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Attract professional composters to your city’s waste management table 

Composting high volumes of source-separated organics (SSO) is not for the faint of heart.  It takes skill, experience, and science to recycle one of the messiest urban waste streams.  But while composting done right doesn’t come cheap, it is possible to build modern composting infrastructure without public financing. 

Instead of bemoaning a lack of composting infrastructure and doing nothing about it, municipalities and regional authorities can set the stage for organics diversion.   

The result?  Some of the biggest and most experienced composting companies will compete for that business. This delivers a big win for the host community: 

  • No well-intentioned but flawed “solutions” from designers and technology providers with no knowledge of biochemistry and no hands-on experience in the day-to-day operation of industrial composting facilities.  
  • No major issues with regulatory permitting when other facilities of the same type are running successfully elsewhere. 
  • … and here’s the biggie – no public financing required if the population base within 40-60 miles is large enough and the local landfill tipping fees are at or above national averages.  A community/region of around 50,000 could generate a sufficient volume of organic waste to make commercial, high-rate composting economically viable.  (View: Estimating volumes for composting) Private ownership means private financing.  Public/private ownership can also result in private financing if the public entity brings enough to the table to make joint ownership attractive to the private entity.   

But what about – 

  • Facility failure?  Structure the contract to include an option for public takeover should the owner fail to make a success of the project.  
  • Odors?  No matter the technology choice, most climates will require an indoor operation with a good biofiltration system — combined with preventive/preemptive management practices — to solve the odor problems associated with composting putrescibles.  Consider containment, collection, and treatment of air from all active work zones — off-loading to curing.  Typically, if the product has been properly composted and cured, it can be stored outdoors.  However, to preserve product quality, some manufacturers may opt for covered storage here, as well. 
  • Leachate?  Correct blending and indoor processing all but eliminate leachate as a management headache.  But do require RFP respondents to address the issue in their respective proposals. 
  • Product stockpiles?  Make sure the successful respondent has a proven track record in marketing compost in similar markets.  Just remember the sale of soil products tends to be seasonal.  Suitable acreage for large stockpiles must be included in the site plan.  Those stockpiles should dwindle significantly during the planting season(s).  But as a safety net, require a provision for distribution of volumes exceeding market demand after a reasonable market development period. 

Foster and promote compost use 

Composting is efficient, cost-effective, and the only technology offering true sustainability for biodegradable waste.  Returning organic matter to the soil to complete the recycling loop is what makes composting and compost use a sustainable system.   

But policymakers tend to get so caught up in the diversion of organics that they neglect correlating mandates for compost use. 

Compost isn’t just for farmers.  A quality compost can be used by anyone, anywhere – even urban/suburban areas: 

  • Lawns, gardens, and greenspace 
  • Parks, sports fields, and other recreation areas
  • Roadside and rest stops
  • Utility easements and rights-of-way
  • Rainwater catchment zones and pathways 

Parallel to composting infrastructure development, craft internal and external guidelines, policies, and programs to encourage regionwide compost use.   This will not only help build a product market, but also reap financial benefits to the municipality in the form of reduced costs related to stormwater management, synthetic fertilizer use, etc.  

Industrial, high-rate composting:  exploiting the power of microbes

Thirty years ago, beyond the entry sign announcing the location of a composting operation, it wasn’t unusual to see a former cow pasture crowded with long rows of rotting yard waste.

Start-up for these primitive facilities was (and still is) relatively cheap.  A windrow operation is viewed as simple and attracts owners whose primary goal is to get a facility up and running without investing much in capital.

However, in all but the most arid climates, the Great Outdoors is not that great for the microbes responsible for composting’s biodegradation.  Aerobic microbes — the stars of every bona fide composting operation — will only reach peak performance levels if they are protected from the elements, provided with an ample food supply and a bit of water, and live in an environment equivalent to a microbial Goldilocks Zone.

Bring all of these conditions together in one place, and composting doesn’t just happen.  It goes gangbusters.

Today’s industrial composting plants and advanced biodegradation systems are designed to do just that, because the realities of high-volume organics recycling often demand more than the typical windrow can provide.

Science-based recycling systems — exploiting the power of microbes

When serving metropolitan areas, composting operations can be expected to recycle everything from fecal-laden yard waste to industrial by-products — in high volumes. These facilities intake and process hundreds of tons each day.  The larger operations may be processing 100,000 tons or more per year.

