Future-proofing EfW emissions

By John Whitehurst, UK Business Manager, Environmental Applications at Lhoist UK.

Looking ahead at trends in energy from waste, I foresee a larger but more technologically sophisticated sector as use of single-use plastics reduces and emissions targets become tighter.

Lhoist is a significant player in the UK Energy from Waste (EfW) sector. This global business is based on lime and, by tonnage, we are the largest supplier of hydrated lime used to remove pollutants from the flues of EfW plants.

Based in Belgium, Lhoist is the world’s largest producer of lime-based products, with more than 6,000 employees and a turnover of €2.2 bn. Environmental industries and steel are our two biggest markets and we operate in more than 25 countries.

Lhoist UK is based in Hindlow, near Buxton on the edge of the Peak District, and this is an integrated plant, employing 70 people, extracting and processing lime on one site.

Lime-based products are very efficient reagents for capturing contaminants and have been used for this purpose since the 19th Century. Our family of Sorbacal® products deal with the main acidic gases, sulphur dioxide (SO2), hydrogen chloride (HCl) and hydrogen fluoride (HF), while our Minsorb® range eliminates micro-pollutants.

Due to Sorbacal’s high porosity, these products can offer reduced flue gas treatment costs and less residues for disposal, regardless of variations in waste input quality. The UK is regarded as a world leader in EfW waste technology and our innovations, as a company over the last 25 years, have tracked those of the sector as whole.

To put some figures to the industry, there are currently 44 operational EfW plants, burning 11-12 million tonnes of waste annually. The largest plants, such as the Viridor facility in Runcorn, are significant energy suppliers to the grid, providing up to 70 MW of electricity – enough for around 90,000. Some also provide hot water for district heating schemes.

There are also a larger number of biomass plants, burning waste and virgin wood to produce energy. These are smaller in size, in terms of energy outputs and consuming chemicals. Fly Ash from burning biomass can also be used for agricultural purposes, as fertiliser.

Obviously, all of these plants are also preventing massive quantities of waste from going into landfill and we believe that they will continue to provide a valuable service for the foreseeable future. The latest EfW plants use dry injection technology for flue gas treatment (FGT), which, in conjunction with Sorbacal® is far more efficient than the wet systems of the past. Analysers detect the level of pollutants in the hot gas and assess how much lime is needed.

What is coming out of the stack, which has been filtered of particulates, must comply with stringent Environment Agency emissions standards. These are not like the old smoke stacks of the coal-burning era, which is mainly steam. UK air quality has improved dramatically since the 1970s, for example, Defra figures show that emissions of SO2 have fallen by 97% since 1970.

Do I think that’s there’s a healthy future for the EfW sector over the next 20 to 30 years? Definitely. Most large councils, according to the survey, either have, or are planning, an EfW plant. Six or seven are going through their commissioning phase and another 12 have permissions granted or pending by the local authority and the Environment Agency

Of course, I know that EfW plants are never popular and I am sympathetic to the objections – far more plants are rejected because of local opposition than get built. But if people understood what the plants are doing, their potential local benefits such as offering employment and providing energy and heat, and the nature of their emissions, I think that the situation, and attitudes, would be different.

People drop their waste off at the incinerator but they don’t know what goes on inside. They are unaware that the plants are operating under very tight restraints, policed by the Environment Agency. There is a whole process that goes in between what goes in and what comes out.

The Air Pollution Control residue (APCr), for example, can only be disposed of in specially licensed sites which are plastic or clay-lined to prevent leaching. Some of it is encapsulated in aggregates or concrete blocks and this, surely, is part of the ‘circular economy’ that environmental campaigners are calling for. Incinerator Bottom Ash (IBA) can also be recycled into aggregate products and used in construction industry applications.

There is a finite landfill capacity in the UK and it is predicted by the end of 2022 that landfill capability will be very limited. We are shipping over three million tonnes of plastic waste overseas every year, but China states it will not take any more. So are we going to be burning our non-recyclable, re-usable waste or compostable waste for the foreseeable future? It is the easiest and most efficient way to dispose of waste and, in addition, we can produce energy as the by-product.

Plastic waste seems to be in the news all the time these days. Policy makers want it removed from the waste stream, to protect the land and marine environment, and this is a policy that everybody agrees with. Thinking ahead, as the plastic content of Refuse Derived Fuel (RDF) reduces, EfW plant technology will evolve to match the changing nature of waste.

However, hydrated lime-based products, like ours, will continue to be needed in the incineration process, which will still generate sulphur dioxide and hydrogen fluoride. We are formulating new Sorbacal® products which will be efficient in cleaning flue gases with potentially different and more challenging acidic pollutant mixes.

The next generation of plants will be based on advanced conversion technology (ACT), burning waste in low oxygen environments, using pyrolysis and gasification and producing new fuels. In the future, a new generation of Sorbacal® products will be developed that will reduce the volume of reagents that are needed overall.

Readers of this supplement will be aware that the EU’s best available technique reference document (BREF) on incineration techniques is currently being revised. The new version should come into force on in 2021 or 2022. It will set more stringent emissions levels for particulates, HCL, SO2, HF, nitrogen oxides, ammonia, heavy metals, dioxins and furans.

The new BREF may also include a requirement for continuous monitoring for heavy metals, such as mercury, which will pose a challenge to parts of the EfW industry. They will have to consume more reagent and it will put more pressure on their dosing systems. But the more emissions levels go down, the greater the need will be for existing products, like Sorbacal®, and new blended ones, for example including activated carbon. Moving forward, we will work hand-in-hand with the industry, to meet its operational and emissions challenges.

So what will happen in terms of waste over the next 20 to 30 years? We know that there will be greater recycling rates for plastic, so the nature of the feedstock for EfW plants will change. Everyone wants to see a reduction in single-use plastics. The questions are, how we do it, at what costs and what the targets are? Not all plastic is recyclable and there is always going to be an element of it in the waste stream.

You can see, from what I’ve said that EfW plants are not going away. Although no new facilities were built between 1980 and 1993, the EU’s waste incineration directive (2000/76/EC), a commitment since 2011, to use landfill only as ‘an option of last resort’, and cleaner emerging technologies, have reversed the trend. The number of plants has more than doubled since 2012. Last year, six ACT facilities and two biomass plants received funding from the government’s £176m contract for difference programme, designed to promote energy generation from innovative and emerging technologies.

The market for residual waste is strengthening, in terms of tonnages and gate fees, and capital costs are lowering. This year, for the first time, the tonnage of residual waste sent to EfW will exceed the tonnage sent to landfill. The designers and builders of new plants are going to be tasked with making them more efficient, so that energy and water consumption reduce. At the same time, they will be coping with more demanding emissions targets.
Technology to make the reduction of acidic pollution more effective is already happening. I think, in the future, that there will be more of a focus in EfW plants on reducing SO2. Companies like Lhoist have constant product development and an innovation pipeline so that we can react to new technological needs. We have flue gas treatment specialists and chemists working in our R and D facility in Belgium so that we can say to the industry: ‘What’s your challenge? We have what you need’.

Lime is not a boring product that you just dig out of the ground. It has such an interesting range of applications, particularly in the environmental sector. What it is used for, how it works, what it does. There is always something new on the horizon and this is a vibrant, dynamic industry.

For further information please contact John Whitehurst UK Business Manager, Environmental Applications, Lhoist.

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