Commercial vs. industrial composting:  are they the same? 

Commercial vs. industrial composting — no, they are not the same, though the terms may be used interchangeably on the web.  But one word has to do with the money trail and the type of organization that owns the facility.  The other is linked to operational scale and/or manufacturing approach. 

A government-owned operation is not commercial, but it could be industrial in scale. It could also be operated like a commercial facility with a similar structure and profitability goals. 

A privately-owned facility would be commercial but might not have any claim to industrial.  A small facility owned by a nonprofit may be neither.   Big, modern compost manufacturing plants may be both. 

What makes a composting operation commercial? 

A “commercial” facility infers ownership by an individual, partnership or corporation, with profits accruing to the benefit of the owners’/shareholders’ bank accounts.  “Commercial” doesn’t have anything to do with the processing method in use, facility design, throughput, technologies, or manufacturing systems. 

Composting operations owned by municipalities, counties, nonprofit organizations and the like are not commercial, because any profits realized go back into communal coffers to subsidize operations or fund other projects related to their respective missions. 

Government-owned plants are “public-sector” operations, while commercial facilities are “private-sector” operations.  Generally, nonprofits or not-for-profit entities are citizen groups and may also be referred to as non-governmental organizations (NGOs). Sometimes, an NGO may be established by individuals representing governments or agencies.  Like public-sector projects, composting facilities owned by NGOs could look very much like a commercial operation, complete with a revenue stream. 

How big is industrial scale? 

“Industrial” is a relative term, most often associated with factories and manufacturing.  In the 21st century, manufacturing infers mass production, big equipment, automation, systems, and uniformity.  Ergo, industrial scale infers a facility size that would require these things to improve efficiencies and revenues. 

When it comes to commercial and industrial composting, how big does the operation have to be to earn the designation of industrial scale?  How big is big? 

Again, it’s a relative term.  When doing research for this post, one of the findings was this article written in the mid-1990s that classified a 100-tons-per-year operation as industrial.   

Compared to the backyard compost pile, 100 tons is a big number.  But the average throughput of a composting operation in the U.S. is now approaching 4,500 tons per year.  There are 194 facilities processing more than 30,000 tons per year, some in the 100,000-plus category.   

It may be time to add one or two more zeros to the “industrial scale” definition of 1996. 

Still, size is only one indicator of an industrial facility.  But other adjectives that might be used to provide clarity are also quite subjective. 

Commercial vs. industrial composting — is “manufacturing” the key? 

The original definition of manufacturing (manu factum in Latin) literally translates to “made by hand.”  Today’s dictionaries typically describe manufacturing as making something manually or using machines.  But for most folks, the word conjures images of big buildings, lots of machinery, and cookie cutter output. 

Yet, no matter the variations in definition, one thing is clear — when applied to the manufacture of goods in the modern era, making something in an industrial setting requires production through a system that typically includes assembly lines, division of labor, a quality control program, and a sales network to move products out into the marketplace. 

Potato, Potahto 

Does it really matter whether a composting facility is commercial or not?  Industrial or not? 

The important thing is for composting operations of every description to make good compost.  How they do it or where the money goes is secondary and may not even be on a customer’s radar. 

A “commercial” facility may still imply private-sector ownership, but if public-sector owners are serious about their responsibilities to taxpayers, they’ll design, operate, and generate revenue from compost sales like the privately-owned. 

Protecting the integrity of the process and quality of the finished compost matters.  Hiring experienced, qualified compost facility operators matters.  Practicing preemption when it comes to the environment and preventing deterioration of the quality of life for the host community matters.  Providing stellar service to both intake and compost sales customers matters. 

These are the indicators of a successful composting operation, whether commercial or not, industrial scale or not.  At the end of the day, professional and profitable are among the most important descriptors for any composting facility. 

LEARN MORE: 

Compost is soil’s superhero

Sure, compost adds nutrients. But that might be this soil amendment’s least important function. 

Quite often, articles will mention compost as a replacement for some or all of the nutrients that might be provided to plants through applications of synthetic (man-made) fertilizers.   

That’s certainly true.  Compost delivers the macronutrients nitrogen, phosphorus, and potassium (NPK), plus a slew of plant-essential micronutrients that are missing from most synthesized fertilizer products.  Compost provides plants with a wholesome, well-rounded meal, not the nutritional equivalent of junk food. 

But what these fertilizer-focused articles rarely mention is the fact that the real value in compost use is not related to feeding plants, but to feeding soil … and soil does require a wholesome diet to function as a true soil and not a dead substrate. 

Compost feeds soil

Providing plant nutrients is just one of many soil functions.  Worms and other creatures that live in healthy soils help to physically break down food sources, then microbes take over to convert that food into plant-available form. 

Both physical and microbial conversion depend on a soil environment that can support those lifeforms.  If the soil is chronically too wet, too dry, too compacted  yada, yada  then it can’t support a healthy soil ecosystem.  That plot of ground may not be soil at all, but lifeless dirt. 

To countermand the impacts of human activity, disturbed soils require regular program of replenishment that includes organic matter and microbes.  Compost provides both.  Compost feeds soil.

