Urban organics require modern composting technologies

Recovering urban organics

Is it time to ditch antiquated, unreliable technologies in favor of efficient, high-rate composting?

View the SlideShare title:  Recycling urban organics

For the most part, municipal waste management in the 21st century has made notable advances over practices of the old millennium.

Sewer systems were once open channels through which raw waste flowed into cesspools and surface waters.  But managing the waste volume from hundreds, thousands, or millions of people concentrated in a small geographical area required a higher level of safety and efficiency.  Today, underground piping conveys that flow to sophisticated treatment facilities where liquids discharge at near drinking water quality.  Filtered solids are subjected to additional treatment(s) and returned to the soil to “close the loop” for organic material.

For trash collection, multitudes of small, open dumps and unlined burn pits eventually gave way to environmentally-secure mega operations that do a far better job of managing the refuse of today’s urban societies.

Yet, for the most part, composting facilities are still poking along with antiquated designs and technologies. This segment of the waste management industry has not stepped up to the plate to become the efficient, environmentally-preferred recycling engine today’s waste management realities need for recovering urban organics.

Is high-rate composting economically viable?

Food waste, paper, cardboard, vegetation and woody materials are common urban organics. An MSW organics component of 40-60 percent is typically reported for urban areas.

In addition, some materials not grouped with compostables by the EPA can be added to a compost blend.  These include wastes that add value to the finished compost, like ferric sludge from the treatment of drinking water and unpainted/untreated gypsum board.

The vanguard of the industry – high-rate operations that have replaced outdoor windrows with designs and systems offering more robust, efficient technologies – can handle almost any biodegradable material.   This includes challenging ingredients like compostable plastics and some toxicants.

Initial investment for tightly-controlled, indoor operations may be higher than an open-air facility.  But the benefits that come with these advanced systems make the economics work.  Even though waste management is a highly-competitive marketplace,  the processing successes and longevity of these modern composting operations are a testament to the benefits of chucking the old in favor of the new, even when capital investment is higher.

The history of the industry proves high-rate composting can be economically viable if facilities are designed and managed appropriately.

Defining urban organics

Some municipalities with composting operations only manage one or two organic waste streams – sludge and yard waste.  But the menu of what can be composted is much longer.

Typically, sludge is diverted from the wastewater treatment plant while the vegetative waste is source-separated curbside. This results in a clean, compostable waste stream, because the organic fraction is separated from the non-organic at the point of generation.  Since source-separated organics (SSO) are not highly polluted with contaminants from the larger MSW stream, the end product can have a high market value.

In recent years and in some cities, source-separated food waste has been added to the list of organics accepted for composting.  Some of the low hanging fruit – food waste from food processors, grocers and restaurants – have even found their way to regional composting operations in areas without organics recycling mandates.

But all of those streams must be free of non-biodegradables.  Composting highly-contaminated organics rarely results in a product with any market value.

When contamination is high, the compost’s only practical use is as landfill cover or boiler fuel.  Unfortunately, these options generate little to no revenue and defeat the purpose of composting – which is to recover organic matter to recycle back to the soil.  Composting can even add to management costs if the resulting product is so contaminated it must be landfilled or incinerated.

Therefore, any practical plan for recovering urban organics must include a strategy for source separation, as well as education and enforcement, to ensure a contaminant-free stream.

The typical MSW stream includes many wastes that can be composted at a modern, high-rate facility:

  • Sludge (DAF, biosolids, alum, ferric)
  • Digestate/residuals from bioenergy production
  • Unpainted/untreated wood, yard waste, pallets
  • Waxed/unwaxed/dirty paper and cardboard
  • Food waste, including meat and dairy
  • Fats, oil, grease (FOG)
  • Compostable plastics
  • Natural fiber textiles
  • Animal bedding, spoiled feed and mortality
  • Untreated/unpainted gypsum board

Defining a modern composting operation

Modern composting takes place inside an industrial building on a site appropriately zoned for an industrial operation.

It uses a combination of design, technology, and management to rapidly neutralize odors inherent in the incoming feedstock stream and prevent the formation of odors during processing.  Biofilters or other odor-management systems then scrub/treat air from odor-prone work zones prior to venting.

A modern composting facility uses design, technology, and management to eliminate leachate.  It manages its operation to discourage flies, rodents, and birds.

Design and technology also play a significant role in profitability, allowing exponential volume increases in throughput in the same space as a low-tech facility while manufacturing a product with high-dollar value.

The market value of the finished compost is a significant consideration, for to return organic matter to the soil to complete the recycling loop, it needs to be a product that is safe, consistent from batch to batch, and unobjectionable to use anywhere, anytime, by anyone.  It can be problematic for an outdoor operation using a less sophisticated composting technology to reliably deliver on that promise.

Constructed with copious amounts of concrete and steel, a modern, industrial composting plant is a very tight ship with the ability to operate close to sensitive receptors (using a very broad definition) without eschewing every good neighbor policy ever invented.

More importantly, upon the rare occasion when the microbes under management suffer a digestive upset, the people in charge of a modern composting plant can return balance to the system … STAT.

