Does burning as compared to composting produce the same products?

Question

Burning, say, leaves in the garden seems, to me, to be the same process as letting them rot except it is accelerated by heat. Are the same gases produced and in the same quantities for each process?

In response:
Prof Sheed - I find it curious that soil can absorb Co2 and although I am aware of plant life converting Co2 to o2 through their leaves I was unaware that they also enjoyed the gas through their roots.
Albannac - That is a very interesting reply
Hasicit - Why should the same process produce different products?
Bob - I understand that. In short you are saying that the slower process is so slow that it takes thousands of years to complete and when it gets to coal it will eventually convert to Co2 but in a very long time and at that stage - several thousand years later it will have completed its cycle as the burning did in half an hour. So when we burn coal we are accelerating the cycle to Co2

dy/dx and Bubba - You guys are streaks ahead of me on Science and I am digesting your answers

Pinkelip - I think that people seem to be agreed on that in the longer period of time the products are the same if nothing is added. I have had a wormery for a good few years and it is very sucessful and thanks for mentioning it

Answer 1

Not in the same amounts.

If you burn plant matter, you're left with a few ashes, which contain little carbon. Essentially 100% of it is now CO2.

If you compost it, you're left with - compost, which contains some carbon.

Note that decaying/burning plant matter release of CO2 is relatively unimportant to global warming. Surprisingly, it actually matters where the CO2 comes from. In this case that CO2 was very recently taken from the air by plants. Putting it back is no big deal. The big picture is this:

There are a great many natural sources and sinks for carbon dioxide. But the present global warming is (mostly) the result of man made CO2 from burning fossil fuels.

There is a natural "carbon cycle" that recycles CO2. But it's a delicate balance and we're messing it up.

Look at this graph.

http://gaw.kishou.go.jp/cgi-bin/wdcgg/quick_plot.cgi?imagetype=png&dataid=200702142947

The little squiggles are nature doing its' thing. CO2 falls a bit during summer when plants are active, and rises during the winter. The huge increase is us, burning fossil fuels. The scientists can actually show that the increased CO2 in the air comes from burning fossil fuels by using "isotopic ratios" to identify that CO2. The natural carbon cycle buried carbon in fossil fuels over a very long time, little bit by little bit. We dig them up and burn them, real fast. That's a problem.

Man is upsetting the balance of nature. We need to fix that.

EDIT - You've got it.

Answer 2

Absolutely not. Burning destroys all the helpful things in the leaves and pollutes the atmosphere ( even though it gives you a nice nostalgic smell in the air ) You are left with a fine powdery ash which does nothing for soil texture. Though I have used it in stoneware glazes on pottery.
Compost your leaves in a good heap within wire netting or old pallets nailed together. Or in black polythene bags with a few holes made with a garden fork. You can sprinkle with a compost accelerator. Then you will have a lovely sweet smelling product full of bacteria and great for adding texture to your soil. Beech and chestnut leaves take longer to rot. Be patient. S Later...having read all the answers after doing mine I realise mine is a gardeners reply and not scientific. What a lot of clever people out there !

Answer 3

The short answer is no.

In all cases, the law of conservation of mass applies. The same atoms are present in the products as the reactants (almost: there are some radio-isotopes that decay into different atoms ).

Composting will produce different products, depending upon the types of micro-organisms present (a complex mixture with hundreds of species), temperature, pH, available water, oxygen available and many other factors. In general, composting will break down some of the large molecules (carbohydrates) and re-use others (particularly amino and nucleic acids).

Burning is better described as an exothermic oxidation process. Burning will also produce a range of products that depend upon the residence time of the fuel in the fire, the temperature, the turbulence, catalysts and the type and concentration of oxidants. Trace elements present in the fuel form a very complex array of minerals and glasses that can go into the air as fly ash or remain as clinkers.

Answer 4

In the process of burning not only heat generated but also CO2 and .Nitrogen is also released in addition to nitrogen compounds.The abosrption of Co2 by plants from air is slow process.It also increases carbon content in soil.The burning process it self pollutes.
Composting is more eco friendly.It facilitates nitrogen to be conserved in spoil which help further vegitation.Bio fertlizer or compost is the best manure.If you see forest you will admit that decayed material supports growth of plants and trees with out any artificial fertliser.The bio decomposition is totally different from burning besides it retains fertlity of soil.

Answer 5

You already used a word in your edits that describes the difference between burning and composting: digesting.

When you burn material you break down complex organic molecules (sugars, starches, fiber, "hydrocarbons" essentially) into simpler molecules in an exothermic reaction (gives off heat). The byproducts of combustion produce some of the nasty pollutants and greenhouse gasses which are causing so many of our current problems.

When compost is digested by worms, insects, fungi and microscopic bacteria the reaction doesn't break down ALL the complex molecules into simpler components. Rather it changes them into different complex organic molecules that can be used to provide nutrient energy for other living organisms. This is the difference between soil and dirt. Soil is the organic byproducts of digestion (poop), dirt is powdered rock.

It is a cyclical process (plant, animal, plant) which reuses the chemical energy initially provided by the Sun to plants during photosynthesis; it is a much slower process than combustion and stores solar energy as food energy rather than releasing the energy all at once as heat and light and producing harmful combustion gasses in the process.

