Tag: wood pellets

This is how you unload a wood chip truck

30 June 2017

Sustainable bioenergy
Truck raising and lowering

A truck arrives at an industrial facility deep in the expanding forestland of the south-eastern USA. It passes through a set of gates, over a massive scale, then onto a metal platform.

The driver steps out and pushes a button on a nearby console. Slowly, the platform beneath the truck tilts and rises. As it does, the truck’s cargo empties into a large container behind it. Two minutes later it’s empty.

This is how you unload a wood fuel truck at Drax Biomass’ compressed wood pellet plants in Louisiana and Mississippi.

What is a tipper?

“Some people call them truck dumpers, but it depends on who you talk to,” says Jim Stemple, Senior Director of Procurement at Drax Biomass. “We just call it the tipper.” Regardless of what it’s called, what the tipper does is easy to explain: it lifts trucks and uses the power of gravity to empty them quickly and efficiently.

The sight of a truck being lifted into the air might be a rare one across the Atlantic, however at industrial facilities in the United States it’s more common. “Tippers are used to unload trucks carrying cargo such as corn, grain, and gravel,” Stemple explains. “Basically anything that can be unloaded just by tipping.”

Both of Drax Biomass’ two operational pellet facilities (a third is currently idle while being upgraded) use tippers to unload the daily deliveries of bark – known in the forestry industry as hog fuel, which is used to heat the plants’ wood chip dryers – sawdust and raw wood chips, which are used to make the compressed wood pellets.

close-up of truck raising and lowering

How does it work?

The tipper uses hydraulic pistons to lift the truck platform at one end while the truck itself rests against a reinforced barrier at the other. To ensure safety, each vehicle must be reinforced at the very end (where the load is emptying from) so they can hold the weight of the truck above it as it tips.

Each tipper can lift up to 60 tonnes and can accommodate vehicles over 50 feet long. Once tipped far enough (each platform tips to a roughly 60-degree angle), the renewable fuel begins to unload and a diverter guides it to one of two places depending on what it will be used for.

“One way takes it to the chip and sawdust piles – which then goes through the pelleting process of the hammer mills, the dryer and the pellet mill,” says Stemple. “The other way takes it to the fuel pile, which goes to the furnace.”

The furnace heats the dryer which ensures wood chips have a moisture level between 11.5% and 12% before they go through the pelleting process.

“If everything goes right you can tip four to five trucks an hour,” says Stemple. From full and tipping to empty and exiting takes only a few minutes before the trucks are on the road to pick up another load.

Efficiency benefits

Using the power of gravity to unload a truck might seem a rudimentary approach, but it’s also an efficient one. Firstly, there’s the speed it allows. Multiple trucks can arrive and unload every hour. And because cargo is delivered straight into the system, there’s no time lost between unloading the wood from truck to container to system.

Secondly, for the truck owners, the benefits are they don’t need to carry out costly hydraulic maintenance on their trucks. Instead, it’s just the tipper – one piece of equipment – which is maintained to keep operations on track.

However, there is one thing drivers need to be wary of: what they leave in their driver cabins. Open coffee cups, food containers – anything not firmly secured – all quickly become potential hazards once the tipper comes into play.

“I guess leaving something like that in the cab only happens once,” Stemple says. “The first time a trucker has to clean out a mess from his cab is probably the last time.”

Forests, sustainability and biomass – the expert’s view

Matthew Rivers, Director of Corporate Affairs, Drax, Group Special Advisor

6 October 2016

Opinion

It was a forestry catastrophe that first inspired Matthew Rivers’ interest in forests.

Dutch Elm trees, an iconic part of the UK landscape for over 250 years were becoming infected with a fatal and fast-spreading disease. The race was on to save them.

A schoolboy in North London at the time, Rivers joined the after curricular school team tasked with saving its trees – first by injecting them with insecticide, and when that didn’t work, by felling and replanting them. It was an early foundation in how forests work and the challenges of keeping them healthy.

Decades later, Rivers is Director of Corporate Affairs at Drax. It’s a role he finds himself in following a career as a forester, helping to manage forestry businesses, and supporting the setting up of wood product manufacturing plants.

His own estimation of his working life is a humble one, however. “I think I’m probably a failed farmer,” he says.

“A forester always plants in hope.”

Rivers studied forestry at university in Scotland before taking up jobs in the forestry industry across the UK, Uruguay and Finland. Working in this industry, he says, is one that requires patience.

“In the UK we’re talking about 30- or 40-year growth cycles. The trees I planted at the start of my career are only just coming to maturity now,” he explains.

But more than the long investment of time, being a forester relies on faith. “A forester always plants in hope,” he says. When a forester plants a tree, he or she most commonly does not know who the end customer will be.

So when the call came from Drax for a forestry expert to help guide the company through an important transformation – upgrading the power station from coal to biomass – the challenge was one he was ready to take.

“Drax already had ambitions of converting three boilers to run on biomass. That would mean consuming tonnes of compressed wood pellets,” he says. The business needed a supply, and Rivers was drafted in to set this up.

As part of the supply solution, and Chaired by Rivers, Drax set up Drax Biomass, a pellet manufacturing business in the USA that makes and supplies compressed wood pellets to Drax Power Station.

Setting up its own manufacturing plant not only means Drax needs to rely on fewer external suppliers, but also that it can use the learnings about the technologies, the economics and the sourcing of the process to continually hone its supply chain.

To operate responsibly and receive governmental support, Drax has to be sustainable, and this is particularly important when it comes to where and how it sources its fuel. This comes with its own challenges.

No universal definition of sustainability

“To my understanding, there is no universal definition of sustainability,” says Rivers. So how do you proof your business for an unclear entity?

“At its heart, sustainability is about not doing anything today that would prejudice doing the same thing for the next generation or generations to come.”

A responsibly managed forest is one that is as healthy, productive, diverse and useful in 100 or 500 years’ time as it is today. They key to this, is to think of forests as a whole.

Rivers explains: “Think about a single tree – you fell it and use it to heat your home over one winter. But it’s going to take perhaps 30 years for that tree to grow back,” he says. “What do you do for the next 30 years?”

“In a sustainably managed forest you have all different ages of tree represented – one thirtieth devoted to each age- and, when you use an older tree to warm you in winter, you plant a replacement. That way, for every year you’ll have trees reaching maturity ready to provide your power.” It’s a cycle that, if managed responsibly, keeps delivering a useful resource as well as maintaining the health of the forest.

Rivers continues: “Sustainability is the very nature of what a forester does; because if we don’t take care of our forests, and ensure we have a crop to harvest year after year, we lose our livelihood.”

forests_trees_growing_for_winter_heating_smh4nj

Becoming a private forester

Two decades ago, Rivers completed a loop he started decades ago amidst the Dutch Elm crisis and became a forest owner himself. In Scotland, he bought, and now manages, his own private forest.

“We’ve had kids’ birthday parties, we’ve dug out a pond, we harvest chanterelles in the autumn – there’s a millennium capsule buried somewhere,” he says.

It’s not only a family heirloom. It’s a place for him to exercise a passion – maintaining and managing a responsible and healthy forest.