Landfill Energy?

 We are an Automotive Factory. We want to generate electricity from Landfill trash. Our electricity need is 5 MWH. Can anybody tell me how much trash do we need to fill in the land ? and how much space would it take ?
Please reply at following email address
minhajur.rehman@toyota-indus.com

The first thing you should do is get a clear idea of how much electricity you're using.  This quote of "5 MWH" ( 5 mega watt hours?) is a quantity of energy.

This quote by itself is unclear because I don't know the time rate associated with this quantity.  Is this the amount of electricity you use in one month?  In one day?  You should maybe check on that.

Of course if you're simply curious how much garbage does it take to produce 5MWH, consider this quote:
(From the Wikipedia article on trash incinerators.)
The heat produced by an incinerator can be used to generate steam which may then be used to drive a turbine in order to produce electricity. The typical amount of net energy that can be produced per tonne municipal waste is about 2/3 MWh of electricity and 2 MWh of district heating[2]. Thus, incinerating about 600 metric tons (660 short tons) per day of waste will produce about 17 MW of electrical power and 1200 MWh district heating each day.
This quote says 2/3 of a MWh-electric for each ton of garbage.  So that's
5/ (2/3) = 7.5 tons of garbage to make your 5 MWh.  That's using an incineration method.   

There are also other ways recover energy from garbage,
(See http://en.wikipedia.org/wiki/Waste-to-energy)
but intuitively I would expect these to give less energy per ton than just burning it directly in an incinerator.  Thus the quote of 0.667 MWh/ ton should be thought of an upper limit. 

The main problem with the incineration method is that incinerators have a tendency to be dirty.  Typical municipal garbage contains a lot of chlorine-containing plastics, like PVC, and burning these has a tendency to produce dioxins, and that's bad.  There are tricks to reduce these emissions, e.g. control systems to maintain higher temperatures, scrubbers for the exhaust, and of course these make your incinerator more expensive, to build, to get permits for, etc.

The main advantage incinerators have  is you get more energy per ton of garbage. Also I'd expect an incinerator to take up the least amount of space. 

BTW, I don't have any quick answers for how much space, cost, time, it would take to build any of these.  But I think the Wiki articles are a good place to get started.
http://en.wikipedia.org/wiki/Waste-to-energy