I was reading that producing electricity from Garbage / trash is as difficult as making gold into a lead.
Can someone explain further?
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Power, not necessarily electricity, can be generated by anaerobic digestion of organic waste. This is used on a small scale in the UK, but it's very effective in places like farms where organic waste is readily available and the methane can be used for heating. See http://www.biogas-info.co.uk/images/PDFs/baseline.pdf for a summary of the currect status in the UK.
Other waste can be incinerated, but the cost of electricity generated is high compared to normal electricity generators and there are environmental concerns about the products of incineration. I don't think much electricity is generated by waste incineration in the UK though i don't have figures to hand.