Odors emanating from some of these feedstocks can be unpleasant.  The materials can be very wet.  A few will carry chemical residues that require an advanced degradation technology to render them safe for reuse as ingredients in soil amendments.

That’s why more modern plants, those tasked with managing multiple types of organics from large geographic regions, are indoor operations.  Some may still turn under that roof, but others have kicked it up a notch by employing more advanced systems (i.e., aerated static pile or ASP) instead of turning.

While a windrow tends to plod along, controlled aeration accelerates composting, turning stodgy microbes into sleek degradation athletes.  With high stamina and a voracious appetite for all things organic, these Olympians of the microscopic world bring speed, reliability and high performance to an otherwise lackadaisical process.

The industry’s transition from windrow to ASP turbocharged composting, exploiting the power of microbes and giving it the efficiency and predictability required to successfully compete with landfills and incinerators.  But this metamorphosis did not result from genetic manipulation, chemical additives or fairy dust — it was simple biology.

That’s it.  Not engineering.  Not artistry.  Just biology, specifically, exploiting the power of microbes.

Prior to some notable research by scientists beginning in the 1950s, folks may have known how to keep a compost pile chugging, but not why their management efforts worked.  But once researchers figured out the why, they were able to control the process by giving aerobic microbes exactly what they needed to survive and thrive (air, water, food, temperature) in the right amounts and within ideal ranges.

They discovered composting’s Goldilocks Zone.

By the 1990s, this academic exercise had captured the eye of the commercial sector.  With some tweaking to improve efficiency and profitability at scale, a robust, predictable process emerged, one with the ability to cost-effectively recycle high volumes of organics.

But back to those microbes…

After many trials and several errors, industrial composting moved into the waste management mainstream.   But to make biology work as the power behind the progress, both designers and facility operators had to grasp, embrace and deploy a few scientific principles.

At the core was a rudimentary understanding of the two broad categories of biodegradation processes – aerobic and anaerobic.  Each identifier reflects the environment in which the microbes live.

Aerobic organisms require air and water, but like people, they cannot breathe under water.  Conversely, anaerobic microbes are like fish – they’ll die when exposed to air.

Anaerobes live and thrive in much wetter conditions than can be tolerated by aerobes. Both prefer a moderate temperature zone.  Anaerobes will die off at around 150 degrees Fahrenheit (F) or 65.6 degrees Celsius (C).  While aerobes can tolerate more extreme temperatures, the most active phase of aerobic composting takes place between 55 and 155 degrees F (12.8 to 68 C), with a preferred range of about 122-140 degrees F (50 to 60 C).

Anaerobic fermentation generates methane, which can be a good thing if captured and used for heating, cooking and generating electricity.  If not, then it’s a bad thing, a potent greenhouse gas.  When anaerobes are at work, certain compounds are created during intermediate degradation stages that result in unpleasant odors.  That is why some wet, decaying materials carry an offensive stench — the rotting organic matter has “gone anaerobic.”

But an aerobic process neutralizes odors by creating drier conditions, killing odor-causing anaerobes.  Methane is not generated during a well-managed aerobic composting process, and the resulting carbon dioxide emissions are considered carbon-neutral since the gas generation volume is the same as if the materials degraded naturally.

Beneficial bacteria and fungi are among the aerobic microbes that make compost “happen.”  About 2,000 species of bacteria and 50 species of fungi are ably aided in their degradation efforts by a zoo of macro-organisms like beetles and worms.  However, aerobes are the worker bees of the compost pile.  They break down organic matter at the chemical level as opposed to the physical rending of the macros.

Feeding on organic waste, aerobes power the engine that drives moisture from the composting mass, degrades pollutants, and eliminates odors.  The enzymatic action associated with aerobic digestion breaks molecular bonds, releasing by-products (heat, water, carbon dioxide) in the form of steam.  Once these microbes have consumed all available food, they die fat and happy, their microscopic bodies becoming part of the residual mass.

In a controlled composting process, a temperature drop signals a decline in food supplies and a correlating reduction in microbial populations.  Degradation slows, but still continues at the lower temperatures associated with compost curing.

If left to time and nature, organic matter will continue its disintegration until nothing remains.  But long before that happens, biodegradation enters a phase where the residual is relatively stable, while still microbiologically active and chock-full of both macro and micronutrients.  With its soil-like aroma and appearance, the material is pleasant and easy to use – a critical requirement for any product intended for widespread general use — and really, really good for rebuilding depleted topsoil.

