But let's get back to business with today's blog.

In recent years, significant efforts have been made to turn the world's citizens into recyclers of waste.

In parts of the UK such as England, the household waste recycling rate reached 43.2% in 2012/13. Over the previous decade, the amount of waste going to landfill has fallen by over 60 per cent.

This data is encouraging, but 34 per cent of local authority managed waste in England still went to landfill in 2012/13 - over a hundred kilogrammes for each man, woman and child.

I suspect for large parts of the world this is a similar picture, but the trends are positive and the number of landfill sites is decreasing and new developments are being scaled back as we find ways to re-use our waste.

But one aspect of recycling that get's less attention, is what to do with the waste already buried in tens of thousands of landfill sites across the world.

The idea of digging up old rubbish is not new, but it has always been a question of economics and more recently shortages of landfill space in some countries.

The economics are being influenced by taxation in some countries, such as the landfill tax in the UK, and the value of items - such as metals. Not exactly a gold mine, but there's still value buried in our industrial-scale 'middens'.

Landfills are also a potential source of feedstocks for renewable energy. In 2010, a 30-year project was announced that will reuse 16.5m tonnes of municipal waste dumped since the 1960s at a landfill site near Hasselt in Eastern Belgium.

The project is scheduled to become operational in the near future and will use plasma technology to convert the methane produced by the rubbish by a company called Advanced Plasma Power (APP). The waste will fuel a 60MW power plant capable of supplying 60,000 homes.

Safety is also a factor. There are risks from trapped methane and many older sites could contain harmful substances such as asbestos. However, using methane in such a positive way is much more beneficial than the risk of allowing it to be released into the atmosphere, where it is 20 times more damaging to the environment than carbon dioxide.

The scale of work underway to keep our waste out of landfills was featured in an excellent and wide ranging article on the Aljazeera website recently called The afterlife of plastic.

What I enjoyed most reading the article was the attempts to re-cycle some of the most difficult single use plastics such as flower pots, bottoms of plastic cups, plastic wrapping around jars, styrofoam containers and even fiberglass. Most of these plastics still head straight for landfill and are not as appealing as many other low hanging plastic fruits.

In one of their news releases, APP described some of the people working in this field as 'Trash Miners'. This may not be flattering, but it is apt and a field where chemical engineers have an important role and are doing some great work - congratulations.

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Here's some other trash mining projects APP has identified in the USA that you may find interesting.

SW Missouri Tapping Landfill Gas

The Nobel Hill Landfill Renewable Energy Center in Springfield, was constructed in Missouri as a joint venture between the City of Springfield and City Utilities. The plant extracts methane from deep within the landfill to generate up to 3.2 megawatts of electricity. CU transmission lines transfer the electricity to power about 2,080 homes. It offsets the fuel requirement, which is usually 39,000 barrels of oil.

Biodiesel plant Denton, Texas

The plant runs on biogas, collected from a nearby landfill. The most exciting experiment is the renewable energy plant that functions on biogas collected from a nearby landfill. The city of Denton buys 300,000 gallons of biodiesel each year for its 386 garbage trucks and other service trucks and buses.

University of New Hampshire

The first university in the US to receive 85 percent of its electricity and heat from their special project called Ecoline, which utilizes purified methane gas drained from a nearby landfill. The entire cost of the project was $49 million and their efforts are expected to reduce carbon emissions to 57% below 1990 levels. Any excess of electricity produced is returned to the electric grid.

Volkswagen Auto assembly plant

Volkswagen is looking into replacing the standard power source of its auto assembly plant in Chattanooga, Tennessee with renewable energy produced from methane gas. The gas, diverted from a closed landfill nearby, can generate up to 2 MW of electricity each day. The plan has great potential. The initiative will fulfill a considerable portion of Volkswagen’s energy needs, relieving most of its dependency on fossil fuels and improve its LEED status. The city will also benefit by seeing a good resource put to use rather than being uselessly flamed off.

Septage Bioreactor Landfill Technology

An ingenious waste treatment system has been invented by the Viridis Waste Control LLC. The system called Septage Bioreactor Landfill is slated to accomplish two main aims of sustainable energy production: the reduction of landfill usage and creation of renewable fuel on a large scale. Septage Bioreactor Landfill Technology encourages a faster rate of decomposition of organic matter to create methane in a short period of time. The method will supply a sufficient quantity of methane to be viable and reliable source of fuel.