We’re talking at noon on Sunday for our friends at Research Club. It’ll be their 19th Brunch and the first oen featuring composting toilets

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.

As part of the Cewas start up program Mathew and I had a chance on May 19th to visit Tropenhaus, a greenhouse for tropical plants located in the small town of Wolhusen, CH.

The idea for the tropical house began with Johannes Heeb 11 years ago. The motivation was to re-use the waste heat from the natural gas plant in Wolhusen. In 1997 the Swiss parliament passed a law requiring all utilities to re-use at least 60% of their waste heat. With this new mandate Heeb was able to get funding to build two glass greenhouses nearby the natural gas plant. First the natural gas plant runs excess heat through a standard steam generator to create electricity for the greenhouse. next, waste heat from that process is used to heat the greenhouses and a nearby hospital. The heat is directed from the plant to the greenhouse where it is cooled from 540 C to 70 C to help maintain warm air and water in the greenhouse for plants and fish. The greenhouse opened to the public March 2010. the first pilot project of the Tropenhaus was in 1999 in Ruswil, also in the Canton Luzern.

Together, the ‘Tropenhaus’ (literally Tropical house) and the hospital use 40% of the natural gas plant’s waste heat.

Initially the greenhouse was designed purely for production of edible tropical plants like ginger, lemongrass, papaya and bananas. As the project moved along an educational center and restaurant were incorporated in to the plans. The center is now a beautiful break from a cloudy day in the pre-alps and features educational walking tours of the exhibition greenhouse. It was my first time seeing coffee, cotton, pineapple and curry leaves growing in person. I was astounded that I had never had the chance to see, touch and smell these amazing plants that I depend on every day. The exhibition greenhouse features a monthly exhibition, currently about cotton production, a gift shop and a restaurant.

The second greenhouse is just for production. When it was built it was the first time in the world that topical plants like papayas and bananas were grown indoors. Johannes scoured the literature for relevant studies on how to manage such agriculture systems indoors and eventually just began experimenting. Recently they had some problems with insects in the soil around the papaya trees. Chickens are now part of the greenhouse, devouring insects in the soil and providing acoustical performances for visitors. 50 part time staff (instead of 25 full time staff) run the facility and conduct research on the system to share with others who are interested in tropical plant greenhouses. They have much to share, papaya trees are tighed down so they curve like a “J” to all them to grow closer together and keep them shorter while producing fruit.

Tropenhaus is the financially sound manifestation of the 60s dream. They’ve incorporated the best practices of permaculture, aquaculture and polyculture research of the past forty years, and made a profitable business model. The tilapia swim in gigantic tanks which are warmed by the waste heat. The water from the tilapia tank is filtered through a bed of edible plants like water spinach, galgant, lemon grass, and taro which are used in the restaurant. The filtered nutrient rich water is then used to fertilize and irrigate the other plants which grow in the Swiss soil.

While technically fascinating and impressive, the Tropenhaus shines because it’s fun. While we were there several young couples in formal evening wear gathered at the restaurant for drinks, probably heading off to a formal dance. In a small Swiss village, Tropenhaus is (literally) the hottest place to go out. Where else can you where a ballgown in Switzerland in winter? And drink fresh starfruit juice?

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

Streetwork is a great book on environmental education. Nils Norman runs a school at least partly inspired by it in Copenhagen.

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.

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