Black Soldier Fly Digesters – Converting food wastes into feed, fuel and fertilizer

Scalable Biosystems for Sustainable Energy Production

Introduction: Concerns over rising energy demands and dependence on fossil fuels have led to a great deal of research into renewable energy.  While sources like wind and solar show great potential for electricity generation, there will also be a need for renewable sources of liquid and solid fuels for both transportation and biomass gasification. Current sources of University generated waste can be diverted to displace 35%-50% of diesel fuel demand on campus, as well as contribute to biomass production for biomass gasification to supply steam to the West Campus.  The objective of this project is to construct a scalable biosystem for conversion of food wastes into biodiesel fuel, renewable gasification feedstock, animal protein feed and compost.

Our Creative Inquiry on Value added Co-products Stands by the freshly loaded digester

This multi-faceted project aims to displace an additional 4,000 gallons of petro-diesel through algal and pupae lipid production, as well as divert 209,000 lbs of solid organic waste from Clemson University Facility and Maintenance Organization’s ( CU FMO) disposal. Its scalable design will allow further expansion and replication upon proof of concept.  Mr. Tony Putnam, Director of Utility Services for Clemson University, has indicated his support for this project: “ University Facilities takes seriously our role to create, enhance and maintain a high quality learning environment. In particular, we strive to provide ‘living lab’ opportunities for students and faculty collaboration with our organization. This project is especially appealing to me since it examines multiple processes that can be immediately developed and implemented on our campus to minimize landfill waste as well as exploring alternatives to produce our own clean renewable energy to reduce our campus carbon footprint.“

Why BSF? Similar to the common “vermiculture digesters” utilized across many varying scales of production, this proposal offers an alternative to the use of earth worms and nightcrawlers. Instead, the larvae of black soldier fly, Hermetia illuscens, ubiquitous throughout North America, are voracious consumers of nitrogen-dominant decaying materials, such as kitchen food scraps or manures. Dried pre-pupae contain 42% protein and 35% fat, and as a component of a complete diet they can provide an excellent feed for chicks, swine, rainbow trout and catfish (reviewed in Newton et al. 2011).  Additionally, BSF have been demonstrated to digest over 15 kilograms per day of waste per square meter of feeding surface area per day. According to a current Clemson Recycling Services study ~209,000 lbs of food waste could be collected annually from all dining halls on campus. Based on data from previous studies, this amount of dining hall waste could generate:

▪33,551 lbs of dried BSF pupae to process into oil and protein meal using existing equipment

Mature pupae self harvest

▪45 tons of dry compost for use as a soil amendment at the Student Organic Farm

▪4,473 gallons of oil (based on 35% lipid content of pupae by weight) with a biodiesel value of  $16,774 based on $3.75/gallon cost

▪10.9 tons of protein meal by-product from the oil processing procedure with a value of $5,500 based on value of fish meal

Dan Fleetwood and a group of Civil Engineering students helped with our project and put together this informative video:

This is our second week operating the system, and so far the critters have consumed over 400 lbs of cafeteria food waste. This number should increase exponentially as our BSF population increases. We started with 9000 young larvae from Pheonix Worms in Tifton, GA. After a spontaneous 38F night, we lost about 1/3 of our population. We made some adjustments to better control temperature, and utilize the adjacent greenhouse for supplemental heat, and since then, their population is soaring. We now have several adults lingering on the shredded paper which provides a nesting area for pupating larvae that don’t migrate into our harvest buckets.

We expect our population to reach 100,000 over the next two weeks, at which time we will begin harvesting larvae to press into oil and feed. We will test lipid for its Fatty Acid profile and conversion into biodiesel. We will test the feed for its nutrient and market value. The compost will not be harvested until the end of summer. This project is a collaboration between the Clemson Biosystems Engineering Program, the Student Organic Farm, and Facilities and Maintenance Organization.


13 Responses to “Black Soldier Fly Digesters – Converting food wastes into feed, fuel and fertilizer”

  1. those are some attractive student workers…

    • This look an excellent initiative that ticks all the right boxes. Well done – Keep us informed on your progress in the coming months!

