The glycerin “waste” from processing can be utilized to produce soaps, fertilizers and in some cases a component in animal feeds . One possible problem with bio-diesel is long-term storage in warm humid environments, but this can be overcome either by closely matching production to use or with biocides added to reduce microbial degradation of the fuel if long-term storage is necessary. Bio-diesel also offers wide application as a fuel for transport, farm equipment, manufacturing machinery and electric generation.While ethanol and methane can be utilized for electric generation, diesel-electric generation is the worldwide standard for power generation at all levels below large-scale developed world power-grids. From power generation for a small to medium sized developing world community to backup power for large building in the developed world, diesel-electric generators are the most well developed and common method for electric power generation . Species and crops utilized in a FFP system can and will vary widely depending on the location of the operation,vertical aeroponpic tower garden available resources, and the needs of the organization operating the facility and associated community. The FFP approach allows each operation to be tailored to local circumstances and in most cases carefully fitting the facility design and the animal and plant species under culture to local environmental and social circumstances will be necessary to realize the full potential of the FFP approach. In general a FFP system will incorporate fish ponds rearing a finfish or shellfish product. The nutrient-rich water from the fish ponds then flows into an agricultural product.

Possible options include a food algae crop, a water intensive crop such as rice, or a hydroponic system which can incorporate a wide variety of traditional terrestrial agricultural crops. The waste water from all crops then flows into algae ponds designed specifically for algal culture for bio-fuel production. Algae are then harvested from these ponds and in the case of bio-diesel production algae oil is extracted from the crop and converted to fuel. The remaining algal material is then utilized in animal feeds, fertilizers, or for the production of other bio-fuels. Waste water leaving a FFP system should be quite nutrient-poor and have a low pathogen load “clean” .Based on the most current research results the High Rate Pond design seems to be the best performing large-scale algae culture system for the species of algae tested as candidates for bio-fuel production to date . It has been used effectively for both microalgae and macroalgae production. Typical design is a large oval raceway with a center divider. Water flow is maintained in the HRP via a paddle wheel and CO2 is injected in the case of high-density culture operations. HRPs are typically shallow in the case of microalgae culture and deeper in the case of macroalgae culture .The major, and I would argue reasonable, assumption this estimate hinges upon is easily achieving a 1% photosynthetic available radiation efficiency from algae under cultivation. PAR efficiencies of 2% and above have been reported for Miscanthus. Large scale algal culture in early pond systems have achieved 10% PAR efficiencies and relatively long-term trials under laboratory conditions have reported greater than 20% PAR efficiencies with microalgae . Given a moderate level of investment in refining current algal culture technology directed at bio-fuel production, PAR efficiencies of 2% should easily be achievable at a commercial production level and in the near future 10% PAR efficiencies may be commercially achievable.From 1978 to 1996 the US Department of Energy’s National Renewable Energy Laboratory ran the Aquatic Species Program . The main focus of this program was the production of bio-diesel from high lipid-content algae grown in ponds, utilizing waste CO2 from coal fired power plants . In the early years of the ASP program a collection of over 3,000 oil producing strains of organisms was amassed from samples taken from sites in the west, northwest and southwest continental US, and Hawaii.

After screening and characterization efforts the collection was reduced to around 300 promising species, mostly green algae and diatoms. The collection is now housed at the University of Hawaii and is available to researchers . At the height of the ASP program much of the work was focused on the physiology and biochemistry of algae as it related to improving oil production in algal organisms—particularly nutrient deficiency as a trigger for increased oil production . While the ASP program found contradicting results using nutrient deficiency culture techniques, their work clearly provided the foundation for more recent work which has demonstrated the utility of nutrient deficiency as a mechanism to increase oil content in algal cells The latter years of the ASP program were mostly focused on molecular biology and genetic engineering techniques for improved oil production in microalgae, and the development of large-scale algae production systems. This work was a major factor in refining the design of the High Rate Pond system currently used by a number of commercial ventures for the production of Spirulina and other commercial algae species, and the algal culture system suggested for food and fuel poly culture in this paper.The majority of public research conducted during the period the Aquatic Species Program was active was either directly part of the program or contract work funded through the ASP. The program’s basic conclusion was microalgae production of bio-diesel was technically feasible but economically unfeasible. The program concluded the factors effecting cost the most were biological, and not engineering related. Even with favorable assumptions of biological productivity, their projected costs for bio-diesel were two times higher than petroleum diesel fuel costs at the time . At the time this conclusion was made oil was at approximately $25 per barrel. The program was closed by the US Department of Energy in 1996, but a number of the researcher involved continued to work in the area of energy production through the culture of microorganisms.

