Yorkshire’s Game Changer

Upon completion of its ambitious conversion, Drax Power Station will be the world’s largest single-site producer of biomass-derived power.
By Tim Portz | May 21, 2013

Since the commissioning of its first boilers in 1974, the 3,960 MW power plant at Drax, England, has resisted stasis. A decade after coming on line, the plant was expanded and nearly doubled in size to arrive at its current capacity. Since then, it has survived a miners strike, witnessed  the privatization of the power generation industry in England, been owned by an American company, been purchased out of bank possession, and is presently one-third of the way through what is likely the largest coal-to-biomass plant conversion the world will ever see.

The power plant in Drax, instantly identifiable by its collection of 12 massive hyperboloid cooling towers and 850-foot-high chimney (at one time the largest industrial chimney in the world), delivers between 7 and 8 of the United Kingdom’s  electrical power. Drax’s output is double that of its closest U.K. rival, and with the exception of the Belchatow Power Station in Poland, no other power station in Europe is capable of matching its output.

In so many ways, the enormity of the station is an incredible asset. It does, however, possess one glaring liability: as the U.K.’s largest coal-fired power station, Drax Power Station also holds the top spot on the country’s list of carbon dioxide (CO2) emitters, generating more than 20 million tons annually. With growing awareness and an acknowledgment of the consequences of a high carbon energy platform in Britain and Europe, the government acted.

Two policy measures in the European Union and the U.K., intended to spur the region toward a less carbon intensive energy future, set the table for action at Drax.  First, the U.K.’s Renewables Obligation set increasing minimum percentages of electricity that power providers had to obtain from renewable sources. Next, the EU deployed the world’s largest emissions trading platform in 2005, the European Union Emission Trading Scheme, effectively putting a price on CO2 emissions. Together, the two form a classic carrot-and-stick policy combination.

With just one power generation asset in its portfolio, the options for mitigating the risk of escalating carbon prices for the Drax Group were limited. Peter Emery, production director at Drax, notes, “We couldn’t just shut down the coal plant and build gas plants. All the other technology was a long way off, so we needed some sort of plan that gave us a future.”

Therefore, the team at Drax devised a three-part plan to drive down the facility’s carbon profile.

Three-Part Plan

Part one of Drax’s plan to retool its plant for compliance with mandatory policy was to make the facility operate as efficiently as possible, utilizing existing and proven technologies. Part two was to identify a less carbon-dense fuel source, and part three would involve the capture and sequestration of any CO2 that remained in the production profile after the first two measures were implemented.

To make the facility run more efficiently, the Drax team turned toward a modernization of the facility’s steam turbine fleet. The Drax Group made an investment of over £100 million ($153.7 million) and replaced all of the high- and low-pressure steam turbines at the facility, increasing the plant’s overall efficiency by around 5 percent. While that percentage may seem small, Emery warns against discounting the number too much. “That might not sound like a lot, but 5 percent when you are burning 10 million tons of coal is half a million tons of coal, which is 10,000 tons a week and a million tons of CO2 a year.”

While the turbine upgrade began moving the needle toward reducing the plant’s CO2, its effects would be limited to a 5 percent reduction. To further reduce its carbon profile to levels the company was targeting, they moved into the second part of the plan: replacing coal with a more carbon benign fuel source. Biomass offered the Drax Group a fuel source that could be introduced into their production process and cofired with coal, and would drive the CO2 numbers at the facility down to a level the team felt was optimal.

In 2006, as Drax was researching cofiring, the British government announced its intention to reform the Renewables Obligation scheme, and Drax would once more have to adapt to a game change. When the Renewables Obligation scheme was first drafted, all renewable technologies were awarded saleable Renewable Obligation Certificates at the same rate. As the program became established, however, policymakers feared that one or two near-term renewable technologies would be all that would attract investment dollars, and modified the policy to drive investment into a broader portfolio. Most notable for Drax, megawatts derived from the cofiring of biomass were first reduced to 0.5 ROC per MWh, and subsequently to 0.3 ROC per MWh. With the revenue opportunity presented by cofiring biomass reduced by nearly 70 percent, Drax amended its conversion plans during the second quarter of 2012, and decided upon the complete conversion of three of its boilers to  biomass.

Reflecting on this policy shift, Emery notes full conversion is easier for policymakers to defend, suggesting that “instead of having green units with a black tinge—which you are always going to get with cofiring—if you can do a full conversion, you’ve got a green unit. There’s no debate about it.”

Cofiring to Full Conversion

Converting three of its boilers to fire exclusively on biomass will require Drax and its supply chain partners to source, pelletize, ship by sea and rail, unload, temporarily store, and finally, deliver nearly 7 million tons of woody biomass to the plant’s boiler every year. This effort is already underway at the Drax site, at several of the U.K.’s busiest ports, at ports in the U.S., and in the construction of new pellet facilities in the southeastern U.S. The budget for Drax’s share of this ambitious undertaking is currently estimated at £700 million.

Moving and storing massive amounts of solid fuels is not new to Drax, nor the ports and rail partners that work with Drax. The facility currently welcomes 35 coal trains each day, moving nearly 10,000 tons of coal onto the facility property. The difficulty is not the volume, but instead in the handling properties that are unique to biomass. For example, the biomass that will feed Drax’s boilers cannot be allowed to get wet. It must move in covered rail cars, from covered storage sites to enclosed storage containers on site, then along covered conveyers before it is delivered to the boilers.
The first physical sign of Drax’s progress are two of four planned pellet storage domes that have risen just to the west of the plant’s southern cooling towers. Two more domes will be established and completed by the end of 2014, bringing the on-site covered storage capacity to nearly 300,000 metric tons.

Now that the technical challenges are understood and solutions are under development and construction, Drax’s focus is on building a supply chain that achieves the highest degree of sustainability possible. “We’re on the start of a journey, and we think that sustainability is a fundamental building block to that,” Emery says, drawing attention to the sustainability policy drafted and enforced by Drax. Drax’s sustainability policy ensures that the biomass that comes from the nearly 4,600 square miles of forest required for its fuel supply align with current accepted sustainability practices. Recognizing that the science of sustainable biomass is fluid, Drax makes clear its intentions of keeping pace with any changes, noting in its policy, “Over time we will seek to amend or improve them by working with accredited bodies to develop the use of internationally recognized standards and principles which will apply to all of our biomass procurement activities. In so doing, we hope to foster environmental leadership today and in the future.”

Drax’s future as a predominantly biomass-fueled facility and company has become central to the organization’s mission. Its 2012 annual report is titled “Our Transformation Continues,” and features schematic illustrations of a coal yard and the construction of the facility’s pellet domes. Drax is now firing one of its boilers exclusively on biomass, and by the end of the year will have completed nearly half of the planned infrastructure work. Next year, as the infrastructure and supply chain mature, a second boiler will be commissioned for biomass combustion.  Plans are already in place to accelerate commissioning of the third boiler, initially planned for 2016-’17.

In a broad scope, the enormity of Drax’s efforts have catapulted the organization into a leadership role in the biomass industry.  “We are inventing a whole new business from the forests to produce electricity, and that’s a big ask,” says Emery. Recognizing that the conversion was ultimately inevitable, he adds, “we only have this coal facility. We’ve got a big carbon problem, and if we don’t do something, we’re out of business.”

Author: Tim Portz
Executive Editor, Biomass Magazine
[email protected]