How much does compost weigh?

Depending on moisture level, figure 2 to 2.5 cubic yards of compost per ton.  A one cubic foot bag of compost will weigh about 40 pounds (1 cubic yard = 27 cubic feet).

A product shipped at 30 percent moisture will weigh less than one at 60 percent when it crosses the weigh scale, resulting in more cubic yards per ton than the wetter material when delivered.  

This may be good for keeping transportation costs low. But it also means the microbes responsible for aerobic degradation of the composting mass might die of thirst.  Weights that are too high could be indicative of low oxygen levels resulting from compaction and/or too much moisture — again, not good for the beneficial microbial populations.

An ideal compost will be 40-50 percent moisture.

Are compost and fertilizer the same?

Compost and fertilizer are not the same. But compost does have fertilizer value.

Wikipedia describes fertilizer as any material of natural or synthetic origin that is applied to soil or to plant tissues to supply one or more plant nutrients essential to the growth of plants.”

Compost’s nitrogen, phosphorus, and/or potassium (a.k.a. NPK) values are low compared to a synthetic fertilizer.  Some may add ingredients like urea to hike these macronutrient numbers.

That said, compost’s NPK value does have dollar value. The nutrients delivered by a compost product should be a factor in any input decisions involving synthetic fertilizer purchases.  Compost also adds a slew of micronutrients not typically found in common synthetics and improves nutrient uptake.

Compost feeds the soil. In turn, the soil takes care of the plants, offering a smorgasbord of nutrients, pest and disease resistance, and more.   But those nutrients are slow-release, feeding plants over time.  The benefits of a single compost application can stretch over multiple seasons.

Fertilizer’s sole purpose is feeding plants.  The primary function of most synthetic fertilizers is adding N, P, and/or K.  Application gives an immediate burst of nutrition.

Do you need fertilizer if you use compost?

For the home gardener, probably not, especially if that gardener is a long time compost user.

But for a commercial grower?  Maybe.  If the crop likes a punch of nitrogen (for example) at a certain point in the growth cycle, the addition of a synthetic fertilizer may be warranted.

However, the smart grower will carefully weigh the cost of any input against the expected return on investment. Sometimes, a lower yield will still net higher profits if input costs for synthetic fertilizers and pest control products are reduced or eliminated as a crop management expense.

Also, keep in mind that compost-amended soil reduces rainwater and irrigation runoff, which means more nutrients are retained in the soil.   This will impact synthetic fertilizer input requirement, as well.

The Compost Connoisseur 

Compost maturity and stability are not the same 

A mature compost is usually stable, but a stable compost may not be mature.  Yet, both products have their uses.  Though the term“maturity” and “stability” are often used interchangeably to describe compost, they should not be.  

Confused? 

Look at a red and green tomato.  Both are stable and edible.  But the green tomato won’t be mature until it turns red.  This work-in-progress tomato is a bit on the tart side with firmer flesh that holds up when fried.  The mature red one is sweeter, softer, and makes a great sauce. 

As distinct products, mature and immature composts have their specific characteristics and uses, too.  But like red and green tomatoes, they’re definitely not the same. 

Compost maturity and stability 

MATURITY  All organicwill eventually decay until nothing remains but atoms.  The trick is to reach a degradation phase where the easy stuff is gone, leaving only dark, slow-to-degrade, earthy-smelling material behind.  That’s a mature compost. 

Between the raw waste and finished compost, however, are a series of degradation steps that aren’t that beneficial to plants.  In an immature state, compost can release compounds harmful to plants, fight with plants for oxygen, and pull nitrogen out of the soil.  

Compost maturity is best determined by testing, which is a good reason to insist on seeing a recent lab report for the compost under consideration.  Maturity indicators on lab reports include: 

  • C:N ratios  
  • Germination rates  
  • Oxygen uptake  

Maturity assumptions based on curing time are also recognized within the industry, but may not be as reliable as testing. 

STABILITY  If a compost passes the maturity test, it is a stable, market-ready product.  In a mature compost, microbiological activity slows because all the “easy” food has been consumed.  

But there are conditions within the composting mass that can cause product to enter a stable state without reaching maturity. 

