refreshing the colony

May 032009
 

restarting the colony 2009

Starting my third year with the black soldier fly

I’m going into this season with a small colony made up of grubs that were laid last fall. Where I live the winters are mild so it was fairly easy to maintain the colony through the cool months. At the end of last summer my BioPod was full of compost and I should have harvested it.  As a result of that neglect my beautiful compost became anaerobic, dense and a bit smelly. What can I say? It’s been a hectic year. :) I think early fall may be a good time for removing the BSF compost because the grubs are likely to be less active on average in winter versus the warm months. I believe the churning action of a very active colony (summer) is an important factor in keeping the compost aerated and “fresh”. I said early fall for compost harvesting because I’m afraid that if you wait too long in the season you won’t have time to rebuild the colony to near maximum size in preparation for the winter when BSF breeding stops (unless you’re in the tropics).

Spring cleaning

first BSF of 2009

BSF don’t normally land on people,
but this one had just emerged from it’s pupa so I was able to handle it.

I removed all of the compost and washed my BioPod. I hand picked a few hundred of the light colored juvenile grubs from the old compost and added them to the unit along with some fresh food scraps. I didn’t clean the grubs themselves so a small amount of the old compost was transferred along with them. This old material will act as a great attractant to BSF adults who have now started the mating season. A healthy and balanced BSF colony doesn’t have a strong or bad odor, but the females will always be attracted to the faint scent of an established colony. As I mentioned previously, my compost is anaerobic now and therefore smelly, but the typical mild smelling compost from a balanced culture would work just as well.

BioPod-spring cleaning

A new drain

As you can see from the first photo in this post I have replaced the BioPod’s liquid collection jar with a straight drain into the ground. (I hope you won’t be too disappointed with me Dr. Olivier.) I haven’t been gardening and to date I haven’t done anything productive with the liquid (also called “tea”). For that reason I’m opting for the convenience of the straight drain for now. To see how I set up the drain you can go to my “Tips and Tweaks” page.

The pond

You can also see my pond in the photo. I moved the BioPod near the pond because I’ll be feeding fish scraps and culls to my BSF colony this year. I don’t enjoy killing fish, but to maintain the population in a healthy balance I will be removing some of them. I’ll have some help from birds, turtles, and snakes, but the pond is fairly close to the house and wild predators are limited. With the BioPod I’ll be able to convert the excess fish into nutritious black soldier fly grubs and return them to the pond as fish feed. I have a post about my philosophy regarding feeding BSF grubs to other animals here.

Black soldier fly grubs are also fantastic fish bait, so having the BioPod near the pond will be very convenient for fishing. I’ve created a page about BSF as bait which you can find here.

Winter BSF culturing

As I mentioned earlier I did keep the colony going through the winter, but I didn’t keep any records. The one thing I can confirm is that the BSF grubs will interrupt their usual development during the cold season. I had very few BSF laying eggs by October and the last one I observed laid her eggs late in that month. By November I stopped seeing any smaller grubs in my colony. I assume then, that the grubs that  currently make up my colony are at least five months old. During the summer this stage would only last 2-3 weeks. Next winter I want to be better prepared to test cold weather bio-composting and I hope that some of you will participate in it with me. At the end of this summer we should start a thread about this at the BioPod forum to share strategies and results.

Logging this year’s results

My goal this year is to keep a log of all the food I add to the colony and the weight of the grubs produced. I’ll be fairly general about recording the composition of the food scraps so this won’t be a controlled experiment. The fact that I’ll be adding a large amount of whole fish and fish scraps will certainly effect my results. My goal is to provide a general outline of what you might expect. You can find the log in the column on the right of this page under Black Soldier Fly Pages, or simply click here.

solider

Black soldier fly composting in the frigid north

Aug 162008
 

frigid north

Actually, this post applies to any region that has seasonal temperatures below that which support BSF mating. This encompasses the entire continental U.S. except for a few extreme southern areas.

Black soldier flies (Hermetia illucens) are common in tropical and subtropical regions, but their range extends into many northern states of the continental U.S. You can easily operate a BSF bio-composting unit in northern states during the warm months, but you can also maintain the colony through the colder months with a little extra effort.

A black soldier fly colony generates its own heat

Maintaining a BSF unit in cold weather without heating it is possible because the churning action and digestion of the black soldier fly grubs creates heat as a byproduct. Under cold conditions keeping the colony at the optimal temperature range of 85° – 100°F (30°-38°C) is as simple as consistently feeding them and placing an insulating material directly on top of the pile. Simply remove the insulating material, add the food scraps, and then replace it. It’s important to feed the colony consistently in cold weather because without food the temperature will drop and the colony will become dormant. You can think of it like a diesel engine, if it gets cold then it’s hard to get it started again.

