Advanced conversion technologies: A heated debate

For well over a decade now, various forces in the UK have been trying to develop advanced conversion technology (ACT) for the treatment of residual waste as an alternative to landfill or mass-burn incineration. Way back in 2003, the previous Labour government launched its New Technology Demonstrator Programme with the aim of overcoming the ‘real and perceived risks’ associated with technologies like anaerobic digestion (AD), mechanical biological treatment (MBT), mechanical heat treatment (MHT), gasification and pyrolysis. And while AD has since gone on to become the government’s preferred method of dealing with organic waste (there are well over 100 operating AD plants that deal exclusively with waste, and significantly more that deal with agriculture residues and slurries) and MBT and MHT are becoming more common, the advanced thermal treatment (ATT) technologies still haven’t overcome the hurdles that became evident during the 2003 demonstration programme.

Indeed, only one ATT project – the ex-incinerator on the Isle of Wight that Energos retrofitted with gasification technology – was even able to complete the project to a meaningful degree. Three others that received funding didn’t complete the programme: the Novera gasification pilot in East London withdrew for commercial reasons, while the Compact Power gasification and pyrolysis plant near Bristol was unable to commence construction in time for the project (though it was later built and acquired by New Earth Technologies – more of which in a moment) and the Yorwaste pyrolysis plant in Scarborough was never able to start meaningful operation.

Photo: Energos

And despite the passage of 13 years, the technologies still haven’t really taken off as far as the treatment of mixed residual waste goes. New Earth eventually built its ACT plant in Avonmouth near Bristol, and began exporting power in 2013, but, as Director M J Richardson explained in a letter to stakeholders in 2015, ‘the level of performance has consistently fallen well short of targeted levels’ while ‘[o]perational, manpower, maintenance and repair costs have consistently proved to be much higher than originally planned’. His letter warned that the poor performance of the combined gasification and pyrolysis plant increased the risks to the overall New Earth business, and the official decoupling of the firm’s energy and waste interests was not enough to prevent New Earth from going into administration this summer. New Earth’s decoupled energy business, formerly NEAT Technology and now known as Syngas Products Group, is still trading, however.

New Earth is not the only large company to struggle with the technology, either: in 2009, Scotgen opened a 20,000 tonne per annum gasification plant in Dargavel, which it claimed was ‘Europe’s most advanced waste-to-energy facility’. Following a major fire in 2013 and a series of permit breaches, though, it had its environmental permit revoked by the Scottish Environment Protection Agency (SEPA). At the time, Ian Conroy, Technical Support Manager in the South West for SEPA, said: “The facility started operations more than four years ago, and in that time has never achieved a level of compliance which would give SEPA any degree of confidence that future operation would be any different. The facility has consistently failed to meet any reasonable expectation of environmental performance and the predicted level of energy recovery at approximately three per cent is particularly disappointing and unsatisfactory. SEPA has taken this serious and unusual action of revoking the permit following careful consideration and assessment of the regulatory options available.” Scotgen has since gone into administration, but the facility and assets were acquired by Rank Recycling Scotland, which applied for a new permit, though it is unclear if this is still being pursued.

Earlier this year, meanwhile, American gas producer Air Products announced it was leaving the energy-from-waste business altogether, ceasing the development of two mammoth gasification projects in the Tees Valley, which together would have handled 700,000 tonnes per annum (tpa) of waste. The move wasn’t a complete surprise as the company had previously indicated it was experiencing problems: in a 2015 company conference call, CEO Seifi Ghasemi was asked about the then-three-year delay to the project, with Goldman Sachs analyst Robert Andrew Koort querying: “Is that an indictment of the technology or is there some other issue at work?” Ghasemi responded: “It’s just related to the technology. We have always said that there is a chance that the technology will not work.”

This point was reiterated in a January company conference call, when Ghasemi said: “There is a still significant outstanding question about if we will ever be able to get it to work on a sustainable basis... The technology is proving to be a lot more difficult than people thought at the beginning.” Subsequently, this April, after the company had finished construction of one of the plants and started on the other, it announced that it was unable to overcome the ‘design and operational challenges’, and so wrote off the entire project at an estimated cost of US$1 billion (around £700 million at the time) and the loss of hundreds of jobs.

Since then, Energos, the only ATT company to complete the New Technologies Demonstrator Project with its retrofitted gasification plant (a conversion that had its own problems with emission breaches and low levels of energy recovery), has also gone into administration following ‘contractual disputes’. And there are a string of other gasification proponents that have likewise folded or given up on the technology over the years, as highlighted in a recent UK Without Incineration Network (UKWIN) briefing: BCB Environmental; Bioflame; Biossence Renewable Energy; Compact Power Holdings; Interserve; the list goes on. So, what’s going wrong?

