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Composting is Great
Did you know that in the United States, nearly 32% of the total waste generated is from organic sources? Did you also know that 18% of the global anthropogenic methane emissions are derived from landfill waste? One method to alleviate this strain on landfills and the environment is to compost your waste. And composting with BSFL is a great way to reduce greenhouse gases.
Composting can improve the quality and fertility of soils. Perhaps you compost already, but are you getting the full benefits? Have you considered utilizing insects to help in decomposition? Research suggests that black soldier fly larvae (BSFL) are one of the best composting species available. The following article will explain more.
What is Composting?
Composting is the recycling of organic matter and a solution to solid waste management that can reduce total waste output and provide nutrient-rich soils for your garden. Composting can help reduce the release of methane and put organic matter back into the soil; research suggests that production of solid waste is increasing while soils are progressively losing organic matter due to intensive cultivation.
Compost is shown to improve soil structure, retention, and moisture holding capacity. The organic matter in compost stimulates biological activity and acts as a pool of nutrients, which reduces the need for fertilizer applications. The Government of Western Australia states that compost increases the biomass of root systems in plants and can directly increase carbon sequestration.
Composting Reduces Methane
At this point, you might be asking: “If composting is just decomposition, how will it prevent methane emissions?” The answer is the different types of decomposition. Composting utilizes an aerobic process, meaning the breakdown of material in the presence of oxygen. Due to improper aeration, the bio-waste in landfills generates methane. Although methane is a naturally occurring gas found most commonly in wetland ecosystems, its release into the environment has increased with growing landfills.
Methane is a significant contributor to global greenhouse gas emissions, with concentrations of atmospheric methane having risen nearly 150% (1803.2 ppb) since industrialization (~1750). Methane is the primary contributor to the formation of ground-level ozone, and long-term exposure to methane can lead to cardiovascular and respiratory problems. Aerobic processes of decomposition do not produce methane because the methane-producing microbes are anaerobic, meaning they are active when oxygen is not present. Aeration is important to proper composting as this exposes anaerobic bacteria to oxygen and kills them.
Compost Heat Keeps Gardens Healthy
Temperature is also important for the success of your composting operations. According to the Government of Western Australia, the heat generated in the composting process kills pathogens and seed banks of weeds, helping your garden remain healthy and weed-free. Besides reducing the risk of pathogens through biological oxidation, composting generates heat as a by-product that will kill microbes. According to Cornell, a well-designed indoor compost system can reach temperatures of 40–50°C in two to three days, whereas commercial compost systems can reach temperatures 60–70°C. Ideally, compost should be kept below 65°C because hotter temperatures cause the beneficial microbes to die off. Aerating compost will help to dissipate heat.
Keep in mind that composting, like most things in life, requires attention. If you fail to properly manage your compost, it may become a possible source of pathogenic fungi and bacteria to plants and those handling the compost. Improper maintenance may allow bacteria, such as E. coli, Salmonella, and Streptococci, to proliferate and contaminate your soil. This could be because of improper additions to your compost, like meat, or because soil temperatures are poor. If temperatures of your compost are not adequate, it will allow pathogens and weed seeds to survive. Poor maintenance can also lead to pests and complaints of odors.
Conventional Composting - How to Get Started
Compost requires four components:
- (i) organic waste
- (ii) water
- (iii) oxygen
- (iv) microorganisms.
Fortunately, microorganisms will not need to supplement this. Some recommended using a compost starter, organic matter that is used to speed up the decomposition process, while others do not. Regardless of your decision, it is recommended that you put down some straw as bedding; this will help with aeration. Aerobic microbes convert the raw inputs into material suitable for improving soil condition, so make sure to regularly aerate the compost to ensure oxidation. Oklahoma State University recommends turning your compost every three to four days.
Aerate Your Compost for Best Results
The importance of aeration of your compost cannot be understated. There are three different methods to aerate your compost, each based upon different volumes of compost available.
- (i) the static pile
- (ii) passive aeration
- (iii) active aeration
Static Pile Aeration
The first method of composting, the static pile, is the cheapest and simplest form of aeration as it requires no installations—it is also the most commonly used when compost volumes are small. Natural aeration occurs simply by diffusion and is governed by which surfaces are exposed surfaces. This method will require you to churn the compost with either a spade or pitchfork to expose all surfaces.
Passive aeration uses a ventilation system, such as pipes or ducts, under large compost piles. These ducts enhance thermal convective forces that are created by the temperature differentials between the composting material and the ambient air that enters from the system of open-ended perforated pipes placed under the compost. Passive aeration dispenses with the need for mixing/churning and lowers energy costs, though this aeration method works best for large volumes; however, passive aeration appears to result in partially composted material, especially in the center of the windrow, since mixing/churning is omitted.
Active aeration requires the installation of ducts under large compost piles as fans push air into these ducts and throughout the compost piles. Active aeration can lead to excessively cooling the compost, which can lead to large nitrogen losses while inadequate aeration prevents the proper development of stabilizing temperatures.
Industrial composting facilities use animal waste, such as manure, agricultural residues, forestry waste, and treated sewage. For your domestic purposes, we would recommend you stick with composting newspapers, cardboard, and waste from your kitchen and yard. It is not recommended to compost dairy, meat, and fish. This is because of sanitation issues and malodors that can attract pests, like rats. Rotting meat can also spread disease-causing bacteria into your compost, such as E. coli. If contaminated soils are used, they can transfer bacteria to plants that can cause you to become ill if ingested. However, if you decide to compost meat, black soldier fly larva are a great addition, because they can breakdown meat, dairy, and oily products.
