The Shift from Coal to Biomass Is on in Europe

Various schemes are underway in Europe as nations use existing coal-fired power plants to generate electricity without coal as the feedstock. With rising carbon prices, some big utilities are repowering with sustainable biomass.

The European Union (EU) is preparing to fully generate 20% of its electricity by 2020 using only renewable sources. As such, fuel switching from coal to biomass or natural gas is enabling some power plants in the EU to stay open and profitably generate power despite ever-tightening emissions limits. One of the other major pressures driving fuel switching is Europe’s $38 billion-a-year carbon market. Now a decade after the policy was enacted, it’s finally having an effect on regional generation as more plants turn to biomass. Under EU rules, biomass is considered carbon neutral—and a growing number of large coal burners are finding it a viable option.

Coupled with rapidly falling installation costs for renewables, industry is aggressively finding ways to phase out the worst pollution sources—although unevenly across the continent. While to the east, coal is still the biggest fuel source, western Europe is moving quickly away from it—with Germany, not surprisingly, straddling the fence, essentially building a second renewable system on top of a carbon-intensive one.

Timelines Vary, but Coal’s Time May Be Up

Taking it further, several western European nations have formally announced a deadline to end all coal burning. The UK was the first large user to set a drawdown, scheduling the last fires to go out by 2025, propelled even faster by an increased carbon tax. France, a small coal burner, will phase it out altogether by 2022. The Netherlands and Italy have also proposed plans to close their coal-fired power plants by 2030 and 2025, respectively.

Germany, the EU’s largest economy and a perceived champion of clean energy through its Energiewende program, remains Europe’s largest coal burner. The question of a “coal exit” is being hotly debated by the country’s new coalition government, and most experts don’t expect a phase-out to fully take place until 2030 at the earliest. Just the same, recent figures show that hard coal-fired generation in Germany fell by 53.2% in the year ending in January, while lignite coal generation dropped by 6.6%.

Making up the gap were both gas and renewables with wind turbines increasing generation by 89.7% in January compared to the same month last year. But the nation’s actual coal burn only fell five percentage points, from 42% in 2010 to 37% in 2017, leaving it still with the fourth-most-coal-intensive electricity production worldwide.

Despite being the most-dirty fuel, Germany’s large lignite sector (Figure 1) seems so far to be unaffected by Europe’s climate policy. In 2017, the profitability of lignite power plants improved as higher hard coal and gas prices pushed up power prices, while CO2 prices stayed relatively low.

Fig 1_German Lignite
1. Down, but not out. Germany is often recognized as a renewable energy leader due to its Energiewende policy, which lawmakers passed in late 2010. Yet, the country still relies heavily on coal, including lignite from the Garzweiler surface mine, shown here. Courtesy: Bert Kaufmann

Despite the pressure, the future of coal throughout the rest of the EU remains uncertain. According to the London-based think tank Sandbag, only 7 GW of coal power has officially been slated for retirement out of the 157 GW of operational coal plants. Though gas usage is increasing as coal demand falls, prices remain high. Coal is still a cheaper alternative on average, despite carbon taxes, and it continues to supply roughly 25% of Europe’s energy.

Biomass Attractive as Carbon Costs Increase

In an effort to turn the screws even tighter, as prices for carbon allowances rise, EU politicians have passed additional regulations to keep the cost of pollution increasing through 2030. According to a new report published at the end of April by the think tank Carbon Tracker, as EU carbon prices are set to double by 2021, they could quadruple to €55 a tonne by 2030 if the EU aligns its emissions targets with the Paris agreement on climate change. Following recent reforms of the EU’s emissions trading scheme that have increased carbon prices from a low of €4.38 per tonne in May 2017 to €13.82 per tonne in April 2018, prices are now on course to hit €25 to €30 per tonne by 2021, as reforms squeeze out surplus supply, the Carbon Clampdown: Closing the Gap to a Paris-compliant EU-ETS report finds.