Then, when it rains, soil retains that water, reducing runoff.  When runoff is reduced, so is erosion, sedimentation, and water pollution.  Because soil microbial activity also degrades pollutants, any stormwater that does run off is cleaner.  

That same microbial activity can help neutralize some soil-borne diseases, too. 

Improving plant nutrition, aiding in disease control, reducing water pollution, and retaining water are all important soil functions. 

But wait, there’s more. 

Compost as a carbon sink 

The build-up of greenhouse gases in the earth’s atmosphere is cause for concern.  As more greenhouse gases flood the atmosphere, temperatures increase. 

This rise in global temperatures influences many things, erratic and extreme weather being one of the most visible.  Subsequent climate shifts can impact people, crops, and livestock for hundreds of years. 

When used to amend soils, compost sequesters carbon.  This means the soil will act as a carbon “sink,” capturing and holding carbon in stasis – but only as long as the soil remains undisturbed.  When the soil is tilled, that carbon is released. 

Extensive use of compost for perennial crops and other long-term application(grasslands, tree farms, utility easements, etc.) can positively impact atmospheric conditions by reducing greenhouse gases.   

At the same time, the addition of compost rebuilds a topsoil layer that has been eroded or scraped away by farming, development, and other human activity.  Since topsoil loss has been identified as a significant threat to planetary health, second only to population growthits restoration is a global priority.   

At a time when nearly a third of the world’s arable land has become unproductive in just a few decades, compost really can be that superhero swooping in to save topsoil, save water, save the atmosphere, and save the planet. 

Comparing costs per gallon retained 

Soil amendment is one of the least expensive ways to collect and manage stormwater 

Manage water where it falls.” 

This sound advice is the foundation of the Milwaukee Metropolitan Sewerage District’s Regional Green Infrastructure Plana program that identified soil amendment as one of the least expensive ways to manage stormwater.  At 28 cents per gallon, improving soil is second only to native plantings in lowest cost per gallon retained. 

Green roofs?  $4.72 per gallon.  Those fancy-schmancy deep storage tunnels?  $2.42 per gallon.  At $1.59 per gallon, even pretty little rain gardens cost more than five times that of simple soil amendment. 

Milwaukee is not alone in promoting soil amendment as a first line of defense for stormwater management  For example: 

  • Denver and GreenleyColorado, require compost use for new landscaping, as does Leander, Texas. 
  • Some state Departments of Transportation (DOTs) now routinely specify compost.  A few years ago, the Texas DOT said it was the largest single market for compost in the U.S. 

In an urban environment, opportunities for soil amendment abound.  City parks, athletic fields, planters, urban lawns, highway medians and easements, foundation backfill – anywhere there’s soil, there’s opportunity for inexpensive water retention. 

Every 1 percent increase in soil organic matter (SOM) content adds an additional 16,000 gallons of water-holding capacity per acre foot.  A site managed to maintain soil organic matter at only 2 percent can hold all the water of a typical rain event (1 inch or less), which is 27,154 gallons per acre.     

In fact, at 5 percent SOM, the soil can retain the water equivalent of nearly 3-inches of rainfall.  In some regions, this equal95 percent of all storm events. 

Soil amendment may not solve all rainfall issues, especially in downtown areas.  But managing water where it falls can be the most sensible, efficient, environmentally- and economically-prudent strategy for “first line of defense” stormwater management.   

Food waste mandates are only the halfway mark 

Compost use gets organics recycling to the finish line 

Unlike a decade ago, when food waste mandates were few and far between, there is a flurry of activity these days focused on diverting food waste and other residential/commercial biodegradables from landfills and incineration. 

From the U.S. to Italy to northern India, the movement toward more sustainable management of organic waste from households and businesses is real and gaining momentum. 

But while laudable, there’s a big piece missing from some of these programs — mandated compost use.  Just making compost isn’t recycling.  The product must be used – returned to the soil – to be recycled.  That’s what makes the system “sustainable.” 

Landfilling organics isn’t sustainable because they’re buried.  Any thermal or other waste-to-energy (WTE) technology that destroys organics isn’t sustainable, either, no matter how hard technology providers try to paint them as such.  The feedstock – waste – may be considered a sustainable source, but the process is not. 

A possible exception is biochar, carbon-rich, charcoal waste material produced by pyrolysis that is sometimes used as a soil amendment.  However, not all biochar is right for this type of reuse.  It doesn’t offer as many benefits as compost, and — since the use of biochar is relatively new — there is a lack of research related to its long-term use.  While pure biochar is made from organics, of specific concern is contamination resulting from WTE biochar processes that use unsorted municipal solid waste as feedstock.  

But whether biochar or compost, the truth bears repeating — recycled organics must be used to feed the soil for a sustainable system to exist.  This is the only way to close the recycling loop for organics. 

Going the distance with food waste mandates

Football players don’t move the ball to the 50-yard line and then stand around waiting for the pigskin to get itself into the end zone. 

Establishing a curbside or drop-off program for source-separated organics is a good first step … but it’s only half the distance to the goal.   

The finish line for organics recycling is compost use.  Anything a community can do to encourage that use is important.  But sometimes, it takes more than education and outreach to get the ball rolling. 

