Greenhouse Gases, Wormeries, Compost, and Bio-Char, Oh My!

Things aren’t always as they appear………or as we are told.  Like the scarecrow, the tin man, and the cowardly lion, we need good ideas, our heart, and courage to do what is right.  We are told that the planet is heating up, that frightening things are happening (global warming) and like Dorothy, Toto and her companions we are not too happy to hear about these problems.

The mighty Wizard of Oz (scientists) advise us to get the broom.  We’ve got to face the wicked witch of the east and we’ve got to get rid of her creepy flying monkeys (green house gases).  We are supposed to find the answers and get back to the mighty Wizard hoping then he will show us how we get back to Kansas.

Dorothy and her dog Toto left the farm to find “a better place somewhere over the rainbow” only to in the end realize that the answers had always been in their own back yard.

Like Dorothy and her companions, others are taking the yellow brick road to the Emerald City seeking answers hoping the mighty Wizard of Oz will give them good advice.

Leaders around the country look to Seattle, Los Angeles, and San Francisco for those answers.  They want to know what to do with the solid waste, kitchen scraps, and organic solids that we all agree should no longer be placed in the landfills.

Green House Gases

What are the greenhouse gases anyway?  We’ve heard a lot about them but perhaps you too have wondered a lot about them and why some gases are more damaging than others.

It’s really pretty simple and you don’t need an advanced degree or a lot of fancy calculations to get your arms around the problem.  Simply put, anything in the atmosphere (over and above the surface of the earth) can absorb the sun’s energy, become heated, and then irradiate or send that energy back to the surface.

If we had no atmosphere a great deal of energy from the sun striking the planet would be deflected and sent back off into space.  The surface of the earth would be significantly cooler.   It  is warmer here because the gases trap heat. Most of the things in the air are gases…….like water vapor, oxygen, nitrogen and carbon dioxide.  Some of these gases escape the planet and take the heat they have absorbed with them and that has an effect of actually cooling down the planet.  Fortunately for us, we are not loosing a lot of gas.

Gases formed at the surface going back into the atmosphere will heat up and blanket the earth sending heat back to the surface, and this over time results in a kind of steady state temperature for the planet.  Some gases are more efficient at capturing the sun’s energy.  When they form and escape into the atmosphere; they have a greater effect on heating. Other gases that are less efficient at capturing solar energy do little to heat the planet.

So you can already appreciate that we’ve got to think about the amount of gas being put into the atmosphere and how efficient it is at trapping the sun’s heat to get a handle on how bad the problem might get if we don’t change our habits.  A small amount of a very efficient heat trapping gas could be far more devastating for the planet then large amounts of a relatively weak heat trapping gas.

Here’s the good news………..we need our atmosphere and these gases to get the temperature high enough to support life as we know it.  The oxygen, water vapor, carbon dioxide and other gases all contribute to heating up the surface because they catch the heat from the sun on the way to the surface or as it is deflected off the surface distributing and blanketing the earth with a kind of insulation that keeps the temperature about 33 degrees Celsius warmer then it would be without these gases.

University of Michigan Greenhouse Gases Article

Some gases, like methane when released into the atmosphere over time react to form other gases (they are oxidized and broken down) and as you can imagine the chemistry can get complicated.  But the point is that even though the life time of the gas in the atmosphere may vary and change with time, the heat absorbing and re-distributing heat properties of the gases are all contributing to a net gain in planetary temperature.  If we were truly in a steady state where gases going into the atmosphere and leaving the atmosphere were fixed and equal, there would be no further net heating of the planet.  But that is not a fact.

As it turns out the global warming potential of methane is about 21 times greater then the global warming potential of carbon dioxide.  This is just another way of saying that a molecule of methane (and all of its subsequent known oxidized products) will in time be 21 times more effective then carbon dioxide at trapping heat.

Nitrous oxide, a gas produced by earthworms, also found in poorly managed compost piles, is 310 times more potent then carbon dioxide.