What is certain is that renewable generation sharply increased in 2017, with wind, solar, and biomass overtaking coal for the first time. The three combined to increase energy output by 12% in 2017 to 679 TWh, exceeding—albeit only slightly—coal generation’s 669 TWh. That’s remarkable considering just five years ago, coal generation was more than twice that of renewables.

Despite fuel switching, according to analysts at the Berlin, Germany-headquartered Agora Energiewende, biomass generation rose only 3% (the same as in 2016). The majority of this biomass growth was in Denmark and the UK as the two countries shift away from coal or increase co-firing.

Touted as sustainable as well as emissions-free, by some estimates the EU is importing more than 5 million tonnes of wood pellets from the southern U.S. for firing. That figure is set to rise as the UK’s Drax power plant, one of the largest in western Europe, rapidly converts to a combination of biomass, gas, and battery storage. To the north, the Danish-headquartered Ørsted Energy, formerly DONG Energy, is also quickly phasing out coal, and even gas, and turning to locally sourced biomass in combination with other renewables as it swiftly reduces its carbon footprint. As these companies make the switch, will other power generators follow?

Indeed, the technology to conduct these conversions from coal to biomass is already mature. Valmet, a Finnish component supplier specializing in biofuels conversions, helps repower old units—either with new boilers based on bubbling fluidized bed (BFB) or circulating fluidized bed (CFB) technology, or by converting existing grate, oil, or pulverized coal boilers to fluidized bed (typically BFB). One of the company’s newest solutions is biomass gasification, which enables fossil fuel replacement with biomass on a large scale, increasing fuel flexibility and reducing CO2 emissions economically.

“BFBs are able to fire 100% biomass—not necessarily pellets, but wood chips or forest residue also works well. CFBs can fire 100% biomass or 100% coal or anything in between. A CFB with a multi-fuel approach has been the best-selling product for Valmet over the last 10 years,” said Ari Kokko, director of technology and research and development with Valmet’s Energy business unit, in an email exchange with POWER.

Drax Nixes Coal, Embraces Biomass and Storage

Last year, nearly a third of Britain’s electricity was supplied by gas, followed by wind and nuclear at roughly a quarter each. The rest came mainly from coal, biomass burned at the Drax power station in North Yorkshire, and imported energy from France and the Netherlands. But increasingly, coal—with its expensive emissions costs—is simply not viable in the UK.

King Coal’s dethroning there has been swift. Over the last five years, its market share is down 84%. And already this spring there have been long spurts without coal being called upon at all. Faced with declining prospects, two additional coal plants announced they will retire at the end of 2018.

Marching in a different direction, Drax, once a major coal burner and still the largest single power plant in Western Europe (Figure 2), supplying between 7% and 9% of the UK’s energy alone, dramatically announced in April that it was joining the Powering Past Coal Alliance, a joint UK-Canadian initiative and global coalition of countries, states, cities, and businesses committed to ending coal-fired generation by 2030. Vowing to beat the UK’s new self-imposed coal deadline, Drax is converting away from it entirely.

Fig 2_Drax Power Station_Dave-Pickersgill
2. Feeding the beast. Drax Power Station is the biggest single-site renewable energy generator in the UK. Three of its six 645-MW units have been converted from burning coal to biomass in the form of compressed wood pellets. The plant currently burns about 7 million tons of biomass annually. A fourth coal unit will be converted in 2018. Courtesy: Dave Pickersgill

“Unabated coal does not have a long-term role to play in our low-carbon future. The government made it very clear earlier this year that it wants the UK’s power sector to be coal-free in 2025—and we will achieve that, and possibly even beat it,” said Will Gardiner, Drax Group CEO.

According to Drax, the plant started down this road beginning with its early adoption in 1988 of flue gas desulfurization technology, which removed 90% of coal’s SO2 emissions. Since then, in an effort to burn ever-cleaner fuels, it began experimenting with biomass.

“Initially, we found a few distressed cargos of wood pellets and sunflower husks that someone had ordered but didn’t want. We mixed that with coal at very low concentration,” said Jim Price, alternative fuel manager at the time. Finding they could use the plant-based fuel alongside coal at low percentages without it detrimentally affecting the boilers, Drax began working with willow wood, a subsidized energy crop that proved difficult to convert into a fuel that could be used efficiently to power a boiler.

