Progress 06/01/15 to 01/31/16
Outputs
Target Audience:Target audiences include the following: - Rural communities and farmers looking for an new crop and source of revenue to exploit - Farms and concentrated animal feeding operations (such as dairies, poultry, and hog farms) interested in manure reduction and nutrient recycling - Urban, suburban, rural communities, and grocers looking for more environmentally friendly and sustainable ways of disposing of food waste and manure - Government and non-governmental entities looking for ways of reducing the production of greenhouse gases, agricultural run-off, and bacterial counts - Manufacturers and supplies of feed for pigs, poultry, and aquaculture - Waste disposal companies - Suppliers and users of organic fertilizers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Part of the results of this research were included in a proposal to the EPA's Nutrient Recycling Challenge. We are currently preparing a paper regarding the remarkable differential between the greenhouse gas emissions of conventional microbial composting and BSFL-mediated composting. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
BSF larvae do not live deeper than about 7cm within a food pile precisely because oxygen levels are typically not adequate for them to do so. Feed slurries of the type that would be used to process manure and ground up food waste rapidly settle and compact, forcing oxygen out of the pile even in the absence of BSF larvae. These portions of the pile become effectively anaerobic within 10-20 minutes. The depletion of oxygen becomes more rapid in the presence of larvae, probably as a result of the additional oxygen demands caused by respiration. Even when a concentration of larvae as small as 1 larva/cc of volume is present, oxygen becomes depleted in half the time that it otherwise would: roughly 5-7 minutes. Unless oxygen levels can be restored by use of technical means it would be difficult or impossible to grow massive numbers of BSF larvae at depth, and thus within relatively confined spaces such as farm buildings in temperate climates. The burrowing and movement of larvae can serve to aerate an otherwise compacted food pile, but seems to reach a practical limit at a depth of about 25-50mm (1-2 inches). The presence of "bulking agents" such as pine shavings and crushed charcoal appears to substantially enhance the ability of BSF larvae to burrow and move through the feed pile, and may partially correct the adverse effects of settling and compaction on oxygen levels. The addition of a rigid or semi-rigid matrix material to the feed pile is a completely new and unexpected agricultural innovation that is a direct result of this research. Using matrix material to suspend feed within the pile, preserve air spaces, and provide an easy avenue for larval migration at least doubles the maximum depth at which oxygen level can be sustained at approximately 100 hPa - from roughly 75mm (3 inches) to 152mm (6 inches) - even without any additional interventions. The use of matrix materials could be implemented in BSF feeding operations immediately, and promises to at least double feeding productivity per square foot of surface area utilized. The technique can be further combined with other measures such as mixing, turning, or pumping air through the feed pile. The presence of a matrix material alone cannot prevent oxygen levels from falling rapidly within the pile at depths greater than about 6 inches when a substantial concentration of BSF larvae (≥ 2.5 larvae/cc) is present. Although air could be bubbled through the medium in an attempt to replaced oxygen that is used through respiration, the need to replenish both food and oxygen in the deeper portions of the pile suggests that a mixing process such as rotation of the matrix substrate will still be necessary even if a bubbling system is used to replenish the supply of oxygen. BSF larvae "vote with their feet" (or in their case, crawling). Migration experiments appear to support our hypothesis that larval distributions within a pile are primarily a function of oxygen if adequate amounts of food are present. Small concentrations of larvae feeding in a matrix material such as hazelnut shells simply do not seem to care where they are within a pile as long as their respiratory demand does not overwhelm the oxygen available. If this oxygen can be replenished on a regular basis in the presence of a semi-rigid matrix that prevents the pressure on individual larvae from becoming too high, there is no reason to believe that BSF feed piles cannot be made as deep as one might wish without having an adverse impact on growth. This result may have a huge practical impact on future commercial operations. First and foremost, mixing a loose matrix of hazelnut shells, and larvae continuously and for weeks at a time did not appear to have any adverse impact on larval health or their ability to feed, grow, or move. In some respects this is one of the most important finding of the research since it validates active mixing as a potential means of aerating deep BSF feed piles; thereby allowing commercial operations to grow large numbers of these insects indoors. Mixing in general, and mixing by rotation in particular, is an effective means of increasing the level of oxygen deep within feed piles to a depth of at least 19", and very possibly deeper if the rate and/or efficiency of mixing can be increased. Our bin's feed pile during this part of the research had a surface area of 5.92 sq. feet (just about 2 ft. x 3 ft.). In order to grow an equivalent number of larvae in a conventional feeder bin (maximum feeding depth of about 7cm), you would need to have a bin surface area of 37.28 sq. ft., (a square 6.11 ft. x 6.11 feet). From a surface area perspective, this method of cultivation is 6.3x more efficient than a conventional BSF feeder bin, and we are confident that it can be made far more effective - probably at least 10x more efficient. This has profound implications for large-scale BSF larval culture and recycling of the nutrients contained within food waste and manure. Based upon what we've learned from this design, there is considerable room for improving the design and efficiency of mixing feeding bin systems. It should be possible to minimize or eliminate any areas of reduced mixing such as the central "vortex" encountered in this initial experimental design. Containers should be ideally be injection molded into the desired shape if made of plastic, or welded if made of metal. Any joints must be completely tight and/or thoroughly sealed with material (such as "Great Stuff" foam) that does not offer an obvious junction to exploit. It seems likely that the tendency to seek out narrow exits could be used to create migration paths that do not require that traditional ramps be attached to an otherwise enclosed system. This has implications for the design of future larval feeding bins. Our results demonstrate that any commercial BSF farming operation will require access to one or more facilities that are dedicated to mating, egg laying, and egg hatching to ensure a steady and reliable supply of larvae for feeding. To our knowledge, this is the first time that any attempt has been made to quantify the comparative environmental impact of insect-mediated versus microbial composting. We will work to publish these results in the scientific literature. BSF-mediated composting results in substantially fewer greenhouse gas emissions (over 40% fewer) than conventional microbial composting or burying organic materials (manure and food waste) in landfills. If we assume that chicken feed has the same carbon profile as typical food waste, we can estimate the differential effect on GHG production that would occur if food waste were consumed by BSF rather than being composted. According to our calculations, for every 1,000 tonnes of food waste the use of BSF would result in emitting 62.6 fewer tons of carbon dioxide being produced than if the same amount of material were to be aerobically composted using conventional microbes. If one were to take just the un-recycled food waste produced by the U.S. and used BSF to degrade it, it would release 2.39 million fewer tonnes of CO2 into the atmosphere each year. That's all of the CO2 produced by 140,628 average Americans; about the population of Hollywood, Florida or Sunnyvale, California or the whole GHG output of Fiji. (While this is a relatively small amount compared with the CO2 produced by fossils fuels, worldwide use of BSF-mediated composting would have a substantial impact. Worldwide, approximately 1.6 billion tons of food waste is produced each year.) These calculations do not include potential reductions in the amount of greenhouse gases produced by American agriculture each year. Over 335 million tons of farm animal manure "dry matter" is produced in the U.S. annually, compared with only about 12.6 million "dry" tons of un-recycled food waste. This is over 26 times more manure than food waste by weight. Virtually all of this material is a potential feed source for BSF larvae.
Publications
- Type:
Journal Articles
Status:
Other
Year Published:
2016
Citation:
None
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