  2. No girls? I have had some accidental experience in my worm bins. I think this is an excellent project!

  3. Awesome! Its truly remarkable article, I have got much clear
    idea about from this paragraph.

  4. Have you tried extracting any oil yet? How do you plan on doing it?

    • We have extracted our first oil. We dried the pupae in a dehydrator for 3 days then pressed in our Swedish Tabby press. Only pressed 1 lb of meal and got about 20% oil/sediment. Likely we will get better extraction with a smaller plug/die and by processing a larger volume. I made a video of the extraction but seems too large to post on YouTube. So I’ll have to figure that out before sharing. Shawn J from the student organic farm is constructing a solar dehydrator to decrease our energy consumption.

      • One pound, that is impressive. I have been trying to attract and then harvest BSFL from different bins in my backyard. It is dirty work! Of course, I haven’t engineered a decent bin that they will self-harvest from. I thought of using a food dehydrator to dry them, but decided to use the oven in the lab set at 60 degrees Celsius. I did dry them for a couple of days outside in an aluminum pan. Some time this week I plan to try extracting the oil by grinding the dried larvae and then soaking them in hexane. If I don’t forget, I’ll let you know how it goes.

  5. Robin, Hexane is a good method for oil extraction, but will often dissolve other non oil compounds, or some cases some short chained fatty acids that are difficult to convert into biodiesel. Where are you located? Is this a University project?

    This design is easy to replicate for self harvest. The 8’x6′ bin yields close to a pound of wet larvae per week, and we are currently feeding about 120lbs of culled farm produce a week, with 400 lbs in our biggest week. We immediately freeze the larvae after harvest, and then dry using a food dehydrator. A pound of wet dries to about 1/3 lb usually. We hope to scale up to a 50ft digester in a concrete basin this semester, and in doing so, will construct a solar dehydrator to assist with the drying.

    It seems with our Tabby press our yields are only around 20% lipids, but we will have to compare to a hexane extraction to see if there is more lipid available. For hexane extraction we use a polytron sheer mixer to break apart our sample at 55c, then let it sit at 55C for 15 minutes, then evaporate the hexane and repeat the process. Here is a video we produced extracting the lipid from algae by this method.

    • I am a graduate student at Texas Tech University in Lubbock, Texas, but my BSF “farm” is in Abilene. I go there on weekends to harvest my feedstock. I am researching using Lewis acid catalysts instead of the traditional sodium hydroxide in the production of biodiesel. Mostly what I have been working with is castor oil while I wait for my feedstock to reproduce. 🙂 Even though it has been over 100 degrees for many days, my larvae seem to be doing well and I have seen a large increase in the amount. I get spoiled produce from a local grocery store to feed them. The harvesting is getting easier; I have finally found a method that is not so labor-intensive.
      The extraction went pretty well. Here is what I did: I put the ground larvae in a coffee filter and poured hexane through it into a shallow bowl. I dipped the filter down into the hexane for a few minutes and withdrew the the filter and squeezed out the excess liquid. I let it sit under the hood for a couple of hours to evaporate off the hexane. My oil is yellow; there is sediment in it, so I centrifuge it to separate out the junk. I will tell you that it makes for a happier experience if you wash the larvae before you process them.
      Thanks for sharing the videos and the information. All I have to offer right now is some pictures I took. Here is the link to the BSF forum where they are posted:

  6. Here is a short video of our first extraction a few months ago. Sorry for the poor quality. I recorded this by myself with my phone. The next videos are better, but seem to be too large to export from my phone to youtube, so we will record a more tutorial style video as the semester starts.

    • I am currently working on a BSF sustainability project with Federation University Australia.

      Could you please elaborate on how you detrermined your quantity of biofuel product?
      I noticed you quoted your oil yield as 20% by weight; but then quoted your biodiesel yield by volume. :-/

    • What is the current status of your project in 2014?

  7. Has there been any thought to downscale for use in a single household for gardening? I am interested in this but at a much smaller scale.

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