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FAQ: How does compost protect drinking water?

Primary sources of drinking water include wells, lakes, reservoirs, and rivers.  Compost will protect drinking water sources by breaking down pollutants and reducing erosion/siltation in runoff.  Microbial activity and absorption of rainfall energy are among the mechanisms at work.

Soil microbes break down many chemicals — like petroleum products – during feeding activity, severing molecular bonds and reducing complex compounds into simpler, more benign forms.  In fact, compost is used to remediate petroleum contaminated soils at airbases, underground storage tank removal sites, highway accidents, and similar clean-up projects.

Compost’s organic matter content cushions rain or irrigation water.  When water hits the ground, that energy is disbursed, and fewer particles are dislodged.  That same organic matter also absorbs more water, resulting in less runoff.

In addition, the use of compost reduces the need for chemical input on farms, turfgrass, and in the landscape, which also helps to protect drinking water sources.

FAQ: How do I sterilize soil?

When making your own potting soil from native soil or trucked in topsoil, it’s a good idea to sterilize that dirt to kill things like weed seeds and diseases before mixing with compost and other ingredients.  Large swaths of ground can be treated in-situ (in place) using plastic and the sun, but it takes time.  Fortunately,  small batches can also be treated using kitchen appliances.  Here’s a how-to article.  

What is composting and how does it work? 

Composting is the managed degradation of plant and animal matter under aerobic (with air) conditions.  The process mimics natural decay in a controlled environment to speed up the breakdown of these organics. Composting results in a safe and easy-to-use soil amendment — compost.

Insects and bacteria are examples of the types of creatures that feed on discards like food waste and leaves during composting.  The larger animals tend to use mechanical methods, while the microscopic rely on chemicals to degrade these materials.

This feeding activity reduces complex compounds into simple molecules that are benign and odor free. Compost is used to build and replenish soils, closing the recycling loop for organic matter.  

The only byproducts of composting are CO2 and water;  the process produces no waste requiring disposal.  The CO2 is considered “carbon neutral” since its release during composting is the same as if decomposed by nature.

Most municipal, commercial, and non-profit composting facilities rely on microbes to do the bulk of the organic decomposition.  There are mancomposting methods in use, although outdoor windrows are among the most common.  Earthworms are the primary agents of decomposition in the controlled process known as vermicomposting. 

However, some other processes that have the word “composting” attached to their name in the vernacular may not be true composting processes.

Bokashi composting, for example, is an anaerobic (without air) fermentation process. Anaerobic composting is another misnomer.  Because neither is aerobic, neither is true composting.   Both can biodegrade organics, however.  Unfortunately, anaerobic decomposition may generate unpleasant odors since anaerobes produce mercaptan during biodegradation. (Mercaptan is added to odorless natural gas to give the gas its distinctive rotten egg smell.)   

Composting digestate, the by-product of energy extraction using anaerobic digestion, increases both the market value and uses for this waste material if managed for quality compost production.  

While neglected composting piles have been known to “go anaerobic,” too, a well-managed composting process — one that keeps the piles aerated — will not generate unpleasant odors.  Any odors present in the incoming feedstocks will be quickly neutralized, too.

How much compost for my garden?

Compost makes a great addition to any garden plan.  But how much compost do you need?

A new plot in sand may require wheelbarrows of the stuff.  But if you are digging up a patch of lawn that has seen repeated compost applications over the years, the soil beneath the sod should be in pretty good shape.  A sprinkle might be all that’s needed.

How can you tell if the soil is good?  

The best method is soil testing.  (Contact your county Cooperative Extension Service for more information).  But you can use visual clues, too.  

Weeds like purslane, crabgrass, and dandelion are signs of a troubled soil.  

Stick a spade in the ground and turn over a shovelful of soil.  If it’s sticky and looks like modeling clay or dry and resembles beach sand, you’ve got big problems.  Fortunately, your soil is probably somewhere between these two extremes. 

Is it dark brown and loose?  Are there earthworms?  That’s what you want to see.  

How much compost do you need for a garden?

If building raised beds or container gardening, the soil blend should be about 30 percent compost.  When breaking new ground, incorporate 2 to 3 inches into the top 6 to 8 inches of soil.  

If your soil is very hard,  and you are planning deep rooted vegetables like tomatoes,  consider digging a little deeper.  Maintain the compost-to-soil ratio at about one part compost to two parts soil.

For an established garden with decent soil, just rake an inch or two into the surface before planting.   A 1/8 to 1/4 inch layer of compost sprinkled on the surface as needed throughout the growing season can revitalize flagging rows or containers.  The compost will feed your plants when you water. 

Three to 4 inches of compost can also be used as mulch during the growing season or as blankets when putting beds to sleep for the winter.  However, don’t pile compost up against tree trunks and stems of woody ornamentals.   

Our compost calculator can help you determine how much to buy.       

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. 

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. 

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.

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