What about China?

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

One of the key issues at the recent G8 summit was the global increase in the cost of food. As discussed previously, the rising price of staple foods has been linked to the increased cost of oil, which has caused land previously used for food crops to be turned over to crops for bio-fuels.

At the summit in Japan, the World Bank President Robert Zoellick highlighted the growing food shortage and urged the US and ‘rich countries’ in the EU to reform their bio-fuels policies and concentrate on food production. All well and good but it’s hard to believe all this talk is going do much to curb the rate at which your weekly shopping bill is creeping up, especially considering the frequency of missed G8 targets.

But we’re not as helpless as we imagine, the average consumer might not be able to dictate how farmers use their land but we can make sensible choices when it comes to dinner time. You’d think, with the increased prices, that people would be making an effort to make each meal count, but a recent survey estimates the average UK household throws away £8 of leftovers a week and each year in the UK as a whole wastes 4 million tonnes of food. People are spending about 9% of their income on food, with poorer households forking out up to 15% of theirs on staple foods such as milk, eggs and bread – foods that have been hit hardest by price increases in recent months.

This week Gordon Brown urged Britons to stop wasting food and to avoid making unnecessary purchases. But it’s not just the consumers who need to change their habits, the government might be more successful in reducing waste if they tackled supermarkets directly. The Liberal Democrats environment spokesman Steve Webb, blamed the governments “cosy” relationship with supermarkets for their failure to change policies which make it harder for householders to avoid food waste: “They refuse to stock small portions, which are essential for the growing number of one-person households, and offer too many buy-one-get-one-free deals on perishable goods.” Supermarkets also account for a large percentage of waste and throw away large quantities of edible food through poor stock management.

So, what can you do? Try planning your evening meals for the week and using up tins you’ve shoved to the back of the cupboard. Making extra in the evening means you take care of lunch the next day too – and this saves on energy, as you won’t be turning the cooker on again. Cooking for more people always works out more economically so offer to cook for your flatmates or friends and get them to return the favour another night. You can also try avoiding supermarkets; they might seem cheaper at first but in the long term it means smaller shops can’t survive or have to put their prices up further. If you do have to go to the supermarket write a list and stick to it – don’t be tempted by offers which will leave you with a fridge full of out of date food.

Bethan