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Sustainable pelleting in a renewable world

26 March 2018

Conversations around renewable energy often overlook biomass, a sustainable alternative to fossil fuels that is proving to be a critical source of energy. Here, Mark Burnett, VP of the Lubricants and Fuel Additives Innovation Platform at global water, energy and maintenance solutions provider NCH Europe, explores the importance of biomass pelleting and explains why maintenance engineers play a pivotal role in the process.

For several years and on multiple fronts, European countries have positioned themselves as global leaders in renewable energy generation and consumption.

Spain is a prime example of this. The country first pledged to be a global green energy leader in 2007 and, a decade on, the country is making significant progress. Between January and August 2016, just under half of Spain’s power was renewable according to figures reported by Spanish electrical operator Red Electrica de Espana (REE).

This is welcome progress, as the EU has set Spain a target of generating 20 per cent of its overall energy needs from renewables by 2020. Energy companies in the country share this ambition, with Miguel Ezpeleta, boss of Acciona, believing that the country will achieve 100 per cent renewable energy reliance in the future.

Of course, Spain is not alone at the front of the renewable energy revolution. In 2016, Portugal kept its lights on using only renewable power for an impressive 107 consecutive hours — a feat that James Watson, CEO of SolarPower Europe, praised while predicting it “will be commonplace in Europe in just a few years.”

These are just a handful of highlights. Countries such as Germany regularly produce the majority of their energy from renewable sources. With solar and wind power also becoming cheaper than fossil fuels for the first time in 2017, the future seems bright for the industry and for the EU’s target of 27 per cent of power from renewable sources by 2030.

The dark side of renewables

Yet the renewables market isn’t without its criticism. One notable critic, Spanish economist Gabriel Calzada Álvarez PhD, authored a paper in 2009 that warned of the impact of renewable, or green, jobs on the overall employment market.

One of the key points from the study states there were “2.2 jobs destroyed for every green job created” in Spain between 2000 and 2009. Álvarez claims this totals 110,500 jobs, with another key point claiming “each green megawatt installed destroys 5.28 jobs on average elsewhere in the economy.”

While these points can be disputed, they do give rise to concerns about the social impact of renewable energy. As these energies are generated in a significantly different way to traditional fossil fuels, it is difficult to predict the long-term impact of widespread adoption.

However, the Renewable Energy Association (REA) has acknowledged the possibility that >renewables will affect employment. In an article defending the UK biomass industry, Dr Nina Skroupska, the REA’s chief executive, wrote “we are acutely aware of the potential job losses and changes to local communities that such a shift could precipitate.”

This is where the biomass pelleting industry comes into play. Because the generation of power involves the burning of biomass pellets to produce heat and electricity, the process is not too fundamentally dissimilar to traditional fossil fuel power generation.

The key difference is that biomass is more sustainable and environmentally friendly, with plants reporting a significant reduction in carbon emissions of up to 80 per cent.

The pelleting process

However, obtaining the pellets for the energy generation process comes with its own challenges. According to the UK’s National Energy Foundation (NEF), one tonne of wood pellets produces approximately 4,800kWh of heat, or 17GJ of energy, if burned with 100 per cent efficiency. The NEF also estimates that the typical household may require between two and four tonnes per annum.

Making biomass pellets a sustainable alternative to fossil fuels requires the pelleting process to operate effectively and efficiently on a constant basis. To make pellets, the crushed and chopped materials must be compressed under high pressure, at equally high temperatures and with heavy loads.

It goes without saying that these conditions put considerable stress on the machinery and equipment involved, which also increases the risk of breakage due to wear. Vigilant maintenance engineers will regularly inspect this equipment to ensure it remains operational, but this does not address the underlying issue, which in many cases is lubrication.

The challenge for lubricants used in the pelleting industry is the temperatures they are exposed to. At high temperatures, typical machine lubricants lose viscosity, which weakens the lubricant’s ability to create a thin film on surfaces, reduces lubricant longevity and increases wear. Once a lubricant loses too much viscosity, the high pressure of the machinery can displace the lubricant.

Maintenance engineers can prevent this by identifying the signs of frequent wear and specifying an effective lubricant. For the pelleting industry, maintenance engineers must select a high viscosity lubricant, such as NCH Europe’s K Nate HV, to ensure protection against abrasive wear under extreme temperatures and pressures.

An effective way of choosing the right lubricant to withstand the operating conditions is to look at its chemistry. For example, NCH Europe uses a calcium-sulphonate thickener, extreme pressure agents and a high-viscosity base oil in its K Nate HV grease. This allows the lubricant to stay in place at high pressures and temperatures of up to 220 degrees Celsius, while also providing anti-corrosion benefits.

Ensuring continuity in the pelleting industry is in the best interests of not only the maintenance engineers and plant managers responsible for the production process, but also for the wider renewables industry.

This is further emphasised by the REA’s Dr Skroupska, who believes that the biomass industry offers the job market an opportunity to adapt to the new market. She states that, “using wood pellets is an important measure which will give many communities, businesses and, importantly, the UK's electricity grid a window in which to adapt.”

While clean renewable energies such as solar and wind are gaining traction, there is currently an issue of uncertainty, both in terms of the job market and if energy production can meet requirements consistently. Biomass energy bridges this gap. And with EU countries leading the world in wood pellet usage, proper maintenance of machinery will be pivotal in ensuring a promising future for renewables.

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