Compost that has been dried to remove moisture, for example, makes it lighter for shipping, but can exhibit reduced biological activity, as well.  The same thing happens if the pile is deprived of oxygen. 

Unfortunately, once moisture or air has been reintroduced, microbial colonies can reestablish and return to active feeding.  Pathogens can rebloom and odors resurface as the composting process resumes. 

Germination tests remain one of the best indicators of mature stability.  If the compost exhibits no indications of phytotoxicity in conjunction with good pH ranges and slowed microbial activity, then the product has probably passed into the mature range. 

If trying to evaluate stability while standing next to a pile in a landscape supply yard, look for: 

  • A light, porous, evenly-textured product that encourages good air flow 
  • A compost with sufficient moisture to stick together when squeezed in the palm of the hand without crumbling or dripping water 
  • A pleasant, earthy scent 

Selecting the right product 

In the absence of testing information, the easiest way to gauge a product’s maturity is to smell it.  Compost that smells like soil has likely reached a stable, mature state and is ready for use anywhere and by anyone. 

Product that still retains some pungency isn’t stable or mature.  It’s not quite ready for unrestricted use.  But, provided it has met minimum quality standards for pathogen and vector reductions (as specified by regulations), the compost can be applied in rural areas away from sensitive noses where its higher NPK value is much appreciated by farmers. 

Time and nature will finish the job of product maturation and stabilization. 

Food waste collection: Thinking outside the trash can

Food waste collection can be a major hurdle for communities hoping to recycle curbside.  But might the real problem be not the what, but the how?  Is it time to think outside the trash can?

Let’s ponder this a minute.   

Waste 360 recently spotlighted grassroots recycling as a viable alternative to mainstream systems.  The article pointed out the actions of municipalities that, years ago, may have been too eager to turn successful, local recycling efforts over to “big waste haulers.”

The entrepreneurial efforts and business models of food waste collection outfits like CompostNowNOPE, and Compost Cab seem to be working in their respective service regions.  Instead of disrupting existing “Trash Day” collection systems and practices to include source-segregated food waste, these types of operations bypass the big trash truck with a service built on local-centric collection models that are meeting with success in multiple jurisdictions.   

Commercial composters, both large and small, have already demonstrated profitability in providing direct services to high- and low-volume waste generators, too. This success certainly proves that bypassing conventional collection systems is viable.

Looking at the world’s most successful bottle/container bills, we see return and recovery systems totally divorced from trash collection with capture rates approaching 100 percent.  While bottlers and other manufacturers of containerized products have been known to fight these types of programs, deposit and return systems do work. And they appear to work best when deposit amounts encourage those returns.

So, as the U.S. scrambles to rebuild and reshape its recycling infrastructure in the wake of the China debacle, could the long-abandoned local route to resource recovery of recyclables – residential food waste included – actually offer the better solution?  

Should food waste collection be a local thing?

Maybe, the decades-old struggle to integrate recycling within a system designed for mass disposal indicates the entire approach is flawed. Closely associating food waste, plastics, etcetera with trash as a first step to recovery means recyclables must be rescued from the waste stream before recovery can take place. Is this logical?  Is it efficient?  

Adding methane capture systems to landfills in an attempt to neutralize the damaging impacts of anaerobically-degrading organics just adds complications and expense for managing a material that shouldn’t be landfilled.  Similarly, for plastics and other recyclables, the better solution may lie in diversion at the source, not the transfer station.

Minus putrescibles/recyclables,  curbside collection of the real trash might be reduced to once a month (or less).  This disposal stream would be much, much smaller than current volumes … and clean.   With lower fill rates, existing landfills should last longer and cost less to manage, too.

When recyclables are funneled through and filtered by trash systems, does it make diversion more difficult than it needs to be?   Have we been going about recycling all wrong?

What are your ideas for getting recycling right?

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.  

What is compost used for?

“What is compost used for?  What’s the difference between compost and manure, or compost and topsoil, or compost and mulch, or compost and…?”

These questions (or some variation thereof) have been posed in Google searches by thousands of McGill Compost website visitors over the years, suggesting a broad lack of understanding on the part of the general public about soil products, in general, and compost products, in particular.

They tell us there’s much more work to be done before compost becomes a solid, steady blip on the soil amendment radar. 