When governmental entities write ordinances and project specifications requiring compost use, good things happen.  By creating early markets for quality compost productseveryone from green industry pros to stormwater managers to homeowners can clearly see the benefits of amending soil. 

This demonstration leads to voluntary compost use through the manufacture of quality products and product sales to high-value markets.  Product sales, not giveaway programs, is what will keep composting facilities – public or private – economically sound. 

Any community considering organics recycling needs to think about the end game.  To ignore the ultimate goal is to win the battle, but lose the war for organics recycling.  

READ:  Food waste diversion — it’s time to pursue alternatives that make environmental and economic sense

Making sense of research data

Evaluating organic waste management options and cost comparisons

When personal expertise is lacking, people place their trust in experts to facilitate decisions about everything from home additions to medical care.  Governing boards are no different.  They rely on the knowledge of utility directors, staff engineers, and consultants to help them make informed decisions.

But when presented with an avalanche of numbers – from scientific data to cost and operating projections – how do members of city councils and county commissions know if the information contained in that mountain of reports is accurate and unbiased?  How do they know they’re comparing apples to apples and not apples to oranges?

Placing value on studies specific to waste management can be complex.  One report might compare landfilling, incineration, and anaerobic digestion, but leave composting out of the mix.  Another may include composting, but base assumptions on an antiquated window system and not a modern, high-rate technology.  Research could unearth reports about a costly public project but never discover a more efficient, cost-effective commercial system.

This is not to suggest such errors or omissions are intentional.  Sometimes, it’s simply a case of “you don’t know what you don’t know.”  But when combined with the fact that detailed financial or operational data from private-sector owners is rarely made available in public spaces, one begins to understand the difficulty in obtaining good data on which to base conclusions and recommendations when doing composting cost comparisons.

The takeaway?  Assume all research is flawed in some way.  No one knows everything there is to know about every subject.  But there are a handful of questions that members of city councils and town boards can ask to help clarify reported numbers, level the playing field, and present a more accurate picture of construction and operational realities.

Who paid for the research?

Perhaps the most significant influence on any research project is the entity that foots the bill.  Even university research is funded by someone … and it may not be the university.  Non-profits may fund research, but they rely on the support of donors.  Government agencies can be funders, but governments are run by politicians.  When the private sector funds studies, the results may never see the light of day if unfavorable to the funding entity.  Student work may not be funded, but it’s still student work.

Was the research scientifically sound?

Some “research” may not be new research at all, but assumptions or conclusions based on a literature review that includes outdated or invalid findings.  Investigations may have been conducted in a manner that does not reflect “good science,” including a lack of statistically-representative sampling.  Some findings are more opinion poll than science.  But when sifting through millions of scientific papers for data, researchers won’t always pick up on these types of flaws.

Also know statistics can be presented in a manner that makes differences look more (or less) important than they really are.  (See an example in this SlideShare title:  Apples and oranges: comparing waste management technologies)

How old is the research data?

Unfortunately, it’s all too common to discover a case built on multiple levels of citations that eventually trickle down to data or conclusions that may not reflect present day realities.  Knowing the date and technological sophistication of the original study will help decision-makers evaluate the value/validity of the conclusions and recommendations included in the consultant’s report.

Don’t accept a current date on a citation at face value.  Follow the citation trail to the date and circumstances of the original research.

Is data based on full-scale operations using current technologies?

Was the data based on bench scale, pilot scale, field scale, or full scale?  Conclusions reached during early stages of product or system development can fail to “scale up” successfully.   Investigations based on dinosaur technologies of 20 or 30 years ago exclude advancements and enhancements made in recent years, distorting findings.

For composting specifically, ensure that systems and technologies are apples-to-apples comparisons using the most current data available.  If evaluating high-rate systems, include successful private-sector facilities, too, not just municipal.   Net expense and revenue values per ton processed can vary widely between different types of operations.

Using old data and processing systems for dollar comparisons could greatly skew conclusions when comparing composting to other waste management technologies.

Sometimes, imperfect is the only data available for composting cost comparisons

When conducting research in a field like composting, where meaningful research is scant, at best, the imperfect may be all there is.  Knowing and accepting this reality, proactively seeking out the most accurate information, and evaluating results based on a variety of studies and viewpoints can only help decision-makers make better choices for their respective communities.

Read the article:  Valuing composting as an infrastructure investment

3 questions to ask before choosing a composting system

When evaluating choices for organics diversion, system cost tends to be a major influence in whittling down the available options.  But is capital investment a good indicator of true costs over the decades of composting facility operation?

There are many questions decision-makers need to ask before choosing a composting system.  But judging by the number of lackluster operations in existence, here are 3 biggies that don’t get asked nearly enough:

Co-mingled vs. source-separation — do you want to sell this compost?

At first glance, co-mingling organics with either the total municipal solid waste stream or with other recyclables for central separation (either pre- or post-composting) looks like a no-brainer.  No extra collections or special trucks.  No expensive outreach and education programs.

But co-mingling doesn’t work if the ultimate goal is the production of a salable compost product.  Contamination can be so high, it’s almost impossible to sell the stuff.  Sometimes, farmers won’t even take it for free.