If the larvae are exposed to freezing temperatures they will die. Also, any insulation on top of the colony needs to have an air gap between it and the BioPod.

Maintaining a BSF colony during extended periods of sub-freezing weather will probably be a challenge for a novice, but it’s worth tying because at worst you’ll learn more about this fascinating creature. If you aren’t up to the challenge just yet then you can enjoy BSF culturing up to the point where the weather in your area makes it difficult and then resume in the spring. If you can store some or all of the compost through the winter it should make attracting the BSF easier in the spring.

Process more food scraps, harvest less larvae

The time it takes BSF larvae to mature increases in cold weather from the usual few weeks to a period of up to several months. I’ve maintained BSF larvae in the juvenile stage (light color, actively feeding) for five months through winter keeping the unit outdoors with some insulation. The same individual larvae will eat all winter which enables you to continue bio-composting without the need to replenish the colony with visiting females. However, since reproduction doesn’t happen at this time you must stop harvesting larvae if you wish to continue processing waste through the cold season.

In warm weather the colony has a tendency to overheat, so in cool weather the larvae are able to consume food scraps even more efficiently.

How adventurous are you?

I don’t recommend bringing the BSF unit into your living room, but why not try keeping it in the garage or a shed when the temperature drops? Sure, a few larvae might get out, but so what? The adult fly will just emerge from it’s pupae in the spring and then you’ll have the pleasure of gently capturing it and releasing it outdoors. They are harmless creatures after all. I don’t think a heated space would be the best choice though, because it might trick the larvae into developing too quickly. I would guess that 40° – 60°F (5°-15°C) is a good range to try testing this theory, and of course you would need an insulating disc of some sort to keep the colony warm. The degree of insulation would depend on the ambient temperature in the space.

I’m cursed with living in an area that rarely gets cold so if you try this experiment please let me know how it goes. I would love to post photos of your set up (if it works :) ).

Mike made a comment below reminding me of a presentation by ESR about BSF culturing in winter. Here is a link to that article: http://www.esrla.com/winter/frame.htm

solider

I crashed my pod

Jun 262008
 

blimp

Experiment causes black soldier fly larvae colony to crash!

Okay, maybe the blimp image is a little extreme, but it’s difficult to get attention on the internet these days. :P The good news is that bringing my BSF colony (Hermetia illucens) back into balance shouldn’t be all that difficult. In the past when I’ve run into problems I’ve corrected them by lessening the amount of food scraps that I introduced into the unit, and that is what I’m doing currently.

BSF larvae can eat almost anything

BSF grubs will consume almost anything organic except high cellulose materials like woody stems and grasses. They will quickly eat just about anything that has available calories including food waste that would probably be toxic to humans, like decomposing fish for example. The fact that they are able to efficiently digest such a wide range of material is what makes BSF larvae such a powerful tool for processing waste.

About those decomposing fish…

I help my neighbor manage the small pond behind his house. Recently several of his fish died and I did him the favor of removing them a few days after they floated to the surface. The fish weighed about 5 pounds (2.3 Kg) total and by the time I removed them they were already very stinky. Instead of disposing of them like a normal person I decided to see how quickly my BSF would process them. I’m happy to report that my small colony completely consumed the fish within about 2 days. I am unhappy to report that after I added the decomposing fish to my BSF unit it began attracting blow flies and house flies.

Black soldier fly grubs produce an info-chemical that repels pest flies, but there are limits as this test illustrates. The odor of these decaying fish was a powerful attractant to undesirable flies and it overpowered the repellent properties that are normally very effective in a BioPod.

I’m currently using a homemade BSF unit (not any more!) because BioPods are not yet available. My homemade unit is a less efficient design and I’m sure that this made my recent problem worse than it would have been. My unit doesn’t deal with liquids as well as a BioPod so the problem was less contained than it would have been with the commercial product. I will be happy when the first BioPods arrive.

And now the good news

Even the extreme imbalance created by adding these decaying fish to my colony can be corrected with a little time and care. Of course I’m more cautious about sanitation while the pest flies are present, but in reality I don’t need to do much other than stop feeding the colony and let the other flies cycle through. It’s now been about 5 days since I added the fish and my colony is almost back to a balanced state again.

You can avoid this type of problem easily

My test with the decayed fish was something that most people would not have tried, but I’m involved in testing the limits of this technology. If you use BSF larvae to process your normal household food scraps it’s very unlikely that you’ll experience anything like the crash I just created. You can even add food that is somewhat  spoiled and you shouldn’t have a problem like my recent experience.