Qu: Can we make our rubbish into fuel?
Qu: Would it be possible to put waste, i.e. bio-degradable rubbish and sewage into an air-tight container, let it produce methane gas, siphon it off to cook with and power gas-fired central heating, filter off the water, and be left with compost to put on gardens?
Yes – very possible, in fact it’s already being done. It’s called Anaerobic Digestion and the process is widely used to treat wastewater sludges and organic wastes. Anaerobic digestion can reduce the emission of harmful landfill gases into the atmosphere and is a renewable energy source because the process produces a methane and carbon dioxide rich biogas suitable for energy production. Also, as the question suggests, the nutrient-rich solids left after digestion can be used as fertiliser.
So why isn’t this process used everywhere? Anaerobic digesters require a high level of technical expertise to maintain as careful control of the digestion temperature, pH, quality of input and loading rates is crucial. Because of these complexities, despite being recognised by United Nations Development Programme as one of the most useful decentralised sources of energy supply and being less expensive to run than large powerplants, anaerobic digesters are not widely used in industry. (source)
Anaerobic Bioreactors, a type of landfill, can also transform decomposing material into an energy source. By removing oxygen and pumping lechtate (water which has collected waste products from the decomposing matter) and other liquids around the bioreactor the waste produces methane, which can be collected and used instead of fossil fuels. (source)
Perhaps the most exciting and accessible use of the anaerobic production of methane from plant waste is the ‘pyrolysis unit’ – invented for domestic use in India by Ravi Kumar. A family collects waste plants, dries then and puts them into the unit’s circular casing. This casing is sealed to stop oxygen combining with CO2. A small fire is started in the central void; this heats up the plants and causes them to emit gases through small holes in the casing. The gases ignite and burn for long enough to cook dinner (about an hour). Then, brilliantly, the remaining charcoal can be raked out and used as fertiliser – what’s more the soil’s subsequent ability to lock in carbon dioxide also increases. (James Bruges – What About China?- p19)
Hope that helps,
Bethan
September 3rd, 2008 at 12:25 pm
Very interesting indeed.
Particularly encouraging as materials in landfill will have an increasing commercial value in the future compared with the price of raw materials, not to mention the environmental benefits, which are numerous. A number of organisations are creeping into this area.
Have a look also at the U.S Army’s ‘Tactical Biorefinery’ http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=978 , which digests organic and non-organic waste into ethanol, methane and propane. Absolutely ingenious!
Very useful for the disaster relief situations, as well as military operations.
Surely this technology can be used commercially to create useable fuels from landfill.
There is also a microwave technology that coverts plastics into oil and rubber tyres into diesel. One such innovator is Global Resource Corporation (GRC), whose ‘Hawk 10′ machine can recover oil and gases from a variety of waste materials, oil sands and shales. However, the cleverest part is that gases produced in the conversion process are used to fuel the machine, in a closed loop system of sustainable energy use. See: http://www.globalresourcecorp.com/
Not sure how this might or might not affect the advancement of renewables?
September 15th, 2008 at 8:54 pm
Evening all – the issue of mining energy from landfill sites, or converting energy from burned waste in hi-tec plants is one that will keep all the bigwigs busy for years.
I’m more concerned with getting everyday folks to see the resource they have under their noses and getting them to convert that into another form of energy – ‘black gold’ or compost that they can grow a few fruits and vegetables in!
Food waste remains an enormous contributor to landfill, despite the best efforts of great campaigns like Love Food Hate Waste and many more.
Perhaps the energies of the powers that be might be better invested in helping to encourage and convert the general public across to a bit of simple composting. This could be aided by consistent financial concessions for purchasing bins, with statutory bins built on all new housing developments and serious investment in community allotment schemes to begin with, not to mention getting neighbouring boroughs and councils to share their resources and let more green and food waste in via the doorstep collection schemes.
If people get to grips with a little sustainable living, many of our eco-problems could well be kicked into touch.
Rubbishly yours,
Tracey Smith
Author of The Book of Rubbish Ideas
http://www.BookOfRubbishIdeas.co.uk