Mortality Compost And Sourdough Bread

In the words of my mentor, "You cannot make compost until you can bake bread". The complexity of a composting process, the value of a balanced recipe and the importance of proper homogenization of raw materials can best be understood when compared to baking a loaf of sourdough bread.

To make sourdough bread, one would need flour, lard, sugar, salt, water, and yeast. In addition to the ingredients, you also need a number of implements such as a mixing bowl, measuring cup, scale, wooden spoon, table, bread pan and obviously an oven. To knead the dough properly, you need a food processor or a strong pair of arms and a lot of stamina.

The process of preparing the sourdough is really quite simple - mix a specific volume of yeast with tepid water and a little sugar, stir until the mixture is frothy. Mix the yeast mixture with a specific weight of flour, salt , water and lard. Mix all the ingredient thoroughly and knead the dough until a smooth and elastic consistency is achieved. Cover the dough with a wet cloth and place the dough in a nice warm area and allow to rise until double in size. Knock the dough down again and repeat the rising phase. Finally, knock down the dough one more time and place inside a greased bread pan and allow to proof (proofing is the final step of dough-rising prior to baking). Once the dough has proofed properly, put the baking pan into a pre-heated oven and bake for a specific length of time at a specific temperature as called for by the recipe. During baking, the yeast is inactivated. Once fully baked, remove from oven and place onto a cooling rack. After a few minutes, remove the bread from the baking pan and allow piping hot bread to cool down before serving.

So what does baking a loaf of sourdough bread has to do with making compost. The answer is EVERYTHING!

• Preparing the dough requires the baker to manage a very basic biological process that only utilizes a small variety of mesophylic microorganisms, most of which already come conveniently packaged and ready for use. A compost pile requires the management of a vast number of microorganisms, some mesophylic some thermophylic, and none of them comes pre-packed with instructions.

• The value of the following the recipe and proper mixing of the ingredients is blatantly obvious in this example. You don't need to be a rocket scientist to figure out that very specific ratios of ingredients are required to produce a dough that will rise and produce a bread that will taste like the bread we all know and love. To further drive this point home, imagine the fiasco if all the ingredients were just put in a bowl and baked without mixing or kneading. Imagine your compost pile under the same circumstances.

• What a lot of people miss in this example is the importance of strictly following a very specific set of instructions to achieve a good end result. Obscured and often totally overlooked is the interdependency of, and interaction between, the ingredients and the physical environment. After all, the rising of the dough is caused by gasses (CO2) emitted by the yeast while converting some of the starches into sugars. The microorganisms do this in order to achieve their genetically coded primary objective - to multiply faster than the competition in order to secure the source of nutrients. This is also the main objective for any microbe present in your compost pile, except that we are dealing with a multitude of different species and nutrient bases.

• If the dough was allowed to proof in a refrigerator instead of a nice warm spot in the kitchen, not only would the process take substantially longer, but the bread would taste more yeasty and sour due the increased activity of ever-present wild yeast relative to the number of colonies of "domesticated" yeast that was originally added to the dough by the baker. Strange how a small temperature change in the environment can favour one species of yeast over another...

• At risk of pointing out the obvious, without the implements, the ingredients are pretty useless by themselves and vice versa. Many aspirant compost makers conveniently forget that a range of specialized equipment is required to make compost properly. Proper equipment is not an optional extra, it is an essential part of the process and unless you have access to the right equipment, you are in all likelihood going to be wasting your time and money.

• Compost making, like bread making, is an art that requires a specialized skill set and the right equipment to effectively manage a very intricate biological process to a successful conclusion.

So now that we understand a basic relationship between a compost pile and a simple bread recipe, let's move on to bigger and better things.

The general consensus is that mortality composting is best achieved when the animal or animal parts are combined with a carbon source and manure, where after the mixture is brought to the right moisture content and then composted actively or passively using a variety of methods such as mortality bins, windrows, enclosed rotating vessels and even fully contained aerated PVC tubes. There are as many systems as there are companies selling composting equipment, each with their own merits and disadvantages.