Co-mingled may be acceptable if the objective is to dry organics prior to incineration/WTE, but destroying organic matter does nothing to increase rain infiltration across the region, store carbon, reduce reliance on synthetic chemicals or cut erosion.

But to derive the most benefit from compost use, compost manufacture must result in a high-quality product.  That means source-separation supported by a good education and enforcement program.

Does the management plan include a professional sales effort to maximize the dollar value of the compost?

An inferior compost brings in little to no revenue to offset production costs.  But a quality product, supported by a professional sales effort, can net top dollar.

The first step to getting top dollar value from product sales is to manufacture compost that falls into the premium class – dark, nutrient-rich, even-textured and odor-free.  Every manufacturing dollar spent improving an agricultural-grade product can return additional dollars in compost sales to high-value markets like landscaping, turfgrass management and stormwater management.

Before choosing a composting system, make sure that technology is capable of producing quality compost.

But that manufacturing effort will be wasted if the operation lacks a professional sales program designed and run by experienced marketers and sales pros.  Mounting an effective sales effort requires both premium product and premium people.

Hiring experienced sales pros pays off.  If faced with the choice between someone who knows compost but lacks sales experience and a sales pro with a good track record but no composting background, choose the sales pro to lead the team and put him/her in charge of the compost guru.

Why?  The right pro will be able to learn what s/he needs to structure a program and move product.  The compost person may or may not have what it takes to be successful in sales.   But working for and learning from a seasoned pro will make that compost expert the best salesperson s/he can be, generating maximum revenue for the operation.

Does the analyst’s cost:benefit considerations include the advantages of regional compost use?

Irresponsible soil management practices carry a cost.  Options for highest and best use for compost regionwide should be factors in the cost:benefit evaluation.

Analysists need to ask questions like:

  • If raising soil organic matter eliminates runoff and sedimentation from a typical rain event (1 inch or less), what impact would the use of a quality compost have on the region?
  • How could compost use influence current municipal costs to manage stormwater or treat contaminated drinking water sources?
  • What would be the savings to local farmers if they could cut their fertilizer bills in half?
  • Since compost reduces chemical use and the severity of impact injuries on playing fields, how would this influence things like maintenance budgets, player downtime and medical bills for athletic and recreation venues?

Use of compost in a region can have significant positive impact on costs for stormwater management, synthetic fertilizer and pesticide reduction, water treatment costs and much more.   Costs, cost savings and avoided costs should be discussed and considered when weighing pros and cons for a proposed project.

Decision-makers who look only at trees instead of the forest may be doing their communities a great disservice.  When reviewing analyses and recommendations prepared by staff or consultants, be sure those reports take in the big picture, not just impacts to waste management.

keys to successful composting

Composting “done right” can be easy or difficult.  Easy if facility operators understand and manage according to a handful of scientific principles.  Difficult if they do not.

The specific method in use or design of the physical plant may determine the level of difficulty and costs required to get it right, but both are secondary to what really matters – process management.

From the basic outdoor windrow to accelerated in-vessel processing, successful facilities are managed to meet goals linked to specific process influences. Without attention to these details common to every composting operation, even the most advanced, tricked-out facility can get composting wrong.

Here are 7 keys to successful composting, unlocking the full potential of any type of operation:

Feedstock selection

The choice of feedstocks, whether income generators or purchased amendment, can make or break a composting operation.  For most private-sector operators, feedstocks are tied to revenues and, as such, influence profitability based on positive or negative dollars at the gate.

But for all facilities – commercial, government and non-profit — feedstocks also impact the financial health based on ease of processing and how that material will add to or detract from the market value of the finished product.  Each ingredient is unique.  Each adds different variables to the blend.  Some feedstock influences can fluctuate from one load to the next.

It is the sum of these parts that must be considered when evaluating feedstocks and formulating processing blends.  Every aspect of successful processing relies on a good blend, and that blend is based on types and volumes of individual feedstocks.

C:N ratios

Carbon and Nitrogen ratios, a.k.a. C:N or C/N,  reflect the proportions of each in the feedstock blend.  The ratio, comparing the number of parts Carbon to 1 part Nitrogen, is sometimes expressed as a single digit, i.e, “20” as shorthand for 20:1 or “100,” meaning 100:1.

C:N ratios are critical considerations when blending.  Carbon (non-mineral) and Nitrogen (mineral) provide microbes with energy and food.  They also influence processing rate and odor generation potential.

High carbon materials include things like oak (200:1) and wheat straw (80:1), compared to nitrogenous materials like cattle manure (20:1) and alfalfa (13:1).

The ideal is 30:1 for blended feedstocks, but anything in the 25-35:1 range is considered good.  20-40:1 still works, but as numbers creep higher, the process slows.  As numbers drop, the need for more aggressive odor management increases.  (A strong ammonia smell can indicate a low C:N ratio.)

Feedstock testing and/or generic C:N ratio charts like this one, combined with manual calculations or computer modeling, can provide material types and volumes for determining the most efficient blends.

Moisture content

The microbes responsible for biodegradation – aerobes — require moisture, but not too much, since they can’t breathe under water.   Excess moisture blocks air passageways, resulting in oxygen starvation.  Too much water leads to anaerobic conditions, which cause odor and create toxic compounds.

