At the The International Ecotourism Society (TIES) conference at the Patel College of Global Sustainability at USF Tampa in January of 2016, as part of a hands on sustainability workshop, Dr. T.H. Culhane and students from the Patel assembled an early version of the Israeli HomeBiogas system that had been donated to the college through Dr. Culhane for research and education.
The system was an early version of the biodigester with a very heavy steel frame and experimental woven/sewn mesh bags connecting the rubberized digester tank to the exoskeleton frame. The company was exploring more durable and lightweight materials for subsequent models that would help lower manufacture and shipping costs substantially.
The system was displayed empty on stage in the auditorium for the delegates and guests during Culhane's keynote and then the students placed it outside the Patel Building behind the kitchen for photography to show a possible location for the small household scale digester.
The HomeBiogas system was then moved into the elevator and taken to the Patel College reception area on the second floor and put on display as a floor model from January to August of 2016 with literature and brochures explaining its operation.
In mid August of 2016 when Culhane arrived from Germany to begin working at the Patel College he was asked to find a location for the digester where it could be "commissioned", i.e. filled with water and horse manure and put into active use for research and education. Because there were few people familiar with the system and no institutions at that time interested or willing to provide a location, it was determined that the best immediate place for the HomeBiogas system was in the backyard of the home that Culhane was renting, belonging to former Patel student Ryan Whitson, who had been at the TIES conference assembling the system and had accompanied Culhane to West Virginia in March of 2016 to build basement biodigesters in an eco-lodge and had familiarity with the systems and their operation and understood their safety and effectiveness.
Eric Weaver, a Ph.D. student at USF who works at Patel, and his son Chris Weaver , who teaches architecture at USF, transported the system in their pick up truck from the Patel College to the Whitson residence at 3411 West Abdella St. Tampa 33607 and over the next couple of days Culhane began experimentation with the digester.
Innoculant and gas production results with digester:
The first experiment that Culhane ran with the digester was to see if it could begin operation without needing to be innoculated with animal manures. Because Culhane did not have a car and was dedicated to spending the first semester riding bicycles and public transit buses as part of his commitment to sustainability, he wanted to show that the digester could be started using a powdered innoculant that was lightweight and easy to obtain, instead of needing to gather 100 kg or more of fresh horse or cow manure, as is the usual custom. This would enable people in developing countries and poor regions of advanced economies who cannot access or afford pick up trucks get their digesters going with something that can be carried in a hand-bag, substantially lowering the material and labor costs associated with setting up digesters.
Culhane began by obtaining different commercial septic powder preparations: RidX, and SeptiPak. The use of two powders was done to increase the odds of success since there was only one digester and it takes many weeks to see results. There was worry that if a single preparation was used and it didn't work we would lose time before the winter cold set in. In future it would be of interest to try out each different commercial septic powder individually to see which works and which doesn't (they might all work!) and which produces the most immediate and best results for the price.
Culhane then filled the digester tank with water and septic powder and waited. It took 5 weeks before the first flammable gas was produced and Culhane began feeding the digester food waste and grass clippings.
Unfortunately, as can easily happen with small scale biodigesters that are started without the benefit of the fibrous material found in raw animal manures, the methanogens growth rate couldn't keep up with the rate of acidogenic bacteria growth and the system went acid. Soon all it was making was carbon dioxide gas and the effluent began to smell acrid.
On September 11th Culhane found the pH to be as low as 5 and had to remediate the biodigester with 11 Kg of sodium bicarbonate (baking soda) purchased at HomeDepot from the pool section. After balancing the pH to near neutral (7), Culhane reinnoculated the system with more septic solutions:
Once the system had recovered, which took another couple of weeks, the digester worked reliably. By September 28th, fed on food waste and grass clippings, it began to produce enough gas to cook on.
This was important because Kim is helping demonstrate to the city the safety of homebiogas so that appropriate code can be written that will obviate the unreasonable fears that people have about the system and help us move forward in getting it approved for institutions (it is already CE and ISO 9001/9004 listed and approved for households, but some institutions in the US still seem to have concerns that need to be allayed through demonstration.)