Most active composting systems provide additional artificial aeration and frequent turning of the compost whereas the more basic passive systems often involve nothing more complex than layering the animal or animal parts on a bed of course material and covering the mortality layer with alternate layers of manure and straw or wood shavings.

Both active and passive mortality composting systems require that the compost be turned at certain intervals. The turning frequency is usually determined by the specific system used by the compost maker.

The general rule of thumb to be applied to all compost systems, regardless of the system employed, is that the homogeneity of the initial substrate mixture combined with the level of active management will determine the duration and effectiveness of the first phase of the compost process. This brings up the question: what is the first phase?

The first phase of composting, also called the thermophylic phase , is where the physical break-down (biological conversion) of the waste products takes place. Relate this back to your sourdough preparation and proofing stage in the example above.

In composting terms, this process is almost entirely reliant on the level and diversity of the microbial population and the activity of the associated microbial population present in the compost pile at any given time. The level of microbial activity in turn is wholly contingent on the prevailing conditions that exist within the composting substrate and it is the balance of raw materials in relation to each other that determines the availability of nutrients to the microbial population. The most critical components are the levels of nitrogen, carbon, oxygen and water available to sustain the ever-increasing populations of microbes within the compost piles.

It is important to understand that composting is by definition a wholly aerobic process and can therefore only proceed under aerobic conditions. Whilst microbial conversion does continue under anaerobic conditions, the associated microbial conversion pathways are very different, as is the eventual outcome of an anaerobic process when compared to an aerobic process ( remember what happened when the sourdough was proofed in the refrigerator? ). Sufficient to say that unless adequate nutrient, oxygen and moisture levels are maintained throughout the active phase, the composting process will at best be stunted and may even come to a complete standstill. Anaerobic conditions are also responsible for the majority of objectionable odors associated with composting - even more so with mortality composting.

The next crucial step in composting process is turning the compost. Turning is often associated only with providing aeration, but in reality, the turning process does a lot more than just provide aeration. Think back about mixing the ingredients in our bread baking example on top and what the effect would be if we skipped this part. Turning compost is no different. We need to get the, nutrients and microbial populations homogenized and the environmental parameters just right for the microbes to perform at their optimum levels. In the sourdough example, we knocked back the dough twice before baking it. When making compost, we need to turn the compost frequently because with every turn the compost pile will become more homogenous and therefore the composting process will be more homogenous.

The active phase is characterized by high temperatures caused by massive thermophylic (heat loving) microbial activity within the compost pile. An active compost pile will remain in the active phase as long as there are sufficient nutrients available to sustain the thermophylic microbial population. The high temperatures combined with thorough mixing also serve to inactivate some pathogens and other organic contaminants such as weed seeds etc. In the bread example, we know that most yeast species are inactivated at temperatures exceeding 48 degrees Celsius. In mortality compost piles, we unfortunately have to deal with microbes that are much more resistant to heat than yeasts are. There are a number of microbes which will form spores that are resistant to any heat range available in a traditional mortality compost pile.

This shortcoming is one of the main drawbacks of the traditional approach to mortality composting. Acceptable levels of pathogen reduction just are not possible within the environmental parameters of the compost process. It is true that a certain level of pathogen reduction is achieved during traditional composting, but considering the pathogen diversity of the original feedstock present in mortality compost piles, it is definitely not enough to ensure bio-secure end product.

Once temperatures within the mortality compost pile start to decline it is an indication that the compost is nearing the end of the active cycle. This means that compost must will go into the curing or finishing phase. Compare the curing phase to the cool-down period once the freshly baked bread is removed from the oven.

During the curing phase, compost temperatures will gradually subside to ambient temperatures and various mesophylic organisms, worms, ants and other invertebrates will mop up any unconverted or residual nutrient pockets and render the compost into a substrate that is truly useful as an organic medium for plants. During the curing phase the compost must still be aerated and kept moist, but does not require the same levels of active management as is required during the first phase. The curing phase is a lengthy process and can last anything between a month and a year, depending on the prevailing environmental conditions and how well the substrate was managed and homogenized during the active phase.

I want to conclude this article by giving you the same sound advice given to me more than a decade ago. Before you start your first mortality compost pile, go and bake a loaf of good sourdough bread first...

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