Water is also used by microbes to move around the pile and is required for bio/chemical reactions.  If the pile is too dry, biodegradation pretty much grinds to a halt for both aerobic and anaerobic processes.

Like a lot of factors influencing the composting process, moisture has its Goldilocks Zone.  Shoot for a moisture content of 40-60 percent (by weight).

There are a number of testing methods for moisture (including one using the common microwave), plus lots of moisture meters on the market.  Meters start at around $10 for the backyard variety and move on up into the hundreds of dollars.  Compared to testing, which tends to be more precise, meters offer rapid feedback and the ability to quickly sample multiple pile locations to improve accuracy without having to wait for test results.

But the simple “Squeeze Test” can also be a good measuring tool.  Simply grab a handful of the mix and squeeze.    If water runs out, it’s way too wet.  Does it crumble?  Too dry.  But if the handful holds its shape and dribbles little to no water, it’s probably okay.

Regrettably, none of the methods used to determine moisture content are spot-on, even laboratory testing.  But the good news is that moisture level is a parameter with flexibility.

Just remember – the higher the volume of the composting mass, the higher the likelihood for error using crude estimations and monitoring techniques.  Multiple sampling locations and sampling depths will help improve accuracy.

Uniformity – A compost blend needs to be a homogeneous mix of all ingredients with no multi-colored swirls, clumps, or pockets of individual feedstocks. Visually, the blend should look like a single material with both texture and particle size consistent throughout the admixture.

Failure to achieve a uniform blend prevents microbes from degrading target compounds at an equal rate throughout the composting mass, which can lead to zones of unprocessed, smelly, and even toxic material in finished product.

Pore space — The free movement of air and water throughout a composting mass is essential to a successful process. Microbes need oxygen, and that oxygen is delivered as air moves through the spaces between individual particles, a.k.a., pores. This air flow also removes excess heat.  Microbes use those same pores (plus moisture) for migration.

Compaction is the enemy of pore space, and like the lack of uniformity, can retard or kill the process.  Keep loaders and people off piles.

Compost piles can slump as the material degrades.  Prior to curing, turning or screening will restore pore space.  When using a loader instead of a windrow turner, don’t just dump the bucket.  Use a shaking or sifting action to create, restore and/or preserve pore space, whether placing compost in a bay, building a new pile or turning.

Air flow – Composting is supposed to be an aerobic process. If air doesn’t flow, the process isn’t composting.  It’s anaerobic biodegradation.  Anaerobes create odors and toxins, so if a pile smells, lack of air flow is one of the chief suspects.

Keep the air flowing with an initial blend with good pore space and moisture level, augmented by turning or aeration — at the recommended volumes/velocities specific to the system in use.

However, too much air flowing through the pile can dry it out, so monitor moisture and add water, as needed.

Temperature – Heat buildup (not oxygen supply) is often the limiting factor in composting. When air delivery is sufficient to moderate temperature, microbes are being supplied with more than enough oxygen to maintain biochemical functions.

Therefore, keeping temperatures in the right zone for the specific phase of decomposition is composting’s equivalent of the Prime Directive.

There are precise time/temperature targets for pathogen kill.  While originally written for biosolids management, an EPA 503-approved process is now required by many states to kill pathogens inherent in everything from food waste to yard waste.

While reducing pathogens may be a regulatory mandate, those time/temperature requirements represent just one process influence demanding temperature management.  In fact, assuming the operator maintains control of temperatures from the beginning of the process to the end, pathogens cease to be a processing issue once the regulatory requirement has been met.

Far more important is the intentional management of temperature during both the mesophilic and thermophilic phases of composting.

Mesophilic microbes prefer moderate temperatures up to about 40 degrees C or 104 degrees F.  They are the initial decomposers, and their feeding activity generates a lot of heat.

Whenever temperatures within the composting mass rise unchecked, the process grinds to a halt (all microbes die), crashes (there’s no decomposition) and must restart (microbial populations must rebuild).  In nature, this happens repeatedly, which is one reason why Mother Nature’s system is so slow.

But a well-managed composting process stops this hot-cold cycling from happening.  If the blend is right, temperatures will start to climb within a few hours of process initiation.  As temperatures pass out of the mesophilic zone, microbial populations change to thermophiles – the heat-loving bacteria.

Thermophiles continue to work until temperatures reach about 65 degrees C or 149 degrees F – the ceiling of their comfort zone.  The objective of composting is to manage air flow to maintain the level of heat required to meet the time/temperature requirements for pathogen kill (over 55 degrees C or 131 degrees F) without killing the thermophiles.

This thermophilic zone – 131 degrees F to 149 degrees F – is where rapid decomposition takes place.   The longer the composting system holds temperatures within this zone, the faster the process will be.  Systems that do this well are referred to as accelerated or high-rate processes.

Eventually, the thermophiles run out of food.  As they die off, temperatures drop back into the mesophilic zone, where mesophiles slowly finish off remaining food supplies.  This natural decline in temperature signals the beginning of the curing phase of composting.

LEARN MORE:

How does bioremediation work?

