Rising to the twin challenges of energy and waste

A Greenlane biogas upgrader like those Chesterfield BioGas is installing in the UK
A Greenlane biogas upgrader like those Chesterfield BioGas is installing in the UK
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Britain is facing a double energy and waste challenge and Meadowhall-based Chesterfield BioGas could have the answer.

Over the last few years, the country once rich in North Sea Gas has become a net importer.

And, an ever-increasing proportion of that gas – by value if not necessarily volume – has had to be brought in from places like Qatar, Trinidad and Tobago, where either political stability or sheer distance pose serious questions about security of supplies.

If that wasn’t bad enough, the UK has agreed to meet tough European targets to boost the percentage of renewable energy it uses.

Currently, around four per cent of the UK’s energy comes from renewable sources. By 2020, at least 15 per cent must be from renewables and the target for 2050 is 50 per cent.

At the same time, Britain is also committed to reducing the volume of biodegradable waste it dumps in landfill sites to around a third of the amount it used to bury in the mid 1990s.

One answer to both those challenges is to turn that waste into biogas, using a process called “Anaerobic Digestion” – or AD – which uses microbes to break down the waste in the absence of oxygen, producing methane and leaving a material rich in nutrients that makes an excellent fertiliser.

AD can also be used on sewage, energy crops like maize and even material from kerbside waste collections, as long as it has been separated.

When it comes to exploiting biogas, Britain lags behind many other European countries – most notably Germany, which has 60 Anaerobic Digesters for every one in Britain.

The gas produced by digesters has traditionally been used to fuel generators – but that may not be the most sensible thing to do.

In its raw form, biogas may contain carbon dioxide, hydrogen sulphide and chemicals called siloxanes, which do all sorts of nasty things to an internal combustion engine, shortening the generator’s life to as little as seven years.

Using biogas to run the generator also produces a lot of heat. If it is part of a Combined Heat and Power (CHP) plant, then some of that heat can be recovered and used, but, all too often, the nearest premises are too far away and the heat is just vented into the atmosphere.

If that happens as little as 40 per cent of the energy in the biogas may be recovered.

The alternative is to clean up the raw biogas.

That is where Chesterfield BioGas’s technology comes in. Its system – known as an ‘Upgrader’ – uses water, which can be recycled, to clean raw gas, fed in under pressure, leaving it 98 per cent pure.

The clean biogas can be injected directly into the gas mains, albeit that, depending on the original material fed into the AD plant and the national specification for mains gas, some additives may be needed.

Alternatively, if there isn’t a gas mains supply nearby, the biogas can be stored in tanks for transporting later by road tankers to where it is needed.

In either case, between 90 and 95 per cent of the energy in the gas can be put to good use.

On some sites, they even have greenhouses, into which the waste carbon dioxide is injected at night, to encourage the plants inside to grow.