No easy solutions

I always feel slightly guilty flushing the toilet, but where is the option? There is a lot of talk of green toilets. and chemical or solar toilets.
All these need land. They are fine for rural settings, rich people's farm houses, holiday cabins etc, but living in Ameerpet , Hyderabad or Mandaivelli, Chennai, can it be even thought of?
All solutions I have heard of need space-- a lot of space.
In fact, when I built my house, I had a small extra sink put in the kitchen where I planned to wash my rice/veg etc --no vim/detergent. This sink had a drain that simply led to my small back garden. I was very pleased with my design sure that I didn't need sand filter/soak pit etc for this.
I moved in and used this sink for about a month. Soon every time the breeze came through my back window, I could smell something rotting. Sure enough-the drain. I promptly connected the drain to my regular drainage.
I do not have enough space for a grey water treatment system, which is why I had left my washing machine drain alone , but wash water from rice/dal I thought would not need treatment.
Well it does!
Lesson learnt, there are no easy solutions.