Composting Greenhouse Mitigation

Certain trace gases like fluorocarbons used industrially are more then 1000 times as potent as carbon dioxide at trapping heat and they are no longer being used because they so heavily pollute the atmosphere.

We all know now that methane and carbon dioxide are great contributors to planetary heating and it really doesn’t matter rather you think it is man-made or natural causes we don’t fully appreciate that explain the rise in carbon dioxide levels that have been widely observed.  More polluting gases are only going to make things worse.

When carbonized products are oxidized, carbon dioxide is produced.  So fuel used in transporting or processing materials, either goods or waste material will pollute the atmosphere with carbon dioxide.  Of course we’d like people to consume less and produce less waste so we don’t have to transport so much waste to the landfill.  And we will ask them to take the organic waste out of the garbage so it can be processed more efficiently.  We don’t want that methane and carbon dioxide coming out of the landfill and we need more space to bury the non-organic waste.

Seattle to require table scrap collection in April 2009

We’ve already made the point that composting is not the answer and is indeed contributing significantly to the global warming problem.  We can anticipate that the problem will get much worse if more people adopt that policy.  Academics who have taken a closer look at how people compost at home have warned us more then 2 years ago that these practices contribute greatly to global warming.

Check out this recycle article

Professor Jan Gronow of London’s Imperial College has pointed out that “Emissions from home composting and poorly-run composting operations may contribute significant amounts of methane because75% of people’s home composting bins are anaerobic because they do not aerate them.”  The concern was backed up by the head of the waste and energy research group at the University of Brighton, Dr Marie Harder, who asked: “Has anybody stopped to ask whether home composting is good for the environment?”

Over 34% of British households participate in home composting schemes according to the government, which has just completed an initiative handing out one million composting bins via the Waste and Resources Action Program.

Defra’s (the British Government’s equivalent of our USDA’s) long-term waste strategy is currently being reviewed, with a new strategy expected by the end of the year. But Prof Gronow, who was formerly the Environment Agency’s head of waste and remediation science, believes the government was “jumping on the climate change bandwagon” to reach European landfill targets rather than thinking about the real environmental impacts of different recycling and composting processes.

A little house keeping

So some of you who think composting is good may want to site a number of reports where experts have made the claim that in well managed compost operations the contributions to greenhouse gases are reduced. For example Californians Against Waste assert that composting is a greenhouse gas mitigation measure.

And there are primers for Compost Producers that attempt to rigorously prove that composting is beneficial and results in a reduction in GHG emissions.

Here it is very important to look at the assumptions that are made.  We’ve got to question those assumptions to determine if they are truly valid and use a little common sense.

Although they acknowledge an inventory of GHG must be done to determine if policies are truly going to make a difference, the assumptions regarding what is happening when organic discards are processed are flawed.

Organic discards that are high in nitrogen and carbon content (food scraps, grass clippings, etc.) placed in the landfills decompose to produce methane and nitrous oxides.  They pollute badly……… we want them out of the landfills.  We all agree.

It is argued that the value of compost mitigation (to reduce global heating) can be determined by answers to these questions.

  • What would have happened to the feedstock (scraps, clippings, etc.) had they not been composted?
  • How is the compost operation run?
  • What happens to the compost?

The negative impacts are said to be from emissions from diesel powered processing equipment used to handle and process feedstock that is being composted.

Good accounting practices mean you have to account for the cash coming in and going out.  The rate of carbon dioxide produced does not necessarily equal the rate of carbon dioxide taken back out of the atmosphere by plants.  That assumption was made in the mitigation analysis.

The carbon dioxide naturally produced by decaying plants is called biogenic carbon dioxide.  The net balance will be close to zero if there is no polluting program in place.  One assumption about composting that can lead to a great miscalculation is the assumption that the rate of carbon dioxide produced during compost operations equals the rate of removal from the atmosphere by plants that are alive and growing.

As more and more agricultural products are produced to feed the growing world population, the mass of organic waste has escalated.  It is simply unreasonable to assume that the rate of aerated waste material allowed to decompose (by composting) will produce no more carbon dioxide then can be taken up by plants.

