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Ready to explode

Andrew Mourant, freelance journalist

In Part 1 of this 'mini-series,' Andrew Mourant looks at global developments in the nascent field of landfill gas site management and engineering.

It may not be a gold rush, an oil boom, or rank in the same league as the craze for fracking, but exploiting landfill gas is a big business and, say analysts, likely to put on a mid-decade spurt of growth, despite the obstacles in its way.

As Renewable Energy Focus reported in November, revenue from the waste to energy (WTE) plant market globally is predicted to rise from $19 billion in 2012 to $29 billion by 2016. Landfill gas operations, once found principally in mature advanced economies such as those of North America and the European Union (EU), are thought to account for more than 60% of all biogas power generation.

New hot spots include Mexico and China (REF will examine Chinese developments in a future issue). A layman might wonder: what’s taken landfill, as an energy source, so long to take a hold – surely rubbish heaps, forever releasing methane into the atmosphere, are every neighbourhood’s potential power source and a polluter to be clamped down on? 

Like other renewable initiatives, landfill needs to be kick-started by governments and legislation.

For every million tonnes of municipal solid waste, there are thought to be 1.7-2.5 million cubic metres of collectable gas. This can be used to produce 6,500 to 10,000 MWh of electricity annually -- roughly the average power demand of 1,500-2,200 EU households. But however straightforward the technology involved, the politics and economics of landfill gas exploitation are much more complex.

Like other renewable initiatives, landfill needs to be kick-started by governments and legislation. There’s been no shortage of carrot and stick in, for instance, the EU; but less in some other parts of the world. Many elements need to fuse if landfill gas power initiatives are to take off.

The landfill site itself is a singular beast -- a living, organic thing. Consultants who have worked on them around the world agree on one thing: that no two are identical; each is a distinctive as a fingerprint.

Gas formation is influenced by waste composition, landfill storage height and density, air temperature, atmospheric pressure and precipitation levels. Organic carbon is converted to gas by micro-organisms via anaerobic processes.  Production starts one to two years after the waste is dumped -- and lasts 15-25 years.

Site management

How sites are supervised matters a great deal, yet some are barely managed at all, as Grant Pearson, principal at UK consultants SLR well knows. 

“The greater operational control, the better,” he explains.

“The western European model makes for generally well-managed sites. But in many developing countries, there’s little control – waste disposal can spread over a large area. It’s important to have on-going site management and reliable information as to what’s gone on in the past – local knowledge of local conditions.”

Poor control presents almost intractable problems.

“Fires can be a recipe for disaster,” Pearson notes.

“Burning or hot loads may simply get buried and forgotten, and burn for years, inhibiting effective site management and removing the potential LFG source.”  

One crucial element in doing things properly is controlling leachate, which on some sites is successfully recirculated. ("The right amount of moisture enhances gas production," Pearson explains.)

SLR has learnt from Africa the value of using horizontal gas wells for early gas collection.

“With the higher bio content of waste and warmer climate, producing viable LFG tends to happen more quickly than in the UK,” Pearson stated.

Pearson continues: “It has proven beneficial to construct horizontal wells early in the tipping process … rather than rely only on ‘traditional’ vertical wells to capture gas. The benefits are two-fold: income is generated sooner, and landfill gas that might otherwise have been lost can be captured more swiftly.”

Ian Cooper, business development director at UK-based renewables company ENER-G , which has extensive worldwide landfill gas interests, has worked in 20 countries ‘and never seen two landfills the same’. Moreover, they change as the waste degrades and settles. Regular audits are essential, because settlement and movement can cause condensate blockages, bent well heads and leakage. 

Ideally, a well-run site will, Cooper says, allow for gas extraction from different wells. This way, if one is producing 40% methane, and another 55%, it’s possible to change and blend. There is, he adds, an art to productive landfill management – ‘it involves a huge educational process, and that can be one of the biggest challenges’.

Yet Cooper has seen some sites that aren’t even covered, letting in water and potentially inflammable oxygen. Every financial model for exploiting them has to be tailored accordingly. Their individuality, and the near impossibility of applying one template to a different site, is something finance directors can find hard to comprehend. In some cases, there can be costly trial and error: one project near Durban, South Africa, failed because the landfill was covered in sand so fine-grained that it clogged everything up when it came to extract the gas.