Then in 2005, after building a prototype plant and finding a way to pulverize the willow into a fine powder—called wood flour—and combine it with coal dust, the team hit its first key milestone. In 2009, the team successfully adapted the boilers to combust the new fuel, proving that co-firing wood pellets and coal in one boiler could work.

The response was immediate. Senior management, which supported the project from the beginning, pushed engineers to go further. Eventually, Drax settled on compressed wood pellets. After several more years of re-engineering, by the end of 2016, Drax had converted half of its six units to use wood pellets instead of coal, generating more than 65% of its power from only biomass. Drax will convert a fourth unit from coal to biomass this year, leaving just two remaining coal-dependent units that it plans to replace with two gas-powered combined cycle turbine units capable of generating 3.6 GW. It will also add 200 MW of battery storage.

“Our plan is to be off coal well before the 2025 cut-off,” said Andy Koss, CEO of Drax Power. “We want to either be offering renewable power through our four biomass units or enabling that low-carbon future by providing flexibility.”

Ørsted Energy Phases Out Coal

Ørsted Energy, the Danish energy conglomerate that in November changed its name from DONG Energy, announced an ambitious goal in February 2017 to phase out all coal for generation by 2023. One of the largest developers of offshore wind energy in the world, the company has also reduced its coal consumption by almost 75% through a reduction in the number of power stations it operates and by converting those it does from coal and gas to biomass since the original company formed in 2006.

“We’ve decided to take the final step and phase out the use of coal at all our power stations,” said Henrik Poulsen, Ørsted Energy CEO, at the February 2017 announcement. “The future belongs to renewable energy sources, and therefore we’re now converting the last of our coal-fired power stations to sustainable biomass.”

Ørsted firmly believes that wood pellets and chips from sustainable forestry provide considerable CO2 reductions compared to using coal and gas. The new fuel source primarily comes from residual products such as branches, twigs, and thinning trees as well as from sawdust from the furniture and saw mill industries.

In its company literature, Ørsted claims the conversion from coal to wood pellets is relatively simple. Because both coal and wood pellets are pulverized, they can be airblown into existing boilers with some modifications. One main difference, however, is that wood pellets are sensitive to moisture and need to be kept dry by being stored inside. Their calorific value is also generally lower than coal.

Dust management at coal plants is relatively simple and straightforward, related Morten Reinhold, senior project manager at Ørsted Energy, in an interview with Biomass Magazine. “In the flue gas, an electrostatic filter is used,” he said. “And on the fuel logistics side, only intermediate water spray systems are used to minimize dust from the open coal yards.” But wood pellets are even dustier, requiring conveyor system redesigns. “That means closed storage and conveyor systems with appropriate dust aspiration systems.”

Fig 3_Studstrup Power Station
3. Coal out, biomass in. The Studstrup Power Station, which supplies heating and electricity to Aarhus, Denmark’s second-largest city, began to use wood pellets instead of coal as fuel on October 10, 2016. The huge silo, built to facilitate the transition, can store up to 65,000 tons of pellets. Courtesy: Ørsted Energy

Studstrup Power Station (Figure 3), near Aarhus, made the transition from coal in October 2016, and Avedøre 1, which supplies electricity to Copenhagen, ended its coal burning in December. Following Ørsted’s coal phase-out commitment, two additional facilities, the Asnæs and Esbjerg power stations, must now also be converted to biomass. The company said it’s also in dialogue to discuss converting two combined heat and power plants to use wood chips instead of coal when their respective heating agreements expire. The conversion of Asnæs Power Station was kicked off in late October 2017, and by the end of 2019, it too will be coal-free, bringing the number of fossil fuel plants Ørsted has converted in Denmark to seven. ■

Lee Buchsbaum (www.lmbphotography.com), a former editor and contributor to Coal Age, Mining, and EnergyBiz, has covered coal and other industrial subjects for nearly 20 years and is a seasoned industrial photographer.