It doesn’t matter whether the compost purveyor is municipal, commercial, or non-profit, or if it’s selling B2C or B2B (or both).   Compost manufacturers, distributors, and retailers can all benefit from marketing programs and advertising campaigns that include a healthy dollop of consumer education along with branding, product descriptions, and price points.

In a recent BioCycle article, Dr. Sally Brown reminds us that “… feel good sayings without quantitative information to back them up doesn’t always help to move the product. To a city engineer, these feel good statements can make you sound like a new age guru pushing a dietary supplement rather than a knowledgeable resource with alternative solutions.

Ouch.  

To be fair to all the OGs out there, in the early days of the composting industry, the only thing we had to peddle was feel good. There was little bona fide research or hard facts that demonstrated compost’s effectiveness to a customer,  just anecdotal evidence and side-by-side field photographs comparing compost and no compost applications.

McGill’s own economic impact studies, conducted in the early 2000s and funded by the state of North Carolina, were among the first to investigate dollar benefits related to compost use.  The research may have been simple by today’s standards, but it validated information our agricultural customers had been telling us for nearly a decade – and provided a solid foundation for the growth of our compost sales program into high-value markets.  (READ: the 2000 and 2001 McGill study reports)

But dollars and cents are only one part of compost’s amazing story that started with fertilizer value, but now just keeps going and going and going to include everything from food waste recycling to stormwater management to carbon storage.

Yet, the abundance of compost’s benefits seems to be a message that hasn’t been told loud enough or long enough or often enough to reach the ears of the majority.  There are still too many stormwater plans out there that don’t fix the soil as a critical first step,  communities that burn or bury compostables, and farmers who don’t use compost on conventionally-managed fields.

Talking who, what, when, where, and how when promoting compost is good.  But today, when a potential customer, policymaker, or specification writer is searching the web, s/he also wants to know the why — backed up with facts and figures.  Why is compost the right solution for their particular problem?   Why is it a better choice than amendment X, Y, or Z?

What is compost used for?

Adding macro and micro nutrients, building soil organic matter, replenishing and sustaining soil microbes, improving nutrient uptake and plant disease resistance, creating pore space, adjusting pH, absorbing rain impact energy, degrading pollutants, storing carbon —  it’s a lengthy benefits list for a single product that just happens to be “green.” 

Fortunately, unlike decades past, cyberspace is now loaded with scientific studies that provide meaningful data related to compost performance.  This is news the marketplace needs to hear.    

For example, it’s true to say compost alleviates compaction.  But when presenting to engineers, would it not be better to also include a link to or slide of this table that compares compost’s performance to other solutions, showing it among the best?

Or when a city is making decisions about its stormwater management strategy, why not share some comparative costs per gallon retained for various retention solutions discussed in Milwaukee’s Green Infrastructure Plan (see Page 63)?

“Compost will hold 10 times its weight in water” is good for visualization.  But how does it help a stormwater system designer calculate potential water and cost savings for mandating compost use vs. rain gardens or storage tunnels?  

These are the types of statistics a decision-maker needs to see when considering options:

  • A typical compost is about 50% organic matter. 
  • Every 1 percent increase in soil organic matter adds 16,000 gallons of water-holding capacity per acre foot.  
  • At only 2 percent organic matter, soil can hold all the rainfall from a typical rain event — around 1 inch or 27,154 gallons. 
  • A 1 percent increase in topsoil organic matter also stores about 60 tons of carbon per acre.

While specific numbers may vary depending on the study and/or source, the core message — that compost can be the better choice — remains constant. 

Researchers say the majority of today’s buyers do their due diligence and make purchasing decisions before reaching out to vendors for that all-important “first touch.”   If true, it’s more important than ever that brochures, point of sale displays, websites, or other outreach tools make the effort to quantify as well as entice. 

The environmental benefits of compost use are still an important part of the message. But the days of the easy sell to a predisposed customer base are long gone.  Now it’s time to win over everyone else.

Expansion of both B2C and B2B markets depends on the industry’s ability to effectively silence skeptics, motivate fence-sitters, and educate the uninformed — while keeping products (and services) cost-competitive.

Facts and figures will play a big role in that education effort.

Granted, there are lots of challenges ahead, and we do need more research of relevance to compost users to help fill quantitative gaps.