Although it might well be reasoned that because methane and nitrous oxide are far more heat producing than carbon dioxide alone, and neither of these gases are produced in well run compost operations, it does not prove that composting is the best policy.  There are alternative practices that produce no polluting gases.

It has also been argued that composting puts more carbon into the soil (a form of sequestration).  If you can put the carbon into the soil so less and less is available to oxidize and produce carbon dioxide, then over time the amount of carbon dioxide in the atmosphere has to drop……….right?  This again is not necessarily true.  It depends on the relative rates for producing carbon dioxide and sequestrating the carbon.  If you are producing more and more carbon waste (more food scraps) and composting them, yes it is true more and more carbon is going into the soil, but you are also putting more and more carbon dioxide into the atmosphere.


Some of you are certainly familiar with wormeries and one might be tempted to believe these are going to help us out of this problem.  Although the amount of worm composting is very small and the amount of landfill is large, the worms may not be as environmentally friendly as gardeners who use them have hoped for.

A lot of people love worms and think they do no harm.  However, it is now clear that large commercial worm composting plants may be comparable to the global warming potential of landfill sites of the same scale.

Scientists in Germany have demonstrated that one third of the nitrous oxide emissions coming from the soil are associated with worms.  Although worms are very efficient at breaking down kitchen scraps and other organic materials, they emit nitrous oxide in the process of digesting these materials which as noted is 300 times as effective as carbon dioxide in trapping heat.


What about that idea of trapping carbon in the soil?  Thousands of years ago the natives along the Amazon basin discovered a method of farming that until recently was not fully appreciated as a method of reducing the greenhouse gas effects.  They were able to transform some of the most infertile soils into the most productive of soils that remains today even 500 years after they are gone rich in organic matter and nutrients.

The Terra preta, as it is known, was produced by a slash-and-char policy.  The indigenous people like others in many parts of the world did a slash and burn to clear and prepare the land for crops, but instead of letting the fire burn openly and rapidly, they covered the lit fires with soil and straw to let it smolder.  They reduced the amount of oxygen available for combustion.

The smoldering process puts about 50% of the carbon mass back into the soil where it is then available for plants and microbes in the soil.  It turns out that microbes and plants symbiotically thrive off of the carbonaceous resins that are produced.  The microbes release enzymes that are involved in freeing trapped minerals, ions and nutrients fixed in the charred mass that are then delivered to the plant root hairs.  The plants secrete nutrients in return that are used by the microbes.

Because the oxygen levels were reduced in the process of decomposing the organic matter (in this case by slash-and-char), less carbon was released into the air as carbon dioxide.  Carbon was put into the ground (sequestrated) and made unavailable for release into the atmosphere.

The Japanese government approved the use of charcoal as a land management practice in 1990 and we are certain much more work in this area is in process.

The more we examine the facts the more we realize that the processing of the carbon waste and the biomass that is less polluting occurs when oxygen levels are reduced.  Although it is true that anaerobic decomposition in the landfill is polluting, this is because of the type of organisms that are allowed to grow and interact that trigger the release of methane and other polluting gases.  An anaerobic fermentation process with the right kinds of microbes gets around this problem and most importantly produces no polluting gases.  It is also far more efficient and faster then composting.

In the classic 1939 American musical-fantasy film, The Wizard of Oz, when Dorothy and her companions returned to Emerald City, her dog, Toto inadvertently exposes the great and powerful wizard as a fraud.   They find an ordinary man hiding behind a curtain operating a giant console which contains a group of buttons and levers and are of course outraged at his deception.  But the wizard solves their problems through common sense and a little double talk, rather than magic. He explains that they already had what they had been searching for all along and only needed things such as medals and diplomas to confirm that they were qualified to find the solutions to their problems.

They found in the Emerald city the answer they were hoping to get……….and it was surprising to discover it was right at home……… the back yard.  We’ll talk more about microbes and anaerobic fermentation in the next blog.

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