Before we consider the complications of using the technologies at a large scale to treat mixed waste streams, a brief explanation of the technologies themselves is in order. Though they come in a variety of forms – with sometimes bewildering names like fluidised bed, counter-current fixed bed or co-current fixed bed gasification, plasma arc gasification, free radical gasification or flash vacuum pyrolysis – the two technologies, like incineration, are essentially thermal processes. They use high temperatures to break down organic or fossil-fuel based material, such as paper and plastics, to liberate energy. Unlike incineration, however, only a very limited amount of oxygen is present in gasification, while pyrolysis occurs with no oxygen, and both take place at extremely high temperatures (typically above 430°C for pyrolysis, and above 700°C for gasification). Rather than directly releasing energy, the processes produce ‘syngas’, made up of hydrogen and carbon monoxide, which can be used to produce energy through steam turbines, for instance, or can, in theory, be used directly as a fuel, which would result in higher conversion efficiencies.

Photo: Energos

Advocates of the technologies say they have many potential benefits over incineration, including potentially higher efficiency, lower emissions (as there is no flue gas to clean) and the potential to deal with heavy metals (in some versions) by trapping them in a glassy and chemically stable form. Moreover, they can operate through a modular system, allowing for more flexibility than a mass-burn incinerator.

And while both technologies have been widely used by other industries – to treat coal and peat, for instance – as we’ve seen, their success in the waste industry has so far been limited. Shlomo Dowen, from UKWIN, has been outspoken on the drawbacks of the technology, saying after Air Products withdrew from the sector: “Gasification and pyrolysis are synonymous with technology failures, bankruptcies and broken promises. As such, UKWIN is unsurprised that Air Products failed to get an unworkable technology to work.

“We hope this latest admission of defeat acts as a wake-up call for the government, who have been unwisely stoking this whole misadventure with environmentally-harmful subsidies and other unwarranted financial support. Investment should focus on sorting technologies and other infrastructure that will move us towards a circular economy, not wasted on disposal technologies which, even if they worked, would still be destroying valuable materials whilst exacerbating incineration overcapacity.”

Putting aside the (perfectly valid) arguments about the technology’s potential to destroy valuable materials, I ask him what makes the technology so tricky to crack when it comes to the treatment of mixed municipal waste, and he explains: “My understanding of the wider question of gasification failures is that the more heterogeneous the feedstock, the more likely it is to fail... When you are burning a homogeneous feedstock, you can anticipate its behaviour and you can design around that behaviour. But if you have a mix of materials, you can’t be certain that that batch will behave in the same way as your previous batch, because it’s based on compositions. So, it becomes unpredictable, like trying to hit a moving dartboard.”

Scaling up a facility, which inevitably makes structures more complex, can lead to further complications, he says, as “even if the various components have been shown to work separately, the configuration often does not work”. He adds that, while proponents of the technology point to some small-scale demonstrator projects as proof of concept, he isn’t aware of any successful, large-scale facilities relying on a mixed-waste feedstock operating anywhere in the world, adding: “As soon as you scale up from a demonstrator project to a facility that could take 100,000 tonnes of feedstock per year, then you greatly increase the chance of air getting into the gasification unit [a problem that is even more serious in a pyrolysis unit] when you don’t want it to, and then you’ve got all sorts of problems.”

This view is backed up by Peter Selkirk, Chair of PyroPure, which uses pyrolysis and gasification on very small batches of niche waste streams, like medical and hazardous waste, who suggests that technical issues mean that upscaling the technologies can be very difficult (and expensive): “Small-scale plants seem to become unmanageable when upsized to large scale – which is necessary for the huge capital costs to be justified. The root cause of most problems is the intrinsic variability of waste feedstocks.”

A brochure for GoGreenGas’s pilot demonstration plant, which will use gasification (and which says it has overcome the technical hurdles associated with producing clean syngas – more of which in a moment), elaborates: ‘[A]pplying this technology to waste or biomass has proved extremely challenging for previous developers. The primary challenge is producing a syngas that is free of tars. The tars foul catalysts, preventing any conversion of the syngas. However, the structure and composition of waste and biomass feedstocks mean that they are gasified at relatively low temperatures of tar generation. Wastes, and to a lesser extent biomass, contain high levels of contaminants such as sulphur, chlorine and heavy metals. These poison the catalysts used to convert the syngas to methane.’

Dowen suggests that the high-profile failures/withdrawals/administrations, combined with the conclusion of government subsidies in the form of Renewable Obligation Certificates (ROCs) at least, mean that the number of proposed ACT facilities going through the application process has fallen off in recent years (and UKWIN keeps a very detailed list of potential, existing and prevented incinerators – including those that use gasification and pyrolysis technology – on its website), but others insist that the technology is going to expand in the coming years and that the high-profile problems are not representative of the technology in general.

The Tees Valley site of Air Products's two abandoned gasification facilities

Several of the gasification and pyrolysis companies I spoke to seemed reluctant to speculate on the specific cause of Air Products’ failure, and even companies that were involved with the Tees Valley project did not want to be drawn on the problems it faced. In a 2012 press release, Waste2Tricity described itself as the ‘structured solutions provider instrumental in introducing the Tees Valley site’ where Air Products attempted to build the two giant gasification plants, further quoting Managing Director John Hall as saying: “Air Products are the pathfinder in this sea change of energy conversion technologies.” However, neither Waste2Tricity nor Peel Environmental, which are still developing the Bilsthorpe Energy Centre, a proposed 100,000tpa commercial and industrial waste facility due to use technology very similar to that which Air Products failed to get off the ground, were available to speak for the purposes of the article. The companies did, however, send through statements highlighting the “extensive work” they’ve done “to demonstrate how the facility will work, which included obtaining R1 efficiency status during the planning process”. 