But composting is at an unprecedented place in its own history.  For the first time, the general public is eager to know more about what composting and compost use can do to positively impact a wide variety of issues. 

“What is compost used for?”

For the continued growth and wellness of the industry, research-based numbers need to be part of that all-important answer. 

Is composting food waste wasting food?  Until recently,  it’s a question that didn’t get asked.

Recycling organic matter back to the soil is supposed to be a long term, environmentally prudent, carbon sequestration practice — right?  Glowingly green.  Halo worthy.  Self-righteously gratifying.

Unfortunately or fortunately, depending on one’s viewpoint, folks are beginning to question all food waste, including the composting of former edibles.  

If composting was once a way to waste food without guilt, it is no more.  Except for the egg shells, potato peels and the like, that which was once edible food, if allowed to become fodder for the compost bin, is not consumed.  It does not feed anyone.  Ergo, it is wasted. 

Things like that fuzzy green stuff discovered in a leftover container in the back of the fridge, the carton of curdled milk, and the shriveled asparagus stuck to the bottom of the vegetable drawer means the cook prepared too much or a diner ordered too much at the restaurant or the family opted for pizza delivery while groceries languished in the pantry and fridge.

Buying too much prepared food, failing to prepare purchased ingredients, or cooking more than the family or customer will eat wastes food. The fact that the waste is composted does not negate the considerable negative environmental impacts required to get that food from farm to processor to kitchen to table — only to bypass a plate and wind up in the compost bin.

Yes, composting wasted food is far better than most alternatives.  But a critical look at wasteful habits could identify opportunities for improvement.  Chances are, even the most dedicated composting kitchen — whether residential, institutional, or commercial — can find ways to further reduce food waste while still generating enough scraps and culls to feed all those critters living in the compost pile.

READ MORE:  Can I compost oil and cooking grease?

Can I compost cooking oil and grease?

Is it possible to compost cooking oil and grease?

A lot of cooking fat, oil, and grease (FOG) goes down the kitchen drain.  Commercial kitchens install grease traps to collect the mess before it enters public sewer systems, diverting this waste to alternate disposal.

But the typical home kitchen does not, and the practice can clog pipes and negatively impact wastewater treatment systems.

Yes, it is possible to compost FOG.  But for the home composter, volume reduction and reuse is recommended as the first and best management strategy.  Adopt some of these kitchen practices to reduce and reuse to minimize volumes requiring composting or disposal:

REDUCE   

  • Opt for the oven or air fryer instead of deep or pan frying.
  • Spray oil onto food or into pans to lightly coat before cooking instead of pouring oil into the vessel for significant volume (and calorie) reductions.
  • Wipe cooking vessels with a paper towel before washing to remove excess oil.

REUSE

  • Many fats and oils (bacon, peanut, etc.) can be reused.  Cool and pour through a coffee filter or strainer into an airtight container and store in the fridge for up to a month.  
  • Allow cooking juices to cool.  Skim/remove the fat that congeals on the surface and freeze to use later to flavor veggies, soups, etc.   

RECYCLE

  • Check with your public utility to see if there is a FOG drop location in the community.
  • Add cooking grease to the food waste bin if your community composting operation can accept it.

COMPOST AT HOME

  • Small  volumes (up to 1 cup) of plant-based oils are best for home composting.  Simply pour over pile and blend in.  
  • Also compost the paper towels used to wipe oil from pans and kitchen surfaces.      

DISPOSAL

  • Pour waste oil into a non-recyclable can or bottle.  Seal prior to disposal. 

Is it really a good idea to make compostable waste go away and never come back? 

Each year, taxpayers collectively spend millions of dollars to burn or bury compostables.  Much like a tribe of ubiquitous Gollums, they just want garbage — the biodegradable and putrefying fraction of the municipal solid waste stream – to go away and never come back. 

The desire to make disagreeable discards disappear into fiery furnaces or burial mounds is understandable.  But is it wise?  Is it fiscally responsible?  Is it really a good idea to make organic waste go away and never come back? 

Nature recycles everything 

Rocks weather and erode, creating sediment. With heat, pressure, and time, that sediment becomes rock again.  Plants and animals feed and drink from the earth, die, and decompose to replenish the soil that will sustain future generations of flora and fauna.  Water drops from the sky as rain, filters down to aquifers, upwells and evaporates back to the clouds to fall once more. 