Organic waste offers up a smorgasbord to hungry microbes

Unseen by the human eye, microbes are the soil’s equivalent of worker bees.  They are responsible for a slew of soil functions.  Without them, soils don’t work as they should.

“Soil organisms decompose organic compounds, including manure, plant residue, and pesticides, preventing them from entering water and becoming pollutants. They sequester nitrogen and other nutrients that might otherwise enter groundwater, and they fix nitrogen from the atmosphere, making it available to plants. Many organisms enhance soil aggregation and porosity, thus increasing infiltration and reducing runoff. Soil organisms prey on crop pests and are food for above-ground animals.”   — NRCS/USDA

Algae, bacteria, fungi, nematodes, protozoa — aerobic microbes and other soil fauna need oxygen, water, and food.  Other survival influences include environmental factors like temperature and pH.

In a managed setting like composting, microbial feeding activity quickly turns organic waste — including some toxic compounds — into a safe, carbon-rich soil amendment product known as compost.

The organics can be food waste, yard debris, biosolids, petroleum derivatives, or anything else that was once alive.  As long as the waste stream is free of agents that would kill bacteria and the like, the material should compost.

Of course, the time required to break things down depends on the specific type of waste, particle size, the composting process in use, etc.  But for the most part, a few days of controlled, high-rate composting followed by a curing period of several weeks is enough to turn common organics into dark, aromatic compost.

How does bioremediation work?

All matter – including organic waste — is made up of individual atoms.  Atoms join with other atoms to become molecules.  Molecules hook up to become compounds, and they’re all held together by chemical bonds.  For organic material, that bond is commonly of the “covalent” variety.  This means the atoms share, rather than gain or lose, electrons.  This makes for a more stable molecule.

During composting, hungry microbes dine on the waste stream’s inherent sugars and proteins, releasing enzymes as they digest their food.

These critters are mostly after the carbon, but their feeding also releases the nitrogen, potassium and phosphorus that plants use as food.  (There are also some microbes that can pull nitrogen from the air and convert it to plant-available form.)

Their enzymes break chemical bonds, eventually reducing compounds to molecules and molecules to atoms.  Toxic compounds disintegrate.  Along the way, elements and simple compounds realign, creating more benign substances like carbon dioxide and water.

Controlling the composting environment ensures ideal conditions for these microbes, setting the stage for rapid biodegradation.  Where decomposition and stabilization could take months (or years) in a natural setting, composting achieves the same outcome in a matter of weeks.

The tighter the control, the faster the bioremediation process.

How does bioremediation work?  Very well.

Can compost and perennial food crops save the planet?

A match made in food science heaven has the potential to forever change agriculture’s environmental impact.

Long ago, humans abandoned the hunter-gatherer lifestyle in favor of agriculture. They tweaked deep-rooted perennial grasses, turning them into shallow-rooted annual grain crops with higher yields.

But farming came at a price.  Domestication of wild edibles set off a destructive cycle of soil depletion.

Seasonal tilling loosened soil particles. Wind and rain carried topsoil away. With it went the earth’s ability to store water and sequester carbon.

In the last 200 years alone, the top 2 meters of the earth’s soil have lost 133 billion tons of carbon.

Soil loss has turned into a big problem for today’s humanoids. Topsoil is at a fraction of historic levels.  Storage capacity is dwindling.  Greenhouse gases are building, and global temperatures are rising.

No-till agriculture was once thought a solution to soil loss. By planting in the rubble of the previous crop, farmers didn’t need to plow the soil.  But many no-till farmers rely on heavy doses of chemicals to control weeds. This, we now know, generated its own set of problems.

But no-till put agriculture on the right track.

Perennial crops like orchard fruit, tree nuts, berries, and asparagus produce food.  Because the soil remains undisturbed season to season, these crops are also no-till.

Through photosynthesis, they sequester carbon in the soil for many years.  By adding carbon-rich compost before planting and throughout the crop’s lifecycle, carbon storage becomes even more significant.

But from maize to melons, most of today’s plant-based foods are annuals. These dead-within-a-year plants constitute 85 percent of human calorie intake.  Yet they offer no long-term carbon sequestration and require tillage year after year.

Compost application may boost soil productivity on annual cropland. But much of its carbon is released with the next tilling, too.

So scientists began to ask:

Is it possible to revert more crops, especially grains, to perennial form? Could agriculture meet this goal without sacrificing yields?

Back to the future with Kernza®

The answer appears to be a resounding … could be. Probably … yes. A cautious … quite likely.

Researchers have gone back through time to marry the characteristics of two crops. One is an ancient perennial wheat-like grass. The other is a modern, annual wheat.

Together, they have produced a perennial wheat with the trademarked name, Kernza. This year, General Mills’ Cascadian Farms plans to produce 6,000 boxes of a breakfast cereal featuring the grain as a research fund-raiser. Though total acreage is still small, other commercial applications for Kernza include bread and beer.

In photographs, Kernza kernels look more like a wild rice (a grass) than a wheat berry. But it is considered flavorful and can be harvested using conventional farming equipment.