This stuff, of course, is compost.

Microbes just keep going and going and…

When talking microbes, conversion of waste to valuable product is only half the job.  Once that compost has been added to soil, the little critters take on even more tasks:

  • DEGRADATION OF POLLUTANTS – microbes break down synthetic compounds to neutralize the impact of things like petroleum products and fertilizers/chemicals that can negatively impact both soil and runoff quality.
  • IMPROVE NUTRIENT UPTAKE – microbes convert nutrients to plant-available form, making more food available to plants and reducing the need for synthetics.
  • IMPROVE DISEASE RESISTANCE — microbial activity is responsible for the plant disease suppression associated with compost use.

The influence of science on facility design

The biggest problem with outdoor operations is not weather, per se, but the fact that weather cannot be controlled.

If a composting mass needs moisture, rainfall can be a welcome addition.  While it’s common for the sides of a compost pile to “crust,” discouraging rain infiltration, piles can be flattened and then concaved on top to capture rainfall for slow infiltration over time.  In this regard, rainfall can be a compost manufacturer’s friend.

But excess rainwater rolling down the crusted sides of a pile will settle into pools of “black liquor” (a.k.a. leachate) at the base.  Leachate and associated runoff contaminate ground and surface waters, attract flies and harbor unpleasant odors.  If the pile gets too wet too soon, pathogens rebloom.  When composting outdoors, a heavy rainfall can set the stage for nuisance complaints and regulatory intervention.

Conversely, maintaining acceptable processing conditions outdoors during dry spells requires sprinkler systems or a hose brigade if the microbes and the process are to be saved.

Add complications like high winds and ice storms to the mix, and the operation of an outdoor facility becomes more about battling Mother Nature than recycling organics.

Having to reprocess ruined piles and windrows adds cost and retards throughput. When hundreds of tons of waste arrive at the gate each day, a stuttering throughput rate can cause massive pile ups that compound and exacerbate the weaknesses of outdoor facilities.

Exploiting the power of microbes means protecting the creatures from the vagaries of weather is a top priority for modern facility designers.  Solutions can range from a shed roof to encapsulation to full facility enclosure.  Each rung on the containment ladder offers an elevated level of environmental control and protection, as well as fewer operational complications.

On that list are the elimination of materials handling woes related to weather delays and the ability to capture inside air and processing off-gases for biofiltration.  Indoor facilities can also make a composting operation more palatable to the locals by providing visual camouflage and sound buffering.

Making biology work for day-to-day operations

Putting a roof over a composting operation may remove many headaches from the manager’s plate, but design is only as effective as the people running the place.  Any composting facility — from the most basic to the most sophisticated — can still run into trouble if mismanaged.

Exploiting the power of microbes requires a multi-faceted strategy.

Feedstocks like food waste and biosolids can be wet and odor-laden when they arrive at a composting facility.  One of the top priorities for modern composting operations is to get these types of materials blended with dry amendment and aerated as soon as possible to kill off anaerobes and encourage the proliferation of aerobes.

But if the blend isn’t right, a batch can be doomed before the admixture ever hits the composting pad or aeration floor.  Wet or dry pockets impact microbial movement throughout the composting mass.  An irregular texture means patchy distribution of target compounds and uneven exposure to the microbes.  Pockets of untouched raw waste can survive an otherwise successful process, leading to regeneration of odors and reblooming of pathogens.

Particle size needs to be consistent to achieve an even degradation rate for all blend ingredients.  Material placed on the composting pad should not be compacted.  Aeration pipes must be free of debris.  Windrows may need more turnings than required by regulations to keep the process humming.

Many items on the list of best management practices (BMPs) are common to all composting operations, from backyard to industrial.  Many items on the DO list relate to the creation and maintenance of an ideal environment for the microbes responsible for biodegradation.  The DON’Ts focus on discouraging of the kind of microbes that cause and perpetuate odors.

But no matter the design or process, people are ultimately responsible for making the science work as it should, keeping those all-important “bugs” happy and ensuring a trouble-free operation.

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Preemption vs prevention:  Choosing higher standards for composting facilities

Preemption vs. prevention — do you know the difference?  From odors to leachate to low-value products, at almost every stage of facility development and operation is a preemptive choice that will greatly mitigate or eliminate the most problematic issues plaguing composting operations.

