pooling.”

A partnership focused on safety, quality, and reliability

“Quality is maybe the most important thing when you build a ship,” Kalchev states. “You must select the makers carefully because the vessel must be reliable and safe.” As an example, he points to the importance of smooth, flat welded seams on the ships’ plating for reducing resistance in water.

Looking for the right partner to carry this quality strategy into the future, Navibulgar recently entrusted its safety and quality management systems to DNV. Close contact with the head office in Oslo and guaranteed around-the-clock support from DNV were strong arguments for a closer partnership. Navibulgar is an avid user of DNV’s unique DATE service, providing any-time access to technical experts. Now the company is trialling DNV’s Steel Load Planner, which helps prepare optimized and fully safety-approved loading plans for heavy cargo such as steel coils.

How Navibulgar is preparing for its next phase of growth

“I am happy about our broad cooperation,” says Kalchev, “because the majority of our fleet is in DNV class, and it will be better with DNV having a closer eye on the office as well. DNV is a global leader in classification, with deep technical expertise and a strong track record of supporting the maritime industry. As an organization that also strives to lead in our field, we see significant value in partnering with industry leaders who share our commitment to excellence.”

Navibulgar is planning to grow further and potentially enter other segments as well. “I believe that we are doing a lot to make shipping more sustainable and more eco-friendly,” summarizes Kalchev. “We continuously assess developments across the industry and seek to capitalize on new opportunities, while maintaining a modern fleet and striving for excellence in everything we do.”

Contact us

Miroslav Stiliyanov Hristov

Bulgaria Operations Manager, Senior Principal Surveyor