Use a commode (something similar to off-grid toilet for older people) and collect urine in a container. You could use empty milk gallon containers. After every urine deposit, add similar amount of water just to dilute it. In a couple of days when your container is full, use it to water your favorite plants or trees. It is the best fertilizer and you would save at least 15-20 gallons of water per day per person from being flushed down the sewer line. Urine is germ free, antiseptic and if kept diluted will not stink.
If you want to take this further for brown stuff, investigate composting toilets. There are some interesting products that can help you get off grid and off sewer.