Cost issues

This is an industry that's been forced to ride the collapsed price of traded certified emission reduction credits (CERs), devised by the Kyoto Protocol to reduce carbon emissions worldwide. These enabled developing nations to obtain funding from first world economies and help establish projects such as landfill gas capture that otherwise would not have been cost effective.

One of ENER-G's big markets is Mexico, where the increased price for landfill-generated power still makes doing business possible.

“We now have to achieve projects that can be commercially viable,” Cooper stated.

“We're still generating carbon certificates, but there's no value in them.”

Viability also depends on feed-in tariffs, yet these vary even within the European Union. Nevertheless, say analysts Frost and Sullivan, substantial business opportunities lie in the need to modernise established waste to energy plants in Europe, Japan and North America.

Yet in emerging markets, the high capacity of some sites, combined with low prices for dumping rubbish (i.e, “gate fees”), could reduce incentives to produce gas — quite apart from a lack of consistent government policies.

WTE plants can be expensive to set up (the global economic slowdown, which has inhibited all sort of investment, has not helped matters).

“Governments need to create transparent policy incentives and consistent road maps to re-assure investors and operators,” Frost and Sullivan stated.

“Greater collaboration between power-producing and waste management companies will strengthen the market structure and business frameworks.”

Improvements needed

Here's where modernisation could make a big impact. Not only in terms of better site management, but also tweaking the technology of gas extraction. Getting to the stuff is easy enough: perforated tubes are drilled into the landfill, interconnected by a pipework system, and gas is sucked out using a blower. An efficient system will collect gas from various spots, controlling high temperatures, leachate, condensates and air content.

There is, though, always scope to improve things, not least the power-generating engines. For instance, developing better ways to deal with contaminants such as siloxanes, silica compounds that volatise when they enter landfill and can foul up the works.

“These have increased as a result of EU legislation reducing the organic loads of landfill sites,” notes Alex Marshall, head of marketing and compliance at Clarke Energy, another UK company with a substantial international presence.

“One way of dealing with them was an increased maintenance schedule. There are now various clean-up systems.”

Engine development is evolving and, according to Marshall, took a leap forward with the Jenbacher engine, which is able to deal with impurities in the gas.

“These days, we can now squeeze 42% electrical efficiency out of the engine, whereas pre-Jenbacher, it used to be low in the low 30s,” he explained.

Globally GE Jenbacher units are used in more than 1,400 landfill gas system plants, generating about 11 million MWh of electricity annually, enough to supply 2.7million EU homes.

Marshall sees further possibilities for landfill gas plants through Organic Rankine Cycle technology, which uses waste heat to provide additional electrical power. How it works: water is pumped to a high pressure and passed through an evaporator, where it absorbs heat. It changes to a high-pressure vapour, driving a turbine coupled to an electrical generator, before passing through a condenser. The cycle can then be repeated.

“If you can squeeze more heat out, it's better for emissions and more efficient,” Marshall explained.

“But these units are quite expensive though have great potential.”

Landfill gas remains a world still feeling its way around, inching forward technologically, still hungry for subsidy and incentive.

Meanwhile, one scheme awaiting its time is the small, low-cost gas turbine engine. It's been claimed that a 100-140 kw prototype developed in the UK by Vykson Ltd can produce electricity using poor quality renewable fuels ‘that no other engine could.’ The assertion is based on trials using an old landfill site where the methane level varied from 12-30% — gas that would normally be flared or vented. Vykson says it is seeking manufacturers of a biomass boiler and a heat exchanger as strategic partners.

Landfill gas remains a world still feeling its way around, inching forward technologically, still hungry for subsidy and incentive. High gate fees seem an obvious one but don't always do the trick, even if they offer a means to invest and introduce much-needed environmental control systems.

“If some site operators can get away with high fees and not introduce regulations, they'll do so,” one industry insider told Renewable Energy Focus.

“Most people aren't going to do it out of the goodness of their hearts. There has to be something driving it — either money, or a big stick. ” ♦

Andrew Mourant is a freelance ­journalist whose areas of expertise include ­renewable energy, education and the rail industry.

This article was published in the January/February 2014 issue of Renewable Energy Focus magazine.

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