Anaerobic digestion: getting your hands dirty (guest blog)

Written by Andrew Mourant.

It’s hard to imagine a more unsavoury sight than mounds of rotting household rubbish or piles of farmyard dung. And so few prospects are more appealing than turning these into a source of renewable energy.

The worldwide demand for anaerobic digestion (AD) plants to create biogas tells a significant story. Two years ago, a study conducted by US-based market researchers BCC forecast that by 2016, the global market for biogas/AD plant equipment would be $8.6 billion compared with $3billion in 2010 – almost 300% more - and then rise over the following five years at more than 19%.

Small beer compared with investment in oil, gas and nuclear power. But it reflects a strong desire to make the best of the waste in our midst. By the end of the year BCC should have an updated estimate of how future AD investment may pan out. Given the will to drive forward research and understanding, don’t be surprised if their calculations have edged upwards.

It may sound an enticingly simple concept, yet anaerobic digestion initiatives have been plagued with problems and false starts. Much of this is to do with the basics: getting the feedstock right. With the benefit of hindsight, it seems incredible that an ambitious AD plant in Lucknow, India, should have been abandoned in 2004 simply because unsuitable rubbish, with too little organic content, was being tipped in.

Getting the feedstock right requires vigilance, as environmental consultant David Lerpiniere, who recently visited India as part of a UK Trade mission, points out. AD has taken root there - millions of small domestic plants have been installed; but debates about how far the technology can be scaled up continue to exercise the Indian government officials and world at large.

So research goes on. At Michigan State University (MSU), an AD biogas plants recently opened to exploit its considerable waste - food, and slurry from its extensive network of farms. The intention is for MSU to become self-sufficient in home-produced biogas. These are early days but biosystems engineer Dana Kirk who leads the project, believes the model could be exported once refined.

Most things worth having come at a price. Returns are by no means instant on AD investments, though some in the industry say that domestic AD units widely used in India and elsewhere should pay for themselves within three years. But the technology continues to need a helping hand: through grants; subsidies and, sometimes a sore point, feed-in tariffs.

Kirk believes AD technology stands a far better chance of working well if everyone involved knows what they’re doing –education is crucial, he says. He also stresses the environmental benefits of efficient schemes. You don’t need to have your mind boggled by the statistics of waste tonnage in countries such as India: the sight and stench of landfill and fly tipping should convince everyone that AD offers a better future – even it that takes money, time and patience; and there are hiccups along the way.

See our full article on Anaerobic Digestion in the November/December issue of Renewable Energy Focus. Subscribe here.

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