Black Soldier Fly Larvae Composting
Reducing EmissionstComposting with BSFL has major advantages to conventional composting, such as reducing greenhouse gas emissions. Compared with conventional composting, BSFL reared on pig manure was shown to reduce emissions of methane, nitrous oxide, and gaseous ammonia by values as low as 72.63%, 99.68% and 82.30%, respectively.
Powerful BSFL Compost
What is more, BSFL composting does not require a starter nor does it require aeration, and can produce high-quality frass rich in nitrogen, phosphorus, and potassium. Research has even suggested that the nitrogen and phosphorus content in frass compost is higher than in organic compost. Microbial analyses of BSFL frass revealed that common foodborne pathogens were absent and indicated no heavy metal pollutants, making it a suitable soil amendment for agriculture. For more information, be sure to check out our article about the nutrient contents of different insect frass.
BSFL can consume Plastics
Using BSFL for composting comes with benefits such as quickly reducing the volume of waste and preventing the buildup of pest flies. Research has even shown that BSFL can consume polystyrene and other plastics; analyses of frass indicate microplastics and plastic monomers present. (Long-term effects on BSF populations following plastic consumption have not yet been conducted. Until more data is present, we would advise you to not feed plastic-fed BSFL to your animals.)
Reducing Compost odor and Harmful Bacteria
Larvae have also been shown to aerate manure, reducing its moisture and odor, as well as reducing the harmful bacteria such as E. coli and Salmonella enterica. Research has suggested that BSF modifies the microflora of compost through the production of bactericidal and fungicidal compounds. Larvae of BSF were shown to reduce the amount of biowaste by 50–80%, with a waste-to-biomass conversion rate of up to 20%.
In an experiment to investigate the benefits of BSFL on composting, BSFL were shown to decrease moisture in a blend of kitchen scraps/manure (3:1) from 79 to 50% within two months. It is suggested that the moisture content of 50–60% in compost is optimal as values of 65% can cause depletion of oxygen, leading to hypoxic environments and anaerobic fermentation. Reports indicate that the resulting residue that BSFL creates can be harvested after about 14 days.
How to Compost with BSFL
As mentioned in our previous article, optimal temperatures for BSFL are between 77–91°F (25–33°C) and can increase temperatures of shipping containers by at least 57°F (14°C) above ambient environmental temperatures. When considering the heat generated by composting, the additional heat generated by BSFL can kill pathogenic bacteria. In fact, BSFL has been shown to contain fewer microbial species than untreated soils.
The benefits of using BSFL for composting are that it can be used as an animal feed, especially for chickens. In an article we published about feeding chickens, we stated that BSFL makes great treats for chickens because they are packed in protein and calcium. The prepupal stage appears to be the most nutritious. Using BSFL as a composting insect is an efficient way to convert bio-waste into protein-rich and fat-rich biomass suitable for animal feed, most notably chickens. This BSF is said to contain high amounts of methionine, an essential amino acid.
How to Compost using Black Soldier Fly Larvae
For a more detailed article about how to accomplish this, read our beginner’s guide to composting . To quickly summarize, BSF lives for about 40 to 45 days and has a complete metamorphosis. This insect will stay as a larva, which has mouthparts to eat your compost, for about 13 to 18 days. For the next 35 days, the insect goes through a pupal stage before becoming an adult, which has a lifespan of five to eight days. Adult BSF are harmless as they do not have functional mouthparts and will only reproduce. If left unchecked, these insects might become an annoyance to you and your neighbors. You might consider using sticky traps to capture adults or using netting around your compost.
If you are considering adding BSFL to your worm farm (vermicomposting/vermicasting), think again. Besides creating competition for food, your worms will not survive in BSFL compost. Research has suggested that earthworms could not survive in BSFL compost because of the increased acidity and high temperatures generated by the larvae. This is to say that it would be best to segregate your species.
To conclude, there are conflicting reports on the smell of BSFL compost and their frass. Research has suggested the insects can reduce the smell of manure and there are a few anecdotes from people who have said that it produces clean, odor-free compost. Others have said that they can create a foul odor, so much so that it can cause issues in an urban environment. My own experience is that dried frass has a very slight foul odor, but smells reeks when wet. Be sure to leave a comment below about your own experience.
Using compost can improve your soil’s structure and ability to hold onto moisture. It can help reduce methane emissions and improve the quality of your garden’s soil. Although conventional composting is advantageous, including insects to your compost pile can speed up decomposition and improve sustainability. Instead of using bio-waste for conventional composting, repurpose it as a substrate for insect composting! The insects will eat the waste and convert it to macronutrients, making the larvae a protein-rich source for animal feed. Should you choose to include BSFL in your composting regimen, it can provide advantages over conventional composting, like the insects naturally aerating your compost pile for you. The larvae of BSF can be used as protein-rich animal feed if you are raising chickens. The frass of BSFL is rich in nitrogen, phosphorus, and potassium, which can improve plant growth. Lastly, research has indicated that the chitin present in frass can improve the health of plants, strengthening your garden from pathogens.
Carl Bonser, Entomology PhD
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