First, understand that preemption is not the same as prevention.  Prevention is picking up a banana peel before someone slips on it.  Preemption is not buying the banana in the first place.  Prevention is building berms at composting facilities to contain leachate.  Preemption is combining design, technology, and management to make sure no leachate is generated.

From siting to intake to final product storage, there are preemptive choices that provide superior protections and efficiencies over more traditional options.

Admittedly, preemptive siting and design options tend to have higher up-front costs.  But building and operating according to the preemption principle can result in composting facilities that work better with fewer headaches, lower operating costs and higher revenue.

Conversely, a low-end approach can ultimately cost more when factoring revenue loss, increased expenses, reduced throughput, failed tests, poor product quality, regulatory headaches and public relations problems into the design and management equation.

Preemption vs. prevention for site selection

In the case of composting facilities and their neighbors, it is distance that makes the heart grow fonder.  Regulated buffers are minimums, not the ideal.  As a preemptive measure, put the largest buffers possible between active work zones and property boundaries.

Use vegetation, including vegetated berms, to shield operations.  In addition to visual camouflage, well-designed and strategically-placed vegetation and woodland buffers also contribute to noise and odor abatement.

Preemption vs. prevention for odor mitigation

There’s no way to sugar-coat the truth:  Composting facilities are in the business of recycling putrescibles.  The root of the word putrescibles is putrid.  Ergo, facility management can be problematic if the facility has not been designed to tackle odor generation from the get-go.

Odors are generated during biodegradation by anaerobic (without air) microbes.  Typically, this means conditions within the feedstock pile or composting mass are too wet to support aerobic (with air) microbial populations.

The whole point of composting is to create an environment that will encourage the proliferation of the specific aerobic populations responsible for rapid breakdown of complex compounds and neutralization of odors.

That means getting especially odorous feedstocks into blending ASAP and keeping air flowing continuously — in the right amount– throughout processing and curing.  Most of the composting facilities in existence today do not have that capability, because they rely on periodic mechanical turning to aerate the pile.  Advanced composting methods will use some form of automated temperature feedback system to moderate temperatures and keep the piles aerated 365/24/7.

While not impossible, open air composting using any method will have a devil of a time creating and maintaining aerobic conditions if the climate is anything other than arid.  Rain falling on an exposed composting pile can give anaerobes the competitive edge, encouraging the rebloom of pathogens and allowing odor regeneration.

Moving an operation totally indoors will also allow the capture of emissions from all work zones,  including off-loading and blending, as well as facilitate the extraction of stale air from processing bays.

Once collected, this air can be channeled through a biofilter prior to venting.

Choosing an indoor facility with biofiltration is an example of preemptive design.

Preemption vs. prevention for leachate management

Leachate may be generated by rain failing on unprotected piles or the draining of excess moisture from wet feedstocks.  Leachate is the dark “liquor” that pools in open composting yards, contributing to odor generation and the proliferation of flies.

Berms, piping and collection pits are tools used in composting to channel and contain leachate.

The goal of these preventative measures is to capture leachate before it escapes property boundaries or runs into surface waters.  The leachate can then be treated onsite, reused during blending to wet dry feedstocks or piped to a wastewater treatment facility.

Immediate blending of wet feedstocks with the appropriate types/amounts of dry amendment, along with the prevention of rain infiltration, will all but eliminate leachate as a management issue.  Minor seepage from standing piles can be absorbed by dusting puddles with dry compost, which is then returned to the head of the plant for reblending.

Proper blending is an example of preemptive management.  Taking steps to prevent rain from coming in contact with feedstocks and compost piles is an example of preemptive design.

Preemption vs. prevention for product value

Product value is based on multiple influences including feedstock selection, blending, processing and, finally, storage.

Preemption plays a role in feedstock selection by sourcing the best ingredients and avoiding those that add little to the final product or, even worse, lower the value.

Blending to produce a homogeneous mix without marbling or clumps results in an admixture that exposes all raw materials to beneficial microbes and facilitates even air flow throughout the composting mass.

Covering product during processing and long-term storage ensures high market value and maximum revenue from product sales to high-end users like landscapers, athletic field managers, golf course superintendents and landscape supply retailers.

Failure to establish a professional marketing and sales program can result in large piles of unsold product or sale of product below market value.  Hiring experienced sales professionals can make a difference in the overall efficiency and profitability of an operation.

All of these are examples of preemptive management practices.  None are linked to a specific facility design or composting technology.

Every composting operation can practice preemptive management.