The same thing happens in your body. You eat complex hydrocarbons (sugar, starch and fiber) from plants, you breath in oxygen to "oxydize", or slowly burn, the nutrient energy, you breathe out CO2 and the energy provided keeps you warm and provides the energy and raw materials for your body to build new cells. When those cells die off after their function is served they are expelled along with the processed food in your urine or feces. You really ARE what you eat.

Which is a good segue into a question I have for you. Which makes more sense: growing crops to feed animals (including people) which will use the nutrients efficiently and keep circulating that energy within the food web, or burn it all to power machines?

Answer 6

What I'm about to say is of course unqualified as I am not a scientist and is based on what I have read from various sources.

Burning does indeed produce carbon monoxide and carbon dioxide along with some lesser pollutants. And it releases these gasses at a very high rate.

Composting produces carbon dioxide (and I suppose carbon monoxide to a lesser extent) at a much slower rate during the decomposition of the biomass. But it does release significant amounts of carbon dioxide.

However, when composting, there is ANOTHER gas involved that is also a "greenhouse" gas: methane...released from the bacteria that are consuming the garden material in the compost pile.

It seems to me, burning as opposed to composting is a choice between the devil and the deep blue sea.

Answer 7

You are right in a broad sense- respiration (bacteria and fungi respire when "eating" dead vegetation) is a form of combustion. Some of the other by-products are not produced however that enrich the soil and work back into the food chain. And the rate of release of CO2 is different.

Some of the other gases (like NO2 for example) produced are greenhouse gases while the nitrogen is a major nutrient required for plant grow that is not easily available if it is released into the atmosphere.

The CO2 released into the atmosphere is absorbed by plant during photosynthesis and is converted to "food" when combined with water (and other nutrients from the soil) in the presence of sun light. However, many natural and anthropogenic processes produce CO2 and much more is produced than can be absorbed by plants on land or in the ocean.

The problem is that much of the CO2 now "taken out" of the carbon cycle and stored as oil, limestone (formed from diatoms in the ocean millions of years ago), etc is now combusted and released into the atmosphere. Gigatons per year are released by human activity - more than natural processes typically produce and released at a greater rate. A lot of people who don't have any basic understanding of the cycles on the earth cry "natural variation" which is partially true, but now because human activity , much more of the CO2 in the atmosphere is released by people rather than totally natural cycles.

Volcanic activity does put all kinds of gases (and other stuff) in the atmosphere. Volcanic processes typically result in cooling processes because of the aerosols released reflect more sunlight away from the earth instead of letting if pass to the surface and be re-radiated as heat that can cause excessive warming.

CO2 is a long-lived gas that composes only a small part of the gases in the atmosphere. It is essential for life on earth (ALL of our food supply is depended on it), and makes the planet habitable (greenhouse effect makes life on earth as we know it possible - they have investigated the greenhouse effect since the 1800s). But small changes in the proportion (I think Dr. Jello posted some data that showed the proportion contributed has increase 20% since the 1800s - he did the math wrong and said it was only 0.008%, but he posted the data so people can check the number he derived). Water is actually the biggest greenhouse gas (you know that if you have lived in the mountains with low humidity then drive to the beach where it can get stifling).

A small increase in CO2 results in a small increase in atmospheric temperature that allow the air hold more moisture resulting in an increase in water vapor and a bigger bump. NO2, CH4, are other major gases - some of which have a greater impact than CO2. There is no way to prevent the sun from hitting the oceans so we can only work around the edges by manipulating the anthropogenic releases of CO2 and other greenhouse gases. The marginal effect will reduce the positive feedback effects from from water vapor and slow the warming.

The reason CO2 is a big deal is because it is directly related to putting carbon back into the system that was out of the system and is also directly related to other important gases (don't produce one without the others). It is like putting ice cubes into a glass of water. If the glass of water is the atmosphere and CO2 are ice cubes and it is a closed system (don't add more ice cubes than the 3 for instance), you can draw water out of the glass and make more ice then put it back in without over-flowing. However, if you take ice cubes from the freezer (or carbon dioxide out of the ground in the form of fossil fuel) and drop them into the glass, you can overflow the cup. The system will readjust to a new equilibrium and could result in a mess while it is happening.

Biofuels are important because they are not adding new CO2 into the system - it is recycling the CO2 already in the system.

Methane is and example of a gas that is produced by anaerobic process when growing rice or in the stomaches of cattle for example. Cattle actually breathe out CO2 and methane - it's not all just farts! That would be my horse (Junior). Lets one go with every step!

Methane is a relatively short lived gas that soil microbes take up and is absorb by the ocean when reacting with marine chlorine. I am not sure about the methane cycle or how important microbial and ocean processes are for regulating CH4. I mostly have dealt with forest ecosystems, CO2, economics, and removing CO2 using forest resources. I just quit eating beans for my part and hope it helps!

Answer 8

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Answer 9

The short answer is no - others seem to have covered that.
The best way I have found of getting rid of compostable waste is a wormery. They are small and compact and produce loads of good compost and liquid which is great for the garden.
Go to http://www.wigglywigglers.co.uk/

Answer 10

Yes, but the Co2 is released into the plants and soil as opposed to the air. This allows for more plant growth as well as less Co2 in the air.