The level of control inherent in the designs, technologies, and operations protocols employed by modern composting facilities is what makes them ideal for managing the organic fraction of urban wastes.  Remove organics from that stream as the first step toward Zero Waste, and recycling the remainder becomes much, much easier — and cleaner.

The real barriers to recovering urban organics

If neither technologies nor costs are true barriers to recovering urban organics, what is preventing governments from making what appears to be an inevitable commitment?


By not keeping pace with technological advancements, policymakers and regulators erect barriers to modernization of the composting industry.  Regulatory stagnation has encouraged the proliferation of the vestigial, low-tech designs and methodologies that dominate today’s composting industry.   If a government’s true intention is to meet zero waste goals,  reduce greenhouse gases and store carbon, government must craft the laws and regulatory framework required to make modern composting happen.

The wastewater treatment, landfill, and incinerator industries did not modernize out of the goodness of their collective hearts.   They modernized because regulators said upgrades were in the best interest of the public and the environment, and thou shalt do it or shut down.

Without this catalyst, status quo bias could thwart the establishment of a meaningful organics recycling infrastructure.


Outdoor windrow operations may look cheap and easy.  But cheap and easy rarely equate to “reliable” or “efficient,” and neither offer the long-term savings in avoided costs associated with modern composting.

Windrow is the horse and buggy of organics recycling.  Cities will get farther faster if driving down the road to Zero Waste in something with an engine, and an accelerated technology is that engine.

In the public’s eye, because of their inability to successfully manage high volume streams that include challenging feedstocks, low-tech composting facilities reinforce and perpetuate the myth that composting is an inappropriate and ineffective technology for managing the bulk of the MSW stream.  This is a self-inflicted injury.

In addition to feedstock issues, low-tech systems can have difficulty managing high throughput volumes with any degree of reliability or efficiency.  Operating without fouling the air and generating dark puddles of liquor that attract flies and pollute surface waters is a chronic headache for some outdoor operations, too.

Yet composting does have its success stories.  In parts of the country where local tipping fees approach or exceed the national average, industrial composting facilities go head-to-head with disposal and win in competitive bidding environments – without degrading quality of life for the host community or the environment.

This fact seems to prove modernization can make composting operations more efficient and profitable, even in the absence of regulations requiring the necessary upgrades.  Mandates would simply force the laggards to take a serious look at inept waste management systems and do something better.


To manufacture a product with high market value, organics must be separated at the source.  Co-mingling with the total MSW stream and trying to separate either pre- or post-composting produces a no-value end product.

While industrial, institutional, and commercial source-separation has met with some degree of success, few municipalities have been willing to attempt it at the household level.  This reluctance has erected serious barriers to recovering urban organics.

Some of this angst is justified.  A community contemplating curbside collection faces both economic and emotional investments, so an unwillingness to take the risk is understandable.

But there is reason to believe the dark clouds hovering over curbside collection might be lifting.   Residential organics programs in New York, San Francisco, Milan and other major cities are meeting with success.  Some even pair anaerobic digestion with composting to deliver a power-full recycling punch.


All successful composters know a pile must attain a minimum volume or mass for composting to work.  Isn’t it ironic that insufficient mass also hobbles the composting industry?

Composting is dominated by small business and public-entity owners.  The former has no money with which to buy the tools of influence and the latter is focused on its own jurisdiction.  Neither is in a position to bankroll a broad-reaching, public education campaign.  So, for the most part, the industry lacks the ability to pay for a strong voice in the public arena.

Competition from better-funded technologies also plays a role.

From anaerobic digestion to landfill gas recovery to incineration/thermal systems, organics-derived energy seems to have supplanted composting as the “poster child” for sustainable waste management.  This ignores the fact that biomass is among the most expensive ways to generate power in the U.S.  Neither burning nor burial can make legitimate sustainability claims since they don’t return organic matter to the soil.

In addition, the dearth of unbiased studies comparing high-rate composting side-by-side with other modern organics management systems (WTE, AD, LFGE) makes it difficult to assess energy consumption and other economic influences for the various technologies.

But while research can be absent or flawed, the commercial marketplace never misses the mark.  In regions where composting has managed to gain a foothold, it successfully competes for and wins organics management contracts – without subsidies and without big PR budgets and marketing campaigns.

The fact that the industry has achieved this level of success without much in the way of public awareness is a testament to its practicality, efficacy, and tenacity.


As the number of cities and volume waste generators pushing organics diversion grows, traditional disposal companies are investing in organics infrastructure or collaborating with other organics management companies to offer alternatives to burial or burning.

Traditionally, composting facilities linked to landfill operations were mostly for yard waste or biosolids recycling.  But the fact that food waste and other organics are now being diverted by some of the biggest names in the waste business has got to be a sign that things are moving in a good direction.

That this effort sometimes includes the adoption of more modern composting approaches – like aerated static pile technologies — can only be a portent of better things to come for the entire industry.

READ MORE:  Urban organics Table of Contents