SO, Algeria has VERY mild weather, January's average temp is 52F, August averages 79F. Average annual highs and lows range from a low of 43F (Jan, Feb) to a high average of 90F in August.
Rainfall is low to average, about 26" annually, but its shifted seasonally from what most of us are used to in the US. There are three months (Jun, July, Aug) which average less than 1" of rain in total, while while October to February average 3"+ ea (4"+ in December).
Regarding Organics, I've no idea what's required to sell as "Organic" in your country, or what market premium that might command. Here in the States, that term is highly regulated.
As to use of scraps and composts, I suspect you will find that a flock of 100 will eat far more of those than you are likely to generate, and that it won't significantly reduce your feed costs, unless you have a large scale source for scraps. Free ranging, based on your weather patterns, looks to be seasonally difficult as well.
I'm not saying it can't be done, I am saying that it looks to be a challenge, and that you should reach out to local and national resources to potentially assist with understanding applicable regulations, any licensing and training requirements, business plan design, and potentially financial assistance in become established, tested, and certified (as needed).
In the interim, check your local markets - what's being sold, and for how much??? What can you sell product for?? At the same time, look to your supplies - what's it cost to buy birds? If you raise your own flock from a smaller number, you have holding and opportunity costs from diverting production into growth. There's local predation, disease, performance variations, and the chaos we call weather...
Lots of research to do, and resources/references to explore. Then you can start putting a business plan together and decide if its potentially profitable. For the majority of us, what you propose would not be, but the situation in the US is vastly different than any other countries.
Good luck in your efforts, whatever you decide.