Deep-rooted (10-20 ft.), this intermediate wheatgrass grows from a rhizome.  It is planted in the fall (in Minnesota).  Most growers plant in rows, but solid seeding is also used.  Weeds are not a big issue, because as the rhizomes spread, they choke out weeds.

The problem is that the kernel is small, like the yield per acre.  Conventional milling equipment doesn’t work.  And, currently, Kernza growers reap a meager 500 pounds per acre. Their conventional wheat-growing counterparts get an average of 2,856 pounds in the U.S.

After a few years, those thick, horizontal stems can run out of expansion space, too. Yields decrease.  As a result, some growers replant every 3-5 years. At least one farmer is experimenting with chisel plow strips to extend productivity to lengthen the time between replanting.  (More cultivation information:  Farmers voice their experience growing intermediate wheatgrass for grain)

The importance of deep root systems and perennial food crops

Worldwide, several annual food crops, including rice, have become the focus of similar research.  Perennials for biofuel production are being studied, too.

Minimizing soil disturbance is one reason. The benefits that come with deep-rooted crops is another.

Living plants remove carbon dioxide (CO2) from the air. They keep some of the carbon (C) and release the rest, along with the oxygen (O2), back to the atmosphere. The retained carbon resides in stems, leaves, and roots. Plants use water and light to turn that carbon into sugars to fuel growth. When plants die and decompose, the carbon becomes a constituent of soil organic matter (SOM).

Deep roots extend the rhizosphere, the zone where roots, soil, and microbes interact. Microbes aid in the transfer of carbon from plants to soil.  Researchers say increasing this area could raise soil carbon storage.

Deep-rooted crops are a tool of what has become known as “carbon farming.”  The goal is carbon sequestration — removing excess from the atmosphere and storing it in the soil, instead.

Moisture and temperature increases could speed up carbon release at lesser depths.   But research suggests deeper soils buffer that carbon from climatic change.

If true, consider the carbon impact of a 20-ft. Kernza root compared to the typical agricultural plant (~3 ft. root depth).  To better understand the potential, this article includes an image comparing perennial Kernza and annual wheat root systems.

Assessing carbon storage potential of perennial food crops

Estimates of the carbon storage potential of “perennialized” annuals are sketchy, at best. None of the new grains have yet to hit their commercial stride.

Research on deep-soil carbon storage is a bit thin, too. It’s difficult to find sequestration estimates that consider all possible impacts like:

  • Reductions in fossil fuel extraction and use
  • Conversion of annuals to perennial crops+
  • Capture of all organics for composting and reuse

But as food for thought, here are some numbers from recent articles and research papers:

  • The soil carbon storage from improved root growth in agricultural crops could offset human-caused environmental emissions for the next 40 years.
  • Reuters: The U.S. emits around 5 billion tonnes of carbon dioxide per year. Better soil management could boost carbon stored in the top layer of the soil by up to 1.85 gigatonnes each year. This is about the same as the carbon emissions of transport globally.
  • Peak Prosperity: A 1 percent increase in SOM stores approximately 10 tons of carbon per acre. Doing the math: There are about 130 million U.S. acres in major annual grain crops. If converted to perennial varieties, carbon storage potential equals 1.3 billion tons.  That’s roughly 1/5 of the U.S. carbon pollution.
  • Bulletin of Atomic Scientists: Devote 5 percent of the world’s cropland to plants bred for carbon storage. Capture ~50 percent of current global CO2 emissions.  (That’s an area about the size of Egypt.)
  • USEPA: In 2015, about 38 million tons of food waste were burned or buried. Only 2 million tons went to composting. Doing the math: Composting all 40 million tons would produce ~20 million tons of soil amendment. This would cover roughly 600,000 acres in 1/2 inch of compost. Its ~11 million tons of carbon (20 million tons of compost @ 54 percent carbon) could go to deep-soil storage under perennials.
  • Life Cycle Assessment (LCA) of landfilling organic waste vs. composting and recycling estimated a net greenhouse gas mitigation benefit of 23tCO2eq/ha over a 3-year period when organics were composted. That’s 23 tonnes (1 tonne = 1,000 kilograms) of carbon dioxide equivalent per hectare — about 25 tons spread over 57 acres.  As little as a 1.3 cm (about a half inch) topdressing of compost resulted in “substantial” increases in carbon storage on rangeland, too, attributed to better water retention and improved grass productivity.

 Economic benefits add up, too

Looks like there’s yet one more reason to bank on perennials — economics.

Agricultural investors say annualized income for perennials rose ~13 percent over 10 years. Income from annual cropland stagnated at about 4 percent during the same period.

And in a few spots, Kernza is generating more profit than the more traditional corn and soybeans. In addition, Kernza leaves and stems remain green at ripening, making its hay more valuable than wheat straw.

Commercialization of annual-to-perennial food crops is a tantalizing possibility.  The day may come when “perennial food” labels sway consumer purchases, just like organic, gluten-free, and other profitable food-niche certifications.

But most enticing is this factoid — at $0-$100 per ton, soil carbon sequestration is the cheapest carbon mitigation tool currently available.

It should be noted that soils can eventually reach a point where no additional C can be absorbed.  Sequestration is not a miracle cure.  People still need to work on reducing CO2 generation.