After the closure of the Aquatic Species Program the majority of public research work on microalgae for bio-diesel production shifted to academic institutions—mostly in the US, Japan, Israel, and more recently China. The vast majority of this work has been high-tech in nature and only really appropriate for further development and application in industrialized nations. The focus of this recent work is split to opposite ends of the spectrum. The majority of the work is narrowly focused on lab-scale research on the characteristics of individual microalgae species – such as lipid profiles– or oil extraction and processing techniques . A much smaller collection of work has focused on rough calculations of the economics and engineering of utilizing microalgae for bio-fuel production as a method to replace large portions of the world’s energy needs—such as replacing all petroleum used by the US for transportation . Through an extensive literature search I was unable to find any public research work moving towards application of algae culture for bio-fuel production to small or medium scale ideas/projects. Though it does appear that some research at this level is being conducted in the private sector, but results –for obvious reasons– have not been published.A primary hurdle encounter culturing microalgae outside of a lab environment –particularly large-scale production in open ponds– are problems with species dominance and predation. Indigenous species of algae frequently will out-compete domesticated species under culture replacing a crop of high-lipid algae with an unusable product. Similarly zooplankton predators can invade a pond system and consume a significant portion of the target species under culture. This has been a significant issue for all research work on large-scale production of microalgae for bio-fuels . Huntley and Redalje discuss the use a two part culture system that seems to address the problem of species dominance and predation effectively. In their system a permanent colony of the algae under culture are maintained in a closed photo bioreactor at high densities. The colony in the photo bioreactor is used to inoculate grow-out ponds with an algae harvest cycle of 3-4 days. This method advances target algae species growth in the grow-out pond which allows harvest to occur before problems of species dominance and predation can take hold. This appears to be a major advance in large scale microalgae production. Other difficulties with large-scale culture of microalgae for bio-fuel production include problems maintaining suspension in the water column of the grow-out pond, difficulties with harvesting and extraction of lipids, DO supersaturation, and photo inhibition where algal cells collect moresolar energy than can be utilized in photosynthesis causing damage to the cell . A further hurdle to application to the FFP system is the generally technical nature of current large-scale microalgae culture systems for bio-fuels. Example, most designs utilize CO2 injection to achieve maximum production per given area and to stabilize pH. Some, like the two part culture system described above,vertical gardening in greenhouse incorporate large lab like components in the facility. I would argue that microalgae culture for bio-fuel production holds great promise for the industrialized world, but in the short-term it is likely too technically and engineering intensive for the food and fuel poly culture concept. Long-term, as the culture technology develops and matures, microalgae for bio-fuels could be retooled for use in small to medium scale projects in the developing world.Given the current state of algae culture technology, I would argue that large-scale macroalgae culture for the production of bio-fuels offers a number of significant advantages over microalgae culture and is likely the best candidate for the food and fuel poly culture concept. The poly culture system remains basically the same.

With the only major addition being attachment structures in the High Rate Pond system such as float or rope attachments similar to what is currently already in wide commercial use . Macroalgae culture technology is well established at the commercial level and grown commercially in many parts of the world. Japan has produced around a half million tons annually of Porphyra, Undaria and Laminaria sp. for decades . Culture difficulties such as maintaining target species dominance within the grow-out pond and predation by unwanted organisms are greatly reduced in macroalgae culture when compared to microalgae. Macroalgae harvesting can be accomplished through simple hand or mechanical means, and extraction of lipids would likely be very similar to the techniques used with terrestrial grain crops such as soybeans. In the case of application to a FFP system, the macroalgae component could be designed with the goal of efficient moderate intensity production as apposed to maximum productivity. This would replace the need for CO2 injection with a simpler aeration system, and should eliminate the problems of DO supersaturation and photo inhibition. While a few reviews of the potential for macroalgae to bio-fuels have been published , actual research work on macroalgae culture for bio-fuel production appears to be completely lacking. This leaves two major questions unanswered regarding utilization of macroalgae culture in a FFP system. First, are achievable PAR efficiencies under culture at least close to that of microalgae? At first glance, I would argue macroalgae PAR efficiencies for some species are high enough to fit in the FFP system. Example, Gao and Mckinley projected the production of Laminaria japonica on an annualized basis to be 6.5 times the maximum projected yield for sugarcane on an areal basis. Second, what are the oil and sugar profiles of species with acceptable PAR efficiencies? At this time I am unable to find any published work detailing oil or sugar profiles of macroalgae.The food and fuel polyculture concept offers two distinct opportunities as a conservation tool. First, human generated nutrient-rich waste streams pose a significant threat to aquatic ecosystems around the world. Remediation of nutrient-rich waste streams is inherent to the FFP system—the concept values agriculture and aquaculture “waste” as a commodity to be captured and converted into fuel. The conservation action of reducing discharge of nutrient-rich waste should occur with little or no political/economic input. Second, production of world capture based fisheries has peaked and continued over exploitation likely will lead to even lower production in the future. Aquaculture will be key to meeting future world demand for fisheries products and reducing fishing pressure on the world’s aquatic ecosystems. Reduction of fishing pressure on local ecosystems is an opportunity presented within the FFP concept, but NOT inherent to the concept.