Friday, April 6, 2012

From Rubbish Bin to Jet Engine

By Omogen Reed

Waste management and disposal is big business. Each of us helps create many kilograms of waste each year. Exactly how much varies, but in the United States (the world ‘leader’ in waste generation), the figure is 760 kilograms, per person, per year. Much of it ends up in landfill, and much of it will stay there for decades. Burying waste in landfill can cause serious environmental problems. Landfill waste can work its way into groundwater, polluting it. It can encourage vermin, especially if it is poorly managed or poorly sited (as it often is in developing countries). It makes land prone to subsidence: owners of houses built over landfill better make sure they have good landlords insurance. Couldn’t there be a better way to get rid of our rubbish?
Waste as Fuel
There could. Rather than burying waste in landfill, it can be used as fuel. This helps solve two environmental problems: waste is kept out of landfill, and it is used in place of polluting fossil fuels. Different types of waste can have different applications. Organic waste is perhaps the most useful, as it can be converted into a petrol or diesel alternative. With adaptation, vehicles can easily run on decomposed food waste. General rubbish collected from households can be taken to a processing plant, and the organic waste extracted. Micro-organisms are used to process the fuel into ethanol, and that ethanol can be used to run vehicles. Using organic matter to power cars might sound unlikely, until you remember that oil is itself decomposed organic matter.
Other types of waste can also be used to create electricity. Simply burning it would just create a new set of emissions, but technologies are being developed that can gasify waste, creating electricity from it without the need for incineration. These technologies have yet to reach their potential, but there are several projects worldwide, with interest and funding from the big players in energy generation starting to get involved. Several plants are in the planning stages in the US, including one in Wisconsin, which will supply power to 4000 homes.
One of the most impressive of all the waste-to-fuel projects is British Airways’ plan to convert the household waste generated by Londoners into jet fuel. They intend to build a plant in the city that will be capable of converting half a million tonnes of rubbish into 50,000 tonnes of jet fuel. That is only 2% of their annual fuel needs, but they say that if the plan works, they’ll seek to expand it. With the rising cost of fuel an increasing problem for airlines, BA’s rivals may well be keeping a watchful eye on developments.
At the wackier sounding end of the scale is a plan to convert human waste into fuel. Supported by a grant from the Bill Gates Foundation, researchers at Columbia University are looking to produce biodiesel and methane from ‘fecal sludge’. The biodiesel can be used to power engines, and the methane can be converted into electricity.
Landfill Gas
Projects that keep rubbish out of landfill are welcome, but what about the rubbish that is already there? That, too, can be utilised. As it decomposes, landfill creates methane gas emissions. This methane can be harvested and used to create electricity, and can also be converted into natural gas for use as power. An extraction well is drilled down into the landfill to extract the gas, and a pipeline takes it to a processing plant. As methane is many times more polluting than carbon dioxide, preventing it from being released into the atmosphere from landfill sites is hugely beneficial.
The Future?
Waste looks likely to play an important part in the future of power generation. Some technologies are now well-established, while others still have a way to go. However, with oil reserves dwindling, the use of waste as fuel is attracting some serious investment. Using waste as fuel doesn’t involve any extra production: the waste is already there. In future, just as buildings can be constructed so that they recycle their own greywater, you could see buildings that create their own power using their own waste. Perhaps we might see waste collection departments in cities across the world close down, as residents use their own waste to heat their homes and power their cars?