But in the interim, agriculture offers one opportunity to reduce the human carbon footprint.  And compost under foot makes this challenge easier.

Can compost use impact deep-soil carbon storage?

Atmospheric carbon dioxide (CO2) levels have reached a 3-million-year high.  The overload has been building up since the Industrial Revolution hit its stride about 200 years ago.  One culprit is conventional farming, which releases stored soil carbon, (C) relies on synthetic input, and degrades soils.  The use of fossil fuels — which adds even more carbon to the air — is another major contributor to the increase. 

Impacts include reduction in carbon storage capacity due to topsoil loss, pollution, and climactic changes linked to global warming.

While some say CO2 levels are a non-issue, others believe the opposite and are working to reduce atmospheric carbon by cutting greenhouse gas emissions and sequestering more carbon.

Proposed solutions include ideas like basalt rock injection and ocean storage.   But one of the simplest and most cost-effective options already in play is to simply return carbon to soils.

But there is a catch.  Since soil disturbance releases carbon, farmland dedicated to annual crops offers little to no upper layer storage potential.  Unless the farm — organic or conventional — has adopted no-till practices, the soil is disrupted every year during planting.  Therefore, acres that will remain undisturbed for long periods of time are the best candidates for long-term carbon storage, a.k.a. carbon farming.

This translates into a need for conversion of annual grains and other crops to perennials to maximize soil carbon storage potential.  But developing high-yielding perennial grains is a process that will take time.

Applying compost to both annual and perennial acres is something that can be done now.

Long-term soil carbon storage has two primary pathways — plant-based via deep-rooted perennials (like some trees and grasses) and soil amendment.  Compost leads the pack as the amendment of choice, offering a plethora of soil- and crop-enhancing benefits in addition to carbon storage.

The carbon sequestration benefit of compost use is two-fold.  It adds compost’s inherent carbon content to the soil.  But it also improves soil productivity, increasing above- and below-ground biomass, which stores more carbon.  This positive impact can persist for many years from just one compost application.

Microorganisms and insects like earthworms and ants also influence carbon storage.

Current research emphasis seems to focus on C storage potential in agriculture.  That’s because worldwide, farmers crop 4.62 billion acres — a treasure-trove of carbon storage potential.

But it should be noted there are many more non-ag acres that can offer long-term, deep-soil carbon storage, too.  No need to wait for researchers to develop new perennial grains or convince farmers to make the switch from annuals to perennials.

In the U.S. alone, millions of acres could take and store compost-applied carbon today:

  • 40 million acres of lawns
  • 50 million acres of managed turf including 700,000 athletic fields and 17,000 golf courses
  • 7 million acres of public lands under the jurisdiction of the Bureau of Land Management (FY 2017)
  • Umpteen million acres in government-controlled roadside easements, utility rights-of-way, local and state parklands, and other managed greenspace, both public and private.

Just a 1% increase in soil organic matter (about 20 tons of compost per acre or a 1/4-inch application depth) can store 10 tons of carbon per acre

While it may not be practical or possible to add compost to all those acres, the potential for long-term, compost-based carbon storage in the U.S. alone is … well … pretty big.  And the deeper the storage, the longer the retention time.  Even annually tilled acres can offer C sequestration if that carbon can find a pathway to deeper soils below the plow layer.

But how does compost-applied carbon migrate from upper soil levels to deep-soil storage?

Below the plow layer — deep-soil carbon storage

A “plow layer” is the layer of soil disturbed when a plow (plough) is dragged through a field.  Depending on the type of plow used and its settings, the layer depth can range from a typical 8 inches to 20 inches or more.

The trick is to facilitate the movement of carbon from the plow layer to deeper soils where it can lie locked up and undisturbed for centuries.

Typically, the root systems of trees and perennial grasses grow deeper than annuals.  As the root systems of plants bury themselves in soil, they do more than just carry carbon in their tissues.

Downward growth also creates passageways for water and a transportation route for microbes.

Critter burrows create pathways for water and microbes, too.  Well below the plow line, termite colonies can be found as deep as 6 meters.  Some types of ants live at depths of 3-4 meters.  (1 yard = .91 meters)

Nightcrawlers will work their way down several meters into the soil, bringing organic matter with them.  Their castings (excreta) have a carbon-to-nitrogen ratio of 12-15:1 and include beneficial microbes.  A healthy soil layer above ensures plenty of available carbon for below-the-plow-layer earthworm storage.

C storage depends on many factors

It is important to remember neither the C cycle nor microbial metabolic processes operate in isolation. These functions are influenced by many factors like:

  • Nutrients
  • Temperature
  • Moisture
  • pH

Climate plays a role, too.  Globally, cool-wet regions tend to have the highest concentrations of soil carbon and deserts the lowest.  One of the more disturbing aspects of a warming planet is that more soil-bound carbon may be released to atmosphere as temperatures rise.

Effective solutions will require wholistic approaches, but compost use continues to rank among the top options due to its affordability, universal applicability, ease of use, and immediate availability.

Bottom line:  The potential for deep-soil carbon storage exists, even on annually tilled cropland, through management programs designed to improve soil health and encourage symbiotic facilitators like nightcrawlers.