Good compost starts with a good recipe 

Whether making a small batch or a big one, following basic instructions will get composting done right. 

While baking relies on an external heat source to trigger a myriad of chemical reactions, and composting generates heat as a result of biological activity, both processes have a great deal in common – including the end result. 

Whether baking cupcakes or making compost, a quality product starts with quality ingredients added in the right amount, at the right time, and in the right order.   

Mess up even one step of the process, and the end product may never be right. 

Ingredients 

Adding a pinch of sugar and 2 cups of salt to a cake recipe (instead of the other way around) could become an inedible disappointment.   

Composting is no different.   

For the process to work as it should, the carbon to nitrogen ratio must be right (25-30:1 by total C and N content, not “brown and green” feedstock volumes) and moisture levels must be in the zone (40-60% by weight). 

Blending 

In baking, improper or incomplete mixing of ingredients can result in gooey or dry pockets within the finished treat.  Batches must be thoroughly blended to distribute ingredients evenly throughout the mixture. 

Goof up a compost blend, and the same thing happens.  Wet or dry pocketsmarbling, and other mixing mishaps mean microbes will not have equal exposure to target compounds, air, or moisture.   

This can create zones of uncomposted materials in an otherwise completed batch, failed laboratory tests, smelly finished product, etc.   

When blending, focus on achieving uniformity in moisture distribution, texture, and porosity. 

Processing 

Convection ovens, equipped with fans that move heated air during the baking process, have become a favored appliance for bakers who once struggled to achieve even baking in older, conventional models. 

But the latest and greatest in kitchen gadgets are no help if temperature settings are wrong.  Heat levels must still be correct to bake a cake or casserole to the center without drying or burning the edges. 

For composting, that zone is 113-160 degrees for initial composting and 70-113 degrees for curing.  The time it takes to complete each processing stage depends on the level of control applied … which is where those fans come to the fore. 

It is possible to compost (and do it well) without an automated aeration system – it just takes more time and trouble.  But it’s not possible to compost without any aeration.  

In nature, it doesn’t matter how long a pile of yard waste or a dead squirrel takes to decompose.  Sometimes, it can take years for nature to work its recycling magic. 

But most composting operations don’t have the luxury of unlimited time.  Speed and effectiveness of the process impacts everything from acreage requirements to the cost of operations.  Managing air flow through the composting mass must be a top priority for any municipal or commercial composting facility that needs to meet both throughput and budget targets. 

Here’s why: 

Remember that 70-160-degree temperature range?  Two types of composting microbes live and work within those zones.  Mesophiles are most active at the lower temps, while thermophiles dominate the higher levels where microbial activity and the resulting biodegradation is quite robust. 

Air flow is the primary mechanism for temperature control within the composting mass.  If temps are allowed to exceed 160 degrees F, thermophiles die off, the entire process crashes, and heat (generated by biological activity) must rebuild to productive levels. 

Every “crash” slows the process.  It’s like opening the oven door every five minutes to check the rise of a souffle — does more harm than good. 

But by using fans to move air through the composting mass, temperatures can be controlled.  More air cools the pile; less air allows warming.  By using sensors linked to microprocessors to automatically adjust those fans to meet specific time/temperature goals, a composting batch can meet regulatory requirements for pathogen kill in a matter of days instead of weeks or months.   

Of course, a manual probe will work, as well, if the budget allows for a person to walk around all day monitoring pile temperatures and making the necessary fan adjustments. 

Cooling/curing 

Food is rarely at its best when consumed straight from the oven.  Most dishes require a cooling/resting period prior to consumption, allowing sauces to thicken, juices to be absorbed and starch retrogradation to “happen.   

Compost, while it can be used fresh once PFRP/VAR requirements are met, is best when allowed to cooltoo. 

This is compost’s curing phase, when temperatures drop into the lower, slower zones preferred by the mesophilic organisms that will finish off the last of the food and bring the composting mass to a stabilized state. 

Farmers may prefer an immature compost because it can offer a slightly higher nutrient value than a more mature product.  But fair warning:  Use a compost before it’s fully cured only when destined for agriculture or other application away from sensitive noses.  Otherwise, wait until the pile offers only the sweet smell of rich, fertile soil before distribution.   

Depending on the initial feedstocks and technology used, the curing phase can last anywhere from a few weeks to several months.  Technologies used during curing can range from controlled aeration to occasional turning of a windrow to static pile.