I'm going to go out on a limb here and venture to say that 90% of the residents of the San Joaquin Valley are farmers of something, including me. With an advantageous climate and generously long growing season, most folks at least have some herbs growing in a sunny window and tomatoes of all kinds flourish in backyard gardens up and down the valley.
Clyde and I give over more backyard space to the vegetable garden every year and every year I endeavor to grow a humongous pumpkin for Halloween. I haven't grown my bean bag chair size specimen yet, but someday. There are no water restrictions yet in our area, but they are coming and I grew up in the 70's when a prolonged drought hit the valley, so water conservation is always a concern for me.
Over the last 10 years I have slowly begun to see my kitchen and my garden as two complementary things rather than two separate things. It is a more holistic approach that stems from my desire to conserve resources and funds, Clyde and I are well known to make it ourselves rather than go out and buy. So I have come to realize that it is not a one way road from garden to kitchen, but a rather well trafficked two way street.
Composting is the first and best use for kitchen scraps of all kinds, from coffee grounds to decaying salad greens, if it's not a protein, toss it in. Composting is almost vital here in the Sacramento area to condition the red clay hardpan into well-drained soft, black dirt which requires less irrigation. Egg shells, paper products, used cooking oil and so many other things go into my compost piles that most people just throw away.
But there is a lot of water in your kitchen to be reclaimed as well, more than just water though, in a way it is plant food that is just being drained away. How many steaming pots of pasta do you make a year? How often do you rinse the rice? Do you just empty bottles of flat soda or sour wine down the drain?
All of those can be used to feed and water your indoor and outdoor plants too. All those wonderful free starches that have come loose from the rice and grains are just another form of nutrition, as are sugars of all kinds. I do recommend diluting very sugary things with water before feeding them to your plants, too much sugar is bad for any creature and attracts unwanted pests. Salty liquids are the exception to this, do not water your plants with salty liquids although it is fine to put those liquids into the compost pile. Also make sure that the reclaimed water is at least room temperature so you don't inadvertently boil any tender roots.
Just about any cooking liquid can be reclaimed for your garden, from the lobster boil to poaching wine to simple syrup. I like to think that my flowers are brighter and my veggies tastier because they benefit from a well rounded diet