As for the Tees Valley development, though, the overriding feeling from other commentators seemed to be that it was a matter of scaling up too quickly with unproven technology. Some even suggested that the setback at the Tees Valley plants was only temporary and that we will still see those plants come online in the future.

And it seems that some investors (and the government) still want to back ACT. Adam Baddeley, Eunomia Research & Consulting’s Head of Energy, says that, from the people he’s spoken with “the investors are really keen, are very interested in ACTs at the moment”, in part (which some might find depressing) because “clean tech investors were putting a lot of money into wind and solar, and that market has gone down, the government has withdrawn support to the extent that people can’t build new wind or new solar at the minute”. Moreover, although the ROCs aren’t available to new proposals, ACT facilities might still be able to get support through the government’s Contracts for Difference (CfD) scheme, which aims to stabilise revenues for investors in low-carbon electricity projects by paying generators the difference between the ‘strike price’ – a price for electricity reflecting the cost of investing in a particular low-carbon technology – and the ‘reference price’ – a measure of the average market price for electricity in the UK’s energy market. 

Although Theresa May’s government appears to have other priorities, a new auction for CfDs is expected soon, and the Department for Business, Energy & Industrial Strategy recently launched a consultation on the matter, asking whether CfD ‘is the right support mechanism’ for ACT technologies. Baddeley explains, though, that if ACTs remain in the ‘less established technologies’ CfD pot, competing against technologies like biomass CHP and off-shore wind, it would continue to incentivise the technologies, giving “them the edge over other technologies – over incineration, anyway, as they can then offer a lower gate fee”.

And as for the technological hurdles, Baddeley suggests that while operators will “have to accept that you are likely to have more downtimes at these plants”, many of the hurdles can be overcome through proper preparation of the feedstock (in addition to choosing the right technology, of course): “I think the main issue with any of these is making sure that you get the right feedstock and that usually needs greater treatment than with a traditional incinerator. But I think at the moment, we are seeing the supply chain for fuels maturing quite a lot – people are realising they have to do it, they can’t just bung any old thing into these plants, and we are seeing more quite sophisticated MRFs being built, so they can supply these plants more effectively.”

Those operating or looking to operate gasification plants, meanwhile, are even more optimistic, with some saying they have developed technology that can handle municipal waste with limited or no pre-treatment. Chinook, which recently began operating the world’s largest industrial waste gasification plant in the West Midlands – capable of processing 160,000tpa of automotive shredder residues (ASR) (a homogenous waste stream, in other words) – says its technology could equally be applied to black bag waste. The company is currently building a 500,000tpa gasifier for mixed waste in the Emirate of Sharjah and has two further projects in the UK – one of which, in Nottingham, will process a mixture of RDF and residual C&I waste – at ‘advanced stage’, awaiting clarity from the government’s CfD Autumn 2016 resource43Featureauction. The key to successfully treating mixed waste through gasification, according to the company, is to rely on batch processing as opposed to the more common continuous process, a move it says eliminates the need to pre-treat waste.

This article was taken from Issue 86

Rolf Stein, CEO of Advanced Plasma Power, a partner in the GoGreenGas project mentioned above, meanwhile, tells me that the project’s use of two “tried and tested and well proven” technologies – fluidised bed gasification combined with a plasma arc converter that cleans the gas by exposing it to high temperatures and UV to crack the problematic tars and hazardous organic materials – means it will succeed where several others have recently failed. In partnership with the National Grid and Progressive Energy and with funding from the Network Innovation Competition and the Department for Transport, Advanced Plasma Power will be launching a GoGreenGas demonstration plant in Swindon in November that will treat waste through gasification to create bio-substitute natural gas (BioSNG), a step further than the syngas typically produced by gasification (used to run steam turbines), as it can be injected into the National Grid or even used as a fuel for heavy goods transport. The project will still be at a fairly small scale – scaling up to 10,000tpa from a 1,000tpa pilot – but Stein anticipates future full-scale commercial plants starting at 50,000tpa.

With regards to feedstock, he also maintains that the technology can get by with limited processing (although a bit of drying, he says, is preferable “because otherwise all you do is heat up that moisture content before cooling it down and then having to deal with liquid effluent at the end of the process”, adding that items like glass and metals should ideally be removed because they have no energy value, though they do, of course, have economic and material value). He adds that the pilot plant was able to handle “a very broad range of RDFs”, as well as even mined landfill waste, and anticipates the scaled-up technology will be able to do likewise.

Asked what problems there are with applying gasification to municipal waste, Stein responds: “The short answer is there aren’t any, really. The problem, I think, has arisen by people trying to do something new.” With several plants due to launch in the coming years, an upcoming decision on CfD scheme financing, and the Green Investment Bank already supporting several projects, the question of whether or not the technology can work to treat municipal residual waste might soon be answered once and for all, at least! Watch this space.