In a fantasy land, it may be possible to keep using resources without a thought to replenishment.  But in the real world, organic waste – the decaying residuals of once-living things – must be recycled back to the soil to maintain life-critical soil functions.   

Some seem to think the destruction of organics to make energy is more important than rebuilding soil.  But pushing an organic-waste-to-energy agenda by sacrificing the soil makes no sense. Humans managed to survive for millennia without electricity and centralized energy systems.  Without soil’s life-essential contribution to food and clean water, people face extinction in weeks.  

So, which is more important, energy or soil? 

Make energy and rebuild soil?   

Organic waste from developed societies includes all types of vegetation, food, manures … even compostable plastics.  When turned into a quality compost, these once-lost resources can be used by anyone anywhere to replenish depleted soil.   

Happily, making energy and building healthy soil does not have to be an either/or proposition.  It is possible to extract energy from organic waste without destroying the beneficial properties that make it valuable to soil.   The organic waste streams from these processes can then be used as feedstocks in the manufacture of compost products. 

Unhappily, energy production from biomass is one of the most expensive ways to make energy.  Even solar and wind power can be more cost-effective. 

Furthermore, bioenergy technologies based on anaerobic digestion of organics are still too pricey to be practical in many places.  Where they do exist, the waste stream (digestate) is not always put to highest and best use (i.e. composted).  Instead, residuals may be landfilled or relegated to low-dollar-value reuse. 

But one day, as more communities opt to restore natural soil replenishment cycles and energy generation technologies become more efficient, extracting energy from biomass, followed by composting and compost use, can become the system of choice for organic waste management. 

In the meantime … 

The importance of healthy soil 

Where humans live, topsoil has been scraped away or eroded.  Nutrients are used up.  Compaction has destroyed the pore spaces essential to the transport of air, water, and microbes.  Without a regular infusion of new organic matter to correct these deficiencies, soil dies.   

There are lots of processes for generating energy, but there’s only one way to replenish disturbed soils in developed areas – feed them a good, wholesome diet derived from organic waste converted into compost.   

From farms to lawns to sports fields, soils require periodic applications of compost.  There’s no other way to easily and economically provide soil with everything it requires to retain water, nurture vegetation, and create the type of environment soil microbes need to support nutrient uptake, contribute to disease resistance, and degrade pollutants. 

The best news? In many metropolitan areas, efficient, high-rate composting – the type needed to successfully manage big, urban waste streams – costs no more than landfilling or incineration.  Often, recycling at a modern, industrial composting operation can be more affordable than traditional disposal.   

Composting makes organic wastes go away, but they come back as enriching soil amendments.  Biodegradables need to keep recycling, just like they have since the beginning of time. 

Breaking the natural soil cycle by incinerating or burying compostable waste is a bad idea that should go away and never come back.

VIEW THE SLIDESHARE:  Addicted to convenience

How to make compost fast

The desire to make compost fast can be driven by space restrictions, the need for more product, or simple impatience.   It’s a common goal for composters everywhere, from the backyard to industrial facilities.

Unfortunately, wishing will never make it so.  The speediest course from raw feedstock to finished quality compost is a series of steps controlled by the person doing the composting.  Skip or bungle just one, and biodegradation could slow or even grind to a halt.

It doesn’t matter whether you make compost by the tumbler or by the ton.  If you want to make compost fast, follow these steps:

  1. Consider carbon-to-nitrogen (C:N) ratios when mixing every batch.  Base mixes on the C and N percentage of each feedstock, not feedstock volume – it’s not buckets of “brown” to buckets of “green.”   Learn more about calculating C:N ratios.
  2. Get the blend right with uniform particle size, good porosity, no clumps or marbling of feedstocks.  
  3. Maintain a desirable moisture level throughout primary processing.  Don’t expose the composting mass to weather or allow it to dry out.  Add moisture, as needed.   Learn more about composting moisture levels.
  4. Keep air moving through the pile.  This allows microbes to breathe and removes excess heat.  Invest in a temperature probe and adjust air flow to maintain ideal temperatures.       

Master these basics to make compost fast.