Integrated Farming And Waste Managment Systems
Thoughts on the relationship of if-wms and Sola Roof and the role of waste treatment using a Bio Digester process
from a letter to Tom Riesing of Oakhaven Permaculuture Center
I have some words of caution about Bio Digester processes that I do not think to be appropriate for discussion on the if-wms list. Dr. Chan is a treasure and has more experience than anyone I have heard of when it comes to waste treatment. The anaerobic system for methane from waste needs to become a DIY accessible and reliable method. Years ago I operated small batch experiments using an approach with nested drums. It is good to learn and try out the technology on a small scale first. It seems that George is suggesting that you jump right into a large Bio Digester that requires quite a bit of metal work and salvage. It is a big job - with the painting and such - not a cheap as it might appear at first glance.
Between non functional models and large scale project there is certainly room for drum size bioreactors that can be used to build up experience. You can even have a contiuous methane supply from small batch systems by having three of four that are at different stages of treatment. Plastic drums that are easily opened (no manhole) and cleaned out (not completely) and recharged are able to work with family/family farm waste. This can be a good learning experience. It is a great learning experience to operate a cooker with biogas and use the sludge in the garden or hydroponic system. The benefit of hands on learning at a smaller scale will give you the chance to gain experience that can then be applied to developing improved systems.
I also what to say that the big conceptual difference between the "vertical" and the "horizontal" digesters is that the purpose of the horizontal method is to move towards a continuous rather than batch process. The continuous process is better than just making a bigger tank. There is less chance that the bioprocess can "go off" and produce ammonia. In your installation you will need to be more careful (with a cold season) about how you will maintain the methane forming bacteria at the right temperature. We used a water jacket to keep the temperature steady.
In a batch system there is a combination of aerobic and anaerobic zones which can be adverse due to mixing as new material is introduced. Problems can arise with when there is an effort to make a continuous additions and extraction from equipment that was first conceived to work as a batch process. In a batch system the sludge is not easily handled with pumps and can cake up and create less treated zones. The horizontal tank creates a better configured process from initial introduction (aerobic zone) to stages further along the process that are fully anaerobic to the final stage of stable sludge. It is not such a good idea to have the liquid effluents flowing through a digester. The amount of liquid should be managed; excess is not good but to dry is also a problem.
Steel is a bad idea even if it is a salvage situation. Plastic film might be cheap but it is too week and would not last for years. Cement can be used to build thin shell horizontal cylinders - like large diameter concrete pipe (which could also be a good choice). DIY horizontal tanks can be made over an inflated fabric cylinder. This fabric "form" gives a smooth inner surface and is deflated and removed. I have a proposal for a horizontal cylinder tank that would include an auger like screw that is used to mix (locally) and move the sludge along from the inlet to outlet end. The idea that the sludge will move by itself is a source of problems.
Crude systems will loose methane to the atmosphere and it is is a powerful greenhouse gas as compared to CO 2. Aerobic treatment of waste generates CO 2 in more robust, reliable and fast through put. It is just as technical but less dangerous; producing organic sludge which is just as safe and nutrient packed as anaerobic.
I love so much of what George is doing with the integrated farming - using the ponds and aquaculture as part of a organic gardening system. Organic waste must be brought back into the cycle of production so that nutrients are not lost. As an energy medium I am not greatly impressed with methane. I do not look at energy from livestock waste as a key to a sustainable future. We are overly focused on livestock and justifying our factory farms and excessive meat consumption by rationalizing that manure can be a positive resource for energy and fertilizer. This is just wrong because no nutrients are created; they are only concentrated. Livestock are not "a source" of organic nutrients; they are a pipeline. Up stream is the source, where agribusiness is not organic but very chemical and non sustainable - so even if we use feedlot waste in a more (locally) environmentally sound way - still this would not undo the damage that is inherent in this food production. What is good about IF is that it is not a cash crop orientated system and it is not the goal to produce feed for factory farms but to produce high quality food for people.
We do not need livestock to supply the fertilizer for the organic food supply for people. Growing algae can produce in abundance all the nutrients needed by higher plants, people, fish and animals. The Sola Roof mass algae culture system will use the roofs of all our structures to produce more than our needs for such nutrients. Then the recycling of some of the nutrients consumed back into production again means that every community would have an abundance of nutrients. At the same time, about 50% of the algae biomass is oil. This biomass is also used directly without any biodigestion. Vegetable oil as a liquid fuel is not a GHG (methane is a powerful GHG - much more dangerous to people and the environment) and when combusted it is not a producer of GHG because this is a CO 2 neutral process. Therefore the foundation of self reliance for energy and nutrients is the algae, which is also the base of the planetary ecology. Therefore there will be a biomimicry of the human Hyper Natural? life support for all of humanity and the pattern of nature that supports all other planetary life.
The basic difference of the if-wms approach to food production, as compared to conventional farming is the recognition of the important role of pond culture, which includes natural algae culture - Sola Roof takes that a step further by providing an enhanced level of productivity through continuous, closed atmosphere and controlled environment production. The Sola Roof method, which can achieve a remarkable improvement in yield, is called Phyto Technology? and one of the advantages of this is that we do not need land for ponds but use instead the urban or village roof area of buildings.
I will post this letter at the Sola Roof Wiki where it will be more suitable to entertain this direction of discussion of if-wms. While I would like to explore the connections between these systems I would also not want to divert any of the energy and flow of developments with the application of the if-wms that is now happening. I want both the land based and the built environment based systems to progress at the same time but not have the work on one crowd the other. They both need independent space to develop.
Hope that this was useful for you and that it helps to see the relationship between our work.