Culhane then used the weekend to modify the grill for use with biogas as documented in the following video:
Culhane demonstrated the success of this easily modified grill to Maryann Bishop from the non-profit organization "Rosebud Continuum" in Land O Lakes, where the family was working with Solar CITIES, Culhane's 501C3, to build a much larger cement Puxin digester (10m3) later that week, to give the family confidence and experience in home scale biogas before they invested in a much larger and more expensive and permanent system built out of concrete:
Durability results for early model of digester:
With continued use of the digester on a daily basis at the residence where Culhane was testing the beta model of HomeBiogas it was noticed that the expansion of the digester bladder over time was causing the hanging bag that attaches it to the frame of the digester to tear:
The unit had been a beta testing demo unit, with a heavy steel frame and hanging bags that were still under test and Solar CITIES has been given the honor of field testing units as they evolve. Since the time that this unit was developed and sent to USF, the company has learned many things and completely changed the materials used to make the digesters. The most recent units are made from different plastics and the heavy steel frame has been replaced with light weight aluminum among other substantial changes.
From a research perspective we learned a lot from this "early adopter" use of the system here in Florida.
Expansion to other Locations before Christmas
By November of 2016, despite the expected slow down in gas production caused by low winter temperatures, Culhane had demonstrated to many Patel students and community visitors the promise of small biogas and got permission to build hand-made Solar CITIES IBC tank varieties of household scale biodigesters in several locations. Working with teachers and students from Blake High School, where Maryann Bishop's daughter is a coach, with funding from the Bishop's for materials, Solar CITIES and Patel students built two IBC tank biodigesters, one for the High School and another for the Faith Lutheran Evangelical Church.
In these locations we experimented with a new design using the lid of the digester as the feeding inlet pipe, finding that it creates more rigidity but that the uniseal needs better sealant.
New Year Location Change and New Experimental Locations
When Culhane returned from the Arava Institute and the Clinton Global Initiative Volunteer Solar CITIES projects in Israel, Palestine and Jordan in January he found that he and Ryan had to move out of the house on Abdella immediately as the house needed renovation.
Culhane was invited to move into the Bishop residence at 22843 Hale Road, Land O Lakes Florida, 34639, on the farm property where the Bishops are building the Rosebud Continuum Educational Center 501C3 that was co-created by former Patel Student Michael Kuras with other graduates of the program (among them Eve Spengler, who runs a composting company, and Ericka McThenia and Mary Bishop) and with Professor Joseph Dorsey. The center has been proposed as a site where the Food Energy Water Nexus can be put into real-time practice where students from High School through Graduate School can come and do research and implement ideas and experiment.
We had already built a Puxin digester there:
Because it was imperative that all of Culhane's belongings be moved out of the residence at Abdella and there was still no location at the college to house the digester, which was by now falling apart,
A decision had to be made about whether it was worth it to continue to try and work with the digester with the worn out materials or retire it (i.e. dispose ot it). Culhane decided it would be within the spirit of the original intent of research and education to see if the system could be repaired.
Eric Weaver came with his truck and we decided to move the digester to the new residence where Culhane would be living in Land O Lakes and try to fix it there and see if we could get more life out of it. We drained the system of all of its biodigestate and lifted it onto the truck.
The picture below shows the torn hanging bag very clearly:
The weather was cold so it took a couple of weeks to begin producing gas again, but the repairs Culhane and students made were a success.
After his Keynote speech to the Recycle Florida Conference, visitors from the Recycle Florida group, organized by Key West City Planner Dee Dee Green, who had met with Patel professors and students to discuss Biogas potential at Key West City Hall, when Dr. David Randle and Louis Zunguze and Culhane conducted their Keys Marine Lab field trip, were invited to come see the digester in operation.
Extending the Project based on lessons learned:
In late January, seeing the enthusiastic response of the students in the new Navigating the Food/Energy/Water Nexus class at the Patel for getting involved with hands-on research on small biodigesters, Culhane funded his own Solar CITIES 3 IBC biodigester system to be placed at the Veteran's Garden at the Sustainability Living Center by the Salvation Army across from the Lowry Park Zoo and invited students to come on the weekend and build with the other community volunteers to gain the "biogas bricolage" experience.
In addition to this, following a presentation and meetings Culhane had made in November and December at the Museum of Science and Industry for/with STEM/STEAM Science educators, the class was invited in the new year to share their expertise at the Butterfly Garden. The plan was to build a Solar CITIES hand-made system which the students had experience with, and Culhane donated one of the new and improved and more robust HomeBiogas systems he had purchased to MOSI so that they and the MOSI community could get hands on experience building/assembling digesters and have an active system within easy walking distance of the Patel College that they can begin doing research on.
Culhane is equipping the system with Arduino microcontrollers and temperature sensors and the students will begin to gather and log real-time data that correlates feeding rate and feedstock with temperature and pH and gas production.
Future projects being planned through the Patel College are to extend this work to the city of St. Petersburg, starting with USF project sites at the St. Petersberg Eco-hostel, the Marina, the Yacht Club and even the Amara Zee caravan boat, which can spread the knowledge around the world.