A lack of toilets are a persistent problem at Ephemerisle. Arranging a way to handle your biowaste in a sanitary fashion is a key responsibility of every attendee.
The sewage holding tanks on boats tend to be very small, and are expensive to pump out at Ephemerisle. Never use someone's toilet without asking first.
If you've built a platform / art boat that guests will be living on, you will need a way to handle your guest's waste. A bucket toilet system is probably the simplest waste management system that is practical for a camp of 4 - 10 people.
A number of islands have rented Porta Potties and put them on barges or docks.
Boat Holding Tanks
Most boats have a built in holding tank that stores waste and needs to be pumped out before they fill up.
Septic Brothers comes around at least once during the week to pump out holding tanks. In 2021, I think the prices had been raised to $100/boat.
A more sophisticated bucket composting system:
How to properly dispose of human compost
A Perfect Composting Toilet For Camping Or Emergencies
Portable Emergency Toilet Seat for 5 Gallon Bucket (https://www.amazon.com/Portable-Emergency-Buckets-Outdoor-Luggable/dp/B07RZQBQNH/)
(Alternatively, make a lid from a hardware store toilet seat: (https://www.instructables.com/DIY-Camping-Toilet-Bucket))
Compostable trash bags, 8 gallon, 50 count (https://www.amazon.com/gp/product/B07TFMGX3Z/ref=ewc_pr_img_1?smid=AJVD03PRD8VF4)
Wood pellets, 40 lb (https://www.lowes.com/pd/Golden-Fire-40-lb-Wood-Pellets/3522746) Wood pellets, 20 lb (https://www.homedepot.com/p/20-lbs-BBQ-Oak-Blend-Pellets-PEL344/312450526)
Gamma seal lid (https://www.amazon.com/Gamma2-4123-Gamma-Seal-Lid/dp/B0089QJQTS/) Home Depot brand screw top bucket lid (https://www.homedepot.com/p/Bucket-Companion-5-gal-and-3-5-gal-Screw-Top-Bucket-Lid-in-Black-LD5GRLBK006/303808738)
Scoop, 32 oz - for distributing cover material (https://www.amazon.com/Rubbermaid-Commercial-Service-64-Ounce-FG288500WHT/dp/B000HHM4KA/)
Paper towel dispenser - for hands free towel dispensing (https://www.amazon.com/Pacific-Blue-Basic-Previously-23304/dp/B000JKA9Q6)
Paper towels - c-fold style - for washing hands after use (https://www.amazon.com/Pacific-Blue-Basic-Previously-23304/dp/B000JKA9Q6)
Spray bottle, 1% bleach solution - for periodically wiping down external services (https://www.amazon.com/Bealee-All-Purpose-Spraying-Cleaning-Adjustable/dp/B07QXNYRM6)
Hand sanitizer - for cleaning hands after toilet use (https://www.amazon.com/Rubbermaid-Sanitizer-Alcohol-Based-Bottles-2140739/dp/B08CY4ZYTG/)
Camp table - for holding paper towels, spray bottle, etc (https://www.amazon.com/Camp-Field-Camping-Adjustable-Backyards/dp/B07K7DY22F/)
Paracord / bungee cord (https://www.amazon.com/TOUGH-GRID-550lb-Green-Paracord-Parachute/dp/B06VWK5Z5N)
1. Insert two composting bags into bucket. The extra bag helps prevent leaks if one bag is punctured. 2. Secure the bags to toilet with a bungee cord or paracord using a constrictor knot. 3. Attach toilet lid. 5. Put a couple of scoops of cover material (wood pellets) into the inner before first use. You want a layer 2.5 - 5 cm deep. This will help absorb urine and prevent bad smells. 6. Poop / pee. Wipe with toilet paper and drop paper into bucket. 7. After use, scoop pellets over poop / pee from the second bucket until waste is no longer visible. It should take 2 - 3 cups. 8. Wash hands with alcohol spray and dry with paper towels. 9. To extend the use of toilet, put paper towels in trash can, not composting toilet. 1. Periodically wipe down bucket seat with bleach solution. 1. When bucket is full, tie bags together and transfer to a second bucket, and attach gamma lid until waste can be disposed. 1. Dump bags into compost bin, compost pile, or trash bin.
The average person produces 12 ml/kg/day of urine and 5 g/kg/day fecal matter. The average adult in the US weighs 82 kg (180 lbs), so that means each person produces ~1 L (34 oz) of urine, and ~0.41 kg (1 lb) of feces per day. If we assume that feces has the same density of water (1 g/mL), then 0.41 kg of feces takes up 0.41 L.
Total volume of waste is therefore 1 L urine + 0.41 L feces = 1.41 L
If we assume cover material and toilet paper are equal in volume, that means that the average person will produce a 3 L volume of waste per day.
A 5 gallon bucket has a volume of ~19 liters. So, the average person will fill a bucket in about 6 days.
A 40 lb (18.14 kg) bag of wood pellets contains 640 oz. A single bag should last a single person about 12 days, assuming 1.41 kg (50 oz) is used per day).
So, a camp will need 1 bucket/person/week plus 20 lb bag of pellets/person/week.
For a 10 person camp, that would be 10 buckets plus five 40 lb bags of pellets.
Note - This was apparently prepared for Burning Man or Plan B. Out on the water, some people, sometimes, might pee in the waters of the Delta instead (despite it being against the law).