This could really set composting toilets back in the US. Coverage in the NYT here. Hyphae Design Lab, a design firm in Oakland is claiming three totally erroneous things, and it looks like the city of SF might buy their load of…

1) The revenue from nutrients recovered from excrement can pay for toilet servicing. A year of your urine is worth about $4.13 based on its nutrient value. If its impossible to service a toilet in the Philippines for the value of urine, its not going to work at US wages.  Also, the 19th century sewage systems of Paris, the collection systems of Manchester, UK, all failed to turn a profit.  Didn’t work then, doesn’t work now.

2) Urine diverting toilets work in public facilities.  To be blunt, people crap in the pee hole.   I don’t have a good single citation for this, just conversations with Seecon and others who have tried UDDTs in public areas.  To quote:

When new user-interfaces or management approaches have been introduced, such as Urine Diversion Dehydration Toilets (UDDT) or a new system for composting of kitchen waste, which heavily rely on the correct operation from the user’s side, the end-users have to be properly trained to ensure that they will operate the systems correctly.

3) UV sterilizing lights, can be used both as “lanterns” to attract users and to kill germs.  This isn’t possible, because looking at UV-C rays causes blindness.

So a note to Hyphae– please spend more time on research, less time making press-friendly vector graphics.

I wanted to host here Earle’s finished presentation on toilets, following the nitrogen pollution in Cape Cod back to its point source.  Here is the PDF

Our first problem running aeration tests is to measure the effective aeration of our system. As detailed below, the New Alchemy Composting Greenhouse -our inspiration- doesn’t appear to have done this calculation right. No wonder, when we couldn’t find an accurate low-speed air flow meter, let alone afford one. Even $500 units for HVAC testing weren’t accurate at really low speeds.

So we built our own meter- an inflatable tube that has 1 cu ft volume for every foot of length. It took about 20 minutes, and cost less than $0.20 because I build a lot of balloons and have lots of plastic. The circumference of the tube is 3.545 feet, if you’d like to make one. I like this solution a lot, although using it looks totally ridiculous:

Our Aeration Rate-

We have about 200kg of compost with a volume of almost 1 cu meter (0.94 cu m), and an effective aeration rate of 3cu ft per minute (85 liters). Our maximum aeration rate is therefore 0.43 l/kg/minute.  Given our review of existing research, we ran our first test with the fan on continuously.  The center of the pile got to above 170 degrees for 4+ days, but the edges barely heated up at all.  Although this is fairly typical of a compost pile, we’re hoping to get a broader temperature increase.

Our Next Test

During our next test we’ll decrease the aeration rate to slow down biological activity in the middle, and hopefully allow more heat retention on the sides.  This decision would seem to contradict the findings of Yamada, et al, so lets go look at the research!

Forced Aeration according to Yamada, et al (Waste Management):

Yamada, et al got the best results with 2 l/kg/min.  We can’t even get that high, and will probably overheat the center of our pile if we increase aeration.

Forced Aeration according to New Alchemy:

Review of the numbers below, but there are issues with their calculation- the rate is somewhere between 0.02-0.62 l/kg/min.  From their documentation:

A single 1/15-HP (50-watt) Dayton 2-speed blower rated at 310 cubic feet per minute (8.8 m3/min) at 0 inches static pressure pulls oxygen-rich air from the greenhouse atmosphere and blows it underneath and through the compost. We use the fan at its lower setting where it moves about 190 cubic feet per minute (5.7 m3/min), with power consumption of about 80 watts. This blower is timer-controlled to come on for 15 minutes every 6 hours, or a total of 1 hour every 24 hrs. The compost chamber therefore receives about 12,000 cubic feet (340 m3) of air per day under normal operating conditions.

Pg 9 “The Composting Greenhouse at New Alchemy Institute: A Report on Two Years of Operation and Monitoring” March 1984-January 1986. New Alchemy Institute Research Report No. 3, Bruce Fulford.

Given our blow tests we know that 0″ static pressure is completely unrealistic in a compost pile. At 0″ static pressure we should get 75 cu ft/ min. Under 1 yard of compost we’re getting 3 cu ft/min. New Alchemy’s bins were 25 cu yards, and if they had a mixed density like our compost (about 0.2kg/l), and therefore 3800kg of manure in their bins, given their average aeration rate of 83cu ft/ min (12,000/day) (2350 l/min) they had a rate of 0.62 l/kg/min, if we trust their numbers. If their blower performed like ours (and we have no reason to believe it did) they’d have gotten 7.2 cu ft/ minute, not 190 out of it, and their actual aeration rate could have been as low as 0.02-0.03 l/kg/min.

“We are developing Protei : a low-cost open-source oil collecting robot that autonomously sails upwind, intercepting oil sheens going downwind. Protei combines conventional technologies in an innovative design that we can implement in the short term to address timely environmental crisis.”

 

Design Observer: Flush with Inequality: Sanitation in South Africa by Barbara Penner

Jonathan also used us as an example of DIY infrastructure projects at the DIY Citizenship conference at U. Toronto’s Center for the Study of the United States.  Thanks!

Continuous interaction with cottage owners has been essential to the success of this project. Many cottage owners were apprehensive about abandoning a unique and functional waste disposal method that they had used since child- hood. Others voiced concerns about potential odors, mechanical failures, and operation and main- tenance responsibilities.

Also:

The city’s remaining pail service employee has been incorporated into the watershed inspection team, allowing for a more productive use of staff-hours.

What I find most interesting is that despite buying SunMar and other under-seat composters, the need for additional composting was recognized.   They built 1-yard bins and empty their toilets into the bins! they could’ve just gone from